Download Spinal cord injury

Anesthesia in trauma
part 2
Future Developments in Resuscitation:
improvement in diagnosis and control of bleeding
high resolution CT SCAN & focused assessment by
sonography (FAST)in trauma SONOGRAPHY
Angiographic embolization
topical use during emergency surgery
Topical preparations of thrombin and fibrinogen
can facilitate immediate clot formation.
Fibrin glue
oozing
surfaces and organs that are difficult to suture or
cauterize, such as the lung or liver.
Continuous
 Future formulations of thrombin and fibrinogen will come layered on
collagen-based dressings for rapid control of large injuries to solid
visceral organs or the musculoskeletal system.(Iraq and Afghanistan)
 Newer hemostatic which have small hydrophilic particle
Zeolite and chitosan

recombinant (rFVlla):

Factor VII in physiologic doses works by triggering a thrombin
burst on the surface of platelets activated by exposed tissue
factor
Prospective studies :
 Elective open prostatectomy
 Rapid reverse coagulopathy in patient received warfarin
Retrospective studies :
GI bleeding
Bleeding after cardiovascular surgery
Liver transplantation and intracranial hemorrhage

other anticipated in development in the field of resuscitation
include:
 Prevention of organ damage or ischemia may be possible in future
through the administration of agents that regular cellular function
and humoral signaling.

Possibilities include manipulation of shock-related
pathophysiologic alterations such as complement and
granulocyte activation, endothelial activation, leukostasis, and
edema formation with resultant organ injury.

use of oxygen carriers ,antioxidants, nitric oxide scavengers,
and anti endotoxin compounds.
Trauma to the central nervous system:

CNS trauma accounts for almost half of all trauma deaths

TBI remains the leading cause of disability in children
and young adults.
)As with hemorrhagic shock( CNS trauma:
1-primary injury tissue disrupted by mechanical force.(neuronal cell body- axon
vasculture)
2-secondary response body reaction to injury
secondary brain injury accounts for much of the death and disability
after trauma. (aggravated by hypoxia, ischemia and inflammatory
responses)

The initial management of this patients can
significantly affect the outcome.

Continues
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Drugs such as free radical scavengers, antiinflammatory agents, and ion channel blockers in
animal .

Brain injury is classified as mild,
moderate, severe
Mild:
traumatic brain injury (GCS score of 13 to 15) who
maintain a stable GCS for 24 h are very unlikely to
deteriorate further but “postconcussive” effects is
common

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Moderate TBI:

(GCS score of 9 to 12) may be manifested as intracranial lesions
that require surgical evacuation, and early cranial CT is strongly
indicated.

Early intubation and mechanical ventilation
close observation because of catastrophic consequences of
respiratory depression or pulmonary aspiration

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Treatment of secondary brain injury is accomplished by early
correction and subsequent avoidance of hypoxia, prompt fluid
resuscitation, and management of associated injuries.

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The timing of indicated non cranial surgery in this patient is highly
controversial.
Recent review of surgical timing …..
Serial Monitoring of consciousness, motor and sensory
Invasive ICP monitoring is indicated if:
 Anesthesia longer than 2 hours

need for aggressive analgesia
 prophylaxis against delirium tremens

Deterioration of the GCS is an indication for urgent repeat cranial CT
to establish the need for craniotomy or invasive monitoring of ICP.

mortality from moderate TBI is low, almost all patients will suffer
significant long-term morbidity.

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Severe TBI :
is classified as a GCS score of 8 or less at the time
of admission and carries a significant risk for
mortality.
Early, rapid management focused on restoration of
systemic homeostasis and perfusion -directed care
of the injured brain will produce the best possible
outcome in the difficult population
Airway and Ventilatory Management :
 A single episode of hypoxemia (Pa02 <60 mm Hg) in a patient with
severe TBI is associated with a near doubling of mortality.
Prehospital intubation?
In past field intubation.
Two retrospective study shown worsened outcome.

The patient should be transported as rapidly as possible to a facility
capable of manger sever TBI or to the nearest facility capable of
intubating the patient and initiating systemic resuscitation
The main point is systemic oxygenation.
 The classic teaching of no or low-level positive end-expiratory
pressure (PEEP) to prevent elevated ICP is inappropriate because
it may fail to correct hypoxemia.

