Mild hypothermic cardiopulmonary resuscitation improves outcome after prolonged cardiac arrest in dogs

Abstract

Background and methods: This study was designed to explore the effect of mild cerebral and systemic hypothermia (34 degrees C) on outcome after prolonged cardiac arrest in dogs. After ventricular fibrillation with no flow of 10 min, and standard external CPR with epinephrine (low flow) from ventricular fibrillation time of 10 to 15 min, defibrillation and restoration of spontaneous normotension were between ventricular fibrillation time of 16 and 20 min. This procedure was followed by controlled ventilation to 20 hr postarrest and intensive care to 72 hr postarrest. In control group 1 (n = 10), core temperature was 37.5 degrees C; in control group 2 (n = 10), cooling was started immediately after restoration of spontaneous normotension; and in group 3 (n = 10), cooling was initiated with start of CPR. Cooling was by clinically feasible methods.

Results: Best overall performance categories achieved (1 = normal; 5 = brain death) were better in group 2 (p = .012) and group 3 (p = .005) than in group 1. Best neurologic deficit scores were 36 +/- 14% in group 1, 22 +/- 15% in group 2 (p = .02), and 19 +/- 18% in group 3 (p = .01). Brain histopathologic damage scores were also lower (better) in groups 2 (p = .05) and 3 (p = .03). Myocardial damage was the same in all three groups.

Conclusion: Mild cerebral hypothermia started during or immediately after external CPR improves neurologic recovery.