Download 7 Clinical Anesthesia

PREOPERATIVE ASSESSMENT.
CLINICAL ANESTHESIOLOGY.
2016
VITEBSK STATE MEDICAL UNIVERSITY
Content
Preoperative Assessment ........................................................................................................................ 2
Preoperative evaluation ...................................................................................................................... 2
Elements of the Preoperative History ................................................................................................. 5
Cardiovascular Issues. ..................................................................................................................... 5
Pulmonary Issues ............................................................................................................................. 7
Endocrine and Metabolic Issues ...................................................................................................... 7
Coagulation Issues ........................................................................................................................... 8
Gastrointestinal Issues .................................................................................................................. 10
Elements of the Preoperative Physical Examination......................................................................... 10
Airway assessment ........................................................................................................................ 11
Preoperative laboratory testing ........................................................................................................ 12
Premedication ....................................................................................................................................... 13
Anesthesia for abdominal surgery ........................................................................................................ 14
General consideration ....................................................................................................................... 14
Laparoscopic surgery ......................................................................................................................... 17
Anesthesia for Orthopedic and Trauma Surgery ................................................................................... 20
Advanced trauma life support ....................................................................................................... 25
Obstetric Anesthesia ............................................................................................................................. 29
Physiologic changes during pregnancy.......................................................................................... 29
Analgesia for labor......................................................................................................................... 32
Anesthesia for cesarean delivery .................................................................................................. 34
Pediatric Anesthesia .............................................................................................................................. 36
Anatomy and physiology relevant to pediatric anesthesia ........................................................... 36
Ambulatory anesthesia ......................................................................................................................... 43
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Preoperative Assessment
Preoperative evaluation
The cornerstones of an effective preoperative evaluation are the medical history and
physical examination, which should include a complete account of all medications taken by the
patient in the recent past, all pertinent drug and contact allergies, and responses and reactions
to previous anesthetics. Additionally, this evaluation should include any indicated diagnostic
tests, imaging procedures, or consultations from other physicians. The preoperative evaluation
guides the anesthetic plan: inadequate preoperative planning and incomplete patient preparation
are commonly associated with anesthetic complications.
The preoperative evaluation serves multiple purposes. One purpose is to identify those
few patients whose outcomes likely will be improved by implementation of a specific medical
treatment (which in rare circumstances may require that the planned surgery be rescheduled).
For example, a 60-year-old patient scheduled for elective total hip arthroplasty who also has
unstable angina from left main coronary artery disease would more likely survive if coronary
artery bypass grafting is performed before the elective procedure.
Another purpose is to identify patients whose condition is so poor that the proposed
surgery might only hasten death without improving the quality of life. For example, a patient
with severe chronic lung disease, end-stage kidney failure, liver failure, and heart failure likely
would not survive to derive benefit from an 8-hour, complex, multilevel spinal fusion with
instrumentation.
The preoperative evaluation can identify patients with specific characteristics that likely
will influence the proposed anesthetic plan (see Figure 1). For example, the anesthetic plan may
need to be reassessed for a patient whose trachea appears difficult to intubate, one with a family
history of malignant hyperthermia, or one with an infection near where a proposed regional
anesthetic would be administered.
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Figure 1 The anesthetic plan. Source: John F. Butterworth IV, David C. Mackey, John D. Wasnick - Morgan & Mikhail’s Clinical
Anesthesiology. 5th Edition
Another purpose of the evaluation is to provide the patient with an estimate of anesthetic
risk. However, the anesthesiologist should not be expected to provide the risk-versus-benefit
discussion for the proposed procedure; this is the responsibility and purview of the responsible
surgeon or “proceduralist.” For example, a discussion of the risks and benefits of robotic
prostatectomy versus radiation therapy versus “watchful waiting” requires knowledge of both
the medical literature and the morbidity–mortality statistics of an individual surgeon, and it
would be most unusual for an anesthesiologist to have access to the necessary data for this
discussion.
Finally, the preoperative evaluation is an opportunity for the anesthesiologist to
describe the proposed anesthetic plan in the context of the overall surgical and postoperative
plan, provide the patient with psychological support, and obtain informed consent for the
proposed anesthetic plan from the surgical patient. By convention, physicians in many
countries use the American Society of Anesthesiologists’ (ASA, official web site:
http://www.asahq.org/ ) classification to define relative risk prior to conscious sedation and
surgical anesthesia (s. table below). The ASA physical status classification has many
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advantages over all other risk classification tools: it is time honored, simple, reproducible,
and, most importantly, it has been shown to be strongly associated with perioperative risk.
But, many other risk assessment tools are available.
ASA physical status classification system (October 2015)
ASA PS
Definition
Examples, including, but not limited to:
A normal healthy
Healthy, non-smoking, no or minimal alcohol
patient
use
A patient with
Mild diseases only without substantive
mild systemic
functional limitations. Examples include (but not
disease
limited to): current smoker, social alcohol
Classification
ASA I
ASA II
drinker, pregnancy, obesity (30<BMI<40),
wellcontrolled DM/HTN, mild lung disease
ASA III
A patient with
Substantive functional limitations;
severe
One or more moderate to severe diseases.
systemic disease
Examples include (but not limited to): poorly
controlled DM or HTN, COPD, morbid obesity
(BMI ≥40), active hepatitis, alcohol dependence
or abuse, implanted pacemaker, moderate
reduction of ejection fraction, ESRD undergoing
regularly scheduled dialysis, premature infant
PCA < 60 weeks, history (>3 months) of MI,
CVA, TIA, or CAD/stents.
ASA IV
ASA V
A patient with
Examples include (but not limited to): recent (<3
severe
months) MI, CVA, TIA, or CAD/stents, ongoing
systemic disease
cardiac ischemia or severe valve dysfunction,
that is a
severe reduction of ejection fraction, sepsis, DIC,
constant threat to
ARD or ESRD not undergoing regularly
life
scheduled dialysis
A moribund
Examples include (but not limited to): ruptured
patient who is
abdominal/thoracic aneurysm, massive trauma,
not expected to
intracranial bleed with mass effect, ischemic
survive
bowel in the face of significant cardiac pathology
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without the
or multiple organ/system dysfunction
operation
ASA VI
A declared braindead
patient whose
organs are
being removed for
donor
purposes
*The addition of “E” denotes Emergency surgery:
(An emergency is defined as existing when delay in treatment of the patient would lead to a
significant increase in the threat to life or body part)
Elements of the Preoperative History
Patients presenting for elective surgery and anesthesia typically require a focused
preoperative medical history emphasizing cardiac and pulmonary function, kidney disease,
endocrine and metabolic diseases, musculoskeletal and anatomic issues relevant to airway
management and regional anesthesia, and responses and reactions to previous anesthetics.
Cardiovascular Issues.
The focus of preoperative cardiac assessment should be on determining whether the
patient’s condition can and must be improved prior to the scheduled procedure, and whether
the patient meets criteria for further cardiac evaluation prior to the scheduled surgery. Clearly
the criteria for what must be done before elective arthroplasty will differ from what must be
done before an operation for resectable pancreatic cancer, given the benign results of a delay in
the former procedure and the potential life-shortening effects of a delay in the latter procedure.
In general, the indications for cardiovascular investigations are the same in surgical patients as
in any other patient. Put another way, the fact that a patient is scheduled to undergo surgery
does not change the indications for such measures as noninvasive stress testing to diagnose
coronary artery disease.
Cardiovascular complications account for 25% to 50% of deaths following noncardiac
surgery. Perioperative myocardial infarction (MI), pulmonary edema, congestive heart failure,
arrhythmias, and thromboembolism are most commonly seen in patients with preexisting
cardiovascular disease.
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Cardiovascular disease that important for anesthesia:
 Hypertension. Regardless of the level of preoperative blood pressure control, many patients
with hypertension display an accentuated hypotensive response to induction of anesthesia,
followed by an exaggerated hypertensive response to intubation. Hypertensive patients may
display an exaggerated response to both endogenous catecholamines (from intubation or
surgical stimulation) and exogenously administered sympathetic agonists.
 Ischemic heart disease. Patients with extensive (three-vessel or left main) coronary artery
disease, a history of MI, or ventricular dysfunction are at greatest risk of cardiac
complications. Sudden withdrawal of antianginal medication perioperatively—particularly
β-blockers—can precipitate a sudden, rebound increase in ischemic episodes. The
overwhelming priority in managing patients with ischemic heart disease is maintaining a
favorable myocardial supply–demand relationship. Autonomic-mediated increases in heart
rate and blood pressure should be controlled by deep anesthesia or adrenergic blockade, and
excessive reductions in coronary perfusion pressure or arterial oxygen content are to be
avoided.
 Mitral stenosis. The principal hemodynamic goals in managing mitral stenosis are to
maintain a sinus rhythm (if present preoperatively) and to avoid tachycardia, large increases
in cardiac output, and both hypovolemia and fluid overload by judicious administration of
intravenous fluids.
 Mitral regurgitation. Anesthetic management of mitral regurgitation should be tailored to
the severity of regurgitation and to the underlying left ventricular function. Factors that
exacerbate the regurgitation, such as slow heart rates and acute increases in afterload, should
be avoided. Excessive volume expansion can also worsen the regurgitation by dilating the
left ventricle.
 Aortic stenosis. Maintenance of normal sinus rhythm, heart rate, vascular resistance and
intravascular volume is critical in patients with aortic stenosis. Loss of a normally timed
atrial systole often leads to rapid deterioration, particularly when associated with
tachycardia. Spinal and epidural anesthesia are relatively contraindicated in patients with
severe aortic stenosis.
 Aortic regurgitation. Bradycardia and increase in systemic vascular resistance (SVR)
increase the regurgitant volume in patients with aortic regurgitation, whereas tachycardia
can contribute to myocardial ischemia. Excessive myocardial depression should also be
avoided. The compensatory increase in cardiac preload should be maintained, but excessive
fluid replacement can readily result in pulmonary edema.
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 Congenital heart disease. In patients with congenital heart disease, an increase in SVR
relative to pulmonary vascular resistance (PVR) favors left-to-right shunting, whereas an
increase in PVR relative to SVR favors right-to-left shunting. The presence of shunt flow
between the right and left hearts, regardless of the direction of blood flow, mandates the
meticulous exclusion of air bubbles or particulate material from intravenous fluids to
prevent paradoxical embolism into the cerebral or coronary circulations.
Pulmonary Issues
Perioperative pulmonary complications, most notably postoperative respiratory
depression and respiratory failure, are vexing problems that have become seemingly more
common as severe obesity and obstructive sleep apnea have increased in incidence.
The risk of postoperative pulmonary complications is closely associated with these
factors, and with the following: ASA class (class 3 and 4 patients have a markedly increased
risk of pulmonary complications relative to class 1 patients), cigarette smoking, longer surgeries
(>4 h), certain types of surgery (abdominal, thoracic, aortic aneurysm, head and neck, and
emergency surgery), and general anesthesia (compared with cases in which general anesthesia
was not used). Efforts at prevention of pulmonary complications should focus on cessation of
cigarette smoking prior to surgery and on lung expansion techniques (eg, incentive spirometry)
after surgery in patients at risk.
