Potential Deleterious Interactions between Certain Chemical Compounds and a Thermoplastic Polyurethane Heat Exchanger...

Extracorporeal membrane oxygenation (ECMO) has become a powerful tool in the race to reverse failure to rescue events. Rapid implementation set the stage for the advent of the 30-day wet-priming storage as a standard practice. A recent alert regarding methylene blue (MB) unidirectional leach from patient's circulation through the oxygenator thermoplastic polyurethane (TPU) heat-exchanger membrane into the heater-cooler unit (HCU) water bath led us to believe that despite reassurances, the reverse process might be possible. To that effect, we performed a pilot in vitro experiment. We tested three adult ECMO sets (Adult Quadrox iD Oxygenator, Getinge, Doral, FL) probing for the transfer of MB between the water bath of a Sarns Dual Heater Cooler (Terumo Corporation, Ann Arbor, MI) and the circuit stored wet-primed for 30 days. In each test, 1,500 mg of reconstituted MB (HiMedia, Mumbai, India) were added to the 7.5 L of water in the HCU, circulated for 6 hours on which the water lines were disconnected and the setup was stored for 30 days. The primed circuit was tested for MB transfer at days 0, 13, and 30 by means of optical density (OD) at 665 nm and 26.5°C. Transference of MB from the HCU water bath into the ECMO circuit could be detected as early as day 13 after setup, achieving significant values by day 30 (median OD .019 (.014-.021). Expected OD if no diffusion present: 0. The complete separation of water interfaces between the patient's circuit and the HCU water bath may prove to be more dogma than fact when certain chemical substances are used in conjunction with TPU membrane oxygenators. Whether the transfer of substances is due to chemical processes or molecular weight needs further evaluation. Meanwhile, the use of chemicals for the cleaning of the HCU should be mindful of potential noxious effects.