As we all know, the risk of intraoperative hypothermia increases when the patient's body core temperature drops below 36 ?C (96.8 ?F) under general anesthesia or intravenous sedation. Hypothermic patients may suffer from shivering and slowed awakening from anesthesia, resulting in delayed discharge, decreased drug metabolism, delayed wound healing or increased frequency of cardiac dysrhythmias. There is good news, however. Preventing intraoperative hypothermia is easily accomplished if you employ a well thought-out, comprehensive warming plan that keeps patients comfortable and safe.

How patients get cold
In the perioperative period, radiation heat loss occurs when patients are exposed to the cold operating room environment. Conductive heat loss occurs as a patient's body heat warms any object it comes in contact with, such as a cold Mayo stand, the OR table, positioning devices or IV fluids. Patients under general anesthesia experience redistribution hypothermia as core blood, and thereby core heat, is redistributed to the body's periphery through vasodilation.

During my training, my preceptor and mentor, Charles Fisher, CRNA, of Memorial Sloan Kettering Cancer Center in New York City, encouraged warming of all patients. "A warm blanket is the pharmacological equivalent of a couple milligrams of midazolam," he would say. "It helps the patient relax and stay warm and comfortable." That's why I insist that all my patients are warmed before, during and after surgery.

How we warm patients
At our surgery center, each bed in the holding area, OR and PACU has its own forced-air warming machine. When a patient arrives, the holding area stretcher has been pre-warmed with a forced-air warmer connected to a disposable, forced-air warming blanket. Patients routinely comment on how nice it feels to get into a warm bed.

We pre-warm the OR table with the hose from the forced-air warmer. When the patient is brought into the OR, the bed sheet, blanket and forced-air disposable blanket we used in pre-op accompanies them. We then connect the disposable blanket to the forced-air warmer in the OR for use during surgery.

We perform this warming process the same way post-operatively. The PACU nurse pre-warms the recovery stretcher so it's warm when the patient is moved from the OR table. Again, the same bed sheet, thermal and forced-air blanket accompany the patient to the PACU.

At our facility, primary liposuction procedures present warming challenges. These patients usually undergo a circumferential prep, resulting in convection and radiation heat loss. The prep also causes evaporative heat loss (the same way sweating cools our bodies) and robs the patient of any warming done in the pre-op holding area. With these patients, it's important for us to step up our warming protocols to preserve normothermia. In addition to pre-warming the patients, we warm the prep and tumescent solutions. Placing convective warming blankets under these patients is also very effective in staving off body cooling.

How we maintain patients' warmth
Maintaining a patient's core temperature requires adequate insulation, defined as a good vapor barrier and sufficient R-value. That value is the measure of an insulator's ability to impede heat flow — the more efficient the insulator, the higher the R-value. Properly insulating the patient's extremities that lie outside the surgical field, or using forced-air warming on those areas, is an effective way to protect against intraoperative heat loss.

We've also discovered an opportunity to go green in our efforts to maintain normothermia in the OR. With the help of the OR nurses, I recycle the thick plastic packaging from our custom packs and prep packs. I use the smaller prep kit bag to make a warming hat for patients. (Momma always told us we lose 80 percent of our heat through our heads.) We also divide the over wrap from the custom pack, creating vapor barriers for the arms. Cotton blankets or towels also increase the insulation's R-value, further protecting the patient from the onset of hypothermia.

Warming IV and irrigation fluids can also help maintain normothermia. However, purchasing an inline fluid warmer is not cost-effective for most outpatient facilities where there is seldom the need for large volumes of intravenous solution or blood products.

We've discovered an alternate, more cost-effective way to warm fluids: We store fluids near equipment that emits heat. For example, placing fluid near sterilizers or video monitors can increase its temperature 10 to 20 degrees above room temperature. That means IV and irrigation fluids are always warm, but not hot. Since all the fluid is stored near warm equipment, there's always a ready supply on hand and no one's left to wonder, "Who took the last bag of saline and forgot to refill the fluid warmer?"

A word of caution
Warming devices carry the potential for significant harm. In fact, burns resulting from patient warming account for 58 percent of all burn injuries in the OR, according to an article by Kimberly Kressin, MD, in the June 2004 issue of the American Society of Anesthesiologists Newsletter. "Hosing"— using a forced-air warmer without a warming blanket — can cause significant burns; medical literature reports incidences of third-degree burns resulting from this practice. Using electric blankets on patients under anesthesia can also result in burns. Warming fluids in the microwave can cause uneven heating or overheating of the fluid, another potential cause of patient burns. Heating IV bags in the microwave and using them as hot water bottles to warm the groin or axillary area can also cause contact burns.

The clinical staff has an obligation to use appropriate methods in maintaining normothermia, while management is obligated to provide the clinical staff with the tools they need to provide good care. The proper warming of patients is everyone's job, not just the responsibility of your anesthesia provider. Through consistent application of a few simple but effective patient-warming steps, you can easily prevent intraoperative hypothermia and increase the safety and comfort of your patients before, during and after their procedures.