Pre-Operative, Intra-Operative, and Post-Operative Warming

Maintaining normothermia  (normal body temperature) throughout the perioperative period is a critical component of patient safety and recovery. Perioperative hypothermia, defined as a core body temperature below 36°C, is a frequent and preventable complication associated with anesthesia and surgical procedures. Hypothermia can result in a range of adverse outcomes, including increased risk of surgical site infections, coagulopathy, prolonged hospitalization, and delayed wound healing (1). As a result, perioperative teams may opt to use patient warming strategies, which can be implemented throughout the pre-operative, intra-operative, and post-operative settings.

Pre-operative warming is a proven method for reducing the risk of redistribution hypothermia, a condition that typically develops within the first 30 to 60 minutes following induction of general anesthesia. This occurs due to rapid vasodilation, which causes heat to shift from the body’s core to its peripheral tissues. By increasing peripheral temperatures before anesthesia is administered, prewarming minimizes the core-to-periphery temperature gradient, thereby reducing the initial drop in core body temperature. Techniques such as forced-air warming are commonly used and have demonstrated effectiveness in this setting. Even brief periods of pre-operative warming (ranging from 10 to 15 minutes) can significantly improve intra-operative thermal stability (2).

Intra-operative warming strategies counteract the thermal challenges posed by anesthetic agents, surgical exposure, and fluid administration. Active warming devices, such as convective warming blankets and circulating water garments, are commonly used and supported by guidelines. The use of warmed intravenous fluids and irrigation solutions is also important, especially in surgeries involving large fluid shifts or open cavities. These interventions are particularly important for elderly patients and those undergoing longer procedures, as thermoregulatory mechanisms become less effective with age and duration of exposure (3). Studies have demonstrated that maintaining intra-operative normothermia reduces perioperative blood loss, shortens recovery times, and decreases wound-related complications. Continuous intra-operative core temperature monitoring is essential for guiding and evaluating the adequacy of warming interventions.

The post-operative phase is crucial for reinforcing normothermia and supporting patient recovery, yet it is often overlooked in thermal management. Patients often enter the post-anesthesia care unit (PACU) with hypothermia due to the effects of anesthesia and environmental exposure during surgery. In this context, hypothermia is associated with an increased incidence of postoperative shivering, which can raise oxygen consumption and metabolic demand. This can potentially compromise patients with limited cardiopulmonary reserve. Furthermore, hypothermia has been shown to delay emergence from anesthesia and exacerbate subjective discomfort. When needed, active rewarming in the PACU should be prompt and carefully monitored to avoid overheating or thermal injury. Patients who receive effective pre-operative and intra-operative warming are significantly less likely to experience post-operative hypothermia, which supports the concept of a bundled or continuous approach to temperature management throughout the surgical continuum (4).

Institutional implementation of perioperative warming protocols improves compliance and outcomes. Standardized care bundles that specify the initiation of warming in the preoperative holding area, its maintenance during surgery, and its continuation as needed in the recovery unit have demonstrated reductions in hypothermia rates and associated complications. Despite this, variability in clinical practice persists. Surveys across multiple health systems have identified disparities in temperature monitoring frequency, warming equipment availability, and staff adherence to established protocols (3). Addressing these disparities requires ongoing education, audit-feedback mechanisms, and investment in appropriate technologies.

References

1. Wang J, Fang P, Sun G, Li M. Effect of active forced air warming during the first hour after anesthesia induction and intraoperation avoids hypothermia in elderly patients. BMC Anesthesiol. 2022;22(1):40. Published 2022 Feb 7. doi:10.1186/s12871-022-01577-w
2. Shim JW, Kwon H, Moon HW, Chae MS. Clinical Efficacy of 10 Min of Active Prewarming for Preserving Patient Body Temperature during Percutaneous Nephrolithotomy: A Prospective Randomized Controlled Trial. J Clin Med. 2024;13(7):1843. Published 2024 Mar 22. doi:10.3390/jcm13071843
3. Carella M, Beck F, Piette N, Lecoq JP, Bonhomme VL. Effect of preoperative warming on intraoperative hypothermia and postoperative functional recovery in total hip arthroplasty: a randomized clinical trial. Minerva Anestesiol. 2024;90(1-2):41-50. doi:10.23736/S0375-9393.23.17555-9
4. Oh YJ, Jun IJ. The Effect of Brief Warming during Induction of General Anesthesia and Warmed Intravenous Fluid on Intraoperative Hypothermia in Patients Undergoing Urologic Surgery. Medicina (Kaunas). 2024;60(5):747. Published 2024 Apr 30. doi:10.3390/medicina60050747