Treatment of Hypothermia

Hypothermia can be defined as body temperature below 35° Centigrade or 95° Fahrenheit. Hypothermia is again subdivided into 3 subcategories mild hypothermia (35°C – 32.2°C or 95°F – 90°F), moderate hypothermia (less then 32.2°C – 28°C or less then 90°F – 82.4°F) and severe hypothermia (below 28°C or below 82.4°F), depending on severity of hypothermia.

In patients with hypothermia the cardiovascular system and target organs do not usually respond or if responds minimally to most medications. Moreover, repeated doses of medication can cause toxicity during re-warming because of increased binding of drugs to proteins, and there is also impairment in metabolism and excretion of drugs.

Re-warming of hypothermia patient is most important aspect of the treatment. Re-warming can be active and passive depending of the clinical condition of the patient. Passive external re-warming involves covering and insulating the patient in a warm environment with head also covered. The rate of re-warming should be 0.5° to 2.0°C per hour normally. Passive external re-warming is ideal for previously healthy patients who develop acute, mild primary accidental hypothermia and who have sufficient glycogen to support endogenous thermo-genesis. Active re-warming is required when core temperature is less than 32°C, cardiovascular instability, age extremes (very old or very young), CNS dysfunction, hormone insufficiency, or there is suspicion of secondary hypothermia due to some underlying disease. The best way of active re-warming is done with forced-air heating blankets. Other methods of active re-warming are by radiant heat sources and hot packs.

The main aim of therapy of hypothermia should be achieving a mean arterial pressure of at least 60 mmHg in the early stage of treatment. For achieving this objective crystalloids and colloids (normal saline and ringer lactate) should be administered (infused by intra-venous route) and if they fail to raise the blood pressure low-dose dopamine (2–5 ?g/kg per minute) support should be given. For improving tissue perfusion low-dose IV (intra-venous) nitroglycerin should be considered.

Hypothermia may cause atrial arrhythmia and also ventricular arrhythmia. Most of the cases of atrial arrhythmia do not need any treatment, because re-warming will correct atrial arrhythmia unless there is preexisting arrhythmia. For treatment of ventricular arrhythmias bretylium tosylate is the drug generally given (class III ventricular anti-arrhythmic of choice).

Hypothermia can mask sign and symptoms of infection (shaking rigors due to infection may be mistaken for shivering) and empirical treatment with broad spectrum antibiotic should be given in patients with hypothermia, especially in the elderly, neonates, and immune-compromised patients.

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