Moderate superficial hypothermia prolongs bleeding time in humans

In vitro and in vivo studies have shown that mild systemic hypothermia influences platelet adhesion and aggregation and coagulation reactions. We wanted to test the hypothesis that mild local hypothermia in healthy volunteers with preserved core temperature increased bleeding time. A secondary aim was to evaluate if local cooling influenced whole blood coagulation measured by thrombelastograph (TEG) in the same setting.

Bleeding time was measured at the left volar forearm at a baseline skin temperature of 32 degrees C and after cooling to 30 degrees C and 28 degrees C in a water bath. Skin temperature was continuously measured by contact thermistors. Measurements of coagulation by TEG were performed at baseline skin temperature before cooling and after cooling to 28 degrees C skin temperature. Tympanic membrane temperature was continuously measured.

Compared with baseline, bleeding time was significantly prolonged at 30 degrees C skin temperature and further prolonged at 28 degrees C skin temperature. No significant differences were measured in any of the TEG parameters. During the procedure, tympanic membrane temperature did not change.

Lowering the skin temperature from 32 degrees C to 30 degrees C and 28 degrees C with a preserved core temperature more than doubled the bleeding time. Whole blood coagulation measured by TEG was not influenced by the local cooling. In addition to core temperature, local temperature may offer information in understanding the surgical site of bleeding.