The effect of heparin versus citrate on blood echogenicity in vitro: The role of platelet and platelet-neutrophil aggregates

There is no consensus among investigators regarding which anticoagulant to use when studying the causes of in vitro blood echogenicity, despite the fact that heparin and calcium-chelating anticoagulants may have disparate effects due to their differing effects on platelets. This study quantitated the echogenicity of heparinized blood compared to citrated blood and found that it was greater in heparinized blood than in citrated blood when paired samples from the same donor, drawn at the same time were compared. By microscopic examination of the blood, this difference appeared to be due to the formation of platelet and platelet-neutrophil aggregates in the heparinized blood. This hypothesis was tested by comparing the echogenicity of heparinized blood to that of heparinized blood following platelet and white cell depletion. The results showed that taking away platelets and white cells virtually eliminated the echogenicity of heparinized blood; the impact of this result is discussed in the context of in vivo spontaneous contrast.