Acute effects of exposure to cold on blood pressure, platelet function and sympathetic nervous activity in humans.

To clarify the mechanism for cold-related thrombosis, we evaluated responses of blood pressure, platelet function, and sympathetic nervous activity after cold exposure in ten healthy male volunteers (33 +/- 2 years old). Mean blood pressure, beta-thromboglobulin, platelet factor 4, and plasma noradrenaline were increased after cold exposure associated with significant falls in skin, oral, and urine temperature. The increase in plasma noradrenaline significantly correlated with the change in platelet aggregation (3 microM ADP: r = 0.73, P less than .02, 3.0 micrograms/mL epinephrine: r = 0.65, P less than .05), and with mean blood pressure in the warn environment (r = 0.76, P less than .02). These results suggest that the cold-related increase in sympathetic nervous activity may contribute to enhancement of platelet function. This provides a possible explanation for the risk of thrombosis in cold weather in essential hypertension.