Patients with asthma, particularly those receiving suboptimal medical management,
have a greater risk for bronchospasm during airway manipulation. Appropriate use of analgesia
and monitoring are key strategies for avoiding postoperative respiratory depression in patients
with obstructive sleep apnea.
Endocrine and Metabolic Issues
The underproduction or overproduction of hormones can have dramatic physiological
and pharmacological consequences. Therefore, it is not surprising that endocrinopathies affect
anesthetic management.
 Unfortunately, many diabetic patients presenting for elective surgery do not maintain blood
glucose within the desired range. Other patients, who may be unaware that they have type 2
diabetes, present with blood glucose measurements above the normal range. Adequacy of
longterm blood glucose control can be easily and rapidly assessed by measurement of
hemoglobin A1c. In patients with abnormally elevated hemoglobin A1c, referral to a
diabetology service for education about the disease and adjustment of diet and medications to
improve metabolic control may be beneficial. Elective surgery should be delayed in patients
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presenting with marked hyperglycemia; this delay might consist only of rearranging the order
of scheduled cases to allow insulin infusion to bring the blood glucose concentration closer to
the normal range before surgery begins. Diabetic autonomic neuropathy may limit the patient’s
ability to compensate (with tachycardia and increased peripheral resistance) for intravascular
volume changes and may predispose the patient to cardiovascular instability (eg, postinduction
hypotension) and even sudden cardiac death.
 Incompletely treated hyperthyroid patients can be chronically hypovolemic and prone to an
exaggerated hypotensive response during induction of anesthesia.
 Patients with glucocorticoid deficiency must receive adequate steroid replacement therapy
during the perioperative period.
 In patients with a pheochromocytoma, drugs or techniques that indirectly stimulate or promote
the release of catecholamines (eg, ephedrine, hypoventilation, or bolus doses of ketamine),
potentiate the arrhythmic effects of catecholamines (classically halothane), or consistently
release histamine (eg, large doses of atracurium or morphine sulfate) may precipitate
hypertension and are best avoided.
 Obese patients may be difficult to intubate because of limited mobility of the
temporomandibular and atlantooccipital joints, a narrowed upper airway, and a shortened
distance between the mandible and sternal fat pads.
Coagulation Issues
Three important coagulation issues that must be addressed during the preoperative
evaluation are:
 how to manage patients who are taking warfarin on a long-term basis. Warfarin (brand names:
Coumadin, Jantoven) is a prescription medication that interferes with normal blood clotting
(coagulation). It is also called an anticoagulant. Many people refer to these medicines as "blood
thinners," although they do not actually cause the blood to become less thick, only less likely
to clot. Warfarin is used in people who have already developed a harmful blood clot, including
some patients who have had a stroke, heart attack, a clot that has traveled to the lung (pulmonary
embolism or PE), or a blood clot in the leg (deep vein thrombosis or DVT). The major
complication associated with warfarin is bleeding.
 how to manage patients who are taking clopidogrel and related agents. Clopidogrel is an
oral, thienopyridine-class antiplatelet agent used to inhibit blood clots in coronary artery
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disease, peripheral vascular disease, cerebrovascular disease, and to prevent myocardial
infarction (heart attack) and stroke.
 how to safely provide regional anesthesia to patients who either are receiving long-term
anticoagulation therapy or who will receive anticoagulation perioperatively.
In the first circumstance, most patients who undergoing anything more involved than
minor surgery will require discontinuation of warfarin 5 days in advance of surgery to avoid
excessive blood loss. The key question to be answered is whether the patient will require
“bridging” therapy with another agent while warfarin is discontinued. In patients deemed at
high risk for thrombosis (eg, those with certain mechanical heart valve implants or with atrial
fibrillation and a prior thromboembolic stroke), warfarin should be replaced by intravenous
heparin or, more commonly, by intramuscular heparinoids to minimize the risk. In patients
receiving bridging therapy for a high risk of thrombosis, the risk of death from excessive
bleeding is an order of magnitude lower than the risk of death or disability from stroke if the
bridging therapy is omitted. Patients at lower risk for thrombosis may have warfarin
discontinued and then reinitiated after successful surgery. Decisions regarding bridging therapy
often require consultation with the physician who initiated the warfarin therapy.
Clopidogrel and related agents are most often administered with aspirin (so-called dual
antiplatelet therapy) to patients with coronary artery disease who have received intracoronary
stenting. Immediately after stenting, such patients are at increased risk of acute myocardial
infarction if clopidogrel (or related agents) and aspirin are abruptly discontinued for a surgical
procedure. Therefore, current guidelines recommend postponing all but mandatory emergency
surgery until at least 1 month after any coronary intervention and suggest that treatment options
other than a drug-eluting stent (which will require prolonged dual antiplatelet therapy) be used
in patients expected to undergo a surgical procedure within 12 months after the intervention
(eg, in a patient with colon cancer who requires treatment for coronary disease).
The third circumstance—when it may be safe to perform regional (particularly
neuraxial) anesthesia in patients who are or will be receiving anticoagulation therapy—has also
been the subject of debate among hematologists and regional anesthetists. The American
Society of Regional Anesthesia publishes a periodically updated consensus guideline on this
topic, and other prominent societies (eg, the European Society of Anaesthesiologists) provide
guidance on this topic.
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Gastrointestinal Issues
Since Mendelson’s 1946 report, aspiration of gastric contents has been recognized as a
potentially disastrous pulmonary complication of surgical anesthesia. It has also been long
recognized that the risk of aspiration is increased in certain groups of patients: pregnant women
in the second and third trimesters, those whose stomachs have not emptied after a recent meal,
and those with serious gastroesophageal reflux disease (GERD). Although there is a consensus
that pregnant women and those who have recently (within 6 h) consumed a full meal should be
treated as if they have “full” stomachs, there is less consensus as to the necessary period of time
in which patients must fast before elective surgery. Proof of the lack of consensus is the fact
that the ASA’s guideline on this topic was voted down by the ASA House of Delegates several
years in a row before it was presented in a form that received majority approval. The guideline
as approved is more permissive of fluid intake than many anesthesiologists would prefer, and
many medical centers have policies that are more restrictive than the ASA guideline on this
topic. The truth is that there are no good outcomes data to support restricting fluid intake (of
any kind or any amount) more than 2 h before induction of general anesthesia in healthy patients
undergoing elective procedures; indeed, there is evidence that nondiabetic patients should be
encouraged to drink glucose-containing fluids up to 2 h before induction of anesthesia. Patients
with a history of GERD present vexing problems. Some of these patients will clearly be at
increased risk for aspiration; others may carry this “self-diagnosis” based on television
advertisements or conversations with friends and family, or may have been given this diagnosis
by a physician who did not follow the standard diagnostic criteria. Our approach is to treat
patients who have only occasional symptoms like any other patient without GERD, and to treat
patients with consistent symptoms (multiple times per week) with medications (eg,
nonparticulate antacids such as sodium citrate) and techniques (eg, tracheal intubation rather
than laryngeal mask airway) as if they were at increased risk for aspiration.
Elements of the Preoperative Physical Examination
The preoperative history and physical examination complement one another: The
physical examination may detect abnormalities not apparent from the history, and the history
helps focus the physical examination.
Examination of healthy asymptomatic patients should include measurement of vital
signs (blood pressure, heart rate, respiratory rate, and temperature) and examination of the
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airway, heart, lungs, and musculoskeletal system-using standard techniques of inspection,
auscultation, palpation, and percussion.
Before procedures such as a nerve block, regional anesthesia, or invasive monitoring
the relevant anatomy should be examined; evidence of infection near the site or of anatomic
abnormalities may contraindicate the planned procedure. An
abbreviated
neurological
examination is important when regional anesthesia will likely be used. The preoperative
neurological examination serves to document whether any neurological deficits may be present
before the block is performed.
Airway assessment
The anesthesiologist must examine the patient’s airway before every anesthetic
procedure. The patient’s dentition should be inspected for loose or chipped teeth, caps, bridges,
or dentures. Poor fit of the anesthesia mask should be expected in edentulous patients and those
with significant facial abnormalities. Micrognathia (a short distance between the chin and the
hyoid bone), prominent upper incisors, a large tongue, limited range of motion of the
temporomandibular joint or cervical spine, or a short or thick neck suggest that difficulty may
be encountered in direct laryngoscopy for tracheal intubation.
Airway assessment is the first step in successful airway management. Several
anatomical and functional maneuvers can be performed to estimate the difficulty of
endotracheal intubation; however, it is important to note that successful ventilation (with or
without intubation) must be achieved by the anesthetist if mortality and morbidity are to be
avoided. Assessments include:
 Mouth opening: an incisor distance of 3 cm or greater is desirable in an adult.
 Upper lip bite test: the lower teeth are brought in front of the upper teeth. The degree to
which this can be done estimates the range of motion of the temperomandibular joints.
 Mallampati classification: a frequently performed test that examines the size of the tongue
in relation to the oral cavity. The greater the tongue obstructs the view of the pharyngeal
structures, the more difficult intubation may be.
Class I: the entire palatal arch, including the bilateral faucial pillars, are visible down
to their bases.
Class II: the upper part of the faucial pillars and most of the uvula are visible.
Class III: only the soft and hard palates are visible.
Class IV: only the hard palate is visible.
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Figure 2. Mallampati classification
 Thyromental distance: the distance between the mentum and the superior thyroid notch. A
distance greater than 3 fingerbreadths is desirable.
 Neck circumference: a neck circumference of greater than 27 in is suggestive of difficulties
in visualization of the glottic opening.
Although the presence of these findings may not be particularly sensitive for detecting
a difficult intubation, the absence of these findings is predictive for relative ease of intubation.
Increasingly, patients present with morbid obesity and body mass indices of 30 kg/m2 or
greater. Although some morbidly obese patients have relatively normal head and neck anatomy,
others have much redundant pharyngeal tissue and increased neck circumference. Not only may
these patients prove to be difficult to intubate, but routine ventilation with bag and mask also
may be problematic.
Preoperative laboratory testing
Routine laboratory testing when patients are fit and asymptomatic is not recommended.
Testing should be guided by the history and physical examination. “Routine” testing is
expensive and rarely alters perioperative management; moreover, abnormal values often are
overlooked or if recognized may result in unnecessary delays.
Nonetheless, despite the lack of evidence of benefit, many physicians order a hematocrit
or hemoglobin concentration, urinalysis, serum electrolyte measurements, coagulation studies,
an electrocardiogram, and a chest radiograph for all patients, perhaps in the misplaced hope of
reducing their exposure to litigation. To be valuable, preoperative testing must discriminate:
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there must be an increased perioperative risk when the results are abnormal (and unknown when
the test is not performed), and there must be a reduced risk when the abnormality is not detected
(or it has been corrected). This requires that the test have a very low rate of false-positive and
false-negative results.
The utility of a test depends on its sensitivity and specificity. Sensitive tests have a low
rate of false-negative results and rarely fail to identify an abnormality when one is present,
whereas specific tests have a low rate of false-positive results and rarely identify an abnormality
when one is not present .The prevalence of a disease or of an abnormal test result varies with
the population tested. Testing is therefore most effective when sensitive and specific tests are
used in patients in whom the abnormality will be detected frequently enough to justify the
expense and inconvenience of the test procedure.
Accordingly, laboratory testing should be based on the presence or absence of
underlying diseases and drug therapy as detected by the history and physical examination. The
nature of the proposed surgery or procedure should also be taken into consideration. Thus, a
baseline hemoglobin or hematocrit measurement is desirable in any patient about to undergo a
procedure that may result in extensive blood loss and require transfusion, particularly when
there is sufficient time to correct anemia preoperatively (eg, with iron supplements).
Premedication
A classic study showed that a preoperative visit from an anesthesiologist resulted in a
greater reduction in patient anxiety than preoperative sedative drugs. Yet, there was a time when
virtually every patient received premedication before arriving in the preoperative area in
