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 (19 94 to 1998) randomized patients undergoing coronary artery bypass grafting that required three or more grafts to receive perfusion at either cold (20 degrees C), tepid (32 degrees C), or warm (37 degrees C) temperature. The g oal of the study was to evaluate morbidity, primarily neurologic dysfunctio n and secondarily hematologic factors. One thousand seven hundred seventy-s even patients were screened and 291 enrolled. Neurologic function was studi ed by a dedicated pool of blinded neurologists. A standard test battery ter med the Mathew Scale using three subscales-cognitive function, elemental sk ills, and disability-was used to study central nervous system function. Hem atologic 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 operati on 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 preo perative level at 1 month. Forty-nine patients suspect for cerebrovascular accident had a computed tomographic scan, but only 13 (4.5%) had a document ed 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 degrees C. Thus, increasing perfusate temperature increases fibrinolysis, which was as sociated with reoperation for bleeding in 4% warm group patients, 1% tepid, and 0% cold group patients (0.1 > p > 0.05). No other perioperative compli cations 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 i s not related to a cerebrovascular accident; 2) perfusion temperature has n o relationship to neurologic function after bypass; and 3) fibrinolytic act ivity is greatest at warm temperatures, (C) 1999 by The Society of Thoracic Surgeons.