Maintaining Normothermia in the Perioperative Period

The National Institute for Clinical Excellence defines hypothermia as a core temperature less than 36° C (96.8°F) from one hour before anesthesia induction to 24 hours after entry into the postanesthesia care unit (PACU).¹ Maintaining normothermia during the perioperative period is an essential part of patient care and is a quality objective per the Centers for Medicare and Medicaid Services (CMS) merit-based incentive payment system,² yet, hypothermia remains a common occurrence, occurring in 50-70% of patients undergoing general anesthesia.³

How it Occurs

Administering anesthesia weakens the body’s innate ability to thermoregulate by impairing shivering and vasoconstriction.⁴ Induction of anesthesia causes a temperature decline of up to 1.6 °C.⁵^, ⁶ Hypothermia can result in negative surgical outcomes, including coagulopathies leading to bleeding, increased length of hospital stay, increased risk of infection, and poor wound healing.³^, ⁵^, ⁶

Maintaining Normothermia

Maintaining normothermia should be seen as a process that encompasses the entire perioperative experience, from arrival in the preoperative area to the PACU. Many actions are undertaken in the OR to maintain normothermia, (eg, forced air warming [FAW] blankets, IV fluids warmers, increasing the room temperature). Patient warming can be achieved using passive insulation or active warming devices (Table 1). Passive insulation devices do not require external heat sources (eg, warmed cotton blankets, hot water bottles), while active warming devices use external heat sources (eg, FAW units, heating blankets).

Table 1. Passive Versus Active Warming Devices

Prewarming

Studies show that actively prewarming patients 30 minutes before they enter the OR is the best way to maintain normothermia. Active prewarming may involve the use of an FAW gown system and booties with patient-adjustable temperature control; this system can also be used in the OR and later in the PACU. Prewarming does not prevent a decrease in body temperature after induction of anesthesia, but it does allow patients to tolerate such a temperature drop without becoming hypothermic.⁵^, ⁷

Active Warming

If active warming devices are used, it is essential that they are used safely, following the manufacturer instructions for use. These devices can pose a risk of electrical fire if the unit or electrical cord is damaged. There also is a risk of thermal injury if the hose is not used with an appropriate gown or is placed directly over the patient’s skin. To decrease the risk of entanglement, supervision is necessary when these devices are used for children. In addition, children should not be allowed to adjust settings, as there is a potential for thermal injury if the temperature is too high.  It is crucial to make sure these devices are not damaged, become familiar with the manufacturer instructions and recommendations, and monitor the patient’s temperature while these devices are in use.

Outcomes

It is worth noting how a seemingly small action, such as using FAW devices prior to surgery, can have a major effect on a patient’s surgical outcomes. Although it may seem like one more step in what could be a complex perioperative process, preventing hypothermia not only provides comfort to patients but meets the quality improvement measures set by the CMS.

References

1. National Institute for Health and Care Excellence. Hypothermia: prevention and management in adults having surgery (CG65). Clinical Guideline 65. Published April 23, 2008. Accessed August 29, 2023.
2. Centers for Medicare and Medicaid Services. 2024 Quality Measures: Traditional MIPS. Quality Payment Plan. Published 2024. Accessed February 23, 2024.
3. Simegn GD, Bayable SD, Fetene MB. Prevention and management of perioperative hypothermia in adult elective surgical patients: A systematic review. Ann Med Surg (London). 2021;72:103059. doi:10.1016/j.amsu.2021.103059
4. Link T. Guidelines in Practice: Hypothermia Prevention. AORN 2020;111(6):653–666.
5. Mohan C, Madhusudhana R. Effects of pre-warming and co-warming in preventing intraoperative hypothermia. Cureus. 2023;15(2):e35132. doi:10.7759/cureus.35132
6. Sagiroglu G, Ozturk GA, Baysal A, Turan FN. Inadvertent hypothermia and associated risk factors. J Coll Phyicians Surg Pak. 2020;30(2):123-128.
7. Oh EJ, Han S, Lee S, et al. Forced-air prewarming prevents hypothermia during living donor liver transplantation: a randomized controlled trial. Sci Rep. 2023;13(1). doi:10.1038/s41598-022-23930-2

AORN Resources

AORN members can access:

• Guidelines in Practice: Hypothermia Prevention-AORN Journal
• A Nomogram for Predicting Unplanned Intraoperative Hypothermia in Patients With Colorectal Cancer Undergoing Laparoscopic Colorectal Procedures – AORN Journal
• The Effectiveness of Four Intervention Methods for Preventing Inadvertent Perioperative Hypothermia During Total Knee or Total Hip Arthroplasty – AORN Journal
• The Role of Perioperative Hypothermia in the Development of Surgical Site Infection: A Systematic Review – AORN Journal
• Perioperative Warming Methods Prevent Unintended Hypothermia – AORN Journal
• Perioperative Prewarming: Heat Transfer and Physiology- AORN Journal
• If your facility subscribes to AORN eGuidelines+: AORN Guidelines for Patient Temperature Management – AORN eGuidelines+