Reduction of blood trauma in roller pumps for long‐term perfusion

As part of an attempt to develop a roller pump for long‐term (2 weeks) cardiac assist, factors generating blood trauma in roller pumps were re‐examined. Fresh human blood was pumped for 4 hr in a simple closed circulatory loop. Samples drawn at regular intervals were examined for plasma hemoglobin, lactate dehydrogenase, platelet function, and activation of coagulation factors. Experiments were performed in which tubing diameters were varied (polyvinyl chloride, 1/2‐ and 3/8‐inch internal diameters), roller diameters were varied (3/4, 1 1/8, and 1 3/4 inches), and roller occlusion was varied from total occlusion to 0.020‐inch underocclusion. The results showed more hemolysis when the roller diameters and the tubing diameters were smaller and when the rollers were more occlusive. Changes in platelet function and activation of coagulation factors were observed, but were not correlated with occlusion. These results suggest that when roller pumps are used for long‐term cardiac support, the diameter of the rollers should be as large as possible, the tubing diameter should be as large as practical, and the occlusion setting should be as open as possible while still maintaining required flow rates. New techniques for setting occlusion are suggested.