Patient warming devices meant to maintain normal body temperatures carry their own hazards if misused. Here's a review of the basics of safe patient warming.

Scope of the problem
For a study titled "Burn Injury in the Operating Room: A Closed Claims Analysis," published in the ASA Newsletter's June 2004 issue, Kimberly A. Kressin, MD, sifted the American Society of Anesthesiologists' Closed Claims Project — a compendium of standardized summary data reported from the anesthesia malpractice claims of 35 insurance carriers representing half of the nation's practicing anesthesiologists — for incidents involving intraoperative burn injuries.

At the time of the study, only 145 of the database's 6,449 claims, or 2.2 percent, involved burns. Of those 145 cases, though, 58 percent resulted from devices used to warm the patient, in contrast to 19 percent resulting from cautery-sparked fires and 12 percent from stray cautery burns. The warming devices cited in the study included intravenous bags or bottles, heated and placed on high-blood flow areas of a patient's body (representing 51 of the injuries), heating blankets (16 injuries), heating pads (11 injuries), warming lights (four injuries) and hot compresses (four injuries). Dr. Kressin notes that the majority of the IV bag and bottle burns occurred before 1994, the year that their risks were widely published, after which incidents declined.

Starting points
As with any safety efforts, education and preparation go a long way in terms of prevention. Lisa Thiemann, CRNA, MNA, the acting senior director of professional practice for the American Association of Nurse Anesthetists in Park Ridge, Ill., says periodic staff education sessions regarding each piece of warming equipment and each method currently used are a good place to start. And make sure these sessions are interdisciplinary.

"If you engage all of the providers involved in a patient's procedure, that networking will result in a greater exchange of ideas and concerns," she says.

She also points out that surgical staff members sensitive to the issue of patient hypothermia are more likely to bring their concern for patient safety to the OR table and preparations for a case.

"If your goal is the prevention of hypothermia, then those cautions you take [at the beginning of a case] will similarly help to prevent injury," she says. "Having that dialogue ahead of time as you plan to prevent hypothermia increases safety. It lets the providers, before starting a procedure, ensure that the proper warming devices are properly placed."

Hot air
Convective, or forced air, warming units are the most common method of proactive patient warming. Warmed air generated by a heating component is blown through a hose to an inflatable, single-use blanket covering the patient that evenly vents the warm air to maintain normothermia in patients before, during and after surgery. Their safety comes from their proper assembly. If forced air is applied without the diffusing blanket and the hose's nozzle is instead simply placed beneath a traditional cloth blanket — a practice colloquially known as "free hosing" — the air blowing directly onto the patient may result in burns, especially among patients with limited movement or sensation. Manufacturers of convective warming units report incidents of first-, second- and third-degree burns on the lower body as well as one case in which the resulting muscle necrosis required the above-the-knee amputation of a patient's leg.

Proper use of such equipment seems elementary. However, under the pressures of time and economy, both of which have been known to influence the business of surgery, errors can be made, says Carla McDermott, RN, CNOR, the education specialist for Morton Plant Mease Health Care in Clearwater, Fla.

You might hear, ???It's just a short case, wrap the hose in a blanket and put it under the drape or the blanket,'" she says. Or perhaps covering the patient with the inflatable blanket isn't an option due to the surgical staff's need for access. "But if that hose gets bumped or wiggled, it might come loose," she warns.

Since manufacturers commonly give facilities convective warming systems at no cost under an agreement through which the disposable blankets are then purchased, buying or budgeting is sometimes the culprit, but this is also inexcusable, since the blankets shouldn't break anyone's bank. "If the money's coming out of the anesthesia provider's pocket, then of course it's ???expensive,'" says Ms. McDermott. "But as supplies go, it's not. The full-body blankets cost about $20 a patient."

Convection cautions
Materials managers are advised to keep all of the components of their forced-air warming units in one place so that when the heater and hose are retrieved, the blankets will be right on hand, preventing the need to hunt for separate pieces elsewhere and ensuring that when the heater gets used, the blanket will, too.

Minimizing the incidence of injuries resulting from the improper use of warming blanket components, as with any warming method, depends on a familiarity with the equipment's operating instructions and warnings. Educate your staff on the purpose of the blanket and the risks of off-label use, and if your facility sees occasional turnover, make that information part of your regular orientation and training.

When covering a patient with a forced air warming blanket, remember which way is up, says Ms. McDermott. "The softer side with the vents is the patient side, facing down toward the patient," she says. If it's facing up, not only will all the warmed air exit into the room, but also the patient may end up burned, she adds. "You don't want the hot, plastic side against the patient." Similarly, even an attached hose can burn on contact, so be aware of its positioning near the patient.

Ms. Thiemann stresses the importance of knowing the ins and outs of your equipment. "Understand the temperature selection on the devices," she says, so that they may be adjusted if a patient complains that she is too warm.

Beyond the blankets themselves, a grasp of the procedure being performed and the patient's medical history may play an important role in warming safety. Suppose an abdominal procedure underway requires the temporary occlusion of blood flow to a patient's legs, says Ms. McDermott. "If the legs are warmed, even if it's done properly, they'd have no way to disseminate the heat to the rest of the body." Likewise, she says, "poor circulation in the legs would be a reason not to warm a patient's lower body, or to set it on a lower, cooler setting, as the heat won't be dispersed as readily."

Open and shut
If your facility isn't using forced air warming systems, it's more than likely that you're covering your patients with cotton blankets fresh from a warming cabinet. Whether your cabinet is designed just for blankets and gowns, or has a compartment for warming irrigation and infusion fluids — which don't, of course, actively warm a patient but rather ward off the threat of intraoperative hypothermia posed by the use of large amounts of chilled fluids — observe caution.

Regular maintenance inspections will ensure that a warming cabinet is in proper working order. Checking the operating temperature (or temperatures, for dual-purpose warmers) daily is a safety step some accreditors require. While most warming cabinets have built-in safeguards that prevent them from heating above a certain temperature, you may want to test them periodically to be sure that the temperature setting accurately represents the temperature intended, and that an item warmed inside receives an equal distribution of heat throughout. Be aware, also, that the blanket itself might inadvertently cause harm even after it's out of the cabinet. "It's going to cool off at ambient room temperature, but the fabric could still burn a patient," says Ms. McDermott. "If you're dealing with a patient who's 86 years old, whose skin is very thin, who has poor circulation, and you put two blankets on him, that's going to hold the heat in. If those blankets are 170 ?F — and that's how high a blanket warmer can be set — you may see some injury." Ms. McDermott says the upper limit for her facilities' warmers are 140 ?F.

If you use circulating water mattresses, keep patient positioning and monitoring in mind, says Ms. Thiemann. A tissue compression injury combined with an unchecked warming mattress can put a patient at risk of pressure heat necrosis. "Line the mattress with a thin blanket to reduce contact," she says. Ms. McDermott recommends instead using gel cushioning pads to diffuse the heat and prevent pressure sores.

Above all
One part of patient warming that gets overlooked is knowing a patient's baseline temperature and monitoring it every half-hour, says Ms. McDermott. "Otherwise, how do you know if what you're doing is effective?" Charting the patient's temperature also lets you know whether the patient actually is cold, or just interprets the shivering side effects of some anesthesia agents or pain medications as feeling cold. Above all, however, she emphasizes the importance of awareness for you and your staff. "You don't want to have to say, ???We caused those burns on your legs,'" she says. "Know the patient, and know the procedure. Don't cause a patient more harm than good."