Cannulae and cell saver design: do they make a difference?

Abstract

In the evolution of cardiopulmonary bypass (CPB), it is becoming increasing obvious that minimizing microembolization is critical in protecting the brain. Every component of the CPB circuit and ancillary apparatus must be evaluated and, if necessary, re-engineered with the reduction of microemboli a major focus. Cardiotomy suction has been identified as a major source of lipid microemboli. However, is the alternative blood treatment apparatus, the cell saver, capable of reducing the lipid embolic load and are all cell savers equally efficient? In the event that microemboli do make it to the aorta, is it possible to divert them away from the brain to more robust vascular beds through clever design of the aortic cannula? Is the venous cannula a source of microgaseous emboli? The answer is yes to both questions. Emboli can be directed away from the brain by the positioning and design of the aortic cannula and the venous cannulae may be a source of gaseous microemboli delivered to the oxygenator by the venous line but careful practice will prevent this type of embolic formation.

Figure 1.

Lipid microemboli from human autopsy after CPB. High-magnification photomicrograph of microlipid emboli from patients who died after CPB. Original magnification, ×50. A and B, Microemboli at bifurcation points (arrows) in 100-mm-thick celloidin sections with AP microvascular staining. C, A microembolus stained black with osmium indicates that it is lipid. Swollen astrocytic end-feet (white arrow) and vacuolization in the adjacent neurophil (black arrow) indicate tissue injury. This is a paraffin-embedded, 5-mm-thick osmium-fixed section (courtesy Professors D. Moody and D. Stump, Wake Forest University School of Medicine, Winston-Salem, NC).

Figure 2.

Mean small capillary and arteriolar dilation (SCAD) density ± SE by filter or processed salvaged blood (cell saver) group. Closed bars represent arterial filter group; open bars represent cell saver group. p < .05 for cell saver vs. arterial filter groups; p > .05 for all other intergroup comparisons. (B, Bentley Duraflow II AF-1025D; PL, Pall Leukoguard AL; PS, Pall Stat Prime; M, Medtronic Autolog Cell Saver; LF, Pall RCXL 1 leukocyte removal filter; F, Fresenius Continuous Autotransfusion System) (from Kincaid EH, Jones TJ, Stump DA, et al. Processing scavenged blood with a cell saver reduces cerebral lipid microembolization. Ann Thorac Surg. 2000;70:1296–300, with permission).

Figure 3.

EDAC transducer positioned on simulated left carotid.