Original Article

Blood Surfaces in the Extra Corporeal Circuit: A Scanning Electron Microscopic Study

Department of Surgery, Milton S. Hershey Medical Center, The Pennsylvania State University, Hershey, Pennsylvania 17033

Abstract

Despite advances in cardiovascular surgery and the use of new equipment for extracorporeal circulation (ECC), the goal of indefinitely safe ECC is not a reality yet. One of the limiting factors is trauma to the blood as it traverses the extracorporeal circuit. Of the factors that have been implicated as sources of trauma, obstructions or disturbances to flow and surface roughness are the two upon which this study is focused.

The method used was scanning electron microscopy because of the ability to visualize the microtopography of a typical ECC with great depth of field and high magnification. Unused components were examined and included: cannulae, tubing, connectors, bubble oxygenator, and microemboli filter. Only components from the major system (ie., excluding cardiotomy suction) were examined because most of the blood volume is contained within it and repeatedly comes in contact with its surfaces. Samples were examined at 50° tilt from the horizontal at magnifications ranging 100-2500X, with SOOX and 1000X considered most useful for visualization of the surfaces on a cellular level.

The results are a series of photomicrographs that show a variety of blood surfaces: some are smooth, and some are rough with ridges, crevices, and surface irregularities often larger than blood cells.

We conclude that rough surfaces do exist within the typical ECC system, and these surfaces are probably responsible, in part, for the trauma blood undergoes during ECC. Long term ECC will require a major improvement in the surface structure of many of the currently used components.