With adequate volume resuscitation, PEEP does not increase ICP
or lower cerebral perfusion pressure however, it may actually
decrease ICP because of improved cerebral oxygenation.
Hyperventilation therapy (paco2 of 25 mm Hg)is no longer
recommended as prophylactic treatment.

Current guidelines imply a range of 30-35 mmHg
hyperventilation to 30 mm Hg only for episodes of elevated ICP that can
not controlled with :
 Sedatives

CSF drainage
 neuromuscular blockade

osmotic agents
 barbiturate coma
Hyperventilation during the first 24 hour is of particular concern
because of critical reductions in perfusion during this timeframe.
these recommendations should be taken in context and modified In
unstable clinical circumstances such as expanding mass lesion or
signs of immediate herniation.
10
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Circulation:

The most challenging of all trauma patients are those with
sever Trauma and coexisting hemorrhagic shock.

A single episode of hypotension, defined as systolic BP less
than 90 mmHg, is associated with an increase in morbidity and
doubled mortality after severe TBI.

Hypotension together with hypoxia is associated with threefold
mortality.
Systolic BP less than 90 should be avoided with a goal MAP
greater than 70 mm hg
Maintain in euvolemic state
Hypertonic salt solution is optimal
HCT greater than 30%
CPP 50-70 mmhg
Vasoactive if needed
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Decompressive craniectomy
Used to Control Sever elevated ICP prevent
herniation after stroke
Improve mortality and morbidity
Decompressive laparatomy :
If “coexisting injuries” or “vigorous volume infusion”
increase intra abdominal compartment pressure more
than 20 mmHg
increase intra abdominal compartment pressure
reduce brain drainage.
 Multiple compartment syndrome:
In patient with sever TBI
Fluid therapy or acute lung injury(or both) increase intra
abdominal pressure and intra thoracic pressure and increase
ICP.
further administration of fluids or increasing Ventilatory support
to treat lung injury can exacerbate this problem.
Multiple compartment syndrome:
Need to open abdomen
Hypothermia 33 c (like hyperventilation)
Active rewarming in sever TBI??
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Spinal cord injury:

Occur in 1.5 to 3 %all major trauma.

Most spinal injuries are found in the lower cervical
spine, the upper lumbar region
SCI at mid thoracic levels Is less common.
SCI is commonly accompanied by radiographically
visible injury to the bony spine and concomitant
disruption of the muscles, ligaments, and soft
tissues that support it.
clinically significant injury to the cervical spinal cord
can occur in the absence of visible skeletal injury.
This phenomenon, known as SCIWORA (spinal cord
injury without radiographic abnormality), is more
common in children.
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Primary injury to the spinal cord sustained at the moment of
trauma may be exacerbated by a number of secondary factors

Sensory deficit or motor deficit or both.

Incomplete deficits may be worse on one side than the other
and may improve rapidly in the first minutes after injury.

Complete deficits- representing total disruption of the spinal
cord at one level are much more ominous, with generally little
improvement seen over time.

Cervical spine injuries causing quadriplegia are accompanied by
significant hypotension because of inappropriate vasodilatation
and loss of cardiac inotropy (neurogenic shock).

Functioning of lower cord levels will gradually return, with
restoration of normal vascular tone.
Treatment:
after ABC:

glucocorticoid steroid bolus, administered to any patient with a
complete or partial neurologic deficit.

A bolus dose of 30 mg/kg of methylprednisolone, followed by a
maintenance infusion of 5.4 mg/kg/hr, is given if the patient is less
than 8 hours removed from the time of injury.

This infusion is continued for 24 hours if started within 3 hours of
injury
for 48 hours if started 3 to 8 hours after injury.

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High dose glucocorticoid therapy demonstrated a small, but
statistically significant improvement in neurologic level after
SCI in two large multicenter trials.
Continued(Treatment)
Surgery for cervical lesions
 Supportive bracing or extension casting for lumbar or
thoracic fracture.
 Early intubation for patient with cervical spine fracture and
quadriplegia(Glidoscope & fiberoptic before patient
agitation)
 Ventilatory support absolutely required for deficit above C4
Early intubation is recommended (patient cooperation)


Patient with levels from C6-C7 may still need support

Pneumonia is common and recurrent complication
that necessitate tracheostomy to facilate pulmonary toilet

Intraoperative management of spinal cord injury :

Direct laryngoscopy with in-line stabilization is appropriate in
the emergency setting and in unconscious, combative, or
hypoxemic patients when the status of the spine is not known.

