No. Resuscitation after cardiac arrest longer than 4 to 6 minutes at normal body temperature typically results in irreversible brain injury, coma, or death. Therefore there is a popular belief that the brain “dies” after 4 to 6 minutes without oxygen. This is not true.

There are many interventions that can rescue people after longer periods of warm cardiac arrest, although none are yet in wide clinical use. Perhaps the most promising is post-resuscitation hypothermia, or cooling the patient a few degrees after the heart is restarted. Research has shown that resuscitation without brain injury is possible after up to 10 minutes of cardiac arrest (plus another ten minutes of low flow CPR) if cooling is started at the same time as CPR (Critical Care Medicine 19, 379-389 (1991)). The combination of post-resuscitation cooling and a complex drug protocol can further extend recovery without neurological deficit to 16 minutes of warm cardiac arrest in dogs (Critical Care Research, Inc., unpublished). Finally, isolated brains of monkeys and cats have recovered normal electrical function after high pressure reperfusion following 60 minutes of warm circulatory arrest (Science 168, 375-376 (1970)). This result was later extended to long-term recovery of whole cats after one hour of no blood flow to the brain, although with some neurological deficit (J Neurol Sci. 77, 305-320 (1987)).

Clearly the brain does not die after only a few minutes without oxygen. The primary obstacle to resuscitation after a few minutes of cardiac arrest is not cell death, but something called reperfusion injury. This is a cascade of injury that occurs when blood flow is restarted after cardiac arrest, especially inflammation. Inflammation shuts off blood vessels, preventing blood from reaching brain cells. Without oxygen, brain cells die over a period of hours (not minutes). Post resuscitation cooling and drugs extend the 4 to 6 minute window in part by reducing this inflammatory response.

Successful resuscitation after 15 minutes of warm cardiac arrest in humans seems feasible by aggressive use of methods already available. What will the future hold? Amazingly, living neurons can still be cultured from brains after 8 hours of warm cardiac arrest (Lancet 351, 499-500 (1998)). Basic cell structure must persist even longer before inevitable protein breakdown occurs. When repair tools based on nanomedicine become available, we may conservatively estimate that physicians will work on patients after hours of cardiac arrest instead of the minutes they do today.

Further discussion and references concerning the issue of post-mortem brain changes and cryonics can be found in these articles: