Comparative spallation performance of silicone versus Tygon extracorporeal circulation tubing

OBJECTIVES Reports ranged from mixed to marginal tubing wear and spallation effects as a complication of roller pumps in cardiopulmonary bypass (CPB). Because the rollers constantly compress part of the tubing, we sought to determine whether circuit materials behave differently under a 3-h simulation of CPB. METHODS Two different tubing materials (silicone and Tygon) were tested with a customized experimental circuit, designed to allow in vitro simulation of CPB with priming volumes, pressures, revolutions per minute and temperatures equivalent to the clinical scenario. Samples were analysed with optical and field-emission scanning electron microscopy. We collected 200-ml fluid samples at 4 different times: before starting the CPB (T0), when the predicted revolutions per minute corresponded to about 2 min of CPB (T1), at 90 min (T2) and at 180 min (T3). At the end of CPB, we harvested 2 samples of tubing. Lastly, optical investigations and field-emission scanning electron microscopy observations were used for qualitative and quantitative analysis of circulating fragments. RESULTS T2 and T3 fluid samples showed more particles than T1 samples. Significant differences in terms of particle numbers were detected: silicone tubing released more fragments per millilitre than Tygon tubing, with both materials releasing particles from 5 to 500 µm. Silicone tubing was associated with a time-dependent increase in small particles released (P = 0.04), whereas this did not apply to large particles or to Tygon tubing. Yet, bootstrap estimates suggested that silicone tubing was associated with the release of more small particles whereas Tygon tubing released more large particles (both P < 0.01). Unlike silicone, Tygon samples taken from the portion of the circuit not subjected to the action of the roller pump did not show any erosion on their surfaces. Samples of both materials taken from the portion subjected to the compression of the roller pump showed signs of significant deterioration. CONCLUSIONS Silicone showed a worse spallation performance than Tygon, thus appearing less safe for more complex surgery of prolonged duration or for patients with a prior cerebral ischaemic event. Additional risk and cost-effectiveness comparisons to determine the potential benefits of one type of tubing material over the other are warranted to further expand our findings.

Spallation performance of extracorporeal membrane oxygenation tubing

During the prolonged roller pump use of extracorporeal membrane oxygenation (ECMO), tubing wear generates spallation. The spallation performance of Tygon® S-65-HL was measured and compared with a potential new ECMO tubing, LVA (Portex 800-500-575). Spallation was measured by on-line laser diode particle counting (HIAC) during simulated ECMO. The effects of differing levels of occlusion and pump speed were examined, as was the effect of spallation over time. The spallation produced by Tygon S-65-HL was less than that seen with LVA during 24 h of simulated ECMO ( p < 0.001), and after 72 h had fallen almost to zero. Spallation with Tygon tubing increases with increasing pump speed and decreases over time. There appears to be only a weak correlation with occlusion, which is surprising. The spallation performance of Tygon S-65-HL was variable and under some conditions exceeded that of LVA. Overall, however, Tygon S-65-HL produced less spallation than LVA. Therefore, LVA cannot be recommended for clinical ECMO use.

Simple validation for the hepatic venous cannula implanted chronically in conscious rats

A method for the detection of vena caval contamination in blood taken from hepatic venous cannulas in conscious rats was described. The procedures included 1) bolus injection of tritiated water (50 microCi) through a cannula into the abdominal inferior vena cava and 2) continuous blood sampling (less than 0.2 ml) from the hepatic venous cannula for 2 min into a 180-cm piece of Tygon tubing, starting concurrently with tracer injection. The washout of tritium was determined from samples in 15-cm sections of Tygon tubing. Because circulation from the inferior vena cava to the hepatic vein is interceded by the systemic circulation, the washout of tritium from a valid hepatic venous cannula should resemble the pattern determined elsewhere in the systemic circulation. In the current study, the reference systemic washout was determined in the superior vena cava of a group of rats similarly injected with tritiated water in the inferior vena cava. The maximum of tritium washout derived from a valid hepatic venous cannula should fall in the range encompassed by one standard deviation of the mean of the maximum of the reference (1,400 to 1,930 cpm/sample). The maximum of the washout pattern derived from the invalid cannula, which lay adjacent to the site of injection, was expected to exceed this range. On the basis of these criteria, hepatic blood flow (HBF) was determined by sulfbromophthalein (BSP) extraction in groups of rats with valid and invalid cannulas. HBF in rats with valid hepatic venous cannulas was 2.58 +/- 0.15 in the conscious state and 2.76 +/- 0.26 ml.min-1.g wet wt-1 in the ketamine-anesthetized state.(ABSTRACT TRUNCATED AT 250 WORDS)