HEATED APPROACH Forced-air warming is highly effective, but can't always prevent hypothermia on its own.

It's virtually a given that you're actively warming your patients when they're in the operating room. But that might not be enough. A recent study (osmag.net/r4MXrV) found that patients being warmed with forced air still typically experience periods of hypothermia when general anesthesia kicks in and body heat is redistributed from the core to the periphery. So how can you mitigate the chilling impact of redistribution hypothermia?

1. Focus on the first 30 minutes
Don't wait until patients are in the OR. Start instead by warming patients in pre-op, so body heat content is increased by the time they're ready for surgery. "It's important to bring them into the OR in an optimized fashion," says Shari Burns, CRNA, MSN, EdD, program director and an associate professor of the nurse anesthesia program at Midwestern University in Glendale, Ariz.

Many patients arrive in the chilly early-morning hours. "Just based on circadian cycles alone, people have lower body temperatures then," says Ms. Burns. "Added to that, they're removing clothing in what might be a cold clinical environment." Makes you shiver just thinking about it.

How long does it take to adequately pre-warm patients? A half hour is a good target to shoot for, experts say, but something is always better than nothing. "You certainly would not delay surgery because it's only been 20 minutes," says Daniel Sessler, MD, Michael Cudahy Professor and chair of the department of outcomes research at the Cleveland Clinic. "Pre-warm patients to the extent that it fits into your routine." Ideally, set up your pre-op protocols in such a way that they include half an hour for pre-warming.

Granted, it costs money to pre-warm patients. "But I absolutely think it's a good investment," says Ms. Burns, who notes there are a lot of things in health care we have to spend money on, and there's no physiological reason not to pre-warm everyone. "Here's the other side of that coin," she adds. "If you're going to shorten the hospital stay or shorten the PACU stay (by pre-warming), you're going to save hundreds of thousands of dollars a year. We see it in the PACU. Patients have shorter stays when they don't come in as hypothermic."

If you're not convinced that spending the extra dollars to pre-warm makes total sense, Ms. Burns suggests you at least use pre-warming for particularly high-risk patients. "Those going to have open procedures of any kind, and all pediatric patients as well as those who are frail, elderly or who have multiple comorbidities," she says.

"I can't think of any adults in whom pre-warming would be contraindicated," comments Dr. Sessler. "It requires some effort, but the effect is real and measurable, even if it's relatively small."

2. Double up
The list of reasons to use forced-air warming in the OR is long: It's safe, effective, inexpensive and easy to use. But hypothermia is a powerful foe. So why not augment your arsenal? Pre-warming and using 2 different warming systems are the best ways to do that, suggests Dr. Sessler. "You can also keep anybody warm by increasing ambient OR temperature sufficiently," he adds. "But you have to increase it much more than you'd think, and then you'd make everybody in the room miserable. It works, but it's not a very sophisticated solution."

By combining 2 effective warming systems, you'll have more impact than you would with either alone. "Each warming method involves a tradeoff of cost, ease of use and risk," says Dr. Sessler. "You need to decide what's best in their particular context."

Once the pre-warmed patient is inside the OR, for example, fluid warming can help reduce the cooling effect caused by room-temperature fluids. However, it's only effective in patients who receive large volumes of fluid.

"Often, fluid is given as a larger bolus at the beginning of the case," says Charles E. Smith, MD, director of cardiothoracic and trauma anesthesia at MetroHealth Medical Center in Cleveland, Ohio. "You may give 300 ml or 500 ml to a typical adult. If you keep those fluids warm, you've helped with heat conservation." He says giving patients fluid that matches their body temperature is part of thermal homeostasis: You're maintaining normal blood volume distribution and normal temperature.

3. Warm in the OR
Intraoperatively, the most obvious benefit of pre-warming is likely to be less bleeding, says Dr. Sessler, who notes that platelets don't function as well at lower temperatures. "Platelets are what cause the initial plug that prevents further bleeding after a surgical incision," explains Dr. Sessler. "And they don't have any nervous system, they don't have any memory. All they know is what their current temperature is."

He says there's also a cascade of enzymes that's responsible for forming the formal clot that replaces the platelet plug. And like most enzymes, he adds, they're temperature sensitive and don't work as well in patients who are hypothermic. That might not be a big deal with minor procedures that typically involve a small amount of bleeding, but excessive bleeding is never a positive thing. Anemic patients don't heal as well, and are likely to recover more slowly, points out Dr. Sessler.

Meanwhile, in longer, more complex surgeries, excessive blood loss may necessitate transfusions, or greater numbers of transfusions. If those can be minimized or eliminated by pre-warming, the cost-benefit ratio of pre-warming goes way up. Additionally, says Dr. Sessler, "there's increasing evidence that transfusions are simply bad for you." As outpatient facilities continue to expand the complexity of their offerings, minimizing the need for transfusions is bound to become an increasingly significant concern.

4. Monitor patients in post-op
While outpatient procedures typically involve limited blood loss, the flip side is that the shorter the procedure, the greater the potential impact of hypothermia post-operatively. In longer surgeries, patients typically reach normothermia by procedure's end. "But it's much harder for patients to be normothermic at the end of a short operation," says Dr. Sessler. "It's the 40-minute or 1-hour operation" that presents the biggest challenge."

Autonomic responses to cold, like tachycardia and hypertension, are controlled when patients are under anesthesia, but not after they wake up. Patients who remain hypothermic in the PACU are thus more likely to experience other consequences. The possibility that patients might have a "heart attack or an infection would likely have more to do with how warm they are at the end of surgery," says Dr. Sessler. "It's likely that the relative importance of intra-operative temperature versus final temperature depends on which outcome you're looking at."

Safe to say, however, that whether patients are hypothermic intraoperatively or both intra- and post-operatively, neither is more likely to promote a more favorable outcome.

Awareness needed
Despite a plethora of studies and reams of literature, not enough surgical professionals are getting the whole warming message, says Ms. Burns. "It's about educating not only the nursing staff, but also the surgeons. They have very little to do with the post-op time or the prep of the patient," she says. "But if they knew the data that show why pre-op warming is important, they would want that for all their patients and it would be a simple fix. They'd say: All of my patients who are having abdominal surgery get this. Or all of my total knees."

So surgeon buy-in is key, she says. But they're not always available for educational sessions. "How about adding something about patient warming in their medical staff newsletter? How about including them in an in-service? It doesn't take long," she says. "Fifteen minutes of training a couple of times a year is not a lot, and it's all you need. That should spark the buy-in."

And that spark could light the fire that will keep patients warm.