Download Basic Practice of Anesthesiology final

Basic Practice of
Anesthesiology
Hany El-Zahaby, MD
Preoperative Evaluation
1. History
-Current problem
-Other known problems
-Medical history (allergies, drug intolerance, present
therapy, tobacco and alcohol intake)
-Previous anesthetics, surgeries, deliveries
-Family history
-Review of organ systems
-Last oral intake
Preoperative Evaluation
2. Physical Examination
-Vital signs
-Airway (Thyromental distance, Malampati sign)
-Heart
-Lungs
-Extremities
-Neurological examination
Preoperative Evaluation
3. Routine Laboratory evaluation (healthy
asymptomatic)
Hematocrite: All menstruating women, age >60 y,
anticipated significant blood loss
S. glucose, creatinine: age >60 y
ECG: age >40 y
Chest radiograph: age >60 y
Pregnancy test: fertile women
American Society of Anesthesiology
Risk Classification
ASA Class
Description
1
Normal, healthy (0.06-0.08%)
2
Mild systemic disease (0.27-0.4%)
3
Severe systemic D, not incapacitating (1.8-4.3%)
4
Severe systemic D that is a constant threat to life
(7.8-23%)
5
Moribund, not expected to live 24h (9.4-51%)
6
Care for organ donation
The Anesthetic Plan
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Premedication
Type of anesthesia
General (airway, induction, maintenance, relaxant)
Regional (technique, agents)
Intraoperative management
Monitoring, positioning, fluids, MABL, special
techniques
Postoperative management
Pain control, ICU (ventilation, monitoring)
Preoperative Evaluation
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Informed consent
Gives the patient explanation of the options for
anesthesia and its realistic risks (general, regional,
local, topical, intravenous sedation)
Regardless of the technique chosen, consent must
always be taken for GA if other techniques prove
inadequate e.g. LA
The Anesthetist-Patient relationship
Is The Patient Scared?
Surgery (cancer, physical disfigurement, pain, death)
Anesthesia (loss of control, not waking up, waking up
during surgery, nausea, confusion, paralysis,
headache)
Preoperative Evaluation
1-Unhurried, organized interview
2-Calm reassurance and expression of interest in the
patient’s well being
3-Informing about:
NPO (no solids after m.n., clear fluids up to 2-3 h
unless GER)
Time of surgery
Premedication and other daily medications
Tasks to occur on the day of surgery
Postoperative recovery or ICU
Premedication
Benzodiazepines:
Diazepam (5-10 mg PO 1-2 hours before surgery),
never IM (pain, unpredictable)
Lorazepam (1-2 mg PO), intense prolonged amnesia
and sedation
Midazolam (1-3 mg IV or IM) at the receiving area, 0.5
mg/kg PO for pediatrics
Premedication
Narcotics: painful fractures, planned extensive awake
invasive monitoring devices
Morphine 5-10 mg IM 60-90 min before surgery
Anticholinergics (rare): Not Routine
Glycopyrrolate 0.2-0.4 mg IV to reduce oral
secretions (fibreoptic intubation)
Premedication
Prophylaxis for pulmonary aspiration:
 Pregnant, hiatal hernia, GER, difficult airway, ileus,
obesity, CNS depression
 H2 blockers (ranitidine, 150-300 mg PO before
bedtime and early morning)
 Nonparticulate antacids (sodium citrate 30-60 ml)
 Metoclopramide (10 mg IV 1h before surgery to
enhance gastric emptying)
Premedication
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Goals: Reduce anxiety, pain during vascular
cannulation and regional blocks, facilitate smooth
induction
Reduce the dose or withhold in elderly, debilitated,
upper airway obstruction or trauma, central sleep
apnea, neurologically obtunded, severe pulmonary
or obstructive valvular disease
Monitoring
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Standard monitoring for GA:
