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 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 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 mL/kg by IV over 10 to 15 minutes for seizures, more slowly over 30 to 60 minutes for cramping An additional mL/kg should be infused over the next 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 to 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 mg/kg Consider mannitol 0.25–1 g/kg ... 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,