Anesthetic considerations for Pediatric Chest Trauma

Anesthetic considerations for Pediatric Chest Trauma


ANESTHETIC CONSIDERATIONS FOR PEDIATRIC CHEST TRAUMA
Hala samir El Mohamady, MD
Dept. of Anesthesiology, Intensive Dare, and Pain management, Faculty of Medicine, Ain Shams University
Abstract
Thoracic trauma is a major cause of morbidity and mortality in children.
The anesthesiologist needs to be prepared to manage such pediatric patient who may have severe multisystem injuries
with underlying respiratory derangements, ongoing blood loss, and cardiac dysfunction.
Many principles used in adult patients can be applied in pediatric patients; however the unique anatomy and physiology
of children must always be remembered.
For pediatric patients timely resuscitation and optimal care to avoid secondary injury is a considerable challenge for any
anesthesiologists.
Prevention of childhood injury remains the cornerstone of reducing the number of children who present for posttraumatic
surgical intervention. Beyond prevention, the next best step is the accurate diagnosis and treatment of
traumatic injury. Anesthesiologists contribute to this step by providing timely resuscitation and optimal care to avoid
secondary injury.
Introduction
Blunt and penetrating chest trauma is a major cause of
morbidity and mortality in children. Most pediatric
cases are caused by blunt trauma while penetrating
trauma is more common in adolescent boys.
Fortunately, children have an extremely compliant
body that may absorb considerable force and energy
with minimal external signs of injury. Conversely,
external signs of injury or rib fractures are an indicator
of significant potential soft tissue damage (1, 2). Young
children are less mineralized and more pliable, and
they tend to bend, but not break. Significant
intrathoracic injuries often occur without rib fractures;
however, the risk of mortality increases with the
number of ribs fractured (3) .Also Mortality from chest
trauma increases with the presence of abdominal (20%)
or head injury (35%) (4).
Evaluation and Management
Airway
Just as in the adult, the initial assessment should
concentrate on the A, B, C's (airway, breathing, and
circulation). It is important to remember the differences
in the pediatric airway, which include a large occiput,
large tongue, anterior larynx;
floppy, stiff Q-shaped epiglottis, and short trachea.
Unlike the adult, the cricoid is the narrowest part of
airway and so intubated patients should have a leak
around the endotracheal tube (ETT). The large tongue
and floppy epiglottis can contribute to airway
obstruction in an unconscious child. Appropriate jaw
thrust can lift the tongue off the back of the pharynx
and minimize airway compromise. A shoulder roll may
be required to place the head in an optimal position for
intubation; however, the presence of possible cervical
spine injury may preclude its use (5).
Any child that presents with respiratory compromise
should immediately receive supplemental oxygen with
continuous oxygen saturation monitoring. A changing
or altered mental status may indicate a closed head
injury, or severe hypovolemia.
Intubation should be considered in any child who is
combative, unconscious, or obtunded, to maintain
cerebral oxygenation and perfusion and to help
decrease the risk of secondary brain injury.
Infants and neonates are obligate nose breathers, so
occluded nasal passages from maxillofacial, neck, or
head trauma may prevent them from breathing
effectively.
Oral intubation is preferable to nasal intubation
because it is easier, faster, and less likely to result in
bleeding. Up to 50% of all pediatric trauma patients
will have brain trauma, including possible basilar skull
fracture. The cervical spine must always be protected
and the neck collar should remain in place until the
physician is absolutely sure there is no neck injury. Inline
stabilization (not traction) should be applied while
the patient is being intubated to prevent further spinal
cord injury (6). All pediatric trauma patients should be
considered at risk for aspiration particularly one with
thoracic injuries, rapid sequence induction with cricoid
pressure should be used until the airway is secured.
Cricoid pressure may destabilize an unstable neck in a
small child or infant and should be applied carefully by
experienced personnel. The ideal ETT should have a
leak at pressure <20-25 cm H20 if patient has normal
lungs. In patients with severe pulmonary trauma, a
larger ETT or cuffed ETT will facilitate ventilation. In
these patients, a leak at pressure 25-30 cm H20 will
maximize ventilation without increasing the risk of
developing subglottic stenosis (5).
Breathing
The trachea can be easily compressed; nasal flaring,
use of accessory muscles, and a "rocking boat" pattern
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may indicate tracheal obstruction. The obstruction may
need to be relieved by intubation. Very rarely,
percutaneous cricothyrotomy or tracheotomy may be
required. Infants and small children are much more
dependent on diaphragmatic movement for respiration.
Anything that decreases the efficacy of diaphragmatic
motion will interfere with adequate breathing in these
patients (e.g. abdominal trauma and incorrectly
performed bag and mask ventilation. A nasogastric
tube should be expeditiously placed to deflate the
stomach.