anticipation of surgery. Despite the evidence, the belief was that all patients benefitted from
sedation and anticholinergics, and most patients would benefit from a preoperative opioid. After
such premedication, some patients arrived in a nearly anesthetized state. With the move to
outpatient surgery and “same-day” hospital admission, the practice has shifted. Today,
preoperative sedative-hypnotics or opioids are almost never administered before patients arrive
in the preoperative holding area (other than for intubated patients who have been previously
sedated in the intensive care unit). Children, especially those aged 2–10 years who will
experience separation anxiety on being removed from their parent, may benefit from
premedication administered in the preoperative holding area. Midazolam administered either
intravenously or orally, is a common method. Adults oft en receive intravenous midazolam (2–
5 mg) once an intravenous line has been established, and if a painful procedure (eg, regional
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block or a central venous line) will be performed while the patient remains awake, small doses
of opioid (typically fentanyl) will often be given. Patients who will undergo airway surgery or
extensive airway manipulations benefit from preoperative administration of an anticholinergic
agent (glycopyrrolate or atropine) to reduce airway secretions before and during surgery. The
fundamental message here is that premedication should be given purposefully, not as a mindless
routine.
Anesthesia for abdominal surgery
General consideration
Risk of aspiration
Aspiration, with its associated morbidity, is a potential risk in major abdominal surgery,
whether elective (bariatric surgery, fundoplication) or emergent (acute abdomen, bowel
obstruction) procedures. The incidence of pulmonary aspiration in the perioperative period is
rare (5/10,000 general anesthetic). Measures to prevent pulmonary aspiration of gastric contents
are listed below. Additional considerations include the following:
 The gastroesophageal sphincter (GES) plays an important role in preventing the aspiration
of gastric contents. The GES tone is altered or impaired in clinical conditions such as
morbid obesity and hiatal hernia, and during anesthesia. Most anesthetics and analgesics
alter the GES tone.
 Impaired gastric emptying due to obesity, bowel obstruction, or other disorders will lead to
increased volume and acidity of the gastric contents.
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Figure 3. Strategies to prevent pulmonary aspiration. Essential clinical anesthesia edited by Charles Vacanti.
Fluid management
Abdominal surgery may be associated with significant fluid loss as well as significant
fluid shifts. These fluid changes may occur preoperatively as well as intraoperative.
Preoperative factors include bowel preparation (elective surgery) and vomiting, gastric
decompression and/or drainage, sequestration of fluid, diarrhea, and bleeding (urgent surgery).
Intraoperative, factors include insensible losses (traditionally assumed to amount up to 4–8
ml/kg/h for major abdominal surgery), intraoperative bleeding, gastric drainage, and drainage
of ascites.
Thus, large-bore peripheral intravenous (IV) access may be necessary. Arterial and
central lines may also be chosen to better manage hemodynamic changes associated with fluid
shifts even though central venous pressure (CVP) and/or pulmonary capillary wedge pressure
(PCWP) measurements do not predict fluid responsiveness and therefore are unable to guide
the clinician in optimizing cardiac preload and tissue oxygenation.
Anesthetic technique
General anesthesia continues to be the mainstay of anesthetic management for major
abdominal surgery. Although regional anesthesia (continuous epidural or spinal) could be the
sole anesthetic in high-risk patients with significant pulmonary disease, this approach is rarely
used in modern practice. Low thoracic epidurals are frequently used as adjuncts for
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intraoperative maintenance of anesthesia and for postoperative pain control. The use of thoracic
epidural techniques as adjuncts to general anesthesia for major abdominal surgery has been
shown to improve postoperative analgesia, decrease respiratory failure, and enhance ileus
resolution, but not to decrease mortality. The risk of epidural hematoma and abscess, with a
potential for permanent paralysis, albeit rare, should be kept in mind when deciding to place an
epidural for elective abdominal surgery.
A balanced general anesthetic technique with an inhalational agent and an opioid or total
IV anesthesia are both suitable anesthetic techniques for abdominal surgery.
Muscle relaxation is often needed to improve surgical exposure and to facilitate
abdominal closure. The use of nitrous oxide (N2O) has been debated for years due to its ability
to diffuse into gas-containing body cavities, thus theoretically distending the bowel and
impairing surgical exposure. Therefore, some anesthesiologists avoid N2O in major abdominal
surgery reasoning that additional bowel distention could be harmful.
Most patients undergoing abdominal surgery will be extubated successfully in the
operating room (OR), but patients who require large amounts of fluid and blood products and
who exhibit facial and airway edema and those with hemodynamic or respiratory instability
should be kept intubated and ventilated in the intensive care unit(ICU). Extubation should be
performed when the edema has resolved and hemodynamic and respiratory stability are
achieved.
Intraoperative considerations
Heat loss
Abdominal surgery is associated with significant heat loss; therefore, the patient’s
temperature should be measured routinely. Items used to prevent hypothermia and associated
complications include forced-air warming blankets and humidifiers. Fluid warmers should be
used when large volumes of fluid are to be administered.
Pulmonary complications
Significant retraction, carbon dioxide (CO2) insufflation for laparoscopic surgery, and
Trendelenburg position will elevate the diaphragm and decrease the functional residual capacity
(FRC), potentially leading to hypoxia and hypoventilation. Adding positive end-expiratory
pressure (PEEP) increases FRC and may help improve oxygenation and ventilation.
Mesenteric traction syndrome
This syndrome involves sudden onset of tachycardia, hypotension, and flushing
associated with excessive traction on the mesentery. Although the exact pathophysiology is
unknown, the release of prostacyclin and possibly histamine may play a role in the etiology.
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Cyclooxygenase (COX) inhibitors such as IV ketorolac may be used to prevent the syndrome,
although their use should be discussed with the surgeon, as their platelet-inhibiting effects may
be undesirable during surgery. H1-and H2- antihistamines also play a role in the prevention of
this syndrome.
Postoperative ileus
Ileus is a major complication of abdominal surgery. The etiology involves pain, surgical
stress, electrolyte and fluid imbalance, and the use of opioids. Opioids bind to μ-opioid
receptors, depressing GI motility and worsening the ileus. Therapeutic options to minimize ileus
are mostly supportive and include limiting the use of parenteral opioids, using thoracic epidural
analgesia, instituting early feeding and mobility, and using laparoscopic surgery.
Postoperative infection
Abdominal surgery is an independent risk factor for surgical site infection (SSI).
Although many factors contribute to the risk of SSI, several could be manipulated
intraoperatively by the anesthesiologist. These factors include hypoxia, hypothermia,
hyperglycemia, and blood transfusion. Thus, measures to minimize the likelihood of
postoperative infection should be undertaken, including the use of a hyperoxic gas mixture,
avoidance of hypothermia, tight glycemic control, and minimizing blood transfusion, and
timely administration of appropriate antibiotics.
Laparoscopic surgery
Minimally invasive surgical procedures, when compared to conventional open
procedures, are associated with significantly less trauma and the potential advantages of
reduced postoperative pain, shorter length of hospitalization, rapid recovery, and decreased
health care costs. Laparoscopy produces significant physiologic changes associated with
peritoneal carbon dioxide (CO2) insufflation and alteration in patient position that can have a
major impact on cardiopulmonary function, particularly in patients with significant
comorbidities.
Physiologic effects of laparoscopic procedures
The physiologic effects of laparoscopy are related to the combined effects of creation of a
pneumoperitoneum, alteration of patient position, and effects of systemic absorption of CO2.
 Hemodynamic effects. During laparoscopy, cardiac output decreases to a variable extent
depending on intra-abdominal pressure (IAP) and patient position, despite an increase in
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systemic blood pressure. A characteristic response during the initiation of the
pneumoperitoneum is an initial fall of the cardiac index with a subsequent partial recovery.
Left ventricular end-diastolic volume is reduced during laparoscopy. Intrathoracic pressure
is increased, and that commonly results in increased right atrial and pulmonary artery
occlusion pressures. The heart rate is minimally increased or unchanged.
 Effects of CO2-absorption. CO2 is used for abdominal insufflation, as it is
noncombustible and is more soluble in blood than is O2, nitrous oxide (N2O), or air. The
absorption of insufflated CO2, however, may lead to hypercapnia and respiratory acidosis
that cause a decrease in myocardial contractility, lowered arrhythmia threshold, arteriolar
dilatation, and decreased systemic vascular resistance. The PaCO2 increases progressively
to reach a plateau 15 to 30 minutes after insufflation of CO2 is initiated. This extent of
increase in PaCO2 is unpredictable, particularly in patients with severe pulmonary disease.
The increase in PaCO2results in significant decreases in pH and the requirement for an
increase in minute ventilation.
 Respiratory effects. During laparoscopy, lung volumes are reduced due to a cephalad shift
of the diaphragm caused by abdominal insufflation. The pulmonary compliance is
decreased, resulting in increased peak airway pressures and a reduction in functional
residual capacity (FRC). There is ventilation-perfusion mismatch that may cause
hypoxemia. There is an increase in intrathoracic pressure that adds to the decrease in lung
compliance.
 Effects of patient positioning. Patient position during laparoscopy varies depending on the
procedure performed. For laparoscopic cholecystectomy, reverse Trendelenburg position
with left lateral tilt is chosen to facilitate retraction of the gall bladder fundus and to
minimize diaphragmatic dysfunction. This position improves pulmonary dynamics but may
result in decreased venous return with a reduction in left ventricular end-diastolic volume.
Increased IAP and the head-up position predispose to thromboembolism due to decreased
femoral vein blood flow and lower limb venous stasis. The Trendelenburg position (for
gynecologic procedures), in contrast, increases central blood volume, decreases
diaphragmatic excursion, and causes pulmonary congestion. The ventilation–perfusion
mismatch may result in hypoxemia, particularly in obese patients or in patients with
pulmonary disease. Care should be taken so that the endotracheal tube does not slip into a
mainstem bronchus during position changes.
18
Anesthetic considerations
Although reports about laparoscopic procedures performed under spinal or epidural
anesthesia have been documented, the requirement of a pneumoperitoneum and change in
patient position commonly limits these procedures to general anesthesia. Endotracheal
intubation and controlled mechanical ventilation are required to reduce the increase in PaCO2
and counterbalance the respiratory side effects of the Trendelenburg position.
A balanced anesthetic technique consisting of opioids (fentanyl on induction, and
morphine or hydromorphone for long-acting pain control), muscle relaxants, and volatile
anesthetic is used.
The use of N2O is controversial because it may theoretically diffuse into air-filled
spaces and cause distention of the bowel. In addition, the use of N2O may increase the incidence
of PONV.
An orogastric tube is inserted to decompress the stomach. A urinary catheter may be
inserted to decompress the bladder.
The patient’s muscles should be adequately relaxed prior to the initial trocar insertion
since it is inserted blindly. Perforation of the inferior vena cava and aorta have been reported to
occur during trocar insertion. A vagal response may also occur during trocar insertion.
Intraoperative hypertension should be treated with adequate pain control, deepening of the
anesthesia, and administration of an antihypertensive such as labetalol or metoprolol, if
indicated.
Control of pain may be achieved via a multimodal analgesic regimen combining
opioids, COX inhibitors, and local anesthetic infiltration. The nonselective COX inhibitor
ketorolac (30 mg) is being increasingly administered near the end of procedures.
Laparoscopic procedures are frequently associated with an increased risk of PONV.
Serotonin receptor antagonists (ondansetron, granisetron, dolasetron, and palonosetron),
compared with traditional antiemetics, are highly efficacious for PONV. It is likely that
combined antiemetics with different sites and mechanisms of action would be more effective
than one drug alone for the prophylaxis against PONV, especially in high-risk patients. Adding
dexamethasone to ondansetron or granisetron improves antiemetic efficacy in PONV.
Dexamethasone should be given early during the surgery, preferably before any emetogens.
19
Anesthesia for Orthopedic and Trauma Surgery
Providing optimal anesthesia and perioperative care for orthopedic surgery patients may
be quite challenging for the anesthesiologist due to surgical procedure diversity and various
coexisting diseases. Most common orthopedic procedures can be performed under regional
anesthesia (in the absence of specific contraindications), but because of discomfort in the
unanesthetized areas or long surgical duration, a combination of regional and general anesthesia
may sometimes be a better choice than regional anesthesia alone. Many orthopedic surgery
patients are elderly and present with multiple comorbidities. In addition, the orthopedic
procedures themselves predispose to several common complications, such as venous
thromboembolism, fat embolism, pneumatic tourniquet- or bone cement-associated
hemodynamic instability, and patient positioning injuries. Finally, specific complications could
also be related to neuraxial and other regional anesthetic techniques.
General considerations

