Cardiac arrest, mild therapeutic hypothermia, and unanticipated cerebral recovery

OBJECTIVES:: Animal and human studies support mild therapeutic hypothermia as an effective means of preventing brain injury in comatose patients resuscitated from cardiac arrest. However, there is little clinical experience with predicting neurologic outcome in this patient population. We present 4 comatose patients resuscitated from cardiac arrest treated with mild hypothermia whose in-hospital neurologic prognosis was determined by board-certified neurologists to be grave, yet were ultimately discharged from the hospital with no or minimal neurologic sequelae. RESULTS:: We report 4 comatose patients resuscitated from cardiac arrest treated with mild hypothermia. On hospital admission, all patients had a Glasgow Coma Score between 3 and 6 and a FOUR Score between 1 and 5. Mild hypothermia (32°C-33°C) was implemented for 24 to 40 hours. Examination by board-certified neurologists before and during hypothermia or the rewarming phase suggested a grave prognosis. All 4 patients had sudden and dramatic neurologic recovery 9 to 24 hours after rewarming to normothermia and were ultimately discharged with no or minimal neurocognitive sequelae. CONCLUSION:: This case series suggests that neurologic assessment-based prognosis of patients after cardiac arrest undergoing therapeutic mild hypothermia should be considered unreliable for at least the first 72 hours. Use of additional assessments such as brain injury markers or evoked potentials, in addition to clinical examination, should be strongly considered to help determine an estimated prognosis. Functional reversibility after a global insult could be an intrinsic potential of the brain, similar to myocardial stunning, and deserves investigation.