ECG, non-invasive BP, respiratory rate, oxygen
saturation, end-tidal carbon dioxide, inspired oxygen
concentration
Standard monitoring for regional anesthesia:
ECG, non-invasive BP, respiratory rate, oxygen
saturation
IV access
IV access: (14-16 G if rapid fluid or blood transfusion or
continuous drug infusions, better under local
anesthetic infiltration)
Components of GA
Loss of consciousness
Loss of reflexes (Movement to pain)
Analgesia
Amnesia
Relaxation
Induction of Anesthesia
The environment in OR should be warm with minimal
noise and all attention focused on the patient
Supine position with extremities in neutral position and
head on firm pillow raised to ‘’sniff’’ position
Induction of Anesthesia
Techniques:
1- IV induction preceded by oxygen via face mask until
loss of consciousness using thiopentone or propofol
2- Inhalational anesthetics either by low concentration
with incremental increase every 3-4 breaths or by a
single vital capacity breath technique using
sevoflurane or halothane
Intravenous Induction
Thiopentone
Propofol
3-5 mg/kg
2-2.5 mg/kg
---
IVI 6-10 mg/kg/h
---
Painful injection
Slower onset, slower recovery
Rapid induction, rapid clearheaded recovery
Hypotension ++
Hypotension +++
Depress respiration
Depress respiration
Contraindicated in porphyria
Less N,V
Airway Management
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Face-mask with:
Oro-pharyngeal airway
Naso-pharyngeal airway
LMA
ETT with a muscle relaxant (depolarizing as succinyl
choline or non-depolarizing as tracrium, cistracrium,
rocuronium)
Muscle Relaxants
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Depolarizing MR (succinylcholine) mimics the action
of acetylcholine i.e. causes depolarization of the
motor end plate and muscle membrane but for
longer time than Ach. Used for rapid-sequence
induction in patients with full stomach
Non-depolarizing MR produce reversible competition
with Ach at the motor end plate that produce
relaxation for longer duration
Succinylcholine
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Dose:1mg/kg produce relaxation in 1 min
Side effects:
Muscle pains, ganglionic stimulation, increase S. K+
level by 0.5-1 mEq/L, increase intraoccular pressure,
increased intragastric pressure, increase intracranial
pressure, prolonged block due to decrease or
inhibition or atypical plasma cholinesterase,
malignant hyperthermia
Non-Depolarizing MR
Atracurium: 0.5 mg/kg, Hofmann elimination
Cisatracurium (Nimbex): 0.15 mg/kg, Hofmann
elemination, less histamine release
Vecuronium: 0.1 mg/kg, hepatic metabolism
Rocuronium (Esmeron): 0.5 mg/kg, hepatic metabolism
(short duration)
TOF
Twitch Height After Succinyl Choline
Twitch Height After Non-Depolarizing
Clinical Assessment of the Blockade
Evoked response
Clinical correlate
95% -- single twitch
Good intubating condition
TOF response =1
Surgical relaxation without
inhalation anesth.
TOF response =3
TOF ratio > 0.75
Surgical relaxation with
inhalation anesth.
Possible extubation
TOF ratio = 1
Normal VC
Laryngoscopy and Intubation
Profound sympathetic responses (hypertension,
tachycardia) can be attenuated by hypnotics,
inhalation anesthetics, opioids, lidocaine, or beta
blockers
ETT Size
Premature: 2.5-3
Full term: 3
6 M -1 y:3.5
2 Y: 4.5
Over 2y: 4+(age/4)► 4 +(6/4) ►5.5
Length (at mouth cm): 10+(age/4) ► 10 +(6/4)
►11.5cm
Positioning
Movement of supine anesthetized patient into another
position may cause hypotension due to lack of intact
compensatory hemodynamic reflexes. Patient’s
head and limbs should be protected and padded.
Hyperextension or over-rotation of the neck and
limbs must be avoided.