Anticoagulation. Concomitant thromboprophylaxis presents a unique challenge when
planning the optimal anesthetic, especially when neuraxial anesthesia is considered. Careful
risk/benefit analysis is warranted when trying to balance possible advantages of the different
regional anesthesia techniques against the odds of potentially devastating complications (e.g.,
epidural or spinal hematoma).

Management of blood loss. Perioperative blood loss in orthopedic surgery can be high,
especially in joint replacements, occasionally exceeding several liters in cases such as complex
revision of total hip arthroplasty (THA). The term bloodless surgery refers to a series of
perioperative patient care measures aiming to reduce or avoid the need for allogeneic blood
transfusion. Patient assessment and optimization, including accurate history and physical
examination, are focused on personal and family history of bleeding disorders and medications
that may impair coagulation. Preadmission testing should be done in advance (e.g., 1 month) to
allow time for adequate identification, evaluation, and treatment of any coagulation defect or
anemia. Possible corrective measures include the administration of iron, folate, vitamin B12,
and recombinant erythropoietin. It is important to plan the intraoperative availability of all
equipment necessary to facilitate blood conservation strategies (e.g., cell salvage apparatus).
Surgeons practicing careful hemostasis may help minimize intraoperative blood loss. The use
of electrocautery during surgery, a harmonic scalpel, and local hemostatic aids may also help
reduce bleeding. Various techniques can also be used to reduce transfusion requirements,
20
including controlled hypotension, acute normovolemic hemodilution, and autologous blood cell
salvage.
Multiple pharmacologic agents are also used to decrease bleeding in high-risk patients. These
agents include recombinant activated factor VII, the lysine analogues (ε-aminocaproic acid and
tranexamic acid) that inhibit plasmin-mediated fibrinolysis, and desmopressin that stimulates
the endothelial release of factor VIII and von Willebrand factor, thereby enhancing platelet
aggregation.

Tourniquets. Tourniquets are used frequently in distal extremity procedures to reduce
blood loss and provide a bloodless operating field. They may cause systemic effects due to
ischemia and reperfusion, as well as local effects from the pressure applied to the tissues.
Tourniquet injury has been implicated as a main cause for peroneal and tibial nerve palsies after
total knee arthroplasty (TKA), ranging from mild neuropraxia to permanent neurologic deficits.
The incidence of tourniquet-induced paralysis is approximately 1 in 8000 operations.
Tourniquet time should not exceed 90 to 120 minutes and tourniquet pressure should not be
higher than 150 mm Hg above systolic blood pressure.
Anesthesia for hip fracture
Hip fracture refers to a femur fracture in the region immediately distal to the articular
cartilage of the femoral head to approximately 5 cm below the lower border of the lesser
trochanter. Because the majority of these cases are treated surgically, hip fracture surgery has
become one of the most commonly performed urgent orthopedic procedures. There is
agreement that a delay (more than 24 hours) of surgical management increases the risk of
morbidity and mortality.

Most patients presenting with hip fractures are elderly, and many of them have
significant coexisting diseases, such as coronary artery disease, arterial hypertension, diabetes,
chronic obstructive pulmonary disease, cerebral vascular disease, and/or dementia, all of which
may affect the choice of optimal anesthetic and monitoring strategies. It is important to evaluate
the cause of the fracture because although approximately 90% of hip fractures in both sexes
result from a simple “mechanical” fall, sometimes these “falls” can also be the result of syncope
due to comorbidities such as dysrhythmias, severe aortic stenosis, cardiovascular collapse,
stroke, and so forth. These patients are usually volume depleted because of low oral intake; in
addition, the intravascular volume can be compromised due to occult, but sometimes
significant, blood loss.
21

While patients await surgery, pharmacologic and mechanical (e.g., pneumatic
intermittent compression devices) thromboprophylaxis is strongly indicated for every patient
presenting with hip fracture because of the high venous thrombosis risk.

Venous thrombosis–associated pulmonary embolism (PE) is the third most common
cause of death in hip fracture patients, accounting for 18% of perioperative deaths.

Antimicrobial prophylaxis is usually used for orthopedic surgeries, especially when
foreign material is implanted. Prophylactic antibiotics have lowered the incidence of superficial
and deep wound infection after hip fracture surgery. First-generation cephalosporins have been
the agents most commonly used in prophylaxis (e.g., cefazolin 1–2 g).

No consensus exists regarding the best anesthetic technique for hip fracture. Because of
insufficient evidence from randomized trials comparing regional versus general anesthesia,
clinically important long-term outcomes cannot be confirmed. To obtain good analgesia and
anesthesia of the hip, it is necessary to block the T10 to S2 dermatomes (preferably extending
to T8), easily accomplished with spinal or epidural anesthesia.

Significant blood loss and potential hemodynamic instability should be anticipated,
especially with hip hemiarthroplasty and THA. Large-bore intravenous lines are recommended
in preparation for blood transfusion and rapid fluid resuscitation.

Patients with hip fracture are at an increased risk for perioperative pulmonary
thromboembolism, as well as fat, air, or methyl methacrylate monomer embolism, resulting in
right heart strain, acute ventilation– perfusion mismatch, and decreased oxygen saturation.
Hip arthroplasty
Anesthesia for hip arthroplasty THA is a common orthopedic procedure. Most of these
patients suffered from osteoarthritis, rheumatoid arthritis (RA), congenital dislocation, or
aseptic/avascular necrosis of the hip.

Moderate to large blood loss, necessitating blood transfusion, is common;
Thromboprophylaxis and antibiotic prophylaxis recommendations used in hip fracture surgery
apply to THA surgery as well.

Patients undergoing THA pose challenges to the anesthesiologist similar to those in
patients with hip fracture, such as hemodynamic instability, transfusion requirements, deep vein
thrombosis (DVT), or PE (including fat or cement embolism). THA is usually performed with
the patient in a lateral decubitus position. The patient’s head must be positioned on the side and
the cervical spine aligned with the rest of the body. It is important to protect all pressure points
22
in the lower extremities (e.g., inner legs, dependent greater trochanter) to prevent traction or
pressure injuries of nerves and skin surfaces.

Large-bore intravenous access for rapid fluid resuscitation and/or blood transfusion is
recommended.

Combined spinal–epidural anesthesia offers both the rapid onset and solid block of
spinal anesthesia and the extended postoperative analgesia via an epidural catheter. Regional
anesthetic techniques can be used in combination with general anesthesia. After placement of
the epidural catheter or peripheral nerve block, general anesthesia can be induced. This
combination of techniques may improve the comfort of the patient in long procedures.

Bone cement, polymethyl methacrylate, is frequently used to implant THA prostheses
and has been associated with adverse pulmonary and cardiovascular events. Typical clinical
signs and symptoms (also described as bone cement implantation syndrome) are similar to those
of pulmonary or fat embolism and include tachycardia, hypotension, hypoxemia, tachypnea,
dyspnea, bronchoconstriction, pulmonary hypertension (sometimes progressing to heart
failure), severe systemic hypotension, and cardiac arrest.
Anesthesia for shoulder surgery
Shoulder surgery is frequently performed in patients with osteoarthritis, or in healthy
individuals following shoulder trauma. Common shoulder surgeries include diagnostic and
therapeutic arthroscopy, acromioplasty, rotator cuff repair, and shoulder arthroplasty.
Routine preoperative evaluation should be performed. Preexisting neurologic deficits must be
recognized and documented.

