Turbulence in surgical suction heads as detected by MRI

Abstract

Background: Blood loss is common during surgical procedures, especially in open cardiac surgery. Allogenic blood transfusion is associated with increased morbidity and mortality. Blood conservation programs in cardiac surgery recommend re-transfusion of shed blood directly or after processing, as this decreases transfusion rates of allogenic blood. But aspiration of blood from the wound area is often associated with increased hemolysis, due to flow induced forces, mainly through development of turbulence.

Methods: We evaluated magnetic resonance imaging (MRI) as a qualitative tool for detection of turbulence. MRI is sensitive to flow; this study uses velocity-compensated T1-weighted 3D MRI for turbulence detection in four geometrically different cardiotomy suction heads under comparable flow conditions (0-1250 mL/min).

Results: Our standard control suction head Model A showed pronounced signs of turbulence at all flow rates measured, while turbulence was only detectable in our modified Models 1-3 at higher flow rates (Models 1 and 3) or not at all (Model 2).

Conclusions: The comparison of flow performance of surgical suction heads with different geometries via acceleration-sensitized 3D MRI revealed significant differences in turbulence development between our standard control Model A and the modified alternatives (Models 1-3). As flow conditions during measurement have been comparable, the specific geometry of the respective suction heads must have been the main factor responsible. The underlying mechanisms and causative factors can only be speculated about, but as other investigations have shown, hemolytic activity is positively associated with degree of turbulence. The turbulence data measured in this study correlate with data from other investigations about hemolysis induced by surgical suction heads. The experimental MRI technique used showed added value for further elucidating the underlying physical phenomena causing blood damage due to non-physiological flow.

Keywords: Blood damage; Hemolysis; Magnetic Resonance Imaging; Suction; Turbulence.

Figure 1

Photographs and computer assisted design (CAD) models and drawings of suction heads under investigation (adapted from [59]).

Figure 2

Experimental setup including custom-made water reservoir for MRI measurements.

Figure 3

T1-weighted images of surgical suction heads in water. Increasing flow rates introduce signal void indicating areas of turbulent flow.

Figure 4

MRI signal loss in surgical suction heads calculated from images in Figure 3 with corresponding Reynolds number (Re).

Figure 5

Histograms of relative signal loss images from Figure 4. Distinct yellow bars relate to the occurrence of signal loss.

Figure 6

Noise-maps of suction heads studied (adapted from [59]).