Pumpless extracorporeal lung assist - experience with the first 20 cases

Objective: Long-term extracorporeal lung assist is limited by a significant mechanical blood trauma resulting in bleeding and hemolysis. To reduce the drawbacks of extracorporeal lung assist a new technique has been developed , by which the driving force for the extracorporeal circuit derives from th e patients arterio-venous pressure gradient (pumpless extracorporeal lung a ssist). The aim of this clinical study was to test the feasibility and effe ctiveness of pumpless extracorporeal lung assist in patients with acute res piratory distress syndrome. Methods: Twenty patients (41 +/- 16 years) with acute respiratory distress syndrome of various causes and railing respirat or therapy were enrolled. The minimum hemodynamic requirements included a c ardiac output (CO) > 6 l/min and mean arterial pressure (MAP) > 70 mmHg. Pu mpless extracorporeal lung assist was established using a short circuit art erio-venous shunt including a special designed low-resistance membrane oxyg enator which was placed between the patients legs. Results: At the time of inclusion FiO(2) in all patients was 1.0 (paO(2) 45.9 +/- 7 mmHg, paCO(2) 5 8.9 +/- 17 mmHg). After 24 h of pumpless extracorporeal lung assist FiO(2) was reduced to 0.8 +/- 0.1. A significant improvement in oxygenation (paO(2 ) 84.1 +/- 21 mmHg, P < 0.05) and CO2 removal (paCO(2) 327 +/- 5 mmHg, P < 0.05) was notable. The mean extracorporeal Row was 2.6 +/- 0.6 l/min, which represented approximately 25% of the patients mean CO (10.8 +/- 2 l/min). The median assist time was 12 +/- 8 (1-32) days. Fifteen out of twenty pati ents were weaned off pumpless extracorporeal lung assist. Five out of twent y patients died while on the system (four sepsis, one ventricular fibrillat ion). Three out of twenty patients died after successful weaning on day 8, 30, and 50, respectively. Twelve out of twenty patients were discharged in a healthy state (overall survival 60%). Technical problems included thrombo sis of the venous cannula (n = 5), thrombus formation within the membrane o xygenator (n = 2), membrane oxygenator plasma leakage (n = 2), and membrane oxygenator contamination with Candida albicans. No bleeding complication w as observed. Conclusion: Pumpless extracorporeal lung assist is feasible an d effective in a selected group of patients with acute respiratory distress syndrome but preserved hemodynamic function. By eliminating the pump and r educing the tubing length blood trauma can be minimized. Being very simple the system entails fewer risks of technical complications and also facilita tes nursing care. (C) 2000 Elsevier Science B.V. All rights reserved.