Table 3 Rewarming techniques in accidental hypothermia

Passive rewarming

0.5–4 °C hr^-1 (dependent upon patient’s thermoregulatory function and metabolic reserves) [79, 242].

Protect from further heat loss and allow patient to self-rewarm. Minimal controversy for mild hypothermia if the patient is able to self-rewarm.

Negligible in isolated mild hypothermia. For colder patients and those with secondary hypothermia or comorbid illness, there may be morbidity associated with a prolonged rewarming process if the patient has poor tolerance for the hypothermia-induced organ dysfunction (i.e. hypotension, coagulopathy, arrhythmias, impaired cellular function etc.).

Passive rewarming with active movement

1–5 °C hr^-1

Exercise has been shown to increase afterdrop in physiology studies from ~0.3 °C in controls to ~1 °C in exercised subjects, however the exercised subjects rewarmed more quickly [243].

No reported complications. Some authors highlight the theoretical risk that the slightly increased afterdrop could contribute to morbidity and mortality. No adverse events were noted [243].

Active rewarming e.g. forced air surface [244] Arctic Sun® [245–247]

0.5-4 °C hr^-1

Protect from further heat loss, deliver external heat and (if required) warmed IV fluids. Minimal controversies.

Similar to passive rewarming.

Bladder lavage

Variable. Adds ~0.5–1 °C hr^-1

Helpful if rewarming rate is slow. Minimal controversies. Rewarming is intermittent & slow because of small surface area. Poor control of infusate temperature [242, 248, 249].

Negligible unless difficult catheterization.

Gastric lavage

Adds ~0.5–1 °C hr^-1

Not commonly used due to risk vs. benefit ratio [249].

Potential for aspiration, fluid & electrolyte shifts.

Intravascular catheter rewarming e.g. Icy® catheter (CoolGuard®) [76, 250–252]

Quattro® [253] Cool Line® [254] Innercool® [255]

Device specific (adds ~0.5–2.5 °C hr^-1)

Uncertain indication for use, potential for benefit exists in colder and sicker co-morbid patients with stable circulation.

Potential for haemorrhage or thrombosis, potentially worsening hypotension in unstable patients.

Thoracic [79, 256, 257] or Peritoneal lavage [79, 258]

Adds ~1–2 °C hr^-1

Not commonly used unless patient is unstable and ECLS rewarming is not available.

Potential for haemorrhage, lung or bowel trauma, fluid & electrolyte shifts. Thoracic lavage has the potential to impair CPR quality.

Continuous venovenous haemofiltration [190, 242, 259–261]

Adds ~1.5–3 °C hr^-1

Not commonly used unless ECLS rewarming not available. Requires adequate blood pressure. Heparinisation required.

Problems rare. Local vascular complications. Air embolism. Hypotension.

Haemodialysis [242, 262–266]

Adds ~2–3 °C hr^-1

Not commonly used, patient must be able to increase cardiac output to perfuse the external circuit. Heparinisation required.

Potential for hypotension, haemorrhage, thrombosis, haemolysis, etc.

Veno-venous rewarming (usually with an ECMO circuit) [248]

~4–10 °C hr^-1

Not commonly used. Provides no circulatory or ventilatory support in case of cardiac arrest. Patient must be able to increase cardiac output to provide circuit perfusion.

Potential for hypotension, haemorrhage, thrombosis, haemolysis, etc.

Extra-corporeal life support (VA-ECMO or CPB)

~4–10 °C hr^-1

Preferred rewarming method for patients in cardiac arrest. CPB can use femoral route avoiding need for sternotomy [1, 42]

Potential for haemorrhage, thrombosis, haemolysis, etc. (as with all intravascular devices).