Background-Neuropsychological deficits occur in 30% to 80% of patients undergoing heart surgery and are due in part to ischemic cerebral injury during cardiopulmonary bypass. We tested whether mild hypothermia, the most efficacious neuroprotective strategy found in laboratory studies, improved cognitive outcome in patients undergoing coronary artery surgery. Methods and Results-Patients 60 years or older scheduled for coronary artery surgery were enrolled. During cardiopulmonary bypass, patients were initially cooled to 32°C then randomly assigned to rewarming to 37°C (control) or 34°C (hypothermic), with no further intraoperative warming. Testing was scheduled preoperatively and 1 week and 3 months postoperatively. Eleven tests were combined into 3 cognitive domains: memory, attention, and psychomotor speed and dexterity. A patient was classified as having a cognitive deficit if a decrease of Ն0.50 SD was realized in 1 or more domains. The incidence of cognitive deficits 1 week after surgery, which was the primary outcome, was 62% (62/100) in the control group and 48% (45/94) in the hypothermic group (relative risk 0.77, Pϭ0.048). In the hypothermic group, the magnitude of deterioration in attention and in speed and dexterity was reduced by 55.6% (Pϭ0.038) and 41.3% (Pϭ0.042), respectively. At 3 months, the hypothermic group still performed better on one test of speed and dexterity (grooved pegboard). There was no difference in morbidity or mortality. Conclusions-Our findings support a neuroprotective effect of mild hypothermia in patients undergoing coronary artery surgery and should encourage physicians and perfusionists to pay careful attention to brain temperature during cardiopulmonary bypass.

Laboratory studies demonstrate that mild degrees of brain cooling (2 degrees C to 5 degrees C) confer substantial protection from ischemic brain injury, and that mild elevation of brain temperature can be markedly deleterious. During hypothermic cardiopulmonary bypass (CPB) patients are made hypothermic and then rewarmed at a time when they are exposed to neurological insults. Our studies show that during rewarming, peak brain temperatures near 39 degrees C often are achieved inadvertently. We hypothesize that maintaining brain temperature < or = 34 degrees C during and after CPB will reduce the incidence of postoperative neuropsychological deficits. We present safety data from a study of 30 patients assigned either to conventional hypothermic CPB with rewarming or a protocol where brain temperature is raised only to 34 degrees C at the time of separation from CPB. There was no difference in bleeding, cardiac morbidity, or time to extubation between groups. We designed a neuropsychological test battery to detect postoperative neuropsychological deficits and tested its usefulness in a preliminary sample of 15 patients undergoing hypothermic CPB. We found patient acceptability and compliance were good. Sensitivity also seemed adequate in that 30% of patients were identified as having deteriorated at 1 week postoperatively compared to preoperatively, a result similar to that reported by others. Clinical trials of the efficacy of mild hypothermia in modulating brain injury in humans are needed before techniques of CPB can be designed to optimize neuroprotection.

Background Neuropsychological deficits occur in 30% to 80% of patients undergoing heart surgery and are due in part to ischemic cerebral injury during cardiopulmonary bypass. We tested whether mild hypothermia, the most efficacious neuroprotective strategy found in laboratory studies, improved cognitive outcome in patients undergoing coronary artery surgery. Methods and Results Patients 60 years or older scheduled for coronary artery surgery were enrolled. During cardiopulmonary bypass, patients were initially cooled to 32°C then randomly assigned to rewarming to 37°C (control) or 34°C (hypothermic), with no further intraoperative warming. Testing was scheduled preoperatively and 1 week and 3 months postoperatively. Eleven tests were combined into 3 cognitive domains: memory, attention, and psychomotor speed and dexterity. A patient was classified as having a cognitive deficit if a decrease of ≥0.50 SD was realized in 1 or more domains. The incidence of cognitive deficits 1 week after surgery, which was the primary outcome, was 62% ( \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\frac{62}{100}\) \end{document} ) in the control group and 48% ( \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\frac{45}{94}\) \end{document} ) in the hypothermic group (relative risk 0.77, P =0.048). In the hypothermic group, the magnitude of deterioration in attention and in speed and dexterity was reduced by 55.6% ( P =0.038) and 41.3% ( P =0.042), respectively. At 3 months, the hypothermic group still performed better on one test of speed and dexterity (grooved pegboard). There was no difference in morbidity or mortality. Conclusions Our findings support a neuroprotective effect of mild hypothermia in patients undergoing coronary artery surgery and should encourage physicians and perfusionists to pay careful attention to brain temperature during cardiopulmonary bypass.

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