Regional anesthesia alone is well suited for most patients undergoing short procedures,
as it provides good intraoperative anesthesia, muscle relaxation, and superior postoperative
analgesia. Regional anesthesia also allows for faster recovery time and discharge. To block the
brachial plexus, one can select among several regional techniques, but to achieve anesthesia of
the entire shoulder, it is necessary to perform an interscalene block or a cervical paravertebral
block.

General anesthesia is often considered when prolonged surgery is expected, as well as
in patients who refuse regional anesthesia or present other contraindications. Because airway
access during shoulder surgery is restricted, one should secure the airway when performing
general anesthesia.

Patient positioning (s. bellow) is an important consideration during shoulder surgery.
Almost invariably, surgery is performed with the patient in a modified sitting position, also
23
called the “beach chair position.” The head and neck are stabilized in a neutral position,
avoiding hyperextension of the neck and/or excessive rotation of the head, thus decreasing the
risk of injury to the brachial plexus that is already subject to surgical traction. The thorax is
stabilized with a padded brace or side supports; the legs are slightly flexed at the knees.
Figure 4. Beach chair position

Elastic compressive stockings and pneumatic compressive devices are used for DVT
prophylaxis. Some operating room beds, specially designed for shoulder surgery, have features
that improve patient comfort, safety, and surgical accessibility.

Shoulder surgery is associated with several rare complications. Many complications
occur more commonly in the sitting position, including cardiac arrest, stroke, blindness,
ophthalmoplegia, and air embolism.
Anesthesia for trauma
Trauma continues to be a leading cause of morbidity and mortality worldwide.
Concerted efforts to prevent secondary injuries and development of algorithmic approaches
have improved care and outcomes in patients suffering a wide array of traumatic injuries. The
role of the anesthesiologist in the care of trauma patients varies worldwide, from preanesthetic
assessment and intraoperative management alone in some regions of the world, to directing the
entire continuum from the prehospital resuscitation to the critical care unit in others.
The guiding principles in the care of trauma patients are:

To treat all potentially life-threatening conditions in order of severity,
24

To prevent delay of an indicated treatment, prioritizing it a above establishing a
definitive diagnosis, and

To prevent secondary injuries.
Advanced trauma life support
Advanced trauma life support (ATLS) was developed in the late 1970s to create an
algorithmic approach to the resuscitation of the trauma victims. It has become the standard of
care in the initial evaluation and treatment of the trauma patient, although it has never been
subjected to a randomized trial. The ATLS protocol structures the way the patient is assessed,
beginning with the ABCDE mnemonic (see next paragraph); it also gives clear roles and
responsibilities to each member of the surgical or emergency medicine team to maximize the
efficiency of the initial approach. Life-threatening injuries are treated before the diagnosis is
firmly and fully established, with the goal of minimizing any delay.
Multiple animal and human studies have shown that, for injuries associated with
massive and continuing blood loss, delaying operative treatment in order to further resuscitate
or diagnose leads to worsened outcomes. Unstable patients with insufficient vital organ
perfusion will suffer from any delay, and the more unstable the patient, the less necessary it is
for a definitive diagnosis to be established prior to instituting treatment. Thorough examination,
frequent reassessment, and continuous monitoring, however, are critical as these patients often
have significant findings missed on initial assessment and can suffer rapid clinical status
deterioration. On arrival to the emergency department, patients may already have an airway
device and/or an intravenous (IV) catheter in place and, depending on the perceived initial
severity of the injury, may also have a cervical collar and backboard in place. ATLS begins
with the primary survey, summarized in the mnemonic ABCDE – Airway, Breathing,
Circulation (and hemorrhage control), Disability, and Exposure/Environmental control.
Airway. The need for securing the airway via endotracheal intubation or tracheostomy
is determined by assessing both the current status of the patient and the treatment goals. For
example, patients may be intubated for obstruction or impending obstruction of the airway due
to swelling or hematoma, for mental status changes with failure to protect the airway or
respiratory insufficiency, as well as to allow hyperventilation for severe closed head injuries. If
an airway device is already in place, its correct position must be verified before proceeding
further.
Breathing. Establishing, monitoring, and maintaining adequate ventilation are based on
the respiratory rate, pulse oximetry, capnography, and physical examination of the thorax and
25
abdomen, including observation, auscultation, palpation, and percussion (ultrasound is also
being used increasingly). The goal of the examination is also to rule out tension pneumothorax,
open pneumothorax, flail chest, and massive hemothorax. Initial management includes
supplemental oxygen, ventilatory assistance with a bag-valve-mask device or endotracheal
intubation, placement of a chest tube if necessary, or the decision to perform a thoracotomy
emergently.
Circulation. The next goal is to assess for adequate perfusion of vital organs, including
identifying sources of potentially exsanguinating hemorrhage. On examination, the level of
consciousness, skin color, and pulse quality and rate are immediately assessed; for critically
injured patients, mean arterial pressure of 60 to 65 mm Hg is thought to be adequate, although
for patients with impaired autoregulation from poorly controlled hypertension or impaired
cerebral or coronary vasculature, this value may be insufficient. Rapid circulatory deterioration
during the primary survey can be caused by hemorrhage, massive hemothorax, tension
pneumothorax, or cardiac tamponade. Until another diagnosis is made, the working assumption
for hypotension must be exsanguinating hemorrhage, and resuscitation with lactated Ringer’s
solution should be immediately instituted. Exsanguinating hemorrhage may occur into five
locations – the outside environment, the peritoneum, the retroperitoneal space, the thorax, and
fractured long bones and their surrounding tissues. External bleeding is best controlled with
direct pressure; internal compartments may require emergent surgical control. Large-bore IV
access is established as soon as possible, and resuscitation is initiated with warmed lactated
Ringer’s solution.
Disability.
Disability, or the neurologic status of the patient, is assessed next, by
evaluating the patient’s best prehospital mental status, Glasgow Coma Scale (GCS) score (see
below), the ability to move the four extremities, and pupil size and reactivity. Mental status
changes may be due to insufficient cerebral oxygenation or perfusion, direct cerebral injury,
metabolic derangements, or alcohol or drug intoxication.
26
Figure 5. Glasgow Coma Scale
Exposure and environmental control. This step is the final one of the primary survey.
The patient is undressed and briefly examined from head to toe, and obvious exposures to
ingested and environmental toxins are identified. During the primary survey, monitoring is
instituted including electrocardiogram (ECG), blood pressure, and pulse oximetry. Depending
on the patient’s status and injuries, a urinary catheter and gastric tube may be placed, and initial
blood laboratory samples, often including an arterial blood gas, may be sent. Chest, cervical
spine, and pelvic radiographs along with a diagnostic peritoneal lavage or Focused Assessment
with Sonography in Trauma (FAST) examination, are done as soon as possible. The FAST
examination is meant to rapidly diagnose hemorrhage by using ultrasonography on four primary
views – right upper quadrant, subxiphoid, left upper quadrant, and suprapubic.
The secondary survey begins when the primary survey is complete and resuscitation
efforts are well established. This survey includes a head-to-toe evaluation, a complete history
and physical examination, and any further laboratory tests and imaging studies. A useful
mnemonic for the minimum history required is AMPLE – Allergies, Medications, Past illness/
history, Last meal, and the Events and Environment that caused the injury. The patient’s vital
signs and status are continually reassessed, as yet-undiagnosed injuries may cause rapid
deterioration. During this initial resuscitation, the surgical team seeks to identify immediate
27
threats to the patient’s life; these threats define the surgical priorities. Indications for emergent
surgery include airway compromise (cricothyroidotomy or emergency tracheostomy),
exsanguinating hemorrhage (laparotomy or thoracotomy), or intracranial epidural or subdural
hematoma with mass effect. Indications for urgent surgery include limb threatening injuries,
such as a vascular injury or compartment syndrome; sight-threatening globe injuries; or injuries
with a high risk of sepsis, such as a bowel perforation.
28
Obstetric Anesthesia
Physiologic changes during pregnancy
Pregnancy involves major anatomic and physiologic changes in all the maternal organ
systems. The anesthesiologist caring for the pregnant patient must appreciate these physiologic
changes, to provide safe analgesia and anesthesia to the mother and enable safe delivery of the
fetus.
Cardiovascular system
Oxygen demand and consumption increase during pregnancy because of the growing
feto-placental unit. To meet these demands, maternal heart rate increases, and peripheral
vascular resistance decreases. The cardiac output increases progressively throughout
pregnancy, beginning at 5 weeks and reaching a value 50% greater than that in nonpregnant
women by the end of the second trimester. The next significant increase in cardiac output is
during the active phase of labor. It reaches its peak increase immediately during the postpartum
period, when the uterus contracts and uterine vascular resistance increases.
Aortocaval compression. At approximately the 20th week of gestation, the gravid uterus
starts to compress the aorta and the inferior vena cava in the supine position. Approximately
15% of pregnant patients near term develop the “supine-hypotension syndrome” characterized
by a transient tachycardia followed by bradycardia, hypotension, changes in cerebration,
nausea, vomiting, sweating, and pallor. These symptoms are attributed to a lack of venous return
to the heart because of the uterus compressing the inferior vena cava. Turning the gravid patient
to the left (left uterine displacement) by 15◦ to 30◦ generally improves the symptoms.
Blood volume. Red-blood-cell volume increases by 30% and plasma volume by 50%,
resulting in an increase in the total blood volume of almost 50%. This increase causes a
dilutional or physiologic anemia. A greater increase in blood volume occurs with twin
pregnancies than with singleton pregnancies, which helps to prepare the parturient for the 500ml average blood loss during a singleton vaginal delivery or the approximately 1000-ml blood
loss during a vaginal delivery of twins or an uncomplicated cesarean delivery.
Blood pressure. Systolic blood pressure decreases by only 8% during pregnancy due to
the increased aortic size and compliance. Diastolic blood pressure decreases by 20% due to the
large decrease in systemic vascular resistance.
Respiratory system
Upper airway changes. The nasal and oropharyngeal mucosa progressively become
engorged early in the first trimester. Nasal endotracheal intubation and direct laryngoscopy
29
should be performed with fine movements and extreme caution because oral, nasal, or
pharyngeal bleeding may obscure the laryngoscopic view and make intubation difficult. The
Mallampati score increases during gestation and more so during labor. Because of edema, the
pharyngeal volume becomes smaller as labor progresses; this may be responsible for the
difficult visualization of the vocal cords under direct laryngoscopy. In addition, the false vocal
cords increase in size due to capillary engorgement. Failed endotracheal intubation in obstetric
patients is reported to be 1:200 to 1:750, about 10 times more common than the general
population. In general, it is prudent to use smaller size endotracheal tubes for general anesthesia
during pregnancy.
Changes in respiratory mechanics. The position of the diaphragm rises by as much as
4cm, which would generally cause a decrease in the vital capacity in pregnancy at term. Because
chest excursions are limited because of the expanded thoracic cage in the resting position, the
diaphragm becomes the main inspiratory muscle in term pregnant women. Due to the elevated
resting position of the diaphragm and larger diaphragmatic excursions during inspiration, both
tidal volume and minute ventilation increase. For these reasons, PaCO2 decreases and PaO2
increases. These changes and larger tidal volumes decrease physiologic dead space at term. In
addition, the diaphragm in the resting position pushes up the bases of the lungs, which causes
a reduction in expiratory reserve volume, residual volume, and functional residual capacity
(FRC; expiratory reserve volume + residual volume).
The anesthetic implications of these respiratory system changes are profound. FRC is
reduced to 80% of the nonpregnant value by term gestation, bringing it closer to closing
capacity. For this reason, and due to the increase in oxygen consumption, pregnant women
become hypoxemic more rapidly than do nonpregnant women during episodes of apnea. During
rapid-sequence induction of general anesthesia, the PaO2 of parturients decreases at more than
twice the rate when compared to nonpregnant women (139 mm Hg/min vs. 58 mm Hg/min). In
addition, during induction of anesthesia, the alveolar inhaled anesthetic concentration increases
more rapidly in pregnant women, owing to the decreased FRC and the increased minute
ventilation. The decrease in PaCO2 and plasma bicarbonate levels lower the plasma-buffering
capacity and render the pregnant patient more vulnerable to metabolic acidosis in case of
hemorrhage.
Nervous system
During pregnancy, minimum alveolar concentration (MAC) of volatile halogenated anesthetic
agents decreases by 30%. In postpartum women, MAC returns to that of the nonpregnant state
within 3 days of delivery. Three main factors account for this change during pregnancy:
30

