Summary
Technics have been devised permitting assay of certain coagulation factors in blood despite the presence of heparin in the sample. In the process of developing these methods, heparin and Polybrene were added to whole blood or plasma in varions quantities and a large number of coagulation tests then performed. Considerable differences in the sensitivity of the various assays to the added test substances were evident. It is believed that they were due, at least in part, to the varying dilutions of plasma utilized. The results shed no insight on the mechanisms by which heparin exerts its anticoagulant effects; the inhibitory activity of Polybrene, however, was largely restricted to the stage of thromboplastin generation.
Polybrene had a much weaker inhibitory effect than heparin on all tests, and in many assays it was possible to add a standard amount of Polybrene without altering results. The amount chosen was large enough to neutralize any quantity of heparin likely to be present in a sample obtained from a patient during open heart surgery.
Factor V could be assayed with accuracy only if heparin was neutralized as the sample was collected. Assay of Factor VIII was successful only if the Polybrene was added after, the step of adsorption with aluminum hydroxide. A one-stage prothrombin assay presented no problems, but assays for Factor VII complex provided distinctly different results from those found in a duplicate sample collected in citrate alone.
