In vitro uptake and elimination of isoflurane by different membrane oxygenators

Objective: This study was designed to investigate the effect of membrane oxygenator design and composition on the uptake and elimination of isoflurane. Design: Prospective, in vitro laboratory study. Setting: Bioengineering laboratory. Participants: Three types of membrane oxygenator were tested: the SM-35 (polydimethylsiloxane in sheet form), the CML (polypropylene in sheet form), and the SAFE II (polypropylene in hollow-fiber form). The oxygenators were incorporated into a standard cardiopulmonary bypass circuit. Interventions: Isoflurane was added to the oxygenator input gas and measured in exhaust gas and in (bovine) blood leaving the oxygenator at 1, 2, 3, 5, 7, 10, 15, and 20 minutes. The isoflurane vaporizer was then turned off, and samples were obtained at the same time intervals. The experiment was performed at 28 degrees C and 37 degrees C. Measurements and Main Results: Uptake and elimination of isoflurane were slower via the SM-35 compared with the CML and the SAFE II (p < 0.01). Conclusions: If isoflurane is administered during cardiopulmonary bypass, knowledge of the influence of oxygenator membrane composition on its pharmacokinetics is essential if patient awareness and unexpected cardiovascular depression are to be avoided. Copyright (C) 1996 by W.B. Saunders Company.