Sep 3, 2015

The Science Behind Patient Warming and the Benefits of Normothermia

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Perioperative Patient Warming

Read the study summary – Target Normothermia: A Global Focus on Inadvertent Hypothermia


Under normal circumstances, the body controls its temperature within a very tight tolerance, with the core being 2-4˚C warmer than the periphery. This temperature gradient between the core and the periphery is caused by normal thermoregulatory vasoconstriction. Anesthesia induction results in vasodilation, which allows the warmer blood to flow freely from the core and mix with the blood from the cooler periphery, lowering the core body temperature. Research has shown that in the first 60 minutes under anesthesia unwarmed surgical patients can lose up to 1.6˚C1,a phenomenon known as redistribution temperature drop (RTD).

Unintended perioperative hypothermia

Unintended hypothermia remains a common—but easily preventable—complication of surgery.2 It is estimated that unintended hypothermia, defined as a core body temperature of less than 36.0°C (96.8°F), occurs in more than 50% of all US surgical patients, even those undergoing short procedures (one to one-and-a-half hours).3

Numerous studies have demonstrated that even mild perioperative hypothermia can result in significant complications. Unfortunately, temperature management of the surgical patient remains a secondary consideration in many perioperative settings rather than an essential standard of care.

Benefits of normothermia

The benefits of maintaining normothermia have been thoroughly researched and documented in independent peer-reviewed articles. A number of these studies are randomized controlled studies that document the importance of preventing hypothermia.

In a landmark meta-analysis performed by Chris Brown Mahoney, she captured the essence of earlier research which identified dramatic decreases in the complication rates and the related patient care costs that can be avoided by keeping patients normothermic. Normothermia is a process improvement that touches the entire patient care algorithm. This meta-analysis of 20 studies covering 1,575 patients identified reductions in patient costs in several different areas when normothermia is maintained such as:5

  • Reduction in the use of blood products
  • Shortened length of hospital stay
  • Decreased ICU time
  • Reduced rate of wound infection
  • Decreased likelihood of myocardial infarction
  • Lower mortality rates

There is also a significant financial benefit of reducing hypothermia rates in surgical patients. Maintaining normothermia can result in savings of $2,500 to $7,000 per patient by eliminating the costs of hypothermia-related complications, including surgical site infections.5

Study Summary: Target Normothermia: A Global Focus on Inadvertent Hypothermia

  1. Sessler DI, Current concepts: mild perioperative hypothermia. N Eng J Med 1997; 336: 1730-1737.
  2. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. N Engl J Med 1996;334:1209–1215.
  3. Young VL, Watson ME. Prevention of Perioperative Hypothermia in Plastic Surgery. Aesthetic Surgery Journal. 2006;26(5):551-571.
  4. Sessler DI, Kurz A. Mild Perioperative Hypothermia. Anesthesiology News. October 2008: 17-28.
  5. Mahoney CB, Odom J. Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs. AANA Journal. 1999;67(2):155-164

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