Rapid progressive central cooling to 29 degrees C by extracorporeal circuit preserves cardiac function and hemodynamics in immature swine.

The International Liaison Committee on Resuscitation (ILCOR) consensus statement includes recommendations and guidelines for therapeutic hypothermia in infants and children. The information supporting these recommendations is sparse, and reveals a need for target temperature and cooling mode data in age-appropriate animal models. Accordingly, we determined cardiac function and hemodynamic indices in immature piglets (<28 days) undergoing graded and rapid central cooling from 36 to 20 degrees C over 20 min by directing cardiac output through an extracorporeal circuit. Functional parameters were recorded continuously using aortic flow probes and left ventricular (LV) pressure capacitance catheters. Stroke volume and work increased during temperature reduction, peaking at 29 degrees C, while systemic vascular resistance did not change. Although, heart rate decreased steadily, cardiac output, power, and LV dP/dt(max) was maintained until 29 degrees C. All function parameters decreased below 29 degrees C, implying a critical threshold had been exceeded at lower temperatures. These data show that the temperature range (30+/-1) degrees C maintains cardiac function and that this target should be further evaluated as a target for therapeutic hypothermia.