Unintended Hypothermia: What it is, Why it Happens
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The difference between a positive patient outcome and a complicated recovery can be a matter of degrees. The potentially adverse effects of even mild perioperative hypothermia, defined as a core body temperature of less than 36.0°C¹, are numerous and well-documented.
The major cause of intraoperative hypothermia is the redistribution of heat from the core to periphery due to anaesthetic-induced vasodilation.¹,² Known as redistribution temperature drop, this physiological reaction can cause unwarmed surgical patients to experience a core temperature drop of up to 1.6°C during the first hour of surgery.²
Hypothermia caused by redistribution is almost impossible to reverse quickly.³ Proactively monitoring and managing core body temperature can help you own the normothermic temperature zone (36.0°C - 37.5°C)⁴,⁵ and protect patients from unintended perioperative hypothermia.
Maintaining Normothermia Can Help Reduce Risk
The maintenance of a normal core body temperature, normothermia, is a crucial component of patient care. Core temperatures outside the normal range pose a risk in all patients undergoing surgery and have been associated with an increased risk of surgical complications, including:
Prevention Through Prewarming
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Redistribution is a major cause of unintended hypothermia. Prewarming—actively warming surgical patients before the induction of anaesthesia—is an effective way to help prevent it. Prewarming combined with intraoperative warming using forced-air warming blankets or gowns can reduce the temperature drop associated with redistribution and help maintain normothermia, which has been shown to reduce the rate of hypothermia-associated complications.15-16 The practice of prewarming is being recommended in clinical practice guidelines and quality improvement initiatives across the globe.17⁻21
The Importance of Continuous Core-Temperature Monitoring
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One challenge in the management of patient temperature lies in effective temperature measurement and monitoring. Although core temperature is a vital sign, it is frequently thought of as being less important than other vitals monitored during anaesthesia. Core temperature should be continuously monitored so that it can be effectively managed, helping to ensure patients stay within the normothermic temperature zone.
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References:
1. Sessler DI. Current concepts: Mild Perioperative Hypothermia. New Engl J Med. 1997; 336(24):1730-1737.
2. Matsukawa T, Sessler DI, Sessler AM, Schroeder M, Ozaki M, Kurz A, Cheng C. Heat flow and distribution during induction of general anesthesia. Anesth. 1995 Mar;82(3):662-73.
3. Sessler DI, Schroeder M, Merrifield B, Matsukawa T, Cheng C. Optimal duration and temperature of prewarming. Anesth. 1995 Mar 1;82(3):674-81.
4. Schroeck H, Lyden AK, Benedict WL, Ramachandran SK. Time Trends and Predictors of Abnormal Postoperative Body Temperature in Infants Transported to the Intensive Care Unit. Anesthesiology Research and Practice. 2016:7318137.
5. Hooper VD, Chard R, Clifford T, Fetzer S, Fossum S, Godden B, Martinez EA, Noble KA, O’Brien D, Odom-Forren J, Peterson C, Ross J, Wilson L. ASPAN’s Evidence-Based Clinical Practice Guideline for the Promotion of Perioperative Normothermia: Second Edition. J PeriAnesth Nurs, Vol 25, No 6 (Dec.), 2010: pp 346-365.
6. Kurz A, Sessler DI, et al. Perioperative Normothermia to Reduce the Incidence of Surgical-Wound Infection and Shorten Hospitalization. New Engl J Med. 1996;334:1209-1215.
7. Melling AC, Ali B, Scott EM, Leaper DJ. Effects of preoperative warming on the incidence of wound infection after a clean surgery: a randomized controlled trial. Lancet. 2001;358(9285):876-880.
8. Schmied H, Kurz A, et al. Mild hypothermia increases blood loss and transfusion requirements during total hip arthroplasty. The Lancet. 1996;347(8997):289-292.
9. Rajagopalan S, et al. The Effects of Mild Perioperative Hypothermia on Blood Loss and Transfusion Requirement. Anesth. 2008; 108:71-7.
10. Bush H Jr., Hydo J, Fischer E, et al. Hypothermia during elective abdominal aortic aneurysm repair: The high price of avoidable morbidity. J Vasc Surg. 1995;21(3): 392-402.
11. Frank SM, Fleisher LA, Breslow MJ, et al. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. JAMA. 1997;277:1127-1134.
12. Scott AV, Stonemetz JL, Wasey JO, Johnson DJ, Rivers RJ, Koch CG, et al. (2015) Compliance with Surgical Care Improvement Project for Body Temperature Management (SCIP Inf-10) Is Associated with Improved Clinical Outcomes. Anesth. 123: 116–125.
13. Fossum S, Hays J, Henson MM. A Comparison Study on the Effects of Prewarming Patients in the Outpatient Surgery Setting. J PeriAnesth Nurs. 2001;16(3):187-194.
14. Wilson L, Kolcaba K. Practical Application of Comfort Theory in the Perianesthesia Setting. J PeriAnesth Nurs. 2004;19(3):164-173.
15. Horn EP, Bein B, Bohm R, Steinfath M, Sahili N, Hocker J. The Effect of Short Time Periods of Pre-Operative Warming in the Prevention of Peri-Operative Hypothermia. Anaesth. 2012.67(6).
16. Camus Y, Delva E, Sessler DI, Lienhart A. Pre-Induction Skin-Surface Warming Minimizes Intraoperative Core Hypothermia. J Clinical Anesthesia. 1995;7:384-388.
17. Nelson G, Altman AD, et al. Guidelines for pre- and intra-operative care in gynecologic/oncology surgery: Enhanced Recovery After Surgery (ERAS(R)) Society recommendations - Part I. Gynecologic Oncology. 2016;140:313-322.
18. American Society of PeriAnesthesia Nurses. Clinical guideline for the prevention of unplanned perioperative hypothermia. J Perianesth Nurs. 2001;16:305-314.
19. Guideline for prevention of unplanned patient hypothermia. In: Guidelines for Perioperative Practice. Denver, CO: AORN; 2017:567-590.
20. Ban KA, Minei JP, Laronga C, Harbrecht BG, Jensen EH, Fry DE, Itani KMF, Dellinger EP, Ko CY, Duane TM. American College of Surgeons and Surgical Infection Society: Surgical Site Infection Guidelines, 2016 Update. J Am Coll Surg 2017;224:59-74.
21. Anderson DJ, Podgorny K, et al. Strategies to Prevent Surgical Site Infections in Acute Care Hospitals: 2014 Update. Infection Control and Hospital Epidemiology. 2014;35(6).
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