[Investigation of limulus test during and after cardiopulmonary bypass. Part II. Effect of washing of the bypass circuit].

Previously we reported the presence of Limulus positive substance (LPS) in blood and urine for several days following cardiopulmonary bypass (CPB), and foreign particles in the primining fluids. The purpose of this study was to evaluate the effect of washing of the CPB circuit on appearance of LPS and to define the nature of it. Semi-quantitative Limulus test was performed in patients using washed CPB circuit (n = 54) and without washing (n = 41). LPS in the blood were negative in all patients before CPB. LPSs in the priming fluids did not disappear after washing, however the amounts of it in the blood were significantly lower than those without washing. Especially at second postoperative day. Limulus test were positive in 10% of patients with washed CPB circuit and 60% of those without it (p less than 0.01), and all the urine samples of patients with washed CPB circuit were negative to Limulus test at 1st postoperative day. The number of foreign particles decreased in parallel with the smaller pore size of the filter. Since reactions of Pregell to ethylene oxide gas, ethylene chlorohydrin and ethylene glycol were negative, ethylene oxides did not seem to be the LPS. These results indicate the superiority of employment of washed CPB circuit with micropore filter. However, further exploration is still mandatory to elucidate the LPSs.