The effect of an adrenaline infusion on the splenic blood flow and intrasplenic platelet kinetics.

The effect of an adrenaline infusion on the venous platelet count, splenic blood flow and intrasplenic platelet kinetics was investigated in seven healthy male volunteers by using 111In-labelled platelets and dynamic gamma camera scintigraphy. The infusions were administered in two different doses, 0.2 microgram/kg/min and 0.1 microgram/kg/min, respectively. Regardless of the given dose, adrenaline was found to markedly decrease the splenic blood flow, decrease the exchangeable splenic platelet pool size and to prolong the intrasplenic platelet transit time. In response to the higher dose of adrenaline the splenic blood flow was 1.3 +/- 0.5 (SD) % of total blood volume per min and the intrasplenic platelet transit time 17.3 +/- 2.3 (SD) min. In contrast, after termination of infusion, the splenic blood flow was 7.0 +/- 2.1 (SD) % of total blood volume per min and the intrasplenic platelet transit time was 11.5 +/- 1.5 (SD) min. The present results firmly demonstrate that the splenic blood flow is the immediate variable governing the size of the exchangeable splenic platelet pool, and that the adrenaline-induced depletion of the splenic platelet pool is a consequence of the splenic blood flow reduction. Finally, the splenic perfusion appears to be a major determinant of the intrasplenic platelet transit time.