The mediastinum in young children is very mobile and,
in the presence of a pneumothorax or hemothorax, can
easily allow compression of the heart and great vessels,
leading to a tension pneumothorax. Treatment for
pneumothorax is decompression with either a needle
placed at the mid-clavicular line of the second
intercostal space or placement of a chest tube (7).
Circulation
A change in blood pressure (BP) occurs only after there
is a 30% to 40% decrease in estimated blood volume
(EBV); therefore, BP is not a very good measure of
circulatory status. On the other hand, hypotension
indicates significant blood loss.
A systolic blood pressure of 90 mmHg or less in a child
is considered a predictive indicator of major trauma (8).
Early signs of hypovolemia include persistent
tachycardia, delayed capillary refill, and diminished
pulse pressure. Central pulses should be strong. An
absent or decreased radial pulse indicates
approximately a 10% reduction in intravascular
volume. Weakened axillary or femoral pulses signify a
loss of about 15%. It is important to calculate estimated
blood volume as soon as possible (Table 1).
Balanced salt solution (lactated Ringers or normal
saline 20 mL/kg) is most commonly used for volume
resuscitation. If there is minimal or no response to this
bolus, then an additional 2 boluses can be given while
preparations are being made to transfuse blood. The
initial dose of blood is 10 mL/kg of packed red blood
cells.
Table 1: Estimated Blood Volume in Children (2)
neonate -90 mL/kg
infant - 80 mL/kg
child -70 mL/kg
Estimated wt = (age x 2) +10
Intravenous access can often be difficult to establish in
a small child. It may be necessary to cut down on the
saphenous vein or place an intraosseous line. Femoral
lines are usually the easiest and least risky central lines
to place in these situations. The presence of a cervical
collar or possible neck injury may prevent access to the
internal jugular or subclavian vein (8).
Central Nervous System
The presence of head trauma in a patient with chest
trauma is a significant predictor of mortality. The
Glasgow Coma Scale (GCS) is not reliable in children
under 1 year of age because spontaneous motor
movements after CHI are common, which can
artificially elevate the, GCS also children may not be
able to cooperate and follow commands because of
their age or level of anxiety (9).
Specific Injuries
Pulmonary Contusion
pulmonary contusion (or lung contusion) is the most
frequent injury caused by chest trauma. It is usually
caused by blunt trauma but also explosions or a shock
wave associated with penetrating trauma can cause
lung contusion (10, 11).
Pathophysiology
Pulmonary contusion results in bleeding and fluid
leakage into lung tissue, which can become stiffened
and lose its normal elasticity. The water content of the
lung increases over the first 72 hours after injury,
potentially leading to frank pulmonary edema in more
serious cases. As a result of these and other
pathological processes, pulmonary contusion
progresses over time and can cause hypoxia. The larger
the area of the injury, the more severe respiratory
compromise will be (12).
Ventilation/perfusion mismatch
Normally, the ratio of ventilation to perfusion is about
one-to-one; the volume of air entering the alveoli
(ventilation) is about equal to that of blood in the
capillaries around them (perfusion). This ratio is
reduced in pulmonary contusion; fluid-filled alveoli
cannot fill with air, oxygen does not fully saturate the
hemoglobin, and the blood leaves the lung without
being fully oxygenated. Insufficient inflation of the
lungs, which can result from inadequate mechanical
ventilation or an associated injury such as flail chest,
can also contribute to the ventilation/perfusion
mismatch. So the mismatch between ventilation and
perfusion grows, blood oxygen saturation is reduced
(13). Pulmonary hypoxic vasoconstriction, in which
blood vessels near the hypoxic alveoli constrict in
response to the lowered oxygen levels, can occur in
pulmonary contusion. The vascular resistance increases
in the contused part of the lung, leading to a decrease
in the amount of blood that flows into it (14), directing
blood to better-ventilated areas. Although reducing
blood flow to the unventilated alveoli is a way to
compensate for the fact that blood passing unventilated
alveoli is not oxygenated, the oxygenation of the blood
remains lower than normal. If it is severe enough, the
hypoxemia resulting from fluid in the alveoli cannot be
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corrected just by giving supplemental oxygen; this
problem is the cause of a large portion of the fatalities
that result from trauma (13) .
Management
No treatment is known to speed the healing of a
pulmonary contusion; the main care is supportive (14)
Attempts are made to discover injuries accompanying
the contusion to prevent additional injury, and to
provide supportive care while waiting for the contusion
to heal (19). Monitoring, including keeping track of fluid
balance, respiratory function, and oxygen saturation
using pulse oximetry is also required as the patient's
condition may progressively worsen. Monitoring for
complications such as pneumonia and acute respiratory
distress syndrome is of critical importance (15).
