Shear Frequency Dependent Hemolysis during Cardiotomy Suction as a Necessary Quality Factor to Maintain Blood Integrity—An In Vitro Trial on Human Blood

Background: Intraoperative loss of up to 9% of circulating blood volume is described in standard cardiac surgery. Even if “cellsaving” enables retransfusions, foreign blood transfusions are increased with extracorporeal circulation (ECC). In the long-term immunological complications could be consequences after initially safe transfusions. It is known that forced suctioning leads to misactivation of blood cells and hemolysis. The influence of different frequencies of audible noise as negative repercussion of turbulence, especially during forced suction, is unknown. The aim of this study was to determine the potential of acoustic and mechanical vibrations (AMVs) to damage whole blood, to establish the relationship between shear forces and hemolysis.

Methods: 3D-printed shear force generators were developed to test the influence of AMV on blood integrity (−5 dB to −25 dB, 5 dB steps; 250 Hz to 1.5 kHz, 26 steps). In the shear generator, 1 mL whole blood from the same donor was subjected to different AMVs for 10 minutes. After exposure, the degree of hemolysis was determined photometrically.

Results: At five applied amplitudes, significantly increased hemolysis is observed at 250 Hz and 7.5 kHz. Acoustic vibrations cause more damage to erythrocytes compared with mechanical vibrations. Hemolysis increases with increasing amplitude (250 Hz, −5 dB: fHb. 3 µmol/L; −25 dB: fHb 12.8 µmol/L).

Conclusion: The levels for AMVs show similar patterns at all tested amplitudes with peak values at 250 Hz and 7,500 Hz. It may be thus possible to determine a safe frequency window in which the cells are less affected. The particularly damaging frequency ranges can be avoided by adapting the suction geometries and suitable sensor technology on extracorporeal circulation pump systems and cell savers. Among other factors, this is a hitherto unnoticed way of enabling direct retransfusions without preparation by cellsaver (loss of plasma and platelets).

Publication History

Article published online:
11 February 2025