Does therapeutic hypothermia affect time to awakening in cardiac arrest survivors?

Current guidelines indicate that certain clinical examination findings at 72 hours after cardiac arrest may be useful in prognosis. Some have suggested that hypothermia may alter the examination. We aimed to examine timing of awakening in cardiac arrest survivors treated with hypothermia.

A retrospective review of prospectively identified cardiac arrest survivors from June 2006 to December 2010 at a large academic institution. Data including time to awakening, prognostic variables, systemic complications, cause of mortality, reasons, and timing to withdrawal of life-sustaining treatments were recorded. Outcome measure of in-hospital mortality was assessed.

A total of 227 patients were included. In-hospital mortality was 53%. Of 128 treated with induced hypothermia, 64% survived. Of 99 patients not treated with hypothermia, 24% survived. Median day of awakening was day 2 for both groups and most (91% hypothermic and 79% nonhypothermic) awakened within 3 days. In the hypothermic group, withdrawal of life-sustaining treatments preceded death in 41 patients; the decision was based primarily on poor neurologic prognosis in 29. The average day of death was 5 (range 3-11). In the nonhypothermic group, withdrawal of life-sustaining treatments took place in 69 patients, of which 55 were based on poor neurologic prognosis.

Awakening after therapeutic hypothermia is usually evident within 3 days of cardiac arrest and not delayed compared with nonhypothermia cases. Mortality in the hypothermia group was not uncommonly preceded by consequences of critical systemic illness.