Elevated level of progesterone, which acts on γ-aminobutyric acid (GABA) receptors
and has sedative effects;

Increased central serotonergic activity;

Activation of the endorphin system.
For the same reasons, the induction dose of thiopental in parturients is reduced by 35%
compared to that dose in nonpregnant women. Pregnancy also enhances sensitivity of peripheral
nerves to local anesthetics. Despite enhanced neural susceptibility during pregnancy, epidural
administration of large doses of local anesthetics (100–150 mg of bupivacaine) results in the
same degree of spread in term pregnant and nonpregnant women. With spinal anesthesia,
however, pregnant women exhibit a more rapid onset, longer duration of action, and higher
spread (25% reduction in the segmental dose requirements) than do nonpregnant women, who
receive the same dose of local anesthetic. In addition, women experience an elevation in their
threshold to experimental heat pain at term pregnancy, a phenomenon called pregnancy-induced
analgesia. Dependence on the sympathetic nervous system for maintenance of blood pressure
increases progressively throughout pregnancy. Spinal anesthesia in term pregnant women
frequently results in a marked decrease in blood pressure, whereas nonpregnant women
experience a lesser decrease.
Endocrine system
Pregnancy is associated with insulin resistance due to the hormone secreted by the
placenta – “human placental lactogen.” Maternal hyperglycemia may be associated with fetal
hyperglycemia, because maternal glucose (but not insulin) crosses the placenta. Near term,
oxytocin is secreted by the posterior pituitary (which may initiate labor), and after the birth of
the baby, prolactin is secreted by the anterior pituitary, which enhances the production of breast
milk.
Gastrointestinal system
Pregnancy is associated with an anatomic shift in the position of the stomach caused by
the gravid uterus. This shift changes the angle of the gastroesophageal junction, resulting in a
decrease of the lower esophageal sphincter tone, which results in heartburn in most pregnant
women by term. Many anesthesiologists administer the antacid oral sodium citrate, 30 ml of a
0.3 M solution, prior to anesthesia or labor analgesia, which neutralizes gastric acid and raises
its pH. This antacid may ameliorate the consequences of pulmonary aspiration of gastric
contents should it occur. In addition, some anesthesiologists administer 10 mg of intravenous
metoclopramide, which increases gastrointestinal motility and lower esophageal sphinctertone.
31
It is important to remember that drugs that increase the risk of aspiration, primarily by lowering
the esophageal sphincter tone, include glycopyrrolate, succinylcholine, and opioids.
Gastric emptying of liquid and solid materials is not altered at any time during
pregnancy, but is slowed markedly during labor.
Renal system
The kidneys enlarge and the ureters and renal pelvis and ureters dilate as a result of
increased progesterone levels. The dilation of ureters and the pressure on the bladder from the
enlarging uterus predispose pregnant women to urinary tract infections. Glomerular filtration
rate increases by 50%, resulting in a decrease of blood urea nitrogen (8–9 mg/dl) and serum
creatinine (0.5–0.6 mg/dl) concentrations. The resorptive capacity of the proximal tubules for
glucose decreases, which leads to mild glucosuria. In addition, increased secretion of
erythropoietin by the kidneys leads to an increase in red cell mass.
Coagulation and immune system
Pregnancy is a hypercoagulable state compensated by enhanced fibrinolysis. D-dimer,
a specific marker of fibrinolysis, which results from breakdown of cross-linked fibrin polymer
by plasmin, increases as pregnancy progresses. The majority of coagulation factor levels are
increased. The activated partial thromboplastintime (aPTT) is normal and the prothrombin-time
(PT) is shortened at term pregnancy.
Musculoskeletal system
As the uterus enlarges during pregnancy, lumbar lordosis is enhanced. This change is the
primary cause of low back pain that occurs in 50% of pregnant women. A widening of the pubic
symphysis and the pelvis results in a head-down tilt when a parturient is in the lateral position.
The head-down tilt might increase the rostral subarachnoid spread of hyperbaric local anesthetic
solutions when the injection is made with the patient in this position. Pregnancy does not alter
cerebrospinal fluid (CSF) pressure, so CSF flow from a spinal needle is unchanged (although
uterine contractions during labor do increase CSF pressure).
Analgesia for labor
Labor pain causes extreme discomfort in most parturients, especially nulliparas. Labor
pain has been assessed to be among the most severe types of pain. Therefore, to relieve the pain
of labor is one of the most important services that an anesthesiologist can provide to parturients.
Uterine pain, which occurs during the first stage of labor, is transmitted in the sensory
fibers accompanying sympathetic nerves that end in the dorsal horns of T10–L1. Vaginal and
32
perineal pain, which occurs during the second stage of labor, is transmitted by the afferent fibers
of the pudendal nerve (S2–S4). The transmitted signals are relayed to the sensory cortex after
processing in the spinal cord.
Labor analgesia is most commonly provided by regional anesthesia techniques, but there
are a number of alternatives available.
Inhalational analgesia. A mixture of 50% nitrous oxide (N2O) and 50% O2 which is
widely used in the United Kingdom has never become popular in the United States probably
due to higher epidural rates along with concerns of bone marrow toxicity from prolonged
exposure to N2O. This mode of analgesia requires an anesthetic delivery system in the labor
room and the presence of an anesthesiologist.
Parenteral opioids are generally safe and reasonably effective analgesics. They are often
used in the presence of contraindications to neuraxial techniques or, occasionally, as a means
to defer the timing of epidural placement. The commonly used agents include morphine,
hydromorphone, meperidine, fentanyl, and, recently, remifentanil. The main disadvantages
include sedation, maternal and neonatal dose-dependent respiratory depression, and delayed
gastric emptying.
Neuraxial analgesia. Maternal request is a sufficient medical indication for pain relief during
labor. More specific indications include:

Maternal conditions that complicate or contraindicate general anesthesia (e.g., morbid
obesity, difficult airway, malignant hyperthermia);

Obstetric disease, which places the patient at high risk for emergency delivery (e.g.,
severe pregnancy-induced hypertension);

Increased likelihood for operative delivery, such as mal presentation and multi-fetal
gestation; and

Maternal coexisting disease (e.g., severe cardiac or respiratory disease), where the
sympathoadrenal consequences of unmitigated labor pain may be detrimental.
Contraindications. Patient refusal, an uncooperative patient, uncorrected coagulopathy,
uncontrolled hemorrhage with severe hypovolemia, and epidural site infection qualify as
absolute contraindications. All other contraindications (e.g., elevated intracranial pressure,
local anesthetic allergy, untreated systemic infection) are relative, and the risks versus benefits
need to be carefully considered to make an individualized decision on whether to proceed with
a neuraxial technique.
33
Anesthesia for cesarean delivery
The incidence of cesarean delivery (CD), which is defined as the birth of a fetus through
incisions in the abdomen (laparotomy) and uterus (hysterotomy), has undergone progressive
increases and currently accounts for 15% to 30% of all deliveries in developed countries
worldwide.
Indications.
The common indications for CD include previous CD, cephalopelvic disproportion,
dystocia, fetal malpresentation, placenta previa or abruptio placentae, prematurity, nonreassuring fetal status, and patient request.
Preparation for anesthesia.
A review of the maternal medical, anesthetic, and obstetric history, allergies and
medications, an assessment of baseline hemodynamics, and an airway, heart, and lung
examination should be performed before providing anesthesia care. Acknowledgment of the
risks and benefits of each anesthetic option should be discussed as part of the informed consent.
Major hemorrhage can occur at any time in the peripartum period and remains a leading cause
of maternal mortality. Risk factors for peripartum hemorrhage should be identified and
preparations made. Basic monitors should be applied; invasive hemodynamic monitoring
should be considered in women with severe cardiac or renal disease, refractory hypertension,
pulmonary edema, or unexplained oliguria. An evaluation of the fetal heart rate by a qualified
individual may be useful before and after administration of anesthesia to reduce fetal and
neonatal complications.
NPO status and gastric optimization.
Nil per os (alternatively nihil/non/nulla per os) (npo or NPO) is a medical instruction
meaning to withhold oral food and fluids from a patient for various reasons. NPO status (should
be assessed, although gastric emptying of liquids during pregnancy occurs relatively quickly
and similarly in lean or obese, non-laboring, pregnant women.
The uncomplicated patient undergoing labor or elective CD can drink modest amounts
of clear liquids up to 2 hours prior to induction of anesthesia. Patients with additional risk
factors for aspiration (e.g., morbid obesity, diabetes, difficult airway) or patients at increased
risk for operative delivery (e.g., nonreassuring fetal heart rate pattern) may have further
restrictions of oral intake, determined on a case-by-case basis. Solid foods should be avoided
in laboring patients and in those undergoing elective surgery (e.g., scheduled CD or postpartum
tubal ligation). A fasting period of 6 to 8 hours for solids has been recommended. A
nonparticulate antacid (sodium citrate) is believed to decrease the damage to the respiratory
34
epithelium if aspiration occurs, and is customarily administered. Additionally, metoclopramide
may decrease nausea and vomiting and facilitate gastric emptying.
Selection of anesthetic technique.
In addition to the urgency and anticipated duration of the case, the most appropriate
anesthetic for a CD depends on maternal, fetal, and anesthetic factors. In cases of dire fetal
distress, a rapid evaluation of the patient and the situation should be performed as other
preparations for the provision of anesthesia are being made. Regardless of the degree of
urgency, the anesthesiologist should not compromise maternal safety by failing to obtain critical
information, including previous medical and anesthetic histories and allergies, and to quickly
assess the airway and basic hemodynamics. Overall, neuraxial (epidural, spinal, and combined
spinal– epidural [CSE]) techniques are the preferred methods for providing anesthesia for CD
in both elective and emergent procedures, and specific benefits and risks of each technique
dictate the eventual selection.
Certain conditions or time constraints, however, may contraindicate their use. Such
comorbidities include localized infection or generalized sepsis, severe uncorrected coagulation
disorders, severe hypovolemia, or cardiac pathologies where acute onset of hypotension may
be detrimental. Severe obstetric hemorrhage in the antepartum period, and severe preeclampsia
or hypertension, may also complicate the choice of anesthetic technique. Advantages and
disadvantages of neuraxial and general anesthetic techniques are summarized below.
Advantages/Disadvantages of general anesthesia
Advantages
Disadvantages