In the OR an awake, alert, and cooperative patient can be
intubated by a number of different methods known to produce
less displacement of the cervical spine and presumably less
risk of worsening an unstable SCI.

A common technique in current clinical practice is awake
Fiberoptic intubation.
nasal route is associated with an increased risk of sinusitis in
the ICU if the patient is not extubated.
Oral intubation if patient need mechanically ventilation.
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20
Orthopedic and soft tissue trauma:

Lower extremity fractures are the leading cause of all trauma
admissions.

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Being familiar with regional anesthesia
Fluid balance
length of procedures attention to body positioning
Normothermia
preservation of peripheral blood flow

early stabilization of long-bon, spine and stabular
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fractures.

In one study in femoral fracture …..(2% vs. 38%)

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Dislocations of the hip
are common after high-energy trauma and are
frequently accompanied by fracture of the acetabulum.

significant risk factor for avascular necrosis of the
femoral head.

Reduction typically requires a very deep level of
sedation and may be facilitated by chemical paralysis
of the patient.

Enough attention to risk of aspiration

Whereas the fracture itself can be safely managed on
a delayed basis ,the dislocation is a medical
emergency.

Unlike acetabular fractures, fracture of the “pelvis ring” requires
immediate recognition and management by the trauma team.
Hemorrhage, even exsanguination, is common after major pelvic ring
fracture and is a leading contributor to early death after motor vehicle
accidents.
 Bleeding occurs from multiply disrupted venous beds in the posterior
pelvic bowl.
 Surgical exploration is usually unrewarding because bleeding vessels
not accessed.
 Therapy consists of supportive volume resuscitation,
external fixation of the unstable pelvis, and angiography.


In the absence of an orthopedic specialist, temporary stabilization and
tamponade of some pelvic fractures can be accomplished with the use
of a specially made pelvic binder, the pelvic portion of military anti
shock trousers, or a bed sheet knotted tightly around the bony pelvis.
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Continued
Open fracture should be pulse- lavaged and debrided as
soon as possible even on bed side if patient is unstable
Advantages and disadvantages of GA and RA
Intraoperative TEE has shown that most patient
undergoing long-bone fracture manipulation
experience microembolism of fat and marrow.
some Lung dysfunction in almost always patients
has range from minor laboratory abnormalities to fullblown fat embolism.(FES) 3-10%.
Coexist lung disease and multiple long bone
fractures have additional risk for FES
Signs: hypoxia-mental status changes-petechia rashtachycardia
Failure to awaken after G.A
FES should be considered if:
Diagnosis in the operatory room is based on clinical
findings after ruling out other causes of hypoxia
 fat globules in Urine are not diagnostic but lung
infiltration on CXR confirm the presence of injury
Treatment:
 Early recognition
 Administration of oxygen
 Judgious of fluid management


A change in orthopedic procedure may be indicated
such as converting intra medullary nailing of the
femur to external fixation
Acute compartment syndrome:

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Increased pressure within a limited space
compromise the circulation and function of the
tissue within that space.
With orthopedic trauma the most common cause of
compartment syndrome is edema secondary to muscle
injury and associated hematoma formation.
Also occur as result of:
 Reperfusion injury
 Burns
 drug over dose
 prolonged limb compression

The most common fracture associated with C.S is tibia
shaft and forearm.
Risk factors for development of compartmant syndrome:

Orthopedic
Fracture and operative repair

Vascular
Reperfusion injury
Hemorrhage with hematoma formation
Ischemia from arterial and venous injury

Soft tissue:
Crush injury
Burns
Prolonged compressing
Iatrogenic:
Casts and circular dressing
Use of pneumatic anti shock garments
Intraosseous fluid replacement in infant and child
Extravasation from venous or arteies puncture site

Miscellaneous
Snakebite
30
Classic triad of compartment syndrome
“The 5p”
Pulslessness
 Pallor
 Paralysis
 Parasthesia
 Pain
Presences of these finding associated with established syndrome
and Fasciotomy has poor out come.

