Hypothermia Common Environmental Emergencies
Hypothermia
Definition and overview
Hypothermia is core body temperature < 35.0°C. Clinical severity ranges from mild, readily reversible cold exposure through progressive loss of thermoregulation to life‑threatening cooling with arrhythmia and cardiac arrest.
Key management principles are: stop further heat loss, measure core temperature where possible, choose appropriate rewarming techniques, and apply special ALS modifications when arrest occurs (Resuscitation Council UK).
Grading (adults)
- Mild: 32-35°C
- Moderate: 28-32°C
- Severe: < 28°C
- Profound: < 20°C
If a reliable core temperature cannot be obtained, use clinical (Swiss) staging to estimate severity and guide care (Resuscitation Council UK).
Key pathophysiology points Systemic cooling produces:
- Reduced myocardial contractility and bradycardia leading to lower cardiac output.
- Peripheral vasoconstriction and increased blood viscosity causing impaired tissue perfusion.
- Left shift of the oxyhaemoglobin dissociation curve with reduced O2 off‑loading.
- Ventilation-perfusion mismatch and hypoxaemia.
- Slowed hepatic and renal drug metabolism causing drug accumulation and delayed effects.