Site of temperature monitoring and prediction of afterdrop after open heart surgery.

To determine which of the commonly used "core" temperature sites, remote from the brain, best indicates total body rewarming, the temperatures in the rectum (RT), urinary bladder (UBT) and the pulmonary artery (PAT) at the termination of cardiopulmonary bypass (CPB) were correlated with the decrease in nasopharyngeal temperature (NPT) after CPB (afterdrop) in 29 patients. The amount of afterdrop is inversely related to the adequacy of total body rewarming, smaller values indicating better rewarming. All patients had uncomplicated cardiac surgery and received high pump flows during rewarming on CPB. The UBT showed the best correlation with afterdrop (p less than 0.001) compared with the other temperature sites, the durations of CPB and rewarming during CPB, and the time that the NPT was greater than 37 degrees C during rewarming. The urinary bladder is a simple, non-invasive monitoring site when a urinary catheter is required and our results indicated that the UBT is a better monitor of the adequacy of total body rewarming on CPB than NPT alone. The study also suggested that rewarming to a UBT in excess of 36.2 degrees C prior to the termination of CPB is unlikely to further reduce afterdrop.