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the early presence of pain out of proportion to the injury can be
the first clinical indication of compartment syndrome .
 Treatment:
Fasciotomy is indicated when:
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compartment pressure approaches 20-30 mmhg
below diastolic pressure in any patient with
worsening clinical condition.
major soft tissue injury
history of 4-6 hours of total ischemia of an
extremity.
Prophylactic Fasciotomy may be indicated:
 in patient with warm ischemic time in excess of 4-6 hours
 ligation of the major veins in the popliteal region or distal part
of the thigh

crush injury.
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Crush syndrome:
Crush syndrome is the general manifestation of crush injury
caused by continuous prolonged pressure on one or more
extremities in patients who have been trapped in one position
for an extended period

myoglobinuria, which can lead to acute renal failure and
electrolyte disturbances.

The most critical treatment consists of crystalloid fluid
resuscitation a total body fluid deficit of 15 L may occur in sever
rhabdomyolysis.

Osmotic diuresis with mannitol and alkalization of urine with sodium
bicarbonate is controversial.
The preferred therapy for renal failure secondary to rhabdomyolysis
continuous renal replacement therapy.

Soft tissue trauma:

May be jeopardized by:
Avulsion at the time of injury
Ischemia from elevated compartment pressure
bacterial infection
 All dead or devitalized tissue must be :
debrided
wound irrigated
to reduce the load of bacteria contaminants.
When muscle or fascia involvement is significant at 1-3-day interval
debridment needed.
Vacuum dressing for large soft tissue wounds
When serial debridement establish viable tissue at all margins closure
can be made.
Closure :
 Split thickness graft

Free tissue transfer
Anesthesia:
Vacuum dressing can be made at the bed side with light sedation or
anesthesia
 Need for repeated surgery is an important consideration for the
anesthetic technique
Anesthesia for free tissue transfer is protracted
 Keeping the patient warm, euvolemic and comfortable and
maintain HCT in “rheological favorable” range of 25-30%
 Every effort should be made to facilate perfusion Of the graft
vessels.
 Use of epidural anesthesia and analgesia is controversial :
1-Vasodilatory effect
2-Steal phenomenon (limit flow in denervated tissue)
Amputation is occasionally necessary for Massive crush injury
(**strong emotional)
 Regional anesthesia limit development of phantom limb pain
 GA is better accept.
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Head and neck surgery:

Except zone II most repair of head and neck trauma will occur in sub
acute phase after complete resuscitation and diagnostic studies

Nasotracheal intubation for mandible and maxillary fracture

Switch oral to nasal?

Oral tube secured behind the second molar (to allow dental
occlusion)
Tracheostomy

surgery lead to significant soft tissue swelling after operation thus:
Needs several days of intubation and sedation until sufficient venous
drainage has occurred to allow safe extubation.

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Air leak when the endotracheal tube cuff is deflated
Chest Injuries-Rib Fractures
:
Are the most common injury from blunt chest trauma.
 The fracture itself generally requires no specific treatment and will heal
spontaneously over a period of several weeks.

Therapy is directed at minimizing pulmonary complications secondary to
these fractures:
 Pain

atelectasis
 hypoxemia
 Pneumonia
 elderly (older than 55 years).

Elderly patients have twice the mortality and thoracic morbidity.
Epidural anesthesia should be liberally used:

in patients with severe pain
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elderly
 patients with preexisting compromised pulmonary function.
 Some data support a decrease in morbidity and mortality in the elderly by
6% when epidural anesthesia is used.
 And decreased Hypoxia ,hypoventilation ,tracheal intubation and
mechanical ventilation decreased.
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Continued
Fracture of multiple neighboring ribs will result in flail chest syndrome,
characterized by paradoxical chest wall motion during spontaneous
ventilation.

ventilation and positive pressure for internal chest stabilization, and
endotracheal intubation should be reserved for those who meet the
usual criteria.

Patients who are not initially intubated should be closely observed in
the ICU for signs of worsening respiratory function.

Increasing numbers of reports have described the use of noninvasive
positive-pressure ventilation (NIPPV) for lung injury caused by trauma.

NIPPV is associated with
fewer cases of pneumonia
which may lead to fewer tracheostomies
therefore decreased ICU length of stay.
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Continued
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Concomitant pulmonary injury ,specially lung contusion is
commonly associated with flail chest.
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Pulmonary contusion lead to shunting, this syndrome may progress
rapidly in hours to days.

