Rapid induction of mild cerebral hypothermia by cold aortic flush achievesnormal recovery in a dog outcome model with 20-minute exsanguination cardiac arrest

Objectives: Resuscitation attempts in trauma victims who suffer cardiac arr est (CA) from exsanguination almost always fail. The authors hypothesized t hat an aortic arch flush with cold normal saline solution (NSS) at the star t of exsanguination CA can preserve cerebral viability during 20-minute no- flow. Methods: Twelve dogs were exsanguinated over 5 minutes to CA of 20-mi nute no-flow, resuscitated by cardiopulmonary bypass, followed by post-CA m ild hypothermia (34 degreesC) continued to 12 hours, controlled ventilation to 20 hours, and intensive care to 72 hours. At CA 2 minutes, the dogs rec eived a 500-mL flush of NSS at either 24 degreesC (group 1, n = 6) or 4 deg reesC (group 2, n = 6), using a balloon-tipped catheter inserted via the fe moral artery into the descending thoracic aorta. Results: The flush at 24 d egreesC (group 1) decreased tympanic membrane temperature [mean (+/-SD)] fr om 37.5 degreesC (+/-0.1) to 35.7 degreesC (+/-0.2); the flush at 4 degrees C (group 2) to 34.0 degreesC (+/-1.1) (p = 0.005). In group 1, one dog achi eved overall performance category (OPC)2 (moderate disability), one OPC 3 ( severe disability), and four OPC 4 (coma). In group 2, four dogs achieved O PC 1 (normal), one OPC 2, and one OPC 3 (p = 0.008). Neurologic deficit sco res (0-10% normal, 100% brain death) [median (25th-75th percentile)] were 6 2% (40-66) in group 1 and 5% (0-19) in group 2 (p = 0.01). Total brain hist ologic damage scores were 130 (62-137) in group 1 and 24 (10-55) in group 2 (p = 0.008). Conclusions: Aortic arch flush of 4 degreesC at the start of CA of 20 minutes rapidly induces mild cerebral hypothermia and can lead to normal functional recovery with minimal histologic brain damage. The same m odel with aortic arch flush of 24 degreesC results in survival with brain d amage in all dogs, which makes it suitable for testing other (e.g., pharmac ologic) preservation potentials.