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Microscopic particles of microfibrillar collagen hemostat (MCH) have been shown to pass through a 40-μm 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 μg 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 μg 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.

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Microfibrillar collagen hemostat (MCH) is a topically applicable hemostatic agent which has been introduced in clinical practice recently and is marketed under different trade names and recommended for use in the course of surgical procedures. Because of the possibility that this substanee may pass through different blood-collecting circuits and cause organ damage if reintroduced into the patient’s circulation, a series of in vitro and in vivo experiments were performed. In the course of in vivo experiments the possible passage of MCH through "cell saver" devices was investigated. In Group A the passage of 1-125 labeled MCH was injected through different parts of a "cell saver" circuit. In Group B experiments the same was studied through a passage of 40μum pore-size blood transfusion filters. In the in vivo experiments MCH was injected intravenously into different parts of the' circulatory system of rabbits after different degrees of dilution and filtering after which the animals were killed at different time intervals and the radioactivity was determined in respective brain sections by microradiography. The results of these experiments suggest that the passage of MCH indeed occurs through different blood collecting and filtering devices and results in direct embolization of vital organs. This cannot be prevented even with the application of commercially used filters. Therefore, the authors recommend that the substance should not be used if shed blood is intended to be collected and returned to the patients circulation.

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A study was designed to compare platelet deposition between knitted and woven Dacron grafts in the same patient. Twenty patients received aortoiliac or aortofemoral bifurcated Dacron grafts, each composed of one woven and one double-velour knitted limb. External nuclear graft imaging was carried out after injection of autologous platelets labeled with indium 111. The patients were studied postoperatively in time periods ranging from 6 days to 42 months. Platelet accumulation was almost identical in knitted and woven limbs in all patients. This study appears to indicate that there is no difference in thrombogenicity between knitted and woven bifurcated Dacron grafts in the aortoiliac or aortofemoral positions measured by platelet accumulation.