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Three Part Question

In [severely hypothermic patients who have suffered cardiac arrest] is [core rewarming by cardiopulmonary bypass better than external rewarming] at [re-establishing spontaneous circulation and leading to eventual discharge]?

Clinical Scenario

A 24 year-old woman is brought into the Emergency Department having fallen into a frozen lake. Passers-by heard her cries for help and alerted the Emergency Services who rescued her 15 minutes later. On the way to hospital she suffered a cardiac arrest. Her core temperature on arrival is 25 degrees centigrade. You know that she needs rewarming but wonder whether her eventual outcome will be improved by cardiopulmonary bypass rather than external rewarming.

Search Strategy

Medline 1966-09/00 using the OVID interface.
([exp heart arrest OR cardiac arrest.mp] AND [exp hypothermia OR hypothermia.mp OR hypothermic.mp OR exp body temperature] AND [exp heat OR exp heating OR exp rewarming OR warming.mp OR rewarming.mp]) LIMIT to human AND english

Search Outcome

114 papers found of which 111 were irrelevant or of insufficient quality. The remaining 3 papers are shown in the table.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Vretenar DF et al, 1994, Canada.	68 hypothermic patients with a mean core temperature of 21 degrees centigrade of whom 61 were in cardiac arrest. All patients placed on cardiopulmonary bypass	Review	Overall survival	60%	Publication bias likely as success more likely to be reported than failure.
			Survival if core temperature < 15 degrees	0%
			Return to previous function	60% of survivors
Koller R et al, 1997, Switzerland.	5 patients with core temperature below 30 degrees centigrade of whom 2 were in cardiac arrest	Cohort	Overall survival	100%	Small numbers
			Return to previous function	100%
Walpoth BH et al, 1997	32 of 46 patients in cardiac arrest with core temperature below 28 degrees centigrade. All patients placed on cardiopulmonary bypass	Prospective cohort	Overall survival	15/32 (45%)	Unclear why patients selected for bypass

Comment(s)

None of the studies directly answer the question. It appears that there is a significant functional recovery following severe hypothermic cardiac arrest, and cardiopulmonary bypass seems to be an efficacious treatment. The number of patients treated by external rewarming is very small and more work will be needed before this can be recommended in preference to bypass.

Clinical Bottom Line

In severely hypothermic patients in cardiac arrest cardiopulmonary bypass should be considered.

References

1. Vretenar DF. Urschel JD. Parrott JC. Unruh HW. Cardiopulmonary bypass resuscitation for accidental hypothermia. Annals of Thoracic Surgery. 1994;58(3):895-8.
2. Koller R, Schnider TW, Neidhart P. Deep accidental hypothermia and cardiac arrest - rewarming with forced air. Acta Anaesth Scand 1997;41:1359-64.
3. Walpoth BH, Walpoth-Alsan BN, Mattle HP et al. Outcome of survivors of accidental deep hypothermia and circulatory arrest treated with extracorporeal blood warming. NEJM 1997;337:1500-5.