Maintenance
Depth of anesthesia (surgical anesthesia)
+Muscle relaxation
Signs of inadequate depth of anesthesia:
Somatic responses (movement, coughing, changes of
respiratory pattern)
Autonomic responses (tachycardia, hypertension,
mydriasis, sweating, tearing)
Stages of General Anesthesia
Stage I
Amnesia
From induction to loss of
consciousness, pain perception is
maintained
Stage II
Delirium
Exaggerated responses to noxious
stimulus, dilated pupils, divergent
gaze, irregular breathing
Stage III
Surgical anesthesia
Central gaze, constricted pupils,
regular respiration, no somatic or
autonomic responses
Stage IV
Overdosage
Depressed respiration, dilated
fixed pupils, marked hypotension
Maintenance
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If spontaneous breathing is needed, minimal opioids
with nitrous oxide and inhalation anesthetic
If muscle relaxation is needed, nitrous oxide-opioidrelaxant with minimal inhalation anesthetic and
controlled ventilation (Balanced anesthesia)
TIVA: Continuous infusion of propofol-opioid +
muscle relaxant (nothing through inhalation)
Inhalation Anesthetics
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Blood-gas partition coefficient is inversely related to
the rate of induction
MAC: minimal alveolar concentration that prevent
movement in response to a skin incision in 50% of
patients
Inhalation Anesthetics
Blood/gas PC
MAC
Nitrous oxide
0.47
104
Halothane
2.3
0.74
Isoflurane
1.4
1.15
Sevoflurane
0.69
2.05
Desflurane
0.42
6.0
Ventilation
Spontaneous/assisted:
All inhalation anesthetics depress respiration and
moderately increase PaCO2
Can be affected by positioning, peritoneal
insufflation, open chest, surgical packing and opioids
Ventilation
Controlled Ventilation:
Initial setting with TV=10-15 ml/kg, RR=10-12/min,
notice the PIP, If>30, decrease TV and increase RR
A sudden drop in PIP → circuit leak
A sudden increase in PIP → kink, endo-bronchial
intubation, peritoneal insufflation
IV Fluids
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Maintenance: first 10kg→ 4ml/kg/h
Second 10 kg → 2ml/kg/h
After 20 kg → 1 ml/kg/h
Third-space loss: Tissue edema and evaporation,
varies from 5-10 ml/kg/h
Blood loss: Replaced in 1:3 with isotonic crystalloid,
or 1:1 with blood
IV Fluids (60 kg fit adult fasting for 6h)
1st h
2nd h
3rd h
Fasting
300
150
150
Maintenance
(100ml/h)
100
100
100
3rd space
5x60=300
5x60=300
5x60=300
Blood loss
--
--
--
Total
700
550
550
Estimated Allowable Blood Loss
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70 kg, Hct 35
EABL = EBV X (Hctstart-Hctallowable)
Hctstart
EABL = 4900 X (35 – 27)= 980ml
35
Estimating Volume of Blood to be
Transfused
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70 kg, with present Hct of 23
Volume=EBV X (Hctdesired - Hctpresent)
Hct transfused blood
Volume=4900 X (30-23) =490ml
70
Emergence from GA
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Goals: awake, responsive with full muscle strength
so he can maintain patent airway, cannot aspirate
and can be assessed neurologically
Technique: withdraw anesthetics near the end of
surgery, reverse muscle relaxation with neostigmine
(0.03-0.06 mg/kg) and atropine (0.2-0.4 mg/kg)
Emergence from GA
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Environment: Warm and calm
Positioning: Supine, tonsillectomy if full stomach
Mask ventilation: 100% oxygen, avoid stimulation of
the airway during stage II
Emergence from GA
Extubation:
1-Awake (desirable) with fully recovered protective
reflexes, follow simple verbal commands, breathe
spontaneously with good oxygenation and ventilation
(lidocaine 1mg/kg IV)
2- Deep extubation (during stage III) reduce risk of
laryngospasm and bronchospasm (in asthmatic)
avoid coughing ( eye surgery, hernia repair)
Emergence from GA
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Agitation: due to hypoxia, hypercarbia, airway
obstruction, full bladder, pain or sevoflurane and
desflurane anesthesia. Treated by treating the
cause, fentanyl 25μg IV or morphine 2mg IV
increments
Delayed awakening: Continue ventilatory support
and airway protection and reverse the etiology
Transport
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Stable patient can be transferred without oxygen or
monitor to PACU
Unstable patient should be transferred with oxygen,
monitors, tools for re-intubation to PACU or ICU
Anesthetist should give concise but thorough
summary to PACU or ICU staff
Acute postoperative pain management
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Optimal pain control is an integral component of
accelerated recovery
Although opioids are the most effective, acute
