In vitro variability in fentanyl absorption by different membrane oxygenators.

The membrane oxygenator has replaced the bubble oxygenator in a wide variety of clinical settings. The membrane oxygenators now manufactured can be grouped into three categories based on composition and design: (1) silicone with a true membrane structure; (2) polypropylene with a microporous sheet; and (3) polypropylene with a microtubular structure. The capacity for fentanyl uptake by membrane oxygenators from these three categories was studied in vitro. Representative membrane samples were incubated in solutions containing tritiated fentanyl in Normosol-R (Abbott, North Chicago, IL) with pH adjusted to 7.4 at 37 degrees C. Fentanyl analysis was performed using liquid scintillation and radioimmunoassay techniques. The uptake of fentanyl at various concentrations (340 to 10 ng/mL) was studied. The SciMed (type 1; SciMed, Minneapolis, MN) membrane showed the greatest capacity for fentanyl uptake at all concentrations. The SciMed oxygenator was capable of binding 130 ng fentanyl/cm2 membrane. When presented with a smaller concentration (less than or equal to 20 ng/mL) of fentanyl, the membrane was able to extract all available fentanyl from solution. All of the microporous polypropylene oxygenators (types 2 and 3) absorbed significantly less fentanyl than did the SciMed brand. When exposed to 10 or 20 ng/mL, the Shiley and Omnis brands (type 2) absorbed 0.1 and 0.4 ng/cm2, respectively. Using the higher fentanyl concentrations (greater than or equal to 200 ng/mL) uptake by the Omnis membrane was 11 ng/cm2 compared with only 2 ng/cm2 by the Shiley. The Bentley BCM 7 and Terumo Capiox II 08 microtubular microporous membranes (type 3) did not show absorption of fentanyl using isolated or intact membrane models.(ABSTRACT TRUNCATED AT 250 WORDS)