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Hypothermia

Hypothermia is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • A core temperature of <35°C (95°F)
  • May take several hours to days to develop
  • Patients with cold-water immersion may appear dead but can sometimes still be resuscitated.
  • System(s) affected: all body systems
  • Synonym(s): accidental hypothermia

Epidemiology

  • Predominant age: very young and the elderly
  • Predominant sex: male > female

Geriatric Considerations
More common in elderly due to lower metabolic rate, impaired ability to maintain normal body temperature, and impaired ability to detect temperature changes

Prevalence
Estimates vary widely; typically a secondary issue

Etiology and Pathophysiology

  • Overwhelming environmental cold stress
  • Decreased heat production
  • Increased heat loss
  • Impaired thermoregulation

Risk Factors

  • Alcohol consumption
  • Bronchopneumonia
  • Cardiovascular disease
  • Cold-water immersion
  • Dermal dysfunction (burns, erythrodermas)
  • Drug intoxication
  • Endocrinopathies (myxedema, severe hypoglycemia)
  • Excessive fluid loss
  • Hepatic failure
  • Hypothalamic and central nervous system (CNS) dysfunction
  • Malnutrition
  • Mental illness; Alzheimer disease
  • Prolonged cardiac arrest
  • Prolonged environmental exposure
  • Renal failure
  • Sepsis
  • Trauma (especially head)
  • Uremia

General Prevention

  • Appropriate clothing, with particular attention to head, feet, and hands
  • For outdoor activities, carry survival bags with rescue foil blanket for use if stranded or injured.
  • Avoid alcohol.
  • Alertness to early symptoms and initiating preventive steps (e.g., drinking warm fluids)
  • Identify medications that may predispose to hypothermia (e.g., neuroleptics, sedatives, hypnotics, tranquilizers).

Commonly Associated Conditions

  • Addison disease
  • CNS dysfunction
  • Congestive heart failure
  • Diabetes
  • Hypopituitarism
  • Hypothyroidism
  • Ketoacidosis
  • Pulmonary infection
  • Sepsis
  • Uremia

History

Presentation varies with the temperature of the patient at the time of presentation.

ALERT
History of prolonged exposure to cold may make the diagnosis obvious, but hypothermia may be overlooked in other situations, especially in comatose patients. Always obtain a core temperature if hypothermia is suspected.

Physical Exam

  • Esophageal temperature is most accurate, minimally invasive method of assessing core temperature (1)[C].
    • Must have secure airway
    • Probe inserted into lower 3rd of esophagus
    • Peripheral thermometers (tympanic membrane, temporal artery, axillary, or oral) associated with reduced accuracy
  • Exam findings vary with the temperature of the patient at the time of presentation.
    • Mild (32–35°C)
      • Lethargy and mild confusion
      • Shivering
      • Tachypnea
      • Tachycardia
      • Loss of fine motor coordination
      • Increased BP
      • Peripheral vasoconstriction
      • Hyperactive reflexes
    • Moderate (28–32°C)
      • Delirium
      • Bradycardia
      • Hypotension
      • Hypoventilation
      • Cyanosis
      • Arrhythmias (prolonged PR interval, AV junctional rhythm, accelerated idioventricular rhythm, prolonged QT interval, altered T waves)
      • Semicoma and coma
      • Muscular rigidity
      • Generalized edema
      • Slowed reflexes
    • Severe (<28°C)
      • Very cold skin
      • Rigidity
      • Apnea
      • Bradycardia
      • No pulse: ventricular fibrillation or asystole
      • Areflexia
      • Unresponsive
      • Pupils (dilated <27°C; fixed and dilated <27°C)

ALERT
Use specially designed thermometers that can record low temperatures and measure core temperatures.

Pediatric Considerations
  • Infants may present with bright red, cold skin and very low energy.
  • A child’s body temperature drops faster than an adult does when immersed in cold water.

Differential Diagnosis

  • Cerebrovascular accidents
  • Intoxication
  • Drug overdose
  • Complications of diabetes, hypothyroidism, hypopituitarism

Diagnostic Tests & Interpretation

Initial Tests (lab, imaging)
  • Arterial blood gases (corrected for temperature)
  • CBC and platelet counts
  • Serum electrolytes; BUN/creatinine; glucose; calcium; magnesium
  • Urinalysis
  • Coagulation studies; fibrinogen level
  • Blood culture
  • Liver function studies; amylase
  • Cardiac enzymes
  • Alcohol level and toxicology screen
  • Cervical spine, chest, and abdomen x-rays, if appropriate
  • Bedside ultrasound to assess hemodynamics
  • CT of the head for any concern regarding mental status

Follow-Up Tests & Special Considerations
Serum cortisol and TSH if underlying endocrine dysfunction (hypothalamus stimulates release of hormones in response to hypothermia)

Diagnostic Procedures/Other
ECG

Test Interpretation
Serum potassium >12 mmol/L associated with nonsurvival

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Citation

Stephens, Mark B., et al., editors. "Hypothermia." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816651/1.2/Hypothermia.
Hypothermia. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816651/1.2/Hypothermia. Accessed June 19, 2019.
Hypothermia. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816651/1.2/Hypothermia
Hypothermia [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 June 19]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816651/1.2/Hypothermia.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Hypothermia ID - 816651 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816651/1.2/Hypothermia PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -