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

Objectives: Resuscitation attempts in trauma victims who suffer cardiac arrest (CA) from exsanguination almost always fail. The authors hypothesized that an aortic arch flush with cold normal saline solution (NSS) at the start of exsanguination CA can preserve cerebral viability during 20-minute no-flow. Methods: Twelve dogs were exsanguinated over 5 minutes to CA of 20-minute no-flow, resuscitated by cardiopulmonary bypass, followed by post-CA mild hypothermia (34 degreesC) continued to 12 hours, controlled ventilation to 20 hours, and intensive care to 72 hours. At CA 2 minutes, the dogs received a 500-mL flush of NSS at either 24 degreesC (group 1, n = 6) or 4 degreesC (group 2, n = 6), using a balloon-tipped catheter inserted via the femoral artery into the descending thoracic aorta. Results: The flush at 24 degreesC (group 1) decreased tympanic membrane temperature [mean (+/-SD)] from 37.5 degreesC (+/-0.1) to 35.7 degreesC (+/-0.2); the flush at 4 degreesC (group 2) to 34.0 degreesC (+/-1.1) (p = 0.005). In group 1, one dog achieved overall performance category (OPC)2 (moderate disability), one OPC 3 (severe disability), and four OPC 4 (coma). In group 2, four dogs achieved OPC 1 (normal), one OPC 2, and one OPC 3 (p = 0.008). Neurologic deficit scores (0-10% normal, 100% brain death) [median (25th-75th percentile)] were 62% (40-66) in group 1 and 5% (0-19) in group 2 (p = 0.01). Total brain histologic 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 model with aortic arch flush of 24 degreesC results in survival with brain damage in all dogs, which makes it suitable for testing other (e.g., pharmacologic) preservation potentials.