•Hypotension: To sustain organ perfusion, maintain mean arterial pressure of more than 65 mmHg by fluid administration, consider vasopressors, and monitor central venous pressure.

•Seizures should be controlled by IV benzodiazepines and barbiturates.

•Multiorgan failure: Give supportive therapy until organ function recovers. Stepwise management of hyperthermia is shown in Fig. 72.1.

Step 7: Prevention

•Hyperthermia, caused by physical exertion or hot environment, can be prevented by taking frequent rest breaks and staying hydrated.

•Genetic testing for known mutations of the SKM ryanodine receptor in conjunction with in vitro muscle contracture test can be used to evaluate individual susceptibility in patients from families with a history of malignant hyperthermia.

72.2Hypothermia

An 82-year-old man, a known case of Alzheimer’s disease and hypothyroidism, was found unresponsive on his backyard lawns. He had been taking aspirin, olanzapine, and levothyroxine for the past 3 years. Examination revealed femoral pulse 35/min, blood pressure (BP) unrecordable, Glasgow Coma Scale 3, and temperature 28°C.

Step 1: Initiate resuscitation

Initiate resuscitation as mentioned in Chap. 78:

•The management should start with removal of wet clothing if any and replacing it with warm, dry sheet.

•In severe hypothermia, if indicated, the patient is intubated gently and ventilated with warmed humidified O2 while closely monitoring cardiac rhythm.

•One should be prepared to treat ventricular fibrillation with DC shock (200 J) and cardiopulmonary resuscitation.

•Start IV line and infuse normal saline at 43°C.

Step 2: Diagnose types and severity of hypothermia

Primary

•Normal thermoregulation

•Overwhelming cold exposure

Fig. 72.2 Osborn (J) waves (Marked with arrows)

Secondary

•Abnormal thermogenesis

•Multiple causes (hypothyroidism, burns, hypothalamic abnormalities, sepsis) Hypothermia is defined as temperature less than 36°C.

Severity of hypothermia with presentation is described in Table 72.1.

•ECG may show Osborn (J) waves especially when temperature is less than 33°C (Fig. 72.2).

•It is a positive deflection, and its amplitude is proportional to the degree of hypothermia, usually seen in leads V3–V6 at junction of QRS and ST segment.

Step 3: Manage hypothermia

The patient should be warmed by the following rewarming methods: passive, active external, and active internal.

•Passive rewarming: It allows endogenous heat production to increase the core temperature, but heat conserving mechanisms must be intact (e.g., shivering, metabolic rate, and sympathetic nervous system).

•Remove wet cloths (to prevent conductive and convective heat loss)

•Maintain horizontal position

•Protect against heat loss and wind chill (use blanket and insulating material)

•Avoid rough movement, shaking and excessive activity (to prevent arrhythmias) Monitor core temperature and cardiac activity

Assess responsiveness breathing and pulse

Fig. 72.3 Stepwise management of hypothermia