Prolongation of the safe interval of hypothermic circulatory arrest: 90 minutes.

Twenty-nine adult mongrel dogs were subjected to profound hypothermia and 90 minutes of total circulatory arrest. Pure surface (Group I) hypothermia and combined surface/perfusion techniques with bubble (Group II) and membrane (Group III) oxygenator systems were employed. Circulation was arrested at average esophageal temperatures of 18.4 degrees, 11.9 degrees and 8.5 degrees C in Groups I, II and III, respectively. Three animals in Group I failed to resuscitate. All survivors in the pure surface series developed postoperative gait (hypermetria) disturbances. One intraoperative death occurred in Group II and four of eight dogs arrested at esophageal temperatures above 10 degrees C but less than 15 degrees C developed motor disturbances during a three week neurologic evaluation period. Animals arrested below 10 degrees C (esophageal) did not display postoperative neurological abnormalities. Three dogs in Group III died from a hemorrhagic diathesis of uncertain etiology. None of the survivors (5) that were cooled and arrested below esophageal temperatures of 10 degrees C developed motor or sensory disturbances. We conclude that in the canine model the central nervous system can be protected for 90 minutes of total circulatory arrest at esophageal temperatures less than 10 degrees C.