Fluid warming with parylene-coated enFlow cartridge: Bench and pilot animal study of aluminum extraction due to prolonged use

Abstract

Objectives: Intravenous fluid warming devices with surface heating systems transfer heat using aluminum blocks, which if uncoated elute toxic levels of aluminum into the infusate. This study examined extractable aluminum detected from prolonged use of the updated version of the enFlow® cartridge, which uses a parylene-coated aluminum heating block. Methods: In dynamic bench tests, we measured the concentration of aluminum that leached into three solutions (Sterofundin ISO, Plasma-Lyte 148, and whole blood) that were continuously pumped (0.2 and 5.5 mL min−1) and warmed to 40°C by the enFlow cartridge (parylene-coated) for 5 h. Prolonged quasi-static bench tests measured aluminum concentration in 16 solutions which were gently rocked within the enFlow cartridge (parylene-coated) for 72 h at 40°C. Aluminum concentrations were measured using inductively coupled mass spectroscopy and matrix blank corrected. Measured aluminum concentrations were compared to a Tolerable Exposure limit to calculate Margins of Safety based on the US Food and Drug Administration maximum recommended concentration in parenteral fluids (25 μg L−1). A parallel pilot in vivo animal study was performed using mice injected with fluids warmed for 72 h by the enFlow cartridge (parylene-coated). Results: The enFlow cartridge (parylene-coated) demonstrated low toxicological risks in all tests. Sterofundin ISO resulted in the highest aluminum concentration after simulated prolonged use of the enFlow cartridge (parylene-coated) (3.11 μg device−1), which represents a 99.2% decrease from the enFlow cartridge (uncoated) and Margin of Safety of 1.7. Dynamic tests at two different flow rates with three challenge solutions resulted in concentrations less than the method detection limits (20.6 or 41.2 μg L−1) of the analysis method. The animals in the in vivo study showed no evidence of toxicity. Conclusion: Observed toxicological risk levels associated with the enFlow cartridge (parylene-coated) intravenous fluid warmer were below those set by the Food and Drug Administration and suggest that the use of enFlow cartridge (parylene-coated) is safe with a variety of intravenous solution types and in different therapeutic scenarios.