Background Avoiding inadvertent hypothermia during surgery is important. Intravenous fluid warmers used intraoperatively are critical for maintaining euthermia. We sought to prospectively evaluate the performance of the parylene-coated enFlow™ intravenous fluid warmer in patients undergoing surgery. Methods This was a prospective two-center observational clinical trial performed in inpatient surgical services of two large academic hospital systems. After informed consent, patients were enrolled in the study. All patients were adults scheduled for a surgery that was expected to last for at least 1 h with the administration of at least one liter of fluid warmed prior to infusion. Patient temperature was recorded in the preoperative unit, at the induction of anesthesia, and then every 15 or 30 minutes until the end of surgery. Temperature monitoring continued in the recovery unit. The parylene-coated enFlow™ intravenous fluid warmer was used in addition to the usual patient warming techniques. The primary outcome was the average core temperature, and secondary analyses assessed individual temperature measurements, temperature measurements during specific time periods, and rate of hypothermic events. Results Fifty patients (29 male) with a mean age of 64 years were included in the analysis. The mean surgical time was 195 minutes and patients received an average of 1142 ml of fluids. Core temperature dropped by only 0.3°C approximately 60 minutes after induction and recovered back to the baseline level approximately 60 minutes later. There was no correlation between flow rate and measured core body temperature. Conclusions The parylene-coated enFlow intravenous fluid warmer was able to warm fluids at all flow rates during prolonged surgery. The results showed that enFlow performed as expected. Trial registration The trial was registered prior to patient enrollment at clinicaltrials.gov (NCT04709627, Principal investigator: Mikko Lax, MD, Date of registration: 14 January 2021.)

Objectives: Avoiding inadvertent hypothermia during surgery is important. Intravenous fluid warmers used intraoperatively are critical for maintaining euthermia. We sought to prospectively evaluate the performance of the parylene-coated enFlow™ intravenous fluid warmer in patients undergoing surgery. Methods: This was a prospective two-center observational clinical trial performed in inpatient surgical services of two large academic hospital systems. After written informed consent, patients were enrolled in the trial. All patients were adults scheduled for a surgery that was expected to last for at least 1 h with the administration of at least 1 L of fluid warmed prior to infusion. Patient temperature was recorded in the preoperative unit, at the induction of anesthesia, and then every 15 or 30 min until the end of surgery. Temperature monitoring continued in the recovery unit. The parylene-coated enFlow™ intravenous fluid warmer was used in addition to the usual patient warming techniques. The primary outcome was the average core temperature, and secondary analyses assessed individual temperature measurements, temperature measurements during specific time periods, and rate of hypothermic events. Results: In all, 50 patients (29 males) with a mean age of 64 years were included in the analysis. The mean surgical time was 195 min and patients received an average of 1142 mL of fluids. Core temperature dropped by only 0.3°C approximately 60 min after induction and recovered back to the baseline level approximately 60 min later. There was no correlation between flow rate and measured core body temperature. Conclusions: The parylene-coated enFlow intravenous fluid warmer was able to warm fluids at all flow rates during prolonged surgery. The results showed that enFlow performed as expected.