Dextran and the Prevention of Postoperative Thromboembolic Complications

Abstract

1. The purpose of fluid administration is not only the restoration of blood volume but also the normalization of impaired nutritive flow. 2. Plasma oncotic (colloid osmotic) pressure is the only force which can draw water into the circulation. In shock the infusion of colloid solutions is able to normalize nutritive flow and peripheral resistance almost at once. 3. Five per cent solutions of pasteurized plasma protein or albumin and 6 per cent dextran 70 yield a volume expansion corresponding to the amount infused. 4. The decrease in hematocrit produced by the infusion of these three colloidal solutions is accompanied by a decrease in whole blood viscosity resulting in a rise in cardiac output as well as in nutritional tissue flow. 5. Hemodilution improves oxygen supply as long as the hematocrit does not fall below 30 per cent, although normovolemia is the critical requirement. 6. Transmission of viral hepatitis is still the greatest danger of blood transfusion. 7. The use of large amounts of Ringer's lactate is not advised, as this solution does not reduce the total number of units of blood which need to be given. Pulmonary edema may become a problem. 8. Dextrans are best suited to initial volume replacement in shock. They increase plasma volume, improve blood flow, have antithrombotic properties, and are easily available and relatively cheap. Anaphylactoid reactions are rare. 9. Every third patient undergoing general surgery and every other patient having hip surgery develops a deep venous thrombosis. Widespread prophylaxis to prevent thromboembolic complications is mandatory. 10. The antithrombotic properties of dextran are due to a reduction in platelet adhesiveness, a change in fibrin clot structure, and the increased lysability of thrombi and the improvement of blood flow. 11. In a personal controlled, prospective, randomezed trial comparing subcutaneous heparin and intravenous dextran 40, 35.8 per cent of the controls (n=95), 13.2 per cent of the 83 patients in the heparin group, and 20.5 per cent in the dextran group (n=83) developed deep venous thrombosis. The difference between dextran and heparin is not significant; however, both treatment groups show a statistically significant effect compared to the controls.