Infection Control, October 2003
Temperature Management in the Intraoperative Setting
By Tina Brooks
Surgical site infections (SSIs), the third most frequently reported nosocomical infection, account for 14 percent to 16 percent of all nosocomical infections among hospitalized patients. "Surgical site infections remain one of the most common and serious complications of surgery," says Daniel Sessler, MD, director of the Outcomes Research Institute at the University of Louisville in Kentucky. "The overall incidence is about 2 percent, but in selected operations the risk approaches to 10 percent. The average infection increases the duration of hospitalization by a week, costs thousands of dollars, doubles the risk of ICU admission, doubles mortality."
To find solutions to many of these problems resulting from SSIs, researchers turned to the perioperative setting for answers. Many studies have shown that the utilization of temperature management devices in the intraoperative setting help reduce SSIs, however, more recent research suggests that the optimal use of these devices should begin preoperatively.
SSI and Hypothermia
"Surgical infections are one of maybe six or seven serious consequences of hypothermia," Sessler says. Hypothermia is a core body temperature of less than 36 degrees C, whereas normal core body temperature ranges between 36 degrees C and 37.5 degrees C. Intraoperative hypothermia results because patients are exposed to several factors that contribute to heat loss including cold ambient temperatures in the surgical suite, an opened exposed wound area and administration or irrigation with cool fluids.
The most important factor, though, is internal redistribution of body heat that results from anestheticinduced inhibition of tonic thermoregulatory vasoconstriction.
"As a result, unwarmed surgical patients almost inevitably become hypothermic," says Sessler. "Even patients having short, small operations will become hypothermic during surgery."
It is well documented that low body temperature may increase patients’ susceptibility to SSIs by causing vasoconstriction and impaired immunity. Vasoconstriction decreases the partial pressure of oxygen in tissues, which lowers resistance to infection in humans.
"Prewarming is an effective way of preventing intraoperative hypothermia," Sessler says. "This has been demonstrated in at least four different studies and there’s no question that it works." Forced-air warming devices have been established as the most effective method of preventing and treating heat loss in patients.
A randomized study of patients undergoing elective laparoscopic cholecystectomy showed that a single hour of preoperative skin-surface warming reduced the rate at which core hypothermia developed during the first hour of anesthesia. Prewarming did not alter preoperative core temperature, but it markedly reduced the rate at which intraoperative core hypothermia developed: 1.1 ± 0.1 degrees C/hour in the control group, versus only 0.6 ± 0.1 degrees C/hour in the prewarmed group (<0.05).
Sessler, who was one of the researchers of this study, says that even if patients are pre-warmed for just one half hour, their peripheral tissues temperature is nearly equal to core temperature and there is therefore no redistribution hypothermia after the induction of anesthesia. Core temperature thus remains nearly normal even during large operations in prewarmed patients.
This same study also revealed that the prewarmed patients cooled at half the rate of the control patients, and prewarmed patients and remained significantly warmer even after two hours of surgery.
Although the use of warming devices is becoming standard practice for most major surgeries, their utilization for procedures that last less than an hour is not. Melling et al. aimed to assess whether warming patients before short duration, clean surgery would reduce infection rates. Their findings suggested that a 30- minute period of prewarming patients reduces infection rates from 5 percent to 14 percent. The 421 patients underwent breast, varicose or hernia surgeries.
Beyond the known adverse outcomes of hypothermia, Mahoney and Odom concluded that cumulative adverse outcomes added between $2,500 and $7,000 per surgical patient to hospitalization costs across a variety of surgical procedures.Other studies corroborate that SSIs increase costs as well as length of hospital stay.
Comfort can be an elusive concept, but patients know when it is absent. Comfort, or lack thereof, is often the most memorable experience noted on patient satisfaction questionnaires.
"Surgical patients may not remember much else, but they remember if they were comfortable or freezing to death," says V. Doreen Wagner, RN, MSN, CNOR, assistant professor of clinical nursing at North Georgia College and State University in Dahlonega.
"Traditionally, cotton blankets have been used in the preoperative setting to keep patients warm," Wagner says. However, cotton blankets produce only a small reduction of heat loss. "The sensation of warmth, even when blankets are heated, dissipates quickly."
"Sometimes using both prevention and different kinds of warming devices will actually save money," Wagner says. "Those old tried-and-true practices, like warmed cotton blankets, can be even more costly than one would believe. You use nine to 12 of those blankets during somebody’s whole surgical experience, then you’ve got to tie in the cost of staff time involved in going back and forth to get the blankets, and last but not least, how much patient satisfaction is worth when a patient has to wait for comfort measures."
Vallire Hooper, RN, MSN, CPAN, clinical nurse specialist in surgical services at St. Joseph Hospital in Augusta, Ga., says, "The important thing to remember is that every patient should have preventive warming measures, even if they’re normothermic — those basic common sense nursing interventions. They do not require doctor’s orders. They should be standard practice."
Hooper, who sat on the development panel of a guideline to prevent unplanned perioperative hypothermia held by the American Society of PeriAnesthesia Nurses (ASPAN), says that if a patient is complaining of being cold, even if they have a normal temperature, they are most likely losing heat.
"We should protect our patients from the start in the preoperative arena," Wagner stresses. "Don’t let them get cold to begin with. I know that a lot of clinicians begin trying to warm patients in the operating room. Warming should start in the preoperative phase where patient’s chillines’s and discomfort begins."
ASPAN GUIDELINES ON PERIOPERATIVE HYPOTHERMIA
Research has shown there is a chronic problem with perioperative hypothermia.
To address this concern, the American Society of PeriAnesthesia Nurses (ASPAN) developed practice guidelines for the prevention, care and management of the adult surgical patient with unplanned perioperative hypothermia. Here is a portion of the guidelines that discusses preoperative patient management:
- Identify patient’s risk factors for unplanned perioperative hypothermia.
- Measure patient temperature on admission.
- Determine patient’s thermal comfort level (ask the patient if they are cold).
- Assess for other signs and symptoms of hypothermia (shivering, piloerection, and/or cold extremities).
- Institute preventive warming measures for patients who are normothermic. A variety of measures may be used, unless contraindicated. Passive insulation may include warmed cotton blankets, socks, head covering, limited skin exposure, circulating water mattresses and increase in ambient temperature (minimum 20 degrees C to 24 degrees C or 68 degrees F to 75 degrees F).
- Institute active warming measures for patients who are hypothermic. Active warming is the application of a forced air convection warming system. Apply appropriate passive insulation and increase the ambient room temperature (minimum 20 degrees C to 24 degrees C or 68 degrees F to 75 degrees F.) Consider warmed IV fluids.