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Keeping Patients Warm Throughout Surgery
Think patient warming starts and stops with a heated blanket in pre-op? Think again. You need a combination of techniques to keep patients safe and comfortable.
Shari Burns
Publish Date: April 11, 2010   |  Tags:   Infection Prevention

Warmed IV fluids. Forced-air warming devices. Booties and hats in the OR. No single intervention can prevent perioperative hypothermia on its own. The secret to making sure your patients stay warm is to combine measures to maintain body temperature from the time patients enter your facility through discharge. This offers the greatest likelihood of minimizing body temperature change and maximizing comfort in surgical patients. Here are 4 relatively simple strategies to prevent hypothermia.

1. Warmer rooms
Even short, non-invasive surgery is associated with unintentional hypothermia. A simple solution is to increase the OR temperature. Since 1970, studies have shown that patients who enter ORs with the temperature set to 70 ?F have a significantly reduced risk of hypothermia. While setting the room to 70 ?F may seem warm initially, after the "golden hour" (the first hour in the operating room) you can lower the ambient temperature for the surgical team's comfort. Body temperature drops 1 to 3 degrees during the first hour in the OR. How-ever, after the first hour, body temperature usually stabilizes.

It's important that everyone on the surgical team understands the significance of the patient arriving in an OR with an ambient temperature of 70 ?F and takes the necessary steps to keep the patient warm during the first hour. Unfortunately, that's not always the case. A survey published in the March 2009 issue of ORNurse found that 74% of operating room nurses who responded were unaware of the specific ambient temperature's influence on unintentional hypothermia.

Know Who's at Risk

It's important to know to what extent each patient is at risk for developing unintentional hypothermia. Factors associated with unintentional hypothermia include:

  • age extremes;
  • operating room ambient temperature;
  • length and type of surgery, such as open abdominal procedures;
  • amount of body exposure and the temperature of irrigants and intravenous fluids;
  • pre-operative and intraoperative medications including narcotics and benzodiazepines; and
  • the use of anesthetics, including general and regional anesthesia.

2. Pre-warming
Preventing unintentional hypothermia should be a team effort, beginning in the pre-operative area. Taking patients to surgery when they're already warm (normothermic) helps minimize the loss of body heat while they're in the operating room. Using active warming devices as well as passive warming measures, including cotton blankets and layering, helps maintain body temperature. Research shows that placing a forced-air warming blanket on patients before they're brought into the operating room minimizes the incidence of unintentional hypothermia.

Pre-operative warming decreases heat redistribution. In a classic study, Camus and colleagues found that core body temperature decreased at a rate of 0.6 ?C per hour in pre-warmed patients, but decreased 1.1 ?C per hour in patients who were not pre-warmed. Since this early investigation, published in the Journal of Clinical Anesthesia in 1995, other studies have supported the use of pre-operative warming to avert the problems associated with unintentional hypothermia.

Forced-air blankets seem to work better than cotton blankets. Research shows that patients maintain body temperature to a greater degree when forced-air warming blankets are used pre-operatively, as compared to cotton blankets. In addition to minimizing hypothermia in surgery patients, pre-warming may facilitate IV placement and improve overall patient comfort and satisfaction.

3. Intraoperative warming
During surgery, using warmed IV fluids, blood warmers and warmed irrigants can help to minimize heat loss. Warming irrigating solutions before instilling them into open body cavities promotes blood flow and oxygen delivery to tissues. Storing IV fluids in a warming cabinet can also help you maintain normothermia in your patients.

Minimizing body exposure, layering blankets and using circulating water mattresses and garments can also be used to promote normal thermal balance. Head wraps and warmed humidified anesthetic gases can also contribute to overall maintenance of body temperature. For pediatric patients, radiant heat lamps will aid in averting unintentional hypothermia.

4. Post-op assessment
Measuring the patient's body temperature upon arrival in the PACU lets the nursing staff determine whether the patient is hypothermic. For normothermic patients, blankets help maintain body temperature following surgery and anesthesia. For patients who are hypothermic, forced-air warming offers the best measure to promote a return to normal body temperature and overall patient comfort. As in the OR, warmed IV fluids and warmed, humidified oxygen aid in promoting normal body temperature in the PACU. For hypothermic patients who arrive in the PACU with a core body temperature under 36 ?C (96.8 ?F), American Society of PeriAnesthesia Nurses guidelines recommend measuring the body temperature every 15 minutes. Frequent measurement will help you determine what to do next to maintain normal body temperature.

Not a matter of "set it and forget it"
Keeping patients warm should be a primary concern during their stay in your facility. Unintentional hypothermia can cause physiological changes that affect all body systems and can cause extended anesthesia care, myocardial infarction, coagulopathy and poor wound healing. In fact, wound infection is 3 times higher in hypothermic patients with a core body temperature less than 36 ?C.

The Surgical Care Improvement Project's safety reporting measures emphasize hypothermia's link to post-operative infection. Measure 10 for infection control (SCIP-Inf-10) calls for reporting patient temperature and documenting whether it dropped below 36 ?C from 30 minutes before the anesthesia end time until 15 minutes after the anesthesia end time. This measure applies to patients of all ages who receive general or regional anesthesia for 1 hour or more.

Assessing Body Temperature

The American Society of PeriAnesthesia Nurses' guidelines say assessing body temperature should be a continuous quality measure throughout the perioperative period. Measuring body temperature before, during and after surgery gives the surgical team timely information to guide further interventions that may be needed in order to keep the patient warm.

Where you plan to take the patient's temperature may determine how you do it. For example, in the operating room you may use an esophageal temperature-measuring device for a patient under general anesthesia. But measuring core body temperature before and after surgery is impractical because it requires using an invasive esophageal probe.

As a result, nurses measure peripheral body temperatures before and after surgery. Knowing the patient's temperature from the pre-operative area is helpful because you have a baseline to work from. In the PACU, skin surface temperature or tympanic membrane temperature is usually recorded.

Several technologies are available for measuring body temperature. For peripheral monitoring, you can use liquid crystal temperature monitors that adhere to the patient's skin. These give you continuous measurement from admission through discharge. Although easy to use, with these devices the temperature can vary greatly depending on blood flow to the skin. Regardless, the technology offers the monitoring of trends in body temperature.

During the surgical procedure, you may measure the patient's core temperature or peripheral temperature, depending on the type of surgery and anesthesia. Infrared thermometers, often used to measure tympanic membrane temperatures, are easy to use but provide only intermittent temperature readings. Temperature measurement using an esophageal temperature probe offers continuous data and reflects the brain temperature, but is tolerated only by patients under general anesthesia.

Communicating temperature measurements increases awareness and lets all members of the perioperative team contribute to efforts to minimize body heat loss. With everyone aware of the patient's temperature, it's easier to act when needed. This is important because little research has examined patients who enter surgery already cold. It's better to keep the patient warm using passive and active warming methods pre-operatively than trying to re-warm a patient who arrived cold in the OR.

— Shari M. Burns, CRNA, MSN, EdD

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