Abstract 2278: Functional and Injury Temperature Thresholds for the Neonatal Heart during Central Cooling and Ischemia Induced by Aortic Cross-clamping
The International Liaison Committee on Resuscitation (ILCOR) has recommended cooling to 32° to 34°C in unconscious adult patients with spontaneous circulation, when the initial rhythm was ventricular fibrillation. The advisory statement stressed that numerous factors, which determine therapeutic benefit or risks, still require definition. Prominent among these factors is target temperature, as some human and animal studies have shown either lack of benefit by mild hypothermia or the various adverse effects of profound temperature drops. No recommendations for infants or children have been made by ILCOR. We provide initial target temperature data in neonatal pigs undergoing central cooling by directing cardiac output through an extracorporeal circuit. We determined cardiac function and power using aortic flow probes and pressure-capacitance catheters within the left ventricle. Pigs (n = 5) were cooled from 38°C (esophageal) to 20° and recovered, or underwent 60 minutes aortic cross clamp at 29, 31, 32.5, 34, or 35°C (n= 2–5 per group), while under cardiopulmonary bypass support, and 40 minutes recovery with re-warming. Figure A⇓ shows DP/dt max (% baseline) during cooling; B shows ventricular power, and C shows recovery function compared to ischemic temp after cross-clamp. The data define a clear functional and injury threshold occurring just above 31°C. At this temperature, function is maintained, while providing maximal functional recovery after ischemic insult. The 32 to 34°C range does not provide optimal protection to the neonatal heart. This implies that neonatal protection requires different temperature strategies than adults.