Clear CXR doesn't exclude possibility of the contusion

Treatment of hypoxemia
High degree of suspicion along with a continues search for missed
injuries.
Early and aggressive implementation of lung protective strategy
is crucial in the treatment of patients with significant pulmonary
contusion to minimize progression to ARDS or concomitant
ventilator associated lung injury .
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:
Chest Injuries-Cardiac Injury
Blunt cardiac injury is a rare and poorly understood phenomenon
Bruising or edema of the myocardium is functionally indistinguishable from
IHD

Blunt cardiac injury can be safely excluded if:
patient is hemodynamically stable
ECG does not demonstrate :
 conduction disturbances “

or tachyarrhythmias

new tachyarrhythmia
 conduction disturbance

unexplained hypotension
(other causes should be ruled out)

Right ventricular dysfunction resulting in hypotension may be overlooked
transthoracic echocardiography should be performed.
TEE is superior to TTE in obese patients
.
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Continues
Treatment:
blunt cardiac injury should be managed as ischemic cardiac injury
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Completion of resuscitation
Careful control of fluid volume
Administration of coronary vasodilator
Monitoring and symptomatic treatment of rhythm disturbance
Anticoagulant with aspirin and heparin?(approached on case
by case)
Cardiology consultation patient might benefit from coronary
angiography followed by angioplasty or stenting of stenotic
vessels

Continues
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Penetrating cardiac trauma and blunt trauma causing rupture of one
or more chambers (usually the atria)

Patients who do not die immediately of free exsanguination into the
thoracic cavity will have “pericardial tamponade” and can be
extremely unstable in the first minutes after admission.

Relief of tamponade

Cardiopulmonary bypass may be required.
Chest Injuries-Pulmonary
 Injuries to the lung parenchyma producing a Pneumothorax
 Can be managed by tube thoracostomy.

Bleeding from the low-pressure pulmonary circulation is
usually self-limited.

Thoracostomy :
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evidence of mediastinal injury
chest tube output exceeds 1500 mL in the first hours
tracheal or bronchial injury and massive air leak
hemodynamically unstable with evident thoracic pathology.
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Continued
Hemorrhage necessitating surgery may be from injured
intercostal or internal mammary arteries as well as from the lung
parenchyma.
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Although double-lumen endotracheal intubation is desirable
during urgent thoracotomy, such intubation should not be the
initial approach .

Rapid-sequence intubation with a large-caliber (at least 8.0-mm
internal diameter) conventional endotracheal tube will permit
diagnostic bronchoscopy and will protect the patient from
aspiration until passage of a gastric tube can reduce stomach
contents.
The change to a double lumen tube can then be done under
controlled conditions, that is, in the presence of adequate
oxygenation, anesthesia, and muscle relaxation.

continued
 Tolerance of single-lung ventilation is variable in the trauma
population
 chest trauma requiring pneumonectomy has historically resulted in
mortality approaching 100%.
Intraoperative deaths are the result of :
 uncontrollable hemorrhage
 acute right ventricular failure
 air embolism.

Blunt thoracic trauma requiring pneumonectomy is often
associated with abdominal and pelvic trauma.
Volume replacement must be judicious

Treat right ventricular failure and pulmonary hypertension

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Tracheobronchial injury
can result from either blunt force or penetrating trauma (more
promptly diagnosed).

Blunt trauma most commonly results in an injury to the
Tracheobronchial tree within 2.5 cm of the carina and may
initially be unrecognized.
The presence of :
 subcutaneous emphysema

pneumomediastinum
 Pneumopericardium
 Pneumoperitoneum

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Despite helical CT scan and bronchoscopy small injury never be
delineated.
Complete and incomplete tracheobronchial injury
Chest Injuries-Traumatic Aortic Injury:
 Traumatic aortic injury must be ruled out in high-energy injury
fall & motorcyclet accident
 Aortic injury occurs most commonly just distal to the left subclavian
artery
Diagnosis:
CXR (screen) followed by
Definitive Angiography
CT
TEE
 Surgical or endovascular repair is indicated for most patients with
traumatic aortic injury because of high risk for rupture in the hours
and days after injury.
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Various techniques have been described for it ,with the best result the
reports recently attributed to partial bypass techniques .
Reports of selective nonoperative management of high-risk patients
with traumatic aortic injury have appeared in the recent literature.
ß blockade to minimize the cardiac rate-pressure product.
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Endovascular repair.
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Trauma and Pregnancy :
Trauma to pregnant patients is associated with a high risk of:
 spontaneous abortion

preterm labor
 premature delivery

Early consultation with an obstetrician both for immediate management
and for long-term follow-up.

