Hypothermia-induced platelet aggregation and cognitive decline in coronary artery bypass surgery: a pilot study.

Hypothermia-induced platelet aggregation (HIPA) was previously reported in whole blood exposed to synthetic surfaces at 248/328C in one-third of normal subjects tested. Cardiopulmonary bypass, conducted with hy- pothermia, may lead to such aggregation, resulting in microvascular occlusion contributing to cognitive impair- ment. This pilot study was conducted to explore the relationship between HIPA and cognitive outcome at hospital discharge in patients undergoing coronary artery bypass graft (CABG) surgery as a first step toward a longer-term study. Patients (n /45) undergoing mild to moderate hy- pothermia (328/288C) during CABG surgery underwent cognitive testing preoperatively and prior to hospital discharge. Tests included: visual and verbal memory, mental processing speed, executive function, language, and intellectual function. HIPA was identified using an in vitro assay in which blood flowing in polyvinychloride tubing was subjected to hypothermia, and platelet aggre- gates were detected using microscopy and passing the exiting blood through a 20-mm pore filter. Forty-four percent of patients exhibited HIPA. The entire cohort exhibited significant postoperative cogni- tive decline in verbal memory, mental processing speed and executive function. There was greater cognitive decline in the group with HIPA compared with the group not exhibiting this phenomenon. The patients with HIPA showed significant decline in four of five cognitive measures whereas patients not exhibiting this phenom- enon declined in only two of five cognitive measures. HIPA appears to be associated with an added risk of cognitive decline immediately following CABG surgery employing mild to moderate hypothermia. The findings of our study suggest the long-term cognitive effects of hypothermia-induced platelet aggregation need to be explored. Perfusion (2005) 20, 157/167.