Treatment aims to prevent respiratory failure and to
ensure adequate blood oxygenation (16) . The child with
mild pulmonary contusions may not need more than
good pain control, supplemental oxygen, observation,
pulmonary toilet, and early mobilization (17). More
severe injuries will be progressively more difficult to
treat. The presence of intrapulmonary shunts and
decreased compliance may necessitate mechanical
ventilation and positive end-expiratory pressure
(PEEP) (17). Overhydration can exacerbate edema and
worsen oxygenation; hypovolemia can produce
hypoperfusion and increase the risk of multiorgan
failure. So maintenance of euvolemia is important.
Inotropic agents may be required in patients with
severe pulmonary contusion. The administration of
steroids in these patients can increase the risk of
pneumonia(18).When the contusion does not respond to
other treatments, extracorporeal membranous
oxygenation may be used, pumping blood from the
body into a machine that oxygenates it and removes
carbon dioxide prior to pumping it back in(19).
Rib Fractures
Rib fractures are present in approximately one third of
children who present with thoracic trauma. The
presence of rib fracture should alert the physician to the
possibility of other significant thoracic and
extrathoracic injuries. The severity of other injuries
increased with the number of ribs fractured, as did the
mortality. All children with at least 4 fractured ribs had
other injuries. Treatment consists of maximizing
oxygenation and ventilation as necessary, treatment of
associated injuries, and ensuring good analgesia.
Intravenous opioids, patient-controlled analgesia, or
epidural analgesia can all be effective. The technique
selected will depend on the patient's underlying
condition and age (20).
Airway Obstruction
Maxillofacial trauma or laryngotracheal injury can lead
to airway obstruction. Patients may present with
hoarseness, stridor, subcutaneous emphysema, or
intercostals or sternal retractions. Injuries to the great
vessels in the neck can result in an expanding
hematoma that may compromise the airway.
Management includes jaw thrust, clearing of debris
from the oropharynx, intubation as necessary and
rarely, a cricothyrotomy or tracheostomy (21, 17) .
Pneumothorax
Pneumothorax is the most common immediately or
potentially life-threatening thoracic injury in a child.
Children higher rate of oxygen consumption and
smaller functional residual capacity makes them more
susceptible to hypoxia. The highly mobile and
compliant mediastinum in children allows the
mediastinal contents to shift to the contralateral side,
which can compromise blood return and cardiac output
so decompression of the tension pneumothorax is life
saving.
Definitive treatment is with a chest tube. The
pneumothorax may be stable until positive pressure
ventilation is instituted. Any patient who becomes
hypoxic and/or hypotensive after institution of positive
pressure ventilation, should be considered to have a
tension pneumothorax until proven otherwise.
Persistent air leak after the placement of appropriate
chest tubes may indicate a tracheobronchial tree injury.
One-lung ventilation is often necessary and can be
tricky in a small, unstable patient when operative repair
is needed (7).
Hemothorax
Pulmonary hematoma or massive hemorrhage is rare
unless accompanied by laceration to a vessel as their
lung has high levels of tissue thromboplastin and low
circulatory pressure, thereby limiting bleeding from
parenchymal injuries.
Unexplained hypotension, or chest tube output that is
initially greater than 15 mL/kg or continued bleeding
of 2-3 mL/kg/hr consider hemothorax and chest
exploration may be needed(22).
Traumatic Aortic Rupture
Injury to the great vessels has been shown to increase
mortality to more than 50%. Diagnosis of aortic rupture
is made by history and aortography. Tracheal deviation
to the right, and unequal blood pressures in the arms
may be signs of aortic rupture. On chest radiograph, a
widened mediastinum, abnormal contour of the aortic
knob, nasogastric tube deviation to the right,
depression of the left main bronchus, left hemothorax
may indicate aortic rupture necessitating urgent
exploration (23).
Flail Chest
Immediate treatment consists of applying pressure to
the flail segment to reduce chest wall instability and
minimize circulatory and ventilatory impairment. Most
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children will require internal stabilization with
endotracheal intubation and mechanical ventilation.
Fluid restriction after initial resuscitation and insurance
of adequate gas exchange will minimize complications
(24) .
Myocardial Contusion and Other Cardiac Injuries
Cardiac trauma in children is relatively uncommon.
The severity of injury can vary from cardiac
concussion, which has no histologic manifestations and
is transient, to myocardial muscle or valve rupture.
These children will usually be unstable and mortality is
high (24, 25). The most common ECG abnormalities
included persistent sinus tachycardia, ST-T wave
abnormalities, conduction abnormalities, and
premature ventricular contractions (26).
