Original Article

An Under-Occluded Roller Pump is Less Hemolytic Than a Centrifugal Pump

Program in Extracorporeal Circulation Technology, Clinical Services Department, College of Health Professions, Medical University of South Carolina, Charleston, South Carolina

^* Address correspondence to: Deborah J. Rawn MUSC/ECT 101 Doughty Street, 2nd Floor Charleston, SC 29401

Abstract

The purpose of this study is to measure and compare the hemolysis produced by roller pumps with varied occlusion settings and a centrifugal pump. The null hypothesis is that there is no difference in the Index of Hemolysis (IH=gm Hb/100 L pumped) produced by a roller pump (RP) at four different occlusion settings and a centrifugal pump (CP) at the same blood flow rate (4.5 L/min) and afterload (250 mmHg, ±10 mmHg) over three hours.

Five identical closed-loop circuits were assembled and primed with saline. The pumps were then calibrated and occlusions were set. In three circuits, the occlusion for the RP was opened at 5 RPMs to support 150, 225, or 300 mmHg (±10 mmHg) against a clamped line. In one circuit, a RP was adjusted to a barely non-occlusive setting (1 cm drop/30 inch gradient). The fifth circuit employed a CP. Prior to testing, the saline in each circuit was replaced with one liter of fresh bovine blood (Hct=22±2%). The IH for each treatment was compared in six trials yielding a statistical power> 0.80.

Analysis of variance with multiple comparison (p≤0.05) demonstrated that compared to the barely non-occlusive setting, the IH in the centrifugal pump was not significantly greater. Under-occluded RP settings yielded IHs significantly less than the CP. It appears that opening the occlusion on a roller pump allows a lower IH compared to traditional RP occlusion setting or centrifugal pumping.