PROTHROMBOTIC EFFECTS OF ENVIRONMENTAL-STRESS - CHANGES IN PLATELET-FUNCTION, HEMATOCRIT, AND TOTAL PLASMA-PROTEIN

Mental stress can affect a range of variables relevant to hemostasis a nd thrombosis. However, research has not clarified whether these effec ts occur as part of a generalized sympathoadrenal response or whether stress-induced increases in catecholamines and blood pressure have sel ective and independent effects on hematologic variables. This study as sessed the effects of mental and cold presser stress on platelet activ ation, hematocrit, and total plasma protein and the relationship of th ese changes to sympathoadrenal and hemodynamic mechanisms, Platelet fa ctor 4, beta-thromboglobulin, total plasma protein, hematocrit values, and hemoglobin were measured in 22 healthy men (32 +/- 7 years) durin g rest, mental arithmetic, and cold presser task. A no-stress control group of five male subjects was used to rule out the possible effects of blood withdrawal in producing these changes. Significant increases to mental arithmetic and cold presser (p < .001) were observed in plat elet factor 4 and beta-thromboglobulin. Increases (p < .002) in hemato crit values and total plasma protein also occurred with mental arithme tic and cold presser. Correlational analyses revealed that changes in hematocrit and total plasma protein concentrations were related to inc reased mean arterial pressure during stress, and platelet activation c orrelated positively with norepinephrine and negatively with epinephri ne; The present results indicate that acute psychologic and cold stres s cause concurrent changes in several hemostatic factors (increased pl atelet activation, hematocrit, and total plasma protein) that may play key roles in thrombosis and ischemia. The relationships of hematocrit and total plasma protein to blood pressure increases and the associat ions between platelet activation and catecholamines support the notion that stress-induced increases in catecholamines and blood pressure ha ve selective effects on specific hemostatic variables.