Rapid onset and reliability


Airway control

Less hypotension than neuraxial

Drug-induced fetal cardiorespiratory
anesthesia

Depression

Difficult airway management
Increased
risk
of
pulmonary
aspiration
Advantages/Disadvantages of neuraxial anesthesia
Advantages
Disadvantages

Minimal fetal exposure to drugs

Greater incidence of hypotension

Decreased incidence of maternal

Exposure to
pulmonary aspiration

anesthesia
An awake mother with greater
bonding with the neonate
35
risks of neuraxial
Pediatric Anesthesia
Anesthetic care of infants and children requires an understanding of the differences that
exist between the adult and pediatric population with respect to anatomy, physiology, and
pharmacology. It also requires attention to the unique psychology of the child and family, which
has an effect on the conduct of anesthesia.
Anatomy and physiology relevant to pediatric anesthesia
Respiratory
By approximately 24 weeks gestation, the lung has developed primitive gas exchange.
Over 26 to 35 weeks of gestation, respiratory epithelial cells begin to form terminal sacs (which
will later become mature alveoli), and the cells begin to differentiate and to produce surfactant.
Mature alveoli develop beginning at 35 weeks gestation. At birth, children have approximately
one sixth of their adult number of alveoli; this helps to explain the sensitivity of premature and
newborn lungs to mechanical ventilation and other insults.
The majority of alveoli are formed by the age of 2years, and the adult number is reached
by ∼8years. Relative to body size, infant tidal volumes approximate adult values (7–10 ml/kg).
Respiratory rate is higher to match the infant’s greater oxygen consumption (6 ml/kg/min vs. 3
ml/kg/min in adults) and metabolic rate.
The infant chest wall lacks rigidity, and the lung has poorly developed elastic fibers,
which leads to less negative intrapleural pressure and predisposes to early airway closure and
decreased functional residual capacity (FRC). Compensatory mechanisms are abolished by
anesthesia, causing FRC to fall markedly. High compliance of the infant chest wall means that
less positive airway pressure is required during mechanical ventilation. The infant’s increased
alveolar ventilation to FRC ratio and greater oxygen consumption results in faster oxygen
desaturation during ventilatory depression. Lung mechanics approach the adult state by
1yearofage. Rhythmic breathing begins at approximately 30 weeks gestation, and control of
breathing matures over the first month of life. Periodic breathing (5- to 10-second episodes of
apnea without hemoglobin [Hb] desaturation) is common in full-term and especially in
premature neonates, up to 12 months of age. Apnea of prematurity is defined as apnea ≥20
seconds or a shorter apnea episode (≥10 seconds) associated with bradycardia (heart rate 100)
or oxygen desaturation to 80% to 85%. Apnea is more common in premature infants and in
infants with upper respiratory tract infection (URI).
36
Cardiovascular
At birth, the fetal circulation changes to the neonatal as pulmonary vascular resistance
(PVR) decreases and systemic vascular resistance (SVR) increases. As a series circulation is
established through the lungs and body, there is normally functional closure of the foramen
ovale and the ductus arteriosus, which will close anatomically over the next few months. The
foramen ovale closes anatomically over months to years but remains patent in up to 25% of
adults. Hypoxemia, acidosis, or elevated pulmonary pressures can return a neonate’s circulation
to a fetal-like circulation with shunting. Changes in myocardial function, conduction, and
autonomic innervation also occur during the first days and months of life. The cardiac output
of neonates is especially dependent on heart rate because the less compliant myocardium limits
increases in stroke volume. Neonates have less cardiac reserve than older infants and children
because of higher baseline preload, afterload, and decreased contractility.
Hypoxemia, acidosis, and large anesthetic doses can profoundly depress the neonatal
myocardium. The development of the cardiac conduction system is less well studied, but it is
worth noting that the premature infant and neonate have shorter refractory periods. Arterial
baroreceptors and chemoreceptors are mature at birth, and autonomic–cardiovascular
interactions are well developed although they continue to mature over the first 6 months of life.
Hematologic
At birth, the Hb concentration averages 17 g/dl with approximately 80% HbF, which
has a higher oxygen affinity than does adult HbA. At birth, levels of 2, 3-diphosphoglycerate
(2,3-DPG) increase, compensating for this high oxygen affinity to allow oxygen unloading in
the tissues. The high PaO2 after birth reduces erythropoiesis, and Hb decreases to a nadir of
approximately 10 o11g/dl at 2 to 3months (7–10g/dl at age 6 weeks in premature infants). Over
the first 6 months of life, the switch to HbA occurs. Coupled with the higher 2,3-DPG levels in
infants, the switch to HbA leads to Hb oxygen affinity lower than that of adults (arterial PO2 at
which hemoglobin is 50% saturated with oxygen [P50]of∼30 mm Hg vs. 27 mm Hg in an
adult). These factors slowly approach adult levels over the first decade of life, and, because they
allow more tissue unloading of oxygen, they may be the reason that children normally have
lower Hb levels than adults (11.5–12 g/dl from age 3 months to 2 years, increasing to adult
levels by puberty). The coagulation system matures slowly over the first decade of life. Platelet
function improves over the first few days of life. Vitamin K–dependent coagulation factors at
birth are∼50% of adult values; a single prophylactic dose of vitamin K is generally given to
newborns. Preterm neonates are especially at risk for bleeding.
Neurologic
37
Neuronal growth and development continue throughout childhood. The sympathetic
nervous system matures more slowly than the parasympathetic, leading to exaggerated vagal
responses to stimuli, such as airway manipulation or hypoxia, in infants. Studies in humans
show, however, that pain and surgical stress in neonates lead to long-term effects on pain
sensitivity, behavior, and cognition. Current recommendations are to provide appropriate
anesthesia in neonates for necessary procedures with care to avoid excessively high doses. The
neonatal brain is less tolerant of extremes. In neonates, the blood–brain barrier is more easily
injured by hypoxemia.
Renal and hepatic
Nephrogenesisis complete in the term neonate. Renal blood flow and glomerular
filtration rate are low at birth and increase to adult levels by 2 years of age. Concentrating and
diluting capacity are also low at birth and mature during early childhood. Neonates, especially
preterm, are sensitive to fluctuations in fluid and solute loads and are prone to dehydration,
hyponatremia (which can lead to cerebral edema), hyperkalemia, hypocalcemia, and hypo- and
hyperglycemia.
Temperature regulation
Infants and young children are more easily cooled or warmed because of increased
surface area-to-volume ratio, a thinner subcutaneous fat layer, less keratinized skin, and high
minute ventilation. They are thus more susceptible to hypothermia under anesthesia.
Nonshivering thermogenesis is the major mechanism of heat production in neonates and is
gradually replaced by the more effective shivering thermogenesis by approximately 2 years of
age.
Pharmacology
Pharmacokinetic and pharmacodynamic differences between children and adults are
most pronounced and clinically significant in infants up to the age of 3 to 6 months. In this
population, the volume of distribution is larger, protein binding is reduced, and hepatic
metabolism and renal excretion are diminished, whereas the sensitivity to various drugs may be
enhanced.
Inhaled anesthetics. The minimum alveolar concentration (MAC) of most volatile
anesthetics is greater in infants than in older children and adults, but is lower in term neonates
and especially preterm neonates. In children, nitrous oxide has a blunted effect on the MAC of
sevoflurane and desflurane (60% inspired nitrous oxide reduces the MAC by only 25%).
Inhaled anesthetic drugs increase in concentration in the alveoli more rapidly in children than
in adults due to a higher minute ventilation-to-FRC ratio and higher blood flow to vessel-rich
38
organs. High concentrations of potent inhalational agents can cause bradycardia, hypotension,
or cardiac arrest in infants and young children, particularly when ventilation is controlled.
Halothane causes more pronounced bradycardia and is more of a myocardial depressant than is
sevoflurane; halothane also sensitizes the myocardium to catecholamines. The incidence of
coughing, breath holding, laryngospasm, and bronchospasm may be slightly lower with
sevoflurane. Isoflurane and desflurane are not used for induction due to airway irritation.
Emergence agitation, primarily in preschool-age children, may be more common after
administration of insoluble anesthetic gases such as sevoflurane and desflurane, although the
literature is not conclusive.
Muscle relaxants. The use of succinylcholine in pediatric anesthesia has declined
primarily because of life-threatening complications, such as malignant hyperthermia, and
hyperkalemic cardiac arrest in children with undiagnosed muscular dystrophy. Bradycardia,
junctional rhythm, and sinus arrest may be seen after succinylcholine in pediatric patients, but
pretreatment with atropine (0.02 mg/kg) reduces this complication. Fasciculations are often not
seen because of the small muscle mass. Despite its drawbacks, succinylcholine remains
valuable when immediate securing of the airway is necessary or for treatment of laryngospasm.
It may be used for rapid-sequence induction (RSI) in patients with a full stomach; RSI with
rocuronium (1.2 mg/kg intravenously [IV]) is also acceptable if succinylcholine is
contraindicated. Infants and young children require a larger dose of succinylcholine because of
a larger volume of distribution, and the duration of action is shorter partly because the drug is
more rapidly distributed away from the effector site by a greater cardiac output.
Opioids. Fentanyl is the most commonly used opioid in pediatric anesthesia. Because of
its lipid solubility, its brain concentration is not affected by the immaturity of the blood–brain
barrier, but neonates metabolize fentanyl more slowly than infants do. Significant histamine
release may follow an IV bolus of morphine. Infants and young children require higher bolus
and infusion doses of remifentanil than do adults, reflecting the larger volume of distribution
and increased elimination clearance, respectively. If remifentanil is chosen as the major
intraoperative opioid, adequate longer-acting opioid must be administered for postoperative
analgesia.
Pediatric anesthesia
Patient preparation
Preoperative preparation of pediatric patients must take into account their psychological
development as well as the family dynamics. The goals of preoperative preparation are to
reduce anxiety and stress before induction and minimize behavioral problems that may occur
39
days and weeks after surgery, such as temper tantrums, separation anxiety, enuresis, and sleep
and appetite disturbances. Parental anxiety reduction and satisfaction with the perioperative
experience are also important. Many preoperative preparation techniques have been evaluated
in the literature. Individualized preoperative interventions, such as seeing a child-life specialist
at age-appropriate times before surgery (approximately 1 week for children 6 years old, a
shorter time for ages 3–6, and probably no preparation for those3 years old), are most likely to
successfully diminish patient anxiety in the holding area. Listening to music may reduce anxiety
