About Roller Pumps in On-Pump Cardiac Surgery: A Methodical In Vitro Test of Occlusion Adjustment of the Arterial Roller Pump to Minimize Hemolysis during Extracorporeal Circulation

Background: Every year, more than 98,000 cardiac surgical procedures are performed in German heart centers. Due to the complexity of the cases, increasing urgency rates, and the need for therapeutic anticoagulation cardiac surgery accounts for 15 to 20% of all perioperative allogeneic blood transfusions. The need for transfusion is closely related to the use of extracorporeal circulation (ECC). Shear forces especially in arterial roller pumps (RP) can lead to significant hemolysis. The head of the RP traps the blood in a tube and pushes it to the outlet. The recommended setting of the RPs causes the blood components to become tense, resulting in increased hemolysis. The purpose of these ongoing in vitro tests is to determine the most optimal and applicable method of adjusting the best of occlusion.

Methods: Two identical 3″ roller pump driven circuits were set up to simulate the conditions of a conventional ECC. Each model circulates 110 mL of human whole blood (anticoagulated with citrate, hematocrit set to 30%) for 120 minutes at a flow rate of 100 mL/min. The only difference between the two circuits is the setting of the roller heads (control group A: static occlusion; study group B: dynamic occlusion). To set the static occlusion, a clamped pump line filled with crystalloid must be set to a pressure of 150 mm Hg. The tension of the fixed rollers should allow a pressure drop of up to 10 mm Hg per minute. To set dynamic occlusion, a pressure of 300 mm Hg must be achieved with a continuous flow of 25 mL/min in the clamped tube. Compared with the baseline value of fHb, it is determined every 15 minutes. A different increase in fHb is to be expected due to the different occlusion settings.

Results: In this in vitro study, dynamic occlusion adjustment significantly reduced (to about one-third) the hemolysis caused by shear forces in the roller pumps. The changes in fHb are linear in the time window under consideration. Accordingly, the data were fitted linearly. The slope of the fitted linear function is decisive for the comparison between static and dynamic occlusion setting. According to current research, static occlusion is 30% steeper with a relative error of 5%.

Conclusion: Observed differences between the groups distinguish the effect of dynamic adjusted RPs to reduce hemolysis during extracorporeal circulation.

Publication History

Article published online:
11 February 2025