PT, prothrombin time; PTT, partial thromboplastin time; BUN, blood urea nitrogen; CPK, creatine phosphokinase The severity of the patient’s presentation determines the degree of cardiovascular support If the skin is flushed and BP adequate, lowering body temperature with close attention to heart rate and BP may be sufficient Although severe dehydration and electrolyte disturbances are uncommon, these should be assessed and corrected if necessary Fluids cooled to 4°C (39.2°F) hasten temperature correction but may precipitate arrhythmias on contact with an already stressed myocardium Adult patients rarely have required more than 20 mL/kg over the first hours, but determinations of electrolytes, hematocrit, and urine output, and clinical assessment of central vascular volume should guide precise titration of fluids and electrolytes Inotropic support may be required after a fluid challenge (see Chapter 10 Shock ) Dobutamine is probably most appropriate as its β-agonist properties increase myocardial contractility and maintain peripheral vasodilation Isoproterenol has been used successfully in the past but may cause myocardial oxygen consumption to exceed oxygen delivery and thus may precipitate myocardial ischemia Additional fluid resuscitation may be necessary with the initiation of either dobutamine or isoproterenol to fill the effectively increased vascular space Normal saline should be given to maintain the arterial BP in the normal range Dopamine may also be effective, infused at rates compatible with inotropic support without vasoconstriction (i.e., to 15 mcg/kg/min) In cases of extreme hemodynamic instability, extracorporeal circulation may provide both circulatory support and a means of rapid temperature correction Agents with αagonist characteristics (epinephrine and norepinephrine) are not recommended for initial management as they cause peripheral vasoconstriction, interfere with heat dissipation, and may compromise hepatic and renal flow further Atropine and other anticholinergic drugs that inhibit sweating should be avoided Renal function should be monitored carefully, especially in patients who have been hypotensive or in whom vigorous exercise precipitated heat stroke BUN, creatinine, electrolytes, calcium, and urinalysis for protein and myoglobin should be obtained Once the patient’s vascular volume has been restored and arterial pressure normalized, hourly urine output should be monitored If urine output is inadequate (less than 0.5 mL/kg/hr) in the face of normovolemia and adequate cardiac output, furosemide (0.5 to mg/kg by IV) and/or mannitol (0.25 to g/kg by IV) should be given If the response is poor, acute renal failure should be suspected, and fluids should be restricted accordingly Rapidly rising BUN or potassium should prompt consideration of early dialysis Indications for Admission and Discharge Patients with heat cramps can generally be discharged from the ED after resolution of symptoms Children with heat exhaustion may require admission for ongoing fluid and electrolyte replacement and serial testing Children with heat stroke require admission to the ICU Patients with ashen skin, tachycardia, and hypotension demonstrate cardiac output insufficient to meet circulatory demand and are in imminent danger of death Monitoring of the electrocardiogram (ECG) and arterial BP (with an indwelling arterial line) should determine support ACCIDENTAL HYPOTHERMIA Goals of Treatment The goals of treatment include general supportive measures, cardiopulmonary resuscitation, and rewarming CLINICAL PEARLS AND PITFALLS A high index of suspicion is needed to recognize hypothermia Hypothermia can mimic death; hence rewarming must be done before pronouncing death Current Evidence Hypothermia is defined as a core temperature below 35°C (95°F) and can be classified by temperature into mild (32° to 35°C), moderate (28° to 32°C), severe (25° to 28°C), and profound (