The influence of dextran and saline solution upon platelet behavior after microarterial anastomosis.

Microarterial anastomoses were performed on the central arteries of the ears in rabbits. An untreated control group was compared with two groups treated with saline solution and dextran 70 in saline solution respectively. Anastomotic bleeding times were prolonged in both treated groups. In vivo accumulation of 32phosphorous labelled platelets infused prior to any treatment was measured at the anastomotic sites for two hours after anastomosis. Treatment with saline solution resulted in prolonged periods of platelet accumulation--desaggregation processes and abnormally high levels in 50 per cent of the rabbits. Treatment with dextran resulted in increased quantitative accumulation of platelets at all times compared with the control groups. In some rabbits treated with dextran, platelet accumulation patterns indicated microembolization due to increased platelet thrombus fragility. Despite increased platelet accumulation in the dextran groups all vessels showed good patency and only small amounts of thrombosis material compared with the control and saline solution groups. Poor patency was registered only in one instance in the control group and two instances in the saline solution group. Using ex vivo platelet aggregometry, saline solution slightly decreased and dextran slightly increased platelet aggregability. The conclusion is that dextran does not act as an antiplatelet agent but minimizes formation of dangerous solid fibrin platelet thrombi due to a defective fragile fibrin structure adn perhaps increased fibrinolysis.