Hypothermia is defined as a core body temperature of <35°C

Classification

• Mild (32°C to 35°C): characterised by tachycardia, tachypnoea, vasoconstriction and shivering
• Moderate (28°C to 32°C): may have cardiac arrhythmias, hypotension, respiratory depression, reduced consciousness and may cease to shiver
• Severe (<28°C): markedly reduced consciousness/coma, apnoea, arrhythmia, fixed and dilated pupils

Investigations

ECG changes

• Bradyarrhythmias e.g. sinus bradycardia, atrial fibrillation with a slow ventricular response, slow junctional rhythms and varying degrees of AV block
• Osborne Waves ('J waves') = positive deflection at the J point between the end of the QRS and beginning of the ST segment
• Prolonged PR, QRS and QT intervals
• Shivering artefact
• Ventricular ectopics
• Cardiac arrest (VT, VF or asystole)

Management

• Management involves warming the patient by covering with a warm blanket, and supplying warm drinks
• Passive warming may be supplemented by intravenous administration of warmed fluids and application of warm air (e.g. using a Bair-Hugger)
• Patients are at high risk of cardiac arrest and CPR may be required