Hypothermia Diagnosis and Management

Core Temperature Measurement

Accurate core temperature measurement is crucial for diagnosis and must be obtained with a low-reading thermometer capable of measuring below 35°C, with preferred methods including esophageal, bladder, or rectal thermometry, as peripheral measurements can underestimate severity by up to 1°C 1, 2, 3
Pulmonary artery catheter temperature is the most accurate method, but rarely practical in acute settings 2
Monitor temperature every 5 minutes in moderate-severe hypothermia and every 15 minutes in mild cases 4, 3

Classify severity to guide workup intensity, with categories including cold stress (35-37°C) 4, moderate hypothermia (28-32°C) 4

Obtain cortisol level to evaluate for adrenal insufficiency in all hypothermic patients 4, 3
Coagulation studies, including PT/PTT, are essential as hypothermia impairs platelet function and clotting factors, with PTT increasing from 36 seconds at 37°C to 57 seconds at 28°C 5, 6
Arterial blood gas is necessary to assess metabolic acidosis and ventilation status 5

Obtain 12-lead ECG to identify characteristic changes and arrhythmias, including sinus tachycardia, hypertension, and increased cardiac output in mild hypothermia, and bradycardia, prolonged PR interval, and Osborne (J) waves in severe hypothermia 5, 6
Handle the patient gently during examination to avoid precipitating ventricular fibrillation in severe hypothermia 7

Document mental status carefully, as it correlates with severity, with confusion and uncoordination present in mild hypothermia, and somnolence to coma expected in severe hypothermia 5, 6
Brain death cannot be diagnosed until the patient is rewarmed to at least 34°C, as severe hypothermia mimics brain death 5, 6

Assess respiratory rate, as mild hypothermia causes tachypnea and decreased PaCO2, and severe hypothermia causes medullary depression with decreased minute ventilation 5, 6
Monitor for increased secretions and atelectasis in moderate-severe cases 5

Expect cold-induced diuresis initially, followed by decreased GFR and urine output as temperature decreases 5, 6

Continuous cardiac monitoring is necessary for arrhythmias 4, 7
Serial temperature measurements should be taken as outlined above 4, 3
Watch for rewarming complications, including rewarming shock, arrhythmias, and hypotension 4, 7

A core body temperature of 34.8°C falls into the mild hypothermia range, which is clinically significant and associated with measurable physiological dysfunction, according to the Critical Care society 8
At this temperature, impaired diastolic relaxation begins to occur, marking the onset of cardiovascular compromise, as stated by the Critical Care society 8
Platelet function is already impaired at temperatures between 33-37°C, and clotting factor activity begins to decline below 33°C, as reported by the Critical Care society 8

Cardiac function transitions from compensatory to depressive at this temperature threshold, according to the Critical Care society 8
Expect impaired diastolic relaxation as a primary cardiac manifestation, as stated by the Critical Care society 8
Coagulopathy is already developing, with partial thromboplastin time increasing significantly, as reported by the Critical Care society 8

Platelet aggregation and thromboxane B2 production are inhibited at this temperature, according to the Critical Care society 8
This is particularly critical in trauma or surgical patients where bleeding risk is elevated, as stated by the Critical Care society 8

Neuromuscular blocking agents eliminate shivering thermogenesis, resulting in a decreased metabolic rate, as reported by the Critical Care society 8

Do not ignore coagulopathy risk, as even mild hypothermia impairs hemostasis, which is critical in trauma or surgical patients, according to the Critical Care society 8