PMN elastase in extracorporeal circulation procedures

: Proteolytic enzymes released by polymorphonuclear neutrophils are assumed to be important mediators in the development of shock-induced and sepsis-induced organ failure, especially of ARDS. The most remarkable of these enzymes is elastase because of its relatively high intracellular concentration and low substrate specificity. The release of elastase can be monitored by measuring the plasma concentration of elastase-proteinase inhibitor complex. In this study, the elastase concentration pointed towards side effects of methods of extracorporeal circulation. The elastase concentration rose more than sixfold in 20 patients during membrane oxygenation (mean time 124 min) and 15 patients during bubble oxygenation (mean time 77 min). We found that the elastase concentration was affected by the kind of foreign material surface, the time of perfusion and the perfusion volume. The comparison of in-vitro and in-vivo circulation underlines the importance of the terminal capillary bed (in the lung) and of a pre-existent activation of leukocytes, since elastase levels rose only insignificantly during in-vitro recirculation. These results confirm that extracorporeal circulation seems to be able to induce harmful disturbances of the ARDS type. This fact should be taken into consideration when using methods of extracorporeal gas exchange.