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When should cardiopulmonary bypass be used in the setting of severe hypothermic cardiac arrest?

A best evidence topic was written according to a structured protocol. The question addressed was regarding the indication and timing of the use of cardiopulmonary bypass (CPB), following severe hypothermic cardiac arrest. A total of 284 papers were found using the reported searches, of which nine represented the best evidence to answer the clinical question. The authors, date, journal, study type, population, main outcome measures and results are tabulated. Reported measures were survival, rewarming speed, incidence of arrhythmia during rewarming, resolution of full neurological function, long-term neurological function, evidence of damage on neurological imaging and venous metabolic parameters in hypothermic patients. The most recent of the best evidence studies, a retrospective comparative study of 68 patients, demonstrated CPB rewarming to be far superior to conventional methods of rewarming, with mortality rates of 15.8 and 53.3%, respectively. Another study of similar size, comparing CPB with extracorporeal membrane oxygenation (ECMO) for rewarming, revealed superior survival rates with ECMO, 75 vs 34%. A systematic review of 68 patients demonstrated an overall survival of 60%, and 80% of survivors returning to a previous level of activity. Two smaller observational studies reported survival rates of 73.1 and 45.5%, respectively. A retrospective study analysing long-term neurological outcomes of survivors reported normal history and physical examination in 93.3%, normal neurovascular ultrasound in 100%, normal neuropsychological findings in 93.3% and normal brain magnetic resonance imaging in 86.7%. A small comparative study demonstrated a significant survival benefit when CPB was preceded with emergency thoracotomy, internal cardiac massage and warm mediastinal irrigation compared with CPB alone. We conclude that, following deep hypothermic circulatory arrest, the urgent use of cardiopulmonary bypass is widely indicated for rewarming where it has been shown to provide good survival and neurological outcomes far superior in comparison with conventional methods of rewarming.