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The Guideline for Prevention of Unplanned Patient Hypothermia has been approved by the AORN Guidelines Advisory Board. It was presented as a proposed guideline for comments by members and others. The guideline is effective November 15, 2015. The recommendations in the guideline are intended to be achievable and represent what is believed to be an optimal level of practice. Policies and procedures will reflect variations in practice settings and/or clinical situations that determine the degree to which the guideline can be implemented. AORN recognizes the many diverse settings in which perioperative nurses practice; therefore, this guideline is adaptable to all areas where operative or other invasive procedures may be performed.


This document provides guidance for assessing patients for factors associated with unplanned intraoperative hypothermia, monitoring patient temperatures, preventing unplanned perioperative patient hypothermia, and developing policies and procedures and education for perioperative personnel related to maintaining patient normothermia.

Core body temperature is normally tightly regulated by the body, but this regulatory mechanism is altered by general, epidural, and other regional anesthetic agents and by environmental factors during the perioperative experience that can result in unintentional hypothermia.1-3  Unplanned patient hypothermia may contribute to patient complications (See Recommendation III).

General anesthesia inhibits tonic vasoconstriction of the peripheral vasculature, causing vasodilation and loss of core warming. During the first hour after induction of general anesthesia, the core temperature can decrease from 0.5° C to 1.5° C (0.9° F to 2.7° F).1,4-6  Epidural and spinal anesthesia cause vasoconstriction and shivering to a slightly lesser degree, depending on the level of the anesthetic block.1,4,6 

Environmental factors that contribute to unplanned intraoperative hypothermia include low perioperative room temperatures, less clothing, and other factors unique to surgery that promote excessive heat loss (eg, administration of room temperature IV and irrigation fluids, evaporation of skin-preparation solutions, air movement).1,6  These environmental factors contribute to heat loss through four types of mechanisms: radiant, conductive, evaporative, or convective.7-9 

The temperature value used to define hypothermia varies among sources, but it is frequently stated as lower than 35° C or 36° C (95° F or 96.8° F) and may be further defined as mild (32° C to 35° C [89.6° F to 95° F]), moderate (28° C to 32° C [82.4° F to 89.6° F]), or severe (< 28° C [< 82.4° F]).8  Hypothermia occurs during many types of surgical procedures.10,11 

In a descriptive study, Steelman et al12  identified prevention of hypothermia as one of the top 10 patient safety concerns for perioperative RNs. In this study, AORN members employed in ambulatory and hospital settings (N = 37,022) received an electronic survey. Of the 3,137 returned surveys that contained complete information, 966 respondents (30.8%) identified prevention of hypothermia as a high priority.

Professional guidelines authored by the Best Practice in General Surgery Committee, University of Toronto13 ; the American Society of PeriAnesthesia Nurses (ASPAN)14 ; the Enhanced Recovery After Surgery Society15-17 ; and the National Institute for Health and Clinical Excellence (NICE)18  also recognize the importance of preventing perioperative hypothermia. Hypothermia may cause multiple complications, such as adverse myocardial outcomes, altering the pharmacodynamics of anesthetics and other medications, thermal discomfort, increased length of stay in the postanesthesia care unit (PACU), and shivering.2 

The following topics are outside the scope of this guideline:

  • planned, intentional, or therapeutic hypothermia;

  • rewarming after an intentional or accidental hypothermic event;

  • pharmacological agents used for prevention of hypothermia (eg, amino acids, fructose, carbohydrates);

  • cost-benefit analyses of treatment methods;

  • treatment for shivering;

  • treatment for accidental or extreme hypothermia related to trauma or conditions outside of a health care facility; and

  • care and treatment for patients experiencing a malignant hyperthermia crisis. For guidance in treating malignant hyperthermia, readers should contact the Malignant Hyperthermia Association of the United States (MHAUS) Hotline at (800) 644-9737.

Evidence Review

A medical librarian conducted a systematic literature search of the Ovid MEDLINE® and EBSCO CINAHL® databases on August 23 and September 4, 2013, respectively, and limited results to meta-analyses, systematic reviews, randomized controlled and non-randomized trials and studies, reviews, and guidelines. The librarian also conducted a non-systematic search of Scopus® on September 13, 2013. All searches were limited to literature published in English between January 2007 and the search date. At the time of the initial search, the librarian also established weekly alerts on the topics included in the initial search. The librarian later added terms from subsequent supplementary searches to the alerts and presented relevant results to the lead author. On March 7, 2014, the librarian conducted supplementary searches and on February 2015, reconducted searches to identify articles that had been published since the original searches but that were not captured in the established alerts. The alerts were terminated in April 2015.

Broad search terms included perioperative period, perioperative nursing, normothermia; accidental, unplanned, inadvertent, unintentional, core, and redistribution hypothermia; shivering; operative surgical procedures; anesthesia; heat loss; heat distribution; body temperature regulation; thermal management; thermoregulatory response threshold; thermoregulatory vasoconstriction; and hypothermia. Terms related to rewarming included heat loss; preoperative, intraoperative, and comfort warming; warming technique; warming blanket; energy transfer and thermal pad; forced-air and convective warming; negative pressure rewarming; circulating water garment; cutaneous warming system; resistive heating; inspired gas humidification; intravenous infusing warming; warming irrigation; and brand names of warming devices. Temperature-monitoring terms included intraoperative monitoring; thermography; skin-surface temperature gradient; and types of temperature and thermometers (eg, skin, esophageal, tympanic, temporal artery, oral, axillary). Other search terms included intraoperative and perioperative complications; risk factors (eg, blood transfusion, obesity, diabetic neuropathies, pneumatic tourniquet); pressure ulcers; decubitus ulcers; and burns.

Inclusion criteria were research and non-research literature in English, complete publications, relevance to the key questions, and publication dates within the time restriction unless none were available.

Excluded were non-peer-reviewed publications; literature that examined shivering, traumatic hypothermia, intentional or therapeutic hypothermia, anesthesia techniques to manage hypothermia, malignant hyperthermia, and bundling of treatment or preventative measures. Low-quality evidence was excluded when higher quality evidence was available, and literature outside the time restriction was excluded when literature within the time restriction was available (Figure 1).

Figure 1.
Flow Diagram of Literature Search Results

Flow Diagram of Literature Search Results

Articles identified in the search were provided to the lead author and evidence reviewers for review and critical appraisal using the AORN Research or Non-Research Evidence Appraisal Tools as appropriate. The literature was independently evaluated and appraised according to the strength and quality of the evidence. Each article was then assigned an appraisal score. The appraisal score is noted in brackets after each reference, as applicable.

The evidence supporting each intervention and activity statement within a specific recommendation was summarized, and the AORN Evidence-Rating Model was used to rate the strength of the collective evidence. Factors considered in the review of the collective evidence were the quality of the evidence, the quantity of similar evidence on a given topic, the consistency of evidence supporting a recommendation, and the potential benefits and harms. The assigned evidence rating is noted in brackets after each intervention and activity statement.


Note: The evidence summary table is available at


Editor’s note: MEDLINE is a registered trademark of the US National Library of Medicine’s Medical Literature Analysis and Retrieval System, Bethesda, MD. CINAHL, Cumulative Index to Nursing and Allied Health Literature, is a registered trademark of EBSCO Industries, Birmingham, AL. Scopus is a registered trademark of Elsevier B.V., Amsterdam, The Netherlands.

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