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The relationship between the splenic blood flow and the intrasplenic platelet kinetics on the one hand, i.e. the two factors which govern the size of the exchangeable splenic platelet pool, and the spleen size on the other were assessed in 21 patients afflicted with haematologic disorders and variable splenomegaly. The splenic blood flow and intrasplenic platelet kinetics were measured using 111In-labelled platelets and compartmental analysis of their equilibration between circulating blood and splenic pool; the spleen size was determined by scintigraphy using 99mTc-labelled stannous colloid. Significant correlations were recorded between the spleen size and the splenic platelet pool size (r = 0.76; P less than 0.001) and between the spleen size and the splenic blood flow (r = 0.56; P less than 0.01). Splenic perfusion decreased significantly with increasing spleen size, but there was no relationship between the spleen size and the intrasplenic platelet transit time. However, an association was present between splenic perfusion and intrasplenic platelet transit time (r = -0.44; P less than 0.05). It is concluded that the splenic blood flow is the major determinant of the size of the exchangeable splenic platelet pool in splenomegalic states, and that the determination of spleen size using 99mTc-scintigraphy gives a rough estimation of the pool size. Splenic perfusion appears to be one of the factors which determine the intrasplenic platelet transit time.

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Summary The relationship between the splenic blood flow and the intrasplenic platelet kinetics on the one hand, i.e. the two factors which govern the size of the exchangeable splenic platelet pool, and the spleen size on the other were assessed in 21 patients afflicted with haematologic disorders and variable splenomegaly. The splenic blood flow and intrasplenic platelet kinetics were measured using 111In‐labelled platelets and compartmental analysis of their equilibration between circulating blood and splenic pool; the spleen size was determined by scintigraphy using 99mTc‐labelled stannous colloid. Significant correlations were recorded between the spleen size and the splenic platelet pool size (r= 0.76; P<0.001) and between the spleen size and the splenic blood flow (r= 0.56; P<0.01). Splenic perfusion decreased significantly with increasing spleen size, but there was no relationship between the spleen size and the intrasplenic platelet transit time. However, an association was present between splenic perfusion and intrasplenic platelet transit time (r=—0.44; P<0.05). It is concluded that the splenic blood flow is the major determinant of the size of the exchangeable splenic platelet pool in splenomegalic states, and that the determination of spleen size using 99mTc‐scintigraphy gives a rough estimation of the pool size. Splenic perfusion appears to be one of the factors which determine the intrasplenic platelet transit time.

Circulating platelets differ with respect to size, density and functional ability. In several experimental settings it is of vital importance that a representative platelet-rich plasma (PRP) is extracted from the anticoagulated blood. We therefore investigated the effect of centrifugation time and gravitational force on platelet yield and platelet volume distribution in PRP obtained by a single step slow centrifugation.Methods. From each of 12 healthy male blood donors, 357 ml of venous blood were mixed with 63 ml citrate phosphate dextrose in a plastic bag. 20 ml aliquots of the anticoagulated blood were transferred into 30 ml screwcap polycarbonate tubes (Nalgene Labware). PRP was prepared by a single step slow centrifugation in a microprocessor-controlled bench centrifuge (Hettich Rotanta/RP). The gravitational force was calculated at the bottom of the tube. Centrifugations were performed at 180, 200, 220, 240, 260 g for 10 min, at 180, 200, 220, 240, 260 g for 15 min and at 120, 140, 160, 180, 200 g for 20 min. Three hours after blood collection, the platelet count, mean platelet volume (MPV) and platelet distribution width were determined in PRP and anticoagulated blood with an impedance cell counter (Coulter Counter Model S-Plus VI). Student's t-test was employed for comparison of mean values.Comments. Very precise centrifugation conditions can be provided by using a microprocessor-controlled centrifuge and a "fully representative" platelet population can be isolated with a single step slow centrifugation method.