Influence of cardiopulmonary bypass perfusion temperature on neurologic and hematologic function after coronary artery bypass grafting

Background and Methods. A National Institutes of Health-sponsored trial (1994 to 1998) randomized patients undergoing coronary artery bypass grafting that required three or more grafts to receive perfusion at either cold (20°C), tepid (32°C), or warm (37°C) temperature. The goal of the study was to evaluate morbidity, primarily neurologic dysfunction and secondarily hematologic factors. One thousand seven hundred seventy-seven patients were screened and 291 enrolled. Neurologic function was studied by a dedicated pool of blinded neurologists. A standard test battery termed the Mathew Scale using three subscales—cognitive function, elemental skills, and disability—was used to study central nervous system function. Hematologic function was assessed in 53 of the 291 patients with measurements of postoperative fibrinolytic potential. Results. All preoperative and operative data were comparable between groups. A decrease in Mathew Scale was seen in 69% of patient from before operation to immediately after operation. However, between the early postoperative study and the 1-month follow-up, 48% of patients had returned to baseline. There was no difference noted across temperature groups in any neurologic parameter of function. In all, 55% of the group were at or above their preoperative level at 1 month. Forty-nine patients suspect for cerebrovascular accident had a computed tomographic scan, but only 13 (4.5%) had a documented cerebrovascular accident (4 patients in the warm, 3 in the tepid, and 6 patients in the cold group). Fibrinolytic changes correlated with perfusion temperature documented that fibrinolysis was most active at 37°C. Thus, increasing perfusate temperature increases fibrinolysis, which was associated with reoperation for bleeding in 4% warm group patients, 1% tepid, and 0% cold group patients (0.1 >p>0.05). No other perioperative complications were temperature related. There were 4 deaths (1.4%) (1 in the warm group, 2 in the tepid group, and 1 in the cold group). Conclusions. (1) Persistent postoperative neurologic dysfunction at 1 month occurs in 36% of patients undergoing coronary artery bypass grafting and is not related to a cerebrovascular accident; 2) perfusion temperature has no relationship to neurologic function after bypass; and 3) fibrinolytic activity is greatest at warm temperatures.