postoperative pain management is now based on
multimodal analgesia and opioid sparing
Acute postoperative pain management
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Psychological Preparation
Assessing Pain (0-10 Verbal Analogue Scale is now
the fifth vital sign to be recorded in the record)
Preemptive Analgesia (peripheral injury ►central
sensitization ►increase pain sensitivity
Acute postoperative pain management
Treatment Options:
1- NSADs:
Oral alone ► mild to moderate pain, begin preop.,
gastric irritation, coagulopathy, mask fever
Oral with opioids ►reduce opioid intake
Parentral ►keorolac 30 mg then 15-30 mg/6h,
expensive, can replace opioids
Paracetamol (Perfalgan), 1 gm/6h
Acute postoperative pain management
2- Opioids:
PO (chronic pain)
IM ( morphine 0.1mg/kg, pethidine 1mg/kg) painful,
unreliable
IV-bolus (morphine 2mg every 5 min, max 10-15mg)
IVI ( morphine 10- 20 μg/kg/h)
Monitor the respiratory rate
Acute postoperative pain management
3- PCA:
Provide analgesic doses immediately based on patient
needs using microcomputer-controlled infusion
pumps which avoids extreme swings in plasma
levels. Special order sheet is needed with detailed
pump setting (demand dose, start dose, delay time,
basal rate) and monitoring (pain level, sedation level,
verbal response)
Acute postoperative pain management
4- Epidural Analgesia
Abdominal , vascular & L.L. surgery
Contraindications: patient refusal, coagulopathy,
LMWH, bacteremia, local infection
0.1% Bupivacaine + 1-2 µg/ml Fentanyl ►5-10 ml/h
▼Bupivacaine if hypotension or motor block
▼Fentanyl if pruritis
Complications: Inadequate analgesia, PDPH, epidural
hematoma or abcess
Acute postoperative pain management
5- Neuraxial Morphine (preservative-free)
Epidural: 1-4 mg
Intrathecal: 0.1-0.4 mg (Respiratory depression)
6- Intraoperative Neural Blockade (esp. children)
Local Anesthetics
Ester/ Amide
Aromatic Ring
Amine
Local Anesthetics
Esters: procaine, chloroprocaine, tetracaine
(metabolised by plasma esterase, allergen)
Amides: lidocaine, bupivacaine, ropivacaine (liver
metabolism)
Local Anesthetics
Potency ►lipophilicity
Duration ► protein binding
Onset ► pKa (pH at which 50% are uncharged ions ►
diffuse to nerve membrane)
Local Anesthetics
Sequence of block:
Sympathetic ►pain & temp. ►proprioception ►touch
& pressure ►motor
Additives:
Epinephrine 1:200,000►prolong duration,
▼systemic toxicity, ▲intensity of block, ▼surgical
bleeding
Sodium bicarbonate: 1 meq:10ml lidocaine,
0.1meq:10 ml bupivacaine (avoid ppt)►fasten onset
LA: Systemic Toxicity
CNS Light-headedness, tinnitus, metallic taste, visual
disturbance, cicumoral numbness, muscle twitching,
seizures, loss of consciousness
Treatment: stop injection, oxygen, midazolam 1-2 mg,
thiopentone 50-200 mg
CVS ▼contract., ▼ conduct., VD ►collapse (esp.
Bupivacaine)
Treatment: oxygen, volume, vasopressors ►ACLS
Local Anesthetics: Spinal Anesthesia
Spinal Needle: 25G pencil point with 19G introducer
Position: Sitting or lateral
Level: L3-4, L4-5
Approach: Midline or paramedian
Drugs: Bupivacaine (Heavy) 0.5% 2-3 mls
Local Anesthetics: Spinal Anesthesia
Complications:
Hypotension►0.5-1L of LR before the block, ephedrine
5-10 mg boluses
Bloody tap► if does not clear rapidly, withdraw &
reinsert
Nausea & vomiting ►treat hypotension
Apnea (total spinal) ►support ventilation
PDPH: bed rest, IV fluids, analgesics, caffeine 30mg,
epidural blood patch
Local Anesthetics: Epidural Anesthesia
Epidural Needle: 17G Tuohy needle
Position: Sitting or lateral
Level: L3-4, L4-5
Approach: Midline or paramedian
Drugs: Bupivacaine 0.125- 0.25% 15-20 ml
Techniques: Loss of resistance
Hanging drop method
Test dose: 3 ml lidocaine 1% with epinephrine
1:200,000
Local Anesthetics: Epidural Anesthesia
Drugs: 1.5 ml/segment
Decrease dose 50% in old age
Decrease dose 30% in pregnancy
Epinephrine increase duration
Opioids (fentanyl 50-100 µ) improve the quality
Sodium bicarbonate speeds the onset
Local Anesthetics: Epidural Anesthesia
Complications:
Dural puncture 1% ► Convert to spinal
► Reinsert one space above
Inability to thread the epidural catheter (too lateral,
partial bevel insertion)
Insertion into a vein (withdraw)
Catheter break off (inform patient & leave it)
Local Anesthetics: Combined Spinal-Epidural
Anesthesia
Combine advantages and avoid disadvantages of both
techniques
Rapid onset, solid sacral block, less volume
Longer time, more control on level
Local Anesthetics: Caudal Epidural
Through the sacrococcygeal membrane
Can reach high level in children: 1 ml/kg Bupivacaine
0.2-0.25% with 1;200,000 Epinephrine reach T6-8
level
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