Effect of intravenous fluid warming devices on intraoperative core temperature during maintenance fluid therapy: a prospective randomized controlled trial

Background: We investigated the effects of intravenous fluid warmers on intraoperative core temperatures at low flow rates during the maintenance fluid therapy. Methods: We conducted a prospective, non-blinded, randomized controlled trial in 99 patients, scheduled for elective spinal fusion surgery with more than 3 hours of general anesthesia. They were randomly distributed into groups using Mega Acer Kit (group M; n=30), Ranger (group R; n=32), or ThermoSens (group T; n=32). The infused flow rate of the fluid was determined as one-third of the preoperative fluid deficit (4-2-1 rules) during fasting times, and the third space loss during surgery (2 mL/kg), per hour. The primary outcome was intraoperative final and lowest esophageal temperature (T eso _ Final, lowest T eso ). Results: T eso _Final, lowest T eso , and intraoperative T eso were not significantly different between groups (p=0.512, and p=0.393, p=0.066, respectively). However, the temperature change from baseline T eso to T eso _Final was significantly different between the groups (p=0.044), which of group M were significantly lower than group T (p=0.033). After adjustment with baseline T eso , the differences of least squares means showed the significant differences between groups M and T at 2.5 hours (p=0.020) and 3 hours (p=0.006). Conclusions: The Mega Acer Kit, Ranger, and ThermoSens have a similar effect on intraoperative core temperatures with the low flow rates, but The Mega Acer Kit is more effective at controlling core temperature than the ThermoSens if the fluid infusion time is over 2.5 hours.