Recover of peripheral nerve function after prolong hypothermic cardiac arrest in a porcine model with extra corporeal life support.

OBJECTIVES: Surviving long lasting cardiac arrest following accidental hypothermia has been reported after treatment with extra corporeal life support (ECLS), but there is a risk of neurologic injury. Most surviving hypothermia patients have a prolonged stay in the intensive care unit, where most patients experience polyneuropathy. Theoretically, accidental hypothermic cardiac arrest may in itself contribute to polyneuropathy. This study was designed to examine the impact of three hours of cardiac arrest at a core temperature of 20°C followed by reanimation of peripheral nerve function.

METHODS: Seven pigs were cannulated for ECLS and cooled to a core temperature of 20°C followed by three hours of circulatory arrest where the extremities were packed with ice. After three hours, ECLS was started and rewarming was performed. During the process, neural testing of the ulnar nerve (a somatic nerve) and of the vagus nerve (an autonomic nerve) were performed and blood was drawn for analysis of p-potassium, serum-neuron-specific enolase, and S100b protein.

RESULTS: The ulnar nerve was cooled from 34.9±1.6°C to 12.8±3.8°C and the vagus nerve from 36.2±1.2°C to 15.4±1.4°C. Physiologic function of both somatic and autonomic nerves were strongly affected by cooling, but recovered to almost normal levels during rewarming, even after three hours of hypothermic cardiac arrest. P-potassium rose from 3.9 (3.6-4.6)mmol/l to 8.1 (7.2-9.1)mmol/l after three hours of cardiac arrest, but normalized after recirculation. There was no rise in serum-neuron-specific enolase, but a slight rise in S100b protein during three hours of hypothermic cardiac arrest was observed. All pigs obtained return of spontaneous circulation (ROSC).

CONCLUSIONS: Reanimation after three hours of hypothermic cardiac arrest using ECLS was possible with no or, if present, minor damage to the two nerves tested.