The knowledge that reduction of the temperature of brain tissue with its concomitant lowering of metabolic activity and oxygen requirement permits interruption of cerebral blood flow for extended periods has found practical clinical application in the form of surface cooling for intracranial operations. This method of cooling is, however, limited because of the necessity of maintaining cardiac temperature above the critical range of temperature at which dangerous cardiac arrhythmias are known to develop.
Recently Drew3,4 and others2,6 have demonstrated the feasibility of lowering body temperature to 15 C by means of extracorporeal cooling and cardiac bypass. Since complete circulatory arrest has been achieved with this method, it is now known that the human brain is capable of functional survival following periods of ischemia in excess of 30 minutes, provided that body temperatures are at or near 15 C.
What has intrigued us, as well as others,1,13 is