in the holding area and possibly during anesthesia induction, especially if live-interaction music
is provided by a music therapist. Limiting sensory stimulation (using dim lighting and soft
music and interacting with only one person, usually the anesthesiologist) may also alleviate
anxiety during induction.
Sedative premedication reduces preoperative anxiety and improves cooperation with
mask induction in the majority of children. Reducing parental anxiety can be helpful in calming
pediatric patients as anxious parents are less able to respond to their children and may increase
the child’s anxiety. Informational videotapes and acupuncture for parents have been shown to
allay anxiety about anesthesia preoperatively. Being invited to be present for their child’s
anesthesia induction also increases parental satisfaction with the perioperative experience but
has not been shown to reduce parental or patient anxiety (preoperatively or postoperatively) or
to change the incidence of postoperative behavioral disturbances in pediatric patients, although
it may be beneficial in a subset of child–parent pairs.
Induction
Inhalation induction of anesthesia is the most common choice for pediatric patients in
the United States because most children dread needles, and it is practical due to the rapid onset
in children. Maintaining spontaneous ventilation during induction allows the patient to selfregulate anesthetic depth and may protect against overdose. When an inhalational induction is
inappropriate (full stomach or intestinal obstruction, risk of malignant hyperthermia, acutely
elevated intracranial pressure) IV induction is performed. The pain of venipuncture can be
reduced by EMLA cream (eutectic mixture of local anesthetics) applied 45 minutes ahead of
time or lidocaine delivered via a needleless injection system immediately before IV placement.
Common methods to calm a child include allowing parental presence during induction,
applying a scent to the inside of the mask, and distracting the patient with songs, storytelling,
games, jokes, and so forth. Options for inhalation induction range from starting with a prefilled
breathing circuit of 70% nitrous oxide and 8% sevoflurane in oxygen (pungent smelling but
rapid-acting) to starting with just 70% nitrous oxide in oxygen for a few minutes, slowly
40
introducing sevoflurane, and increasing the concentration every few breaths (often better
tolerated initially but slower).
A larger tongue, smaller oral cavity, and smaller nasal passages predispose children to
obstruction after anesthesia is induced. Airway obstruction is managed by applying gentle chin
lift and jaw thrust, opening the mouth (ensuring that the tongue is not against the roof of the
mouth), obtaining a tight mask fit, and slightly closing the pop-off valve to generate 5 to 10 cm
of continuous positive airway pressure (CPAP). One hand should remain on the breathing bag
as much of the time as possible to confirm adequate, easy gas exchange. When the patient is
sufficiently anesthetized, an oral airway can be inserted if necessary. IM doses of
succinylcholine (4 mg/kg) and atropine (0.02mg/kg) should be readily available in case
laryngospasm or bradycardia develops prior to securing IV access. After the patient has passed
through the excitatory stage and is more deeply anesthetized, an IV cannula is inserted, the
concentration of the agent is decreased, and nitrous oxide is discontinued in preparation for
securing the airway.
Securing the airway. Intubation can be facilitated with muscle relaxant, deep
inhalational anesthesia, a bolus of propofol, or a short-acting opioid. For all but the shortest
cases, endotracheal intubation is usually chosen for infants less than 6 months of age because
of potential difficulty in maintaining upper airway patency, decreased FRC with faster oxygen
desaturation, and higher likelihood of inflating the stomach during mask ventilation. For some
procedures, in children 6 to 12 months or older, maintenance of anesthesia with a mask or LMA
is acceptable. Indications for endotracheal intubation are otherwise similar to those in adults.
There are major anatomic differences in the airway anatomy of infants and children that should
be taken into consideration for pediatric intubation. Infants have a larger occiput, obviating the
need for neck flexion to attain the “sniffing position”; a shoulder roll may allow better ability
to extend the head and open the mouth. The more cephalad larynx (C3–4 in infants vs. C4–5 in
adults) and the proximity of the tongue lead to a more acute angle between the plane of the
tongue and the plane of the larynx. The epiglottis is short and omega-shaped in the infant and
small child, and longer and U-shaped in the older child. It is stiffer, and angled into the lumen
of the airway, making it more difficult to displace during laryngoscopy. The appropriate ETT
size) is approximately the diameter of the child’s fifth finger or nostril.
Maintenance and emergence.
Anesthesia is maintained with the same agents used in adult patients. At the end of the
procedure, all anesthetics are discontinued, muscle relaxants are reversed, and the stomach is
emptied if indicated. Tracheal extubation may take place after the patient is fully awake or
41
during deep anesthesia, depending on the patient and care setting. Before awake tracheal
extubation, the child should be able to maintain regular nonparadoxical breathing, demonstrate
adequate muscular tone (sustained hip flexion, forceful cough, grimace using the eyebrows)
and spontaneously open the eyes or perform purposeful movements.
Some anesthesiologists favor deep extubation for patients with severe reactive airways
disease and for those in whom severe coughing could jeopardize surgical outcome (e.g.,
ophthalmic surgery). Adequate depth must be confirmed prior to extubation (e.g., no reaction
to movement of the ETT). After removal of the breathing tube, an oral airway is placed to
prevent upper airway obstruction and the mask is held for a few minutes to verify ventilation.
The patient is placed in the lateral decubitus position to keep the airway clear; it is important to
understand that these patients remain at risk for laryngospasm and aspiration until full
consciousness is regained. Compared with adults, children develop more coughing,
laryngospasm, and breath-holding during emergence.
42
Ambulatory anesthesia
Over the past three decades, anesthesia techniques and strategies for ambulatory surgery
have grown considerably. Choice of anesthetic technique and perioperative management play
an important role in how the center functions, as do procedures and personnel appropriate to
the center’s marketplace strategy, available equipment, and facility design. Rapid induction and
emergence as well as a thorough knowledge of anesthetic techniques to minimize common
postoperative complications, such as postoperative nausea and vomiting (PONV), require a
thorough understanding of the pharmacology and principles behind the choices made.
Patient selection
An ambulatory procedure can occur in either a free-standing center or as part of a
hospital-based service. Healthy patients or those with minor medical issues do not necessarily
need to go through an on-site preoperative evaluation. They can fill out a form, partake in a
phone screen, or fill out an online form that is reviewed by someone from the preoperative
clinic. For patients with more significant health issues that require active medical management,
an evaluation at a preoperative clinic is usually recommended. This evaluation should be done
several days in advance of the planned surgery as it often takes time to obtain records, review
tests, or perform more assessment. It is also practical to discuss the probable anesthetic choices
and initiate the informed consent process during this initial meeting so that patients have time
to consider any questions they may have for the anesthesia provider on the day of surgery.
Additionally, patients should be informed of the requirement that they will not be allowed to
drive themselves home after surgery but will need to arrange for a responsible adult to take
them home. Patients should understand that not having adequate arrangements before their
surgery will likely disqualify them for ambulatory status, resulting in their surgery being
rescheduled or plans made for an overnight stay.
Anesthetic options
Any anesthetic technique may be considered for the ambulatory patient as long as it is
appropriate before the procedure and adheres to the goals of a rapid recovery.
The newer volatile agents of desflurane and sevoflurane work well for the ambulatory
patient as the drug profiles show a fast onset and recovery with few side effects. Indeed,
recovery indices are achieved more quickly when compared with popular TIVA agents, such
as propofol.
Propofol provides the cornerstone for this technique, and opioids such as sufentanil or
remifentanil are often added. By itself, propofol can provide antiemetic effects, but its recovery
43
profile can be more prolonged when compared with profiles of the newer volatiles. Should an
opioid be added, the risk of PONV increases and may delay discharge.
One of the most common reasons for an unplanned hospital admission after ambulatory
surgery is intractable pain. The use of neuraxial anesthesia (i.e., spinal, epidural, or a combined
spinal epidural) in the ambulatory setting is somewhat controversial as it may delay discharge
as the block recedes, but that does not mean that its use is not an appropriate choice if the patient
and/or procedure are correctly selected. Regional blocks, as are used for surgery on the
peripheral limbs, can correlate with a timely discharge and good pain management well into the
postoperative period. Increasingly, continuous nerve blocks are being used to provide analgesia
beyond the first 24 hours. Ambulatory patients receiving these techniques are often alert,
comfortable, and discharged in a timely manner. A field block, which is the infiltration of local
anesthetics along the incision by the surgeon, can also be an effective way to manage pain.
Discharge criteria
Established algorithms and predetermined protocols are frequently used during the
recovery of patients in the postoperative unit. The nursing staff use these criteria to ensure that
the patients are stable and ready for discharge. It is also their responsibility to make sure that
the patients understand the discharge orders and have adequate transport and coverage for the
required period. As outlined below, there are two distinct phases of recovery from anesthesia
and surgery that apply to ambulatory patients.
Phase I. This phase immediately follows the removal of the patient from the operating
area. Initial monitoring is intensive with one-to-one or two-to-one nursing coverage, and the
patient is watched for maintenance of his or her own airway, stabilization of vital signs, and a
return to baseline alertness. Blood pressure and oxygenation saturation are monitored as is the
electrocardiogram (ECG). After the patient is considered to be stable and has met the defined
criteria, he or she is moved to the second phase of recovery.
Phase II. When the patient is considered hemodynamically stable and alert and does not
require the previous monitors, he or she advances to the second phase of recovery. Family
members can now be present and often are in the ambulatory setting. Ambulation is monitored,
voiding is encouraged, and, although liquids and solids may be offered, for ambulatory patients
it is often prudent to not encourage intake because of the issues of PONV and travel. Analgesia
should be achieved with nonopioid medications and ideally with over-the-counter analgesics.
It is from this phase that the patient is discharged home, and patients must be discharged into
the care of a responsible adult.
44