Hemolysis caused by pumps in extracorporeal circulation (in vitro evaluation of pumps)

To test in vitro the hemolytic properties of pumps used in extracorporeal circulation, a system was made of polyvinyl chloride tubing. Hemolysis was expressed as the rate of accumulation of free hemoglobin in the plasma determined colorphotometrically. Human blood was recirculated with a single pump in the system. Several pumps—the Sigmamotor, the Leonards occlusive roller, the Hercik nonocclusive roller, the MacNeill-Collins and three modifications of the Dale-Schuster were tested under similar conditions. Some pumps in general clinical use produced as much as 19 mg/100 ml of free hemoglobin/hr. A modified Dale-Schuster pump and a Clowes membrane oxygenator also were tested in the system recirculating 800 ml of blood. The hourly production of free hemoglobin was only 3.2 mg/100 ml/hr. The concentration of free hemoglobin was kept constant by exchange transfusion with a modified Dale-Schuster pump and Clowes membrane oxygenator in the system. A formula used to calculate the required amount of blood to be exchanged is presented. Submitted on May 11, 1959