Cardiac Tamponade
Cardiac tamponade is much more common with
penetrating injuries. The classic finding of Beck's triad
(muffled heart tones, increased central venous pressure,
decreased blood pressure) may be difficult to
appreciate in the small, hypovolemic child. Most
penetrating cardiac injuries will present with
hemopericardium and tamponade. Treatment is with
pericardiocentesis (7).
Anesthetic Management
Approximately 20% will require operative intervention
because of abdominal injuries, which may be
associated with massive blood loss (27).
A patient that is not already intubated, should undergo
a rapid sequence induction with cricoid pressure.
Children can desaturate much more quickly than
adults, so a modified rapid sequence induction is often
preferable. Cricoid pressure will need to be applied
carefully in the child with an unstable neck. Most of
these patients will be volume depleted and resuscitation
will be ongoing.
Induction agents that do not decrease blood pressure or
heart rate should be chosen. Ketamine or etomidate are
good choices, although small doses of thiopental or
propofol can be used in more stable patients,
particularly if they have an associated head injury (28) .
Standard monitors should be applied. Pulse oximetry
may be difficult to obtain in a small, cold
vasoconstricted patient; therefore, it is prudent to use
multiple probes in several locations. Respiratory
variation in the waveform of the pulse oximeter may
indicate hypovolemia. Bradycardia usually indicates
hypoxia, ischemia, acidosis, or hypothermia and should
be rapidly corrected. Persistent tachycardia can signify
hypovolemia and acute blood loss. End tidal carbon
dioxide (ETCO2) is less accurate in smaller patients
because they have a relatively higher dead space to
tidal volume ratio than adults. Hypovolemic patients
will have even more dead space, and patients with
thoracic injuries may have increased shunting as well.
A low ETC02 may reflect low cardiac output, because
there is less blood flow to lungs (29).
At least 2 intravenous (IV) catheters should be placed,
preferably one above and one below the diaphragm,
and blood obtained for crossmatch.
If there is difficulty obtaining peripheral IV access, a
central venous or intraosseous catheter can be placed.
Femoral venous catheters are often the easiest to get
access to, have easy landmarks and the lowest
complication rate. A subclavian catheter should always
be placed on the side of the suspected injury, especially
if there is already a chest tube on that side. Maintaining
body temperature with radiant warming lights, warm
fluids, or a forced air warmer is critical. Hypothermia
and vasoconstriction can increase coagulopathy and
bleeding, adversely affecting perfusion. Small children
have a large body surface area to mass, and
temperature control can be exceptionally difficult.
Actively warm patients if they arrive cold. The only
exception is in patients with severe closed head injury,
in whom mild hypothermia is preferred. Rewarming
may lead to increased acidosis (rewarming shock).
Invasive blood pressure monitoring will be important
and can be challenging to place. It may be necessary to
cut down on the radial artery, or to place the catheter in
the femoral, axillary, dorsalis pedis, or post tibial
arteries.
The presence of significant hypovolemia can cause
hypoperfusion and metabolic acidosis. Once
resuscitation has started, perfusion may occur to
previously underperfused areas, causing washout of
acid, vasodilatation, decreased cardiac output, and
continuing hypotension. Metabolic acidosis usually
improves with fluid resuscitation. However, in patients
with severe trauma, the acidosis may need to be treated
with sodium bicarbonate, as long as ventilation is
adequate. The Dose of bicarbonate is wt (kg) x 0.15 x
base deficit. However, since many of these patients
will have a base deficit of more than 10 mEq/L, 2 x
weight is a good starting dose.
The fluids most often used in resuscitation in children
are balanced salt solution (lactated Ringers or
Plasmalyte) or albumin.
Blood should be available and the child should be
transfused for the same indications as in adults.
Consider administration of fresh frozen plasma (FFP)
and platelets after the equivalent of 1 to 2 estimated
blood volumes have been transfused. FFP has the
highest citrate content per unit. Citrate binds with
calcium, so severe hypocalcemia may develop (citrate
intoxication) especially if FFP is administered rapidly.
Citrate toxicity is treated with calcium chloride (CaCl2)
10 mg/kg or calcium gluconate 30 mg/kg.
Hyperkalemia can occur as a result of massive blood
transfusion. One-week-old blood contains 5 mEq/L
potassium; while three-week-old blood, has 22 mEq/L
potassium. In a small child, this amount of potassium
may be significant. Treatment is with CaCl2 10 mg/kg,
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44

hyperventilation, and bicarbonate. If hyperkalemia
persists then glucose (0.5 gm/kg) and insulin (1
unit/5gms glucose) can be administered (7).
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