The best treatment of the developing fetus consists of rapid and
complete resuscitation of the mother.

The best guarantee of a healthy infant is a well mother.

Trauma patients in the first trimester of gestation may not realize that they
are pregnant; for this reason, human chorionic gonadotropin(HCG)
testing is part of the initial laboratory studies for any injured woman of
childbearing age.
Serious trauma occurring during the period of fetal organogenesis
1-hemorrhagic shock
2- radiation to the pelvis
3- medications
may induce birth defects or miscarriage

Indicated radiologic tests should not be deferred, but shielding of
the pelvis should be provided whenever possible.

Trauma occurring in the second or third trimester of pregnancy
necessitates early ultrasonographic examination to determine fetal
age, size, and viability.
continuous
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Preterm labor is very common
ß-agonists or magnesium
Delivery should be delayed as long as the fetus is not an
unacceptable metabolic stress on the mother
Delivery by cesarean section is indicated:

mother is in extremis

uterus itself is hemorrhaging

gravid uterus is impairing surgical control of abdominal or pelvic
hemorrhage.

in Placental abruption Emergency cesarean section is
indicated.
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Continuous
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The Kleihauer-Betke blood test can be used to
determine whether fetal blood has leaked into the
maternal circulation ( is a blood test used to measure the amount of fetal
hemoglobin transferred from a fetus to a mother's bloodstream.)

if the test is positive, anti-Rh0 immune globulin administration
is recommended for any Rh-negative mother carrying an Rhpositive fetus.

Supine hypotension syndrome

Elderly Trauma Patients:

markedly more serious outcome in elderly than in younger
victims.

Decreased cardiopulmonary reserves lead to a higher incidence
of :
postoperative mechanical ventilation
much greater risk for MOSF

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Greater care must be taken with intra operative positioning to avoid
pressure injuries.
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A higher hematocrit with tighter control of administered fluid .
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Post-traumatic myocardial dysfunction is a significant risk,
particularly if the heart rate is elevated secondary to:
blood loss
Pain
anxiety.
TEE or PAC to guide fluid therapy
prophylaxis against DVT
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Pain management :
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pain management challenges:
multiple sites of injury
protracted episodes of care
complicating psychological and emotional issues
and frequently, previous or ongoing substance abuse.
As with pain management practice in other disease
trauma patients are frequently under treated which
can be a significant source of dissatisfaction.
Continued
Individual patients will have widely variant requirements for pain
medications, so induction of analgesia must be carefully
titrated

Early or even preemptive treatment of pain has been shown
to greatly reduce analgesic requirements over time.

Rapidly acting intravenous agents administered in small
doses under pain relief is achieved is recommended.

This allows the practitioner to determine the patients basal
requirement before starting long acting medications or patient
control analgesia.
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Continued
Hypotension developing in response to the appropriate
administration of analgesics should lead to an investigation for
occult hemorrhage or hypovolemia.

The need for analgesic medication and the duration of analgesic
therapy will be minimized analgesic if a comprehensive emotional
support system is available to the patient.

The availability of counselors religious, financial, or legal who
can help patient or family.

The anesthesiologist should refer the patient to counseling services
as needed and should be alert to the potential for post-traumatic
stress disorder in any traumatized patient.
Adventages of pain control:
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60
Early mobilization:
Decrease pulmonary complication
venous thrombosis
decubitus ulcer

Neuropathic pain:
Arises where there is direct injury to a major sensory nerve and is
common after :
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spinal cord trauma
traumatic amputation
major crush injury
is characterized by:
Burning

intermittent electrical shocks
 Dysesthesia
in the affected dermatome distribution.

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it responds poorly to the analgesics used for somatic pain.

This diagnosis should be considered whenever pain control is poor or
the patient has arising requirement for medications unexplained by
the anatomic injuries.


First-line therapy for neuropathic pain
Gabapentin ( an antiepileptic drug with very strong specificity
for this problem)

Gabapentin therapy is typically initiated at a dose of 200 mg
three times daily with daily titration upward to a maximum of 2
to 3 g/day.

If neuropathic pain persists, selective regional anesthesia or
analgesia may be indicated in an effort to "break the cycle" of
spinal cord receptor recruitment.