Authors: Chauhan et al.
Pediatric Anesthesia, first published April 16, 2026
Key Points
Intraoperative hypothermia remains common in neonates undergoing abdominal surgery, even when standard warming measures are used.
This randomized controlled trial compared low-flow anesthesia at 1 L/min with routine-flow anesthesia at 2 L/min.
Low-flow anesthesia significantly reduced the incidence of intraoperative hypothermia.
Neonates in the low-flow group had a smaller drop in core temperature, a higher minimum core temperature, and less surgical time spent below 36°C.
Other clinical outcomes, including extubation time, inotrope use, and hypoxia, were similar between groups.
Summary
This randomized controlled trial evaluated whether low fresh gas flow anesthesia could reduce intraoperative hypothermia in neonates undergoing abdominal surgery. Neonates are especially vulnerable to heat loss because of their small body size, limited thermoregulatory reserve, large surface area relative to weight, and exposure during major surgery. Even with standard warming measures, intraoperative hypothermia remains frequent and may contribute to physiologic instability.
The investigators randomized 160 neonates scheduled for elective or emergency abdominal surgery into two groups. The low-flow group received fresh gas flow at 1 L/min, while the control group received routine fresh gas flow at 2 L/min. Core temperature was continuously monitored during surgery. The primary outcome was intraoperative hypothermia, defined as core temperature below 36°C.
The study found that hypothermia was common in both groups, but significantly less frequent with low-flow anesthesia. Intraoperative hypothermia occurred in 75% of neonates in the low-flow group compared with 90% in the routine-flow group. This suggests that reducing fresh gas flow can provide a clinically meaningful thermoprotective effect.
The low-flow group also had a smaller decrease in core temperature from baseline. Median temperature drop was 0.80°C in the low-flow group compared with 1.20°C in the control group. Minimum intraoperative core temperature was also higher in the low-flow group, with a median minimum temperature of 35.5°C compared with 35.0°C in the routine-flow group.
Another important finding was that neonates receiving low-flow anesthesia spent less time below the hypothermia threshold. The percentage of surgical time spent with core temperature below 36°C was 50.3% in the low-flow group compared with 65.6% in the control group. This matters because both the depth and duration of hypothermia can influence neonatal physiology.
The likely explanation is that low-flow anesthesia increases rebreathing of warmed and humidified gases, helping conserve heat and humidity within the breathing circuit. This may reduce respiratory heat loss, which is especially important in neonates undergoing abdominal surgery.
The study also evaluated several secondary outcomes, including extubation time, blood loss, transfusion requirements, inotrope use, hypoxia, and postoperative ventilation. Intraoperative blood loss was slightly higher in the low-flow group, but the authors noted that the clinical impact was minimal. Other outcomes, including extubation time, inotrope use, and hypoxia incidence, were comparable between groups.
The authors concluded that low-flow anesthesia at 1 L/min is a safe and effective approach for reducing both the incidence and duration of intraoperative hypothermia in neonates undergoing abdominal surgery.
What You Should Know
This study supports low-flow anesthesia as a simple, practical strategy to help reduce intraoperative hypothermia in neonatal abdominal surgery. It does not eliminate hypothermia, since 75% of neonates in the low-flow group still developed temperatures below 36°C, but it significantly reduced both the frequency and duration of hypothermia compared with routine fresh gas flow.
For anesthesia providers, the key takeaway is that fresh gas flow can be part of temperature management. Standard warming measures remain essential, but low-flow anesthesia may add an additional protective effect by conserving heat and humidity.
The results are especially relevant for neonatal anesthesia because even modest temperature differences can matter in this population. Avoiding deeper and more prolonged hypothermia may help support physiologic stability during high-risk abdominal procedures.
Overall, the study suggests that low-flow anesthesia at 1 L/min can be safely incorporated into neonatal abdominal surgery care when appropriate monitoring and equipment are available.
Thank you to Pediatric Anesthesia for allowing us to summarize and share this article.