ObjectiveThis study was done to assess the effects of temperature on bleeding time and clotting time in normal male and female volunteers.DesignOpen study utilizing normal volunteers.SettingUniversity research laboratory.SubjectsFifty-four healthy male and female volunteers, ranging in age from 19 to 35 yrs, who were not receiving medications. The study was done and the samples of venous blood and shed blood collected at the template bleeding time site were obtained at a convenient time for each volunteer.InterventionsSkin temperature was changed from +20 degrees to +38 degrees C and blood samples were obtained from the antecubital vein of each volunteer.Measurements and Main ResultsThe effect of local skin temperature ranging from +20 degrees to +38 degrees C on bleeding time was evaluated in 38 normal volunteers (19 male and 19 female). Skin temperature was maintained at +20 degrees to +38 degrees C by cooling or warming the forearm. At each temperature, measurements were made of complete blood count, bleeding time, and thromboxane B2concentrations in shed blood collected at the template bleeding time site and in serum and plasma isolated from blood collected from the antecubital vein. Clotting time studies were measured in 16 normal volunteers (eight male and eight female) at temperatures ranging from +22 degrees to +37 degrees C.At +32 degrees C, the bleeding time was longer and hematocrit was lower in female than in male volunteers.However, at local skin temperatures of <+32 degrees C, both the males and females exhibited significantly increased bleeding times, which were associated with a reduction in shed blood thromboxane B2. Each 1 degree C decrease in temperature was associated with a 15% decrease in the shed blood thromboxane B2concentration. Clotting times were three times longer at +22 degrees C than at +37 degrees C. Each 1 degree C reduction in the temperature of the clotted blood was associated with a 15% reduction in the serum thromboxane B2concentration.ConclusionOur data indicate that during surgical procedures, it is important to maintain normothermia to ensure that platelets and clotting proteins function optimally.(Crit Care Med 1995; 23:698-704)