Comparison of Four Blood Sampling Sites for Flow-Cytometric Analysis of Platelet Function

Background: The access site used for platelet sampling has been suggested to be an important variable for clinical flowcytometric platelet analysis. In this study, we have evaluated the influence of different blood sampling sites (16 G central venous catheter, 20 G radial artery cannula, 16 G peripheral venous cannula and 19 G hypodermic needle) on platelet activation and aggregation. Material and Methods: Blood samples were collected from 17 adult patients undergoing abdominal surgery who did not have any medication known to alter platelet function. All samples were taken and measured by the same investigator after catheter placement and 2 h later. Surface expression of the glycoprotein IIb/IIIa (CD41), the platelet activation marker P-selectin (CD62P), and the percentage of platelet-leukocyte complexes (CD45+/CD41+) were measured by flow cytometry. Results: Regarding the site of blood sampling, there were no significant differences in the expression of CD41, CD62P and plateletleukocyte complexes. Repeated failure to place a central vein catheter or an arterial cannula resulted in increased platelet activation which was not detectable anymore 2 h later. Conclusion: Besides withdrawal by hypodermic needles (blood sample taken without stasis), samples for flowcytometric platelet function tests could also be taken from arterial cannulae, central venous catheters, and peripheral venous cannulae. Repeated failure of central venous or arterial puncture should be avoided since it results in transient platelet activation.