[Platelet changes during heart surgery with extracorporeal circulation]

The changes in the number of platelets during anesthesia and operation were evaluated in 24 patients (8 females and 16 males) scheduled for cardiac surgery with cardiopulmonary bypass. There was a significant (p less than 0.05) thrombopenia at the beginning of perfusion, which persisted 60 minutes after the end of cardiopulmonary bypass. There were no significant differences when these changes were evaluated depending on the type of oxygenator, the need for transfusion or the duration of cardiopulmonary bypass. There was a reduction in the platelet count at the beginning of the bypass (207 to 124 x 10(9).1(-1), when blood contacts with the synthetic surfaces of the circuits and the oxygenator, al though-the most marked reduction was found at the end of bypass (95.9 x 10(9).1-1), coinciding with protamine administration. The function and number of platelets tended to become normal in the first hours of the postoperative period.