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Symptoms and Signs of Hypothermia

Doctor's Notes on Hypothermia

Hypothermia is defined as a core or internal body temperature (best measured with a rectal thermometer) of less than 95 F or 35 C. Signs and symptoms of hypothermia vary with the decreasing core temperature. Shivering, along with an increase in heart rate, breathing rate and blood pressure are seen at a core temperature of about 95 F or somewhat below; as temperature decreases toward 89.9, heart rate, breathing rate and blood pressure decrease and the person becomes clumsy, confused, speech slurred and apathetic; below 89.9, shivering stops and oxygen consumption drops while the person may develop an irregular heartbeat and may become stuporous. At core temperatures below 82.4, reflexes are lost, cardiac output falls, chances of a dangerous heart rhythm increase, brain activity slows and the patient appears comatose or dead. However, some patients can be revived. Almost all individuals with hypothermia should be evaluated by an emergency medical caregiver (call 911).

The cause of hypothermia is exposure to a cold or frigid environment long enough to not allow the body to sustain a normal core temperature (98-100 F). Cold water immersion can drop core temperatures to dangerous levels in minutes (falling through ice in a lake or river); it may take hours for hypothermia to develop in cold dry environments (homeless, elderly in an unheated house).

Medical Author:
Medically Reviewed on 3/11/2019

REFERENCE:

Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

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