Patients Actively Warmed During Surgery Still Experience Hypothermia

Body temperature decreases during the first hour of surgery, even when patients are actively warmed with forced air, according to a study published in the February issue of the journal Anesthesiology.
Furthermore, patients who experience the most hypothermia are more likely to require blood transfusions.

“Hypothermia is common during surgery because anaesthetics disrupt normal control of body temperature and because operating rooms are kept cool,” said Daniel Sessler, MD, the Cleveland Clinic, Cleveland, Ohio. “Consequently, body temperature typically decreases about 4 degrees Fahrenheit [-15.6 degrees Celsius] in un-warmed surgical patients. This sort of moderate hypothermia can cause serious complications including blood loss and wound infections.”

Warming surgical patients to help prevent hypothermia is now the standard-of-care. The most common type of warming is forced air, which essentially blows warm air through a cover that surrounds the patient. Many studies show that patients warmed with forced air have a normal body temperature at the end of surgery.

The goal of the current study was to evaluate body temperature patterns in warmed surgical patients, and determine whether even short periods of low temperature increased blood loss or prolonged hospital stays.

For the study, Dr. Sessler and colleagues evaluated records of intraoperative core body temperature patterns in nearly 59,000 surgical patients, all of whom were warmed with forced air.

The study found that 64% of surgical patients became hypothermic, with core temperatures <36 degrees Celsius during the first hour of anaesthesia. Nearly half of patients had a continuous core temperature <36 degrees Celsius for more than 1 hour. Twenty percent of patients had a continuous core temperature <36 degrees Celsius for more than 2 hours. Core temperatures then gradually increased, and most patients had normal temperatures by the end of surgery. Patients who became most hypothermic were most likely to need blood transfusions.

In an accompanying editorial, Harriet Hopf, MD, Department of Anesthesiology, University of Utah School of Medicine, Salt Lake City, Utah, wrote: “A critical implication of this study is that current standards and practice routinely lead to intraoperative hypothermia, which is associated with a higher transfusion requirement. These results should be an impetus for changes in practice that lead to lower rates of intraoperative hypothermia. This study starts a new conversation on perioperative temperature management. Future studies should evaluate the effectiveness of interventions to reduce the degree and duration of intraoperative hypothermia and the effect of these interventions on the broad range of outcomes known to be temperature sensitive.”