Abstract 73: Rapid Whole Body Cooling in Large Swine: Effects on Heart Rate and Arterial Blood Pressure
There have been recent reports of a variety of cooling methods for reducing the body temperature of victims of post resuscitative syndrome. In the work reported here we cooled a series of large (> 60 kg) domestic swine (n=6) using a whole body approach. The animals were anesthetized using propofol and buprinorphine and instrumented with arterial pressure monitoring and ECG, and thermocouple sensors in the pulmonary artery (PA), carotid artery, tympanic membrane and esophagus. With an initial average PA temperature at 37 (± 0.3) °C, the swine underwent a rapid cooling sequence. This was performed with a flexible surround suit system that provided for a thin 0.5 cm layer of circulating ice water in direct skin contact held between 0.5° and 1.5 °C. A pumping system was used to circulate the water volume of 20 liters at a rate of 15 liters per minute. The average PA temperature at the start was 37 (±0.3) °C. Cooling was targeted at 34 °C with an average value of 34.1 (±0.3) °C. Time to fall 3°C was13.0 (±3.0) min. At the same time, heart rate dropped (although not significantly) from 71 ± 7.9 BPM to 59.5 ± 11.4 BPM while mean carotid pressure dropped from 100.3 ± 16 mmHg to 77.3 ± 14.9 mmHg (p<.05). We interpret these changes as beneficial reductions in cardiac work while the subject is kept cool. It is hypothesized that this is due to a reduction in total body metabolic demands. Thus it is possible, in addition to positive neurological effects, that the process of rapid whole body cooling also may be effective in reducing total workload seen by the heart, and thus may aid in salvaging myocardium in such patients.