Cerebral, tympanic and colonic thermometry in the piglet.

The temperature of the brain is crucial for the outcome of hypoxic/ischaemic brain damage. In clinical medicine and in animal experiments involving survival after hypoxia/ischaemia, non-invasive measurement of cerebral temperature is needed. We have therefore compared tympanic and colonic temperature with cerebral temperature in the newborn piglet during hypothermia. Ten piglets aged 12-60 h were cooled to 35 degrees C (mild hypothermia) for 150 min and rewarmed. Thereafter, four of the piglets were again cooled to approximately 29 degrees C for less than one hour (moderate hypothermia). During stable mild hypothermia and normothermia the cerebro-tympanic temperature difference in individual piglets was less than +/- 0.4 degrees C (95% confidence intervals < or = 0.18 degrees C) and the cerebro-colonic temperature difference was -0.7 to 0.4 (95% confidence interval < or = 0.28 degrees C). The differences were larger during moderate than during mild hypothermia and largest during rapid changes in body temperature. Then the tympanic temperature correlated with the cerebral temperature significantly better than did the colonic temperature (95% confidence interval -0.3 to 0.3 versus -0.6 to 1.4 for the ten minutes with the least good correlation).