Pediatric emergency medicine trisk 486

TABLE 90.4
CHARACTERISTICS OF HEAT ILLNESS

Severe dehydration is not a necessary component of heat stroke but may play a
role if prolonged sweating has occurred. Electrolyte abnormalities may occur,
especially in the unacclimatized victim if NaCl has not been replaced. In
acclimatized persons, NaCl is conserved but often at the expense of a severe
potassium deficit. Polyuria is sometimes noted, often vasopressin-resistant and
possibly related to hypokalemia. Acute tubular necrosis may be seen in as many
as 35% of cases and probably reflects combined thermal, ischemic, and
circulating pigment damage. Hypoglycemia may also be noted.
Nontraumatic rhabdomyolysis and acute renal failure have been described as
consequences of various insults, including hyperthermia and strenuous exercise in
unconditioned persons. Clinically, there may or may not be musculoskeletal pain,
tenderness, swelling, or weakness. Laboratory evidence includes elevated serum
creatinine phosphokinase (CPK) (300 to 120,000 units) and urinalysis that is
heme-positive without red blood cells and shows red-gold granular casts.


Typically, serum potassium and creatinine levels rise rapidly relative to BUN. An
initial hypocalcemia, possibly a consequence of deposition into damaged muscle,
progresses to hypercalcemia during the diuretic phase a few days to two weeks
later.

Management and Diagnostic Studies
Heat Cramps
Most cases of heat cramps are mild and do not require specific therapy except for
rest and increased oral salt intake. In severe cases with prolonged or frequent
cramps, IV infusion of normal saline is effective. Approximately 5 to 10 mL/kg
over 15 to 20 minutes should be adequate to relieve cramping. Oral intake of
fluids and salted foods or electrolyte-rich sports drinks can then complete

restoration of salt and water balance.
Heat Exhaustion
Heat exhaustion as a result of predominant water depletion is treated with
rehydration and rest in a cooled or well-ventilated place. If the child is able to eat,
he or she should be encouraged to drink cool liquids and be allowed unrestricted
dietary sodium. If weakness or impaired consciousness precludes oral correction,
IV fluids are given as in any hypernatremic dehydration. As with any type of
hypernatremia, it is necessary to correct (reduce) serum sodium slowly to avoid
iatrogenic cerebral edema.
Heat exhaustion caused by predominant salt depletion also requires rest in a
cool environment. Alert, reasonably strong children can be given relatively salty
drinks, such as tomato juice, and should be encouraged to salt solid foods.
Hypotonic fluids (e.g., water, Kool-Aid) should be avoided until salt repletion has
begun. Patients with CNS symptoms or gastrointestinal (GI) dysfunction may be
rehydrated with IV isotonic saline. Initial rapid administration of 20 mL/kg over
20 minutes should improve intravascular volume with return of BP and pulse
toward normal. Further correction of salt and water stores should be achieved
over 12 to 24 hours. In especially severe cases with intractable seizures,
hypertonic saline solutions may be used. The initial dose of 3% saline solution is
5 mL/kg by IV over 10 to 15 minutes for seizures, more slowly over 30 to 60
minutes for cramping. An additional 5 mL/kg should be infused over the next 6
hours.
Heat Stroke


Treatment centers on two priorities: (i) Immediate elimination of hyperpyrexia
and (ii) support of the cardiovascular system (Table 90.5 ). Clothing should be
removed, and patients should be cooled actively. They should be transported to an
emergency facility in open or air-conditioned vehicles. Ice packs may be placed at
the neck, groin, and axilla. Although immersion in ice water may be a more

efficient means of lowering body temperature (offers a cooling rate of –1°C every
3 to 4 minutes), it may complicate other support and monitoring. Among the most
efficient but invasive and rarely used methods is iced peritoneal lavage, which is
contraindicated in the pregnant patient and those with a history of abdominal
surgery. Evaporative techniques in which fans blow room air over subjects
sprayed with 15°C (59°F) tap water are preferred to ice water immersion and iced
peritoneal lavage. Temperature should be monitored continuously with a rectal
probe, and active cooling should be discontinued when rectal temperature falls to
approximately 38.5°C (101.3°F). Sedation and paralysis of the patient can greatly
augment the cooling process.


TABLE 90.5
MANAGEMENT OF HEAT STROKE
Initial management
Remove clothing
Begin active cooling
Transport to cool environment
Cardiovascular support
Laboratory determinations
Complete blood cell count, PT/PTT
Electrolytes, BUN, creatinine, CPK, Ca, P
Urinalysis, including myoglobin
Arterial blood gas
Monitoring
Temperature
Heart rate, electrocardiogram, blood pressure
Peripheral pulses and perfusion
Urine output
Central nervous system function

Treatment
Active cooling
Fluids
Maintenance: 5% dextrose in normal saline at maintenance rates
Resuscitation: ≤20 mg/kg lactated Ringer’s or 0.9% sodium chloride
Additional fluids as determined by electrolytes, output, and hemodynamic
status
Inotropic support
Dobutamine 5–20 mcg/kg/min or
Diuresis for myoglobinuria
Maintain urine output >1 mL/kg/hr
Consider furosemide 1 mg/kg
Consider mannitol 0.25–1 g/kg