The physiology of the cold heart
Below 30°C, the myocardium becomes refractory to defibrillation and pharmacological intervention. Adrenaline accumulates and may cause rebound toxicity on rewarming. ALS requires modification: defibrillate up to three times, withhold further shocks below 30°C, double adrenaline intervals, and use mechanical CPR for any transfer.
Potassium as a prognostic marker
Serum potassium reflects cellular death. K+ <12 mmol/L is associated with survival to discharge in hypothermic arrest. Above 12 mmol/L, profound cellular damage makes survival unlikely — but not impossible. Clinician judgement must integrate context: submersion time, witness status, ALS response, and the HOPE score.
The ECMO decision
eCPR is a genuine intervention in hypothermic arrest. Case series show survival rates of 50–60% in selected patients. Criteria: witnessed arrest, shockable rhythm or VF, age under 75, reversible cause, no prolonged no-flow time, and K+ <12 mmol/L. Contact the regional ECMO centre early — ideally within 30–40 minutes of arrest.
Medicolegal and human dimensions
Every decision in a prolonged resuscitation must be documented with time-stamps. Your reasoning — clinical, ethical, and guideline-referenced — protects your patient and your practice. Involve the team in futility decisions. Involve the family where possible.
References