Analysis of microembolic particles originating in extracorporeal circuits

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Abstract
Silicone tubing is utilised increasingly in extracorporeal circulation (ECC), particularly for prolonged bypass in cases of left ventricular failure following open heart surgery. We compared the spectrum of particle formation in the EC circuit, due to roller pump damage, resulting from wear of silicone tubing with that of polyvinyl chloride (PVC) tubing. The EC circuit was primed with plasmalyte solution for pump runs of up to 24 hours. Samples of the perfusate were taken from either system at prefixed times. Number and size of the particles were determined by means of a Coulter counter, while their chemical composition was analysed by X-ray dispersion (EDXA). The tubing was examined by scanning electron microscopy. When using PVC tubing, the amount of particles of all sizes rose above acceptable standards shortly after activating the roller pump. Following this early upsurge, the number of particles continued to increase for the remainder of the pump run, albeit at a more moderate rate. The silicone tubing continuously generated a marked quantity of particular matter at a steadily increasing rate. Electron microscopic examination of the silicone tubing revealed multiple particles emanating from the inner surface of the tube. The results suggest that filtration of the initial priming fluid may be advisable before connecting the patient to an EC circuit using PVC tubing. The multitude of particles liberated by the silicone tubing implies that its usage in ECC should be curtailed. Utilisation of noncrushing head pumps is recommended in ECC.