Extracorporeal circulation can induce hypotension by both blood-material contact and pump-induced platelet aggregation

Objective: Use of extracorporeal systems in cardiopulmonary bypass and dialysis induces vascular reactions, which can lead to hypotension and lung edema. Methods: To study the contribution of blood-material contact and use of a roller pump, as well as prevention of their adverse effects, we perfused a rat hind leg with a tube connecting a carotid and a femoral artery. Results: Autoperfusion of an uncoated tube caused a fall of aortic pressure and femoral resistance to 66% +/- 16% and 76% +/- 15%, respectively. of their initial values within 2 hours, whereas in control animals without a shunt, these variables hardly changed (to 94% +/- 2.8% and 99% +/- 2.8%. respectively). Lung water content became significantly higher than that found in control animals (79.4% +/- 1.50% versus 77.0% +/- 1.67%). If we coated the tube with albumin, these changes were largely prevented. When the coated tube was placed in a roller pump, aortic pressure and femoral resistance immediately fell to 79% +/- 17.2% and 63% +/- 13.5%, respectively, whereas lung water content did not increase. The vasodilation was caused by platelet aggregation and could be prevented with aurintricarboxylic acid, which inhibits shear-induced platelet aggregation by blocking the binding of von Willebrand factor to platelet glycoprotein Ib receptors. Conclusions: Extracorporeal circulation may induce hypotension and lung edema by means of blood-material contact. Hypotension can be prevented by coating the system with albumin but can still result from pump-induced platelet aggregation.