Alteration of platelet reactivity following a shock-inducing procedure in pigs.

Changes (usually increases) in platelet reactivity occur concomitantly with circulatory shock. This suggests both effects of the shock state on platelets and participation by platelets in sequelae of shock such as shock-lung syndrome. Changes in platelet reactivity have not been documented previously for splanchnic artery occlusion (SAO)-induced shock. SAO shock in pigs produced a decrease in platelet reactivity in the postrelease period. This decreased reactivity was not accompanied by changes in platelet counts or size distribution. Since exposure of the platelets to a submaximal aggregating stimulus prior to the sampling time at 15 minutes postrelease may cause this type of relative refractoriness, it is possible that the platelets may have been in a hyperreactive state very early in the postrelease period or prior to release. Exposure to increased but submaximal ADP levels, or to other submaximal stimuli, could cause the observed decrease in reactivity. Further examination of the time sequence and causes of changes of platelet reactivity in shock are necessary and desirable.