Contaminating fat in pericardial suction blood: a clinical,technical and scientific challenge

Abstract

Stroke and diffuse brain damage after cardiac surgery are too common. It is important to find means to reduce the incidence in view of future competition to surgery from less invasive procedures. Stroke is fairly well defined in clinical terms and with several identified mechanisms. Diffuse brain damage is less well defined and more complex in nature. One suggested mechanism is from cerebral fat microembolization of retrieved pericardial suction blood (PSB). The present study aimed to describe a simple method to measure fat content of PSB, how experimental artefacts interfere with the results, and how the unstable character of a fat-blood suspension can be used to design a simple fat-separation system. The quantity of small amounts of fat can be amplified by centrifugation to the tapered tip of a standard glass pipette. The coefficient of variation after repeated experiments was 9.5%. PSB after coronary bypass surgery contained 0.22±0.04% fat of which 15±3% was bound to the surface of the plastic collecting bag. Experimentation requires standardized routines. Static incubation, blood-fat mixing routines, and transfer steps of blood samples between syringes induce substantial artefacts from spontaneous density separation and surface-adhesion of fat. Soya oil is a common reference substance replacing human fat in technical laboratory science, but is associated with artefacts of its own. These artefacts cause problems during experimentation but the oil is a good resource in the design of a simple fat-separation system