Fentanyl uptake by the scimed membrane oxygenator

Area of Science:

• Anesthesiology
• Pharmacology
• Biomaterials Science

Background:

• Cardiopulmonary bypass (CPB) circuits with membrane oxygenators can cause unexpected drops in circulating fentanyl levels.
• The Scimed (2A-800) membrane oxygenator has been identified as a potential site for fentanyl binding.
• Understanding fentanyl-membrane interactions is crucial for accurate drug dosing during CPB.

Purpose of the Study:

• To investigate the Scimed (2A-800) membrane oxygenator as a site for fentanyl binding.
• To identify the specific components within the oxygenator responsible for fentanyl uptake.
• To characterize the kinetics and influencing factors of fentanyl binding to the membrane.

Main Methods:

• Utilized an assembled CPB circuit for initial experiments.
• Dissected oxygenator components to analyze fentanyl binding sites.
• Employed isolated membrane samples with tritiated fentanyl in both static and moving prime solutions.
• Varied fentanyl concentrations and solution movement to assess binding rates.

Main Results:

• Silicone-based membrane sheets within the oxygenator are the primary site of fentanyl binding.
• The silicone-containing wrapper contributes 1-2% to fentanyl binding.
• Fentanyl binding is rapid, reaching saturation (130 ng/cm²) within 15-30 minutes under suprasaturated conditions.
• Solution movement significantly accelerates fentanyl binding rates, validating the use of isolated membrane models.
• Lower fentanyl concentrations (10-20 ng/mL) slow the binding rate, with complete uptake within three hours.

Conclusions:

• The Scimed membrane oxygenator, particularly its silicone components, significantly binds fentanyl during CPB.
• The rate of fentanyl binding is influenced by membrane surface area, solution movement, and fentanyl concentration.
• Further research into factors like temperature, pH, protein content, and co-administered drugs is necessary before applying these findings to clinical practice.