Effect of skin temperature on platelet function in patients undergoing extracorporeal bypass.

Thirty-seven patients undergoing cardiopulmonary bypass operations were studied to assess the effect of skin temperature on platelet function. Differences in skin temperature between the two arms were created during bypass, at the completion of bypass, and at 2 and 24 hours after the completion of bypass. In each of 37 patients the temperature of one arm was increased with a water-filled blanket set at 40 degrees C. In 11 of these patients the other arm was allowed to equilibrate with the environment, and in the other 26 patients the arm was cooled with ice. Except for the differences in local skin temperature between the two arms, all factors known to affect the patient's bleeding time were similar. Measurements were made of bleeding times and the levels of thromboxane B2 and 6-keto-prostaglandin F1 alpha in shed blood obtained at the template bleeding time site. In the 33 patients not treated with aspirin, local hypothermia produced an increased bleeding time and a significant reduction in the thromboxane B2 level at the bleeding time site, but no reduction in 6-keto-prostaglandin F1 alpha level. Local rewarming produced a significant increase in the shed blood thromboxane B2 level. In the four patients treated with aspirin, local hypothermia produced no differences in bleeding times or shed blood levels of thromboxane B2 or 6-keto-prostaglandin F1 alpha. These data show the benefits of rewarming patients with hypothermia who have nonsurgical blood loss to restore to normal both core and peripheral temperatures before resorting to the transfusion of homologous blood products.