History and exam
Key diagnostic factors
common
presence of risk factors
Risk factors include: general anaesthetic use, extremes of age, immobility, substance misuse, impaired cognition, hypothyroidism, stroke, Parkinson's disease, homelessness, gram-negative septicaemia.
cold exposure and body temperature <35°C (<95°F)
Those inappropriately dressed for a cold climate and who have spent a long time outside or in a cold environment may be hypothermic, as assessed by measurement of a body temperature <35°C (<95°F).
cognitive impairment
Confusion, apathy, and impaired judgement. Typically seen in people with moderate (stage 2) hypothermia.
shivering
Patient may be shivering, or there may be a history of shivering.
Practical tip
Shivering will be absent once the patient’s core temperature drops below a certain level; the threshold varies between patients but is typically 32°C to 28°C (90°F to 82°F).[4]
frostbite
Occurs when the skin and subcutaneous tissue freeze, causing cellular damage. See our topic Frostbite.
Other diagnostic factors
common
tachypnoea, tachycardia, hypertension
Usually seen in people with mild hypothermia (core temperature of 32°C to 35°C [90°F to 95°F]). Note that tachycardia may progress to bradycardia, even in mild hypothermia.
respiratory depression, bradycardia, hypotension
Usually seen in people with moderate hypothermia (core temperature of 28°C to 32°C [82°F to 90°F]). However, note that tachycardia may progress to bradycardia, even in mild hypothermia.
coma and apnoea
Usually seen in people with severe hypothermia (core temperature of <28°C [<82°F]). Some patients may have weak signs of life at temperatures <28°C (<82°F).
Beware of diagnosing death in a patient with hypothermia, even when the patient has fixed pupils or early signs of rigor mortis; signs of life may be minimal if the patient has severe hypothermia.[25]
cold-induced diuresis
Occurs with progression of hypothermia as the kidney loses its ability to concentrate urine.
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