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Hypothermia's Direct Link to SSIs
Active warming is proven to cut down on surgical site infections.
Dan O'Connor
Publish Date: April 29, 2014   |  Tags:   Patient Experience
surgical site infection INCREASED WOUND INFECTION Even mild hypothermia triples the risk of surgical site infection.

You might not think a shivering patient and a surgical site infection go together, but they go hand in hand. As hangovers are to happy hours, SSIs are the delayed and dangerous reactions to hypothermia. Besides being one of the more unpleasant side effects of surgery, hypothermia is one of the most common risk factors associated with SSIs.

But what does a cold patient have to do with a wound infection? Hypothermia may increase patients' susceptibility to perioperative wound infections by causing vasoconstriction and impaired immunity. As the body's core temperature declines, so does its antibody- and cell-mediated immune defenses, and the availability of oxygen in peripheral wound tissues. Hypothermia is associated with a higher risk of SSIs because it causes tissue hypoxia and vasoconstriction, and compromises the body's normal immune function, which includes attacking infections through the bloodstream. Vasoconstriction occurs when the core body temperature decreases, which is a protective mechanism to divert blood to the center of the body and help maintain the normal body temperature. The reduction of nutrient and oxygen supply to wounds will increase the frequency of surgical wound infection.

"Hypothermia can contribute to wound infections both by directly impairing immune function and by triggering thermoregulatory vasoconstriction, which in turn decreases wound oxygen delivery," says Daniel I. Sessler, MD, professor and chair of the department of outcomes research at the Cleveland Clinic in Ohio.

The promising news is that prevention is easy. Active patient warming is a sure cure for SSIs. Study after study has shown that preventing hypothermia before, during and after surgery by using evidence-based practices prevents post-operative hypothermia and the resultant wound infections.

Mild hypothermia matters
A 1- to 3-degree drop in core body temperature is relatively common in surgical procedures, but even mild hypothermia can have deleterious consequences, says Victoria M. Steelman, PhD, RN, CNOR, FAAN, assistant professor of nursing at the University of Iowa. Research has shown that mild hypothermia:

  • triples the risk of surgical site infection in patients undergoing colon surgery;
  • quadruples the risk of morbid cardiac events;
  • increases blood loss;
  • increases the duration of action of anesthesia and neuromuscular blocking agents; and
  • extends post-anesthesia recovery by an average of 90 minutes.
hypothermia CHILL SPELLS ILL In addition to infection, hypothermia can contribute to increased blood loss and extended length of stay.

If you do nothing to thwart hypothermia, chances are that most patients undergoing surgical procedures will experience perioperative hypothermia, says Dr. Steelman, who stresses the importance of warming throughout the perioperative process, not just before, during or after the case. While pre-operative warming can maintain temperatures above 96.8 ?F throughout all perioperative phases, pre-op warming reduces but doesn't eliminate post-induction hypothermia, says Dr. Steelman.

Her message: Don't wait until the patient is wheeled into the OR to begin active warming measures. Applying warmed blankets or a forced-air warmer, for example, pre-operatively as well as intraoperatively will decrease the incidence of hypothermia compared to intraoperative warming alone, she says. Pre-op warming is an evidence-based intervention "inadequately infused into clinical practice," says Dr. Steelman.

Which active warming method?
Which warming interventions — or combinations thereof — are most effective? That's a question Vallire Hooper, PhD, RN, CPAN, FAAN, manager of nursing research at Mission Health System in Asheville, N.C., would love to answer. "We've done a good job of establishing that certain [warming] products work well," she says, "but the next question is which products work well in certain patient populations. I'm not sure we're there yet."

While forced-air systems are the benchmarks that all other warming modalities are rightly or wrongly compared to, Dr. Hooper says the warming method you choose should take certain variables into consideration. For example, take into account the position of the patient, the length of the case and the amount of surgical field exposure when selecting a warming modality. "The more skin you've got exposed, the more heat loss you're going to have," says Dr. Hooper. You may need to deploy multiple warming approaches — warmed blankets, warm irrigation and IV fluids and forced-air warmers, for example — on a single patient at different times during a procedure, she says.

Pre-warming: Like overinflating a balloon
One thing Dr. Hooper is certain of is the value of actively pre-warming patients when it comes to preventing post-op hypothermia. Pre-warming reduces redistribution hypothermia and it decreases core-to-peripheral temperature gradient. Without pre-warming, it's likely your patient will become hypothermic — even if you institute active warming after induction of anesthesia, according to a literature search.

While evidence suggests pre-warming for a minimum of 30 minutes may reduce the risk of subsequent hypothermia, research has yet to definitively show that pre-warming has the same level of efficacy as intraoperative and post-op warming. "Getting those tissues warmed up in pre-op is like overinflating a balloon," she says. "It gives you a little bit of a cushion."

She theorizes that if patients enter the OR with a higher core temperature, they'll be better able to withstand a drop in temperature once anesthesia is administered. "At the very least, pre-warming may help bump up core temperatures, so even when patients naturally lose heat, they won't drop into the hypothermic range," says Dr. Hooper.

Don't forget about regulating room temperatures. Most surgeons prefer cool ORs. Are your OR temperatures within the suggested range, according to AORN's recommended practices and standards? Holly Coble, BSN, RN, CNOR, specialty coordinator at Cone Health in Greensboro, N.C., found out for herself. Ms. Coble monitored selected OR temperatures for 90 days on total joint procedures, documenting variations at specific time periods during the case. Perhaps not surprisingly, Ms. Coble discovered that the suggested temperature range from AORN's recommended practices wasn't occurring in her ORs. Observed temperatures ranged from 60.8 ?F to 64.1 ?F, well outside the recommended temperature range for ORs of 68 ?F to 77 ?F.

Warming's added benefits
In addition to preventing surgical site infections, preventing hypothermia also helps reduce recovery times, and enhances patient satisfaction and comfort. Those benefits have a trickle-down effect for your facility: Shorter patient stays — and happier patients — mean faster turnover times and more efficient surgical throughput.