In vitro effect of a microfibrillar collagen hemostat on platelets.

Microscopic particles of microfibrillar collagen hemostat (MCH) have been shown to pass through a 40-micron blood transfusion filter. This study indicates that MCH passing through the filter retains a significant portion of its ability to aggregate platelets in vitro and the aggregating ability is dose related. The extent of platelet aggregation in the presence of the MCH filtrate or an ADP standard was measured photometrically and log dose-response curves constructed from the data. An ED50 of 3.6 micrograms protein/ml platelet-rich plasma (PRP) was calculated at a protein concentration of 7.6 mg/ml in the MCH filtrate and an ED50 of 5.9 micrograms protein/ml PRP at 12 mg/ml protein in the MCH filtrate. The platelet aggregating ability of the MCH filtrates corresponded to 18.8 and 39.6% of the maximum response produced by adenosine-5'-diphosphate. These findings support the view that blood contaminated with MCH should not be returned to a patient's circulation.