Disseminated intravascular coagulation is a common
complication of heat stroke that is initiated following thermal
injury to the vascular endothelium and is regarded as an important mechanism of heat stroke morbidity and mortality. In
vitro studies have shown that heat (43–44ºC) directly activates
platelet aggregation and causes irreversible hyperaggregation
following cooling 19. Early in heat stroke, widespread activation of coagulation stimulates excess deposition of fibrin in the
arterioles and capillaries along with platelet aggregation that
leads to microvascular thrombosis. Although rapid cooling of
the heat stroke patient may normalize fibrinolysis, coagulation
often persists until platelets and coagulation proteins are consumed at a faster rate than they are produced. Consumptive
coagulation may lead to excessive, prolonged bleeding from
multiple tissue sites (venipuncture sites, gums) and is associated with fatal outcome. The host inflammatory and hemostatic responses are closely associated not only with fatal heat
stroke but also with severe heat stress, especially when combined with physical strain 2, 20.
The prothrombin time provides information about the
extrinsic (tissue factor) and common coagulation pathways 21.
In our study, heat stress combined with intensive physical
activity led to increase in prothrombin time values in soldiers
performed the EHST in hot condition. We observed no difference in the control group, which suggests that the same
intensity of physical strain did not result in increasing of
prothrombin time. Hence, this effect on prothrombin time
can be attributed to heat stress, regardless physical activity.