BEYOND COMFORT Besides providing a feeling of warmth, one of the main benefits of maintaining perioperative normothermia is that it helps to reduce surgical site infections.

If you were to ask your doctors and nurses to list the top 5 consequences of hypothermia, shivering would no doubt be No. 1. "Feeling cold," they'd say. But where would increased wound infections fall? Likely far down the line, behind such other well-known complications like post-operative pain, increased intraoperative blood loss and the need for transfusion, and extended length of stay in recovery waiting for the anesthesia drugs to wear off. Yet evidence is mounting that shivering patients send infection rates skyrocketing. A study presented at this year's American Academy of Orthopedic Surgeons meeting found that the odds of deep surgical site infections were 3.3 times higher in hip fracture patients who developed hypothermia than in those who did not.

What's cold got to do with it?
Hypothermia is common during surgery. Anesthetics disrupt the normal control of body temperature, operating rooms are kept cool and patients' skin is uncovered. But what does being cold have to do with developing an infection? Even mild decreases in core temperature impair the immune function and decrease cutaneous blood flow that reduces tissue oxygen delivery. This in turn increases the chance of a wound infection and also impairs the wound-healing process. When the core body temperature decreases, vasoconstriction occurs, 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 increases the frequency of surgical wound infection.

As more clinicians realize that perioperative hypothermia does its real damage in the days after surgery by impairing wound healing and increasing the risk of an SSI, actively warming patients could become a bigger priority, a matter of patient safety in addition to patient comfort.

"Normothermia as a concept now seems to be tied directly to patient safety and quality of care," says Jacqueline Sions, MSN, RN, CNOR, NE-BC, manager of the OR Center of Excellence at West Virginia University Medicine — Ruby Memorial Hospital in Morgantown, W.V. "[Normothermia] has always been something people have been concerned with, but now it needs to be considered as one of the top priorities."

Patients hate feeling cold, but being chilly is a minor and fleeting discomfort compared to the ramifications of a surgical site infection. A deep SSI in a hip fracture repair, for example, could result in a second surgery — including deep irrigation and debridement — as well as removal of components for infection.

CAUSE OR CURE? Some allege that forced-air warming increases infection risk

What does science say?
A 2001 study found that infections more than tripled for patients who experienced intraoperative hypothermia. Normothermic patients in the study had a 6% rate of infection, while patients whose core temperature had decreased 2 ?C from induction to recovery had a 19% incidence of wound infection.

A study released last month, "Intraoperative Hypothermia During Surgical Fixation of Hip Fractures," is believed to be the first and largest study analyzing the effect of intraoperative hypothermia in patients undergoing operative treatment of hip fractures.

In the retrospective study, researchers from Henry Ford Hospital in Detroit, Mich., analyzed data from 1,525 patients who underwent hip fracture surgery from January 2005 to October 2013. More than 90% of patients received a dose of prophylactic antibiotics 60 minutes before surgical incision and dosing continued 24 hours post-operatively. Key findings:

• Hypothermia occurred in 13.2% of the cases, and in 13.6% of cases when a re-warming device was used.
• Hypothermic patients were on average older — in the middle to late 70s — than normothermic patients, and had a lower BMI.
• The odds of deep surgical site infections were 3.3 times higher in patients who developed hypothermia than in those who did not. The overall infection rate was: 1.2% for deep incisional SSI, 1.5% for superficial incisional SSI, and 4.6% for organ/space SSI.

Craig Silverton, DO, a Henry Ford Hospital orthopedic surgeon and the study's senior author, says the association between hypothermia, advanced age and BMI and post-surgery infections, despite the use of re-warming devices are new, sobering risk factors physicians need to be aware of.

"We know that anesthesia can profoundly affect the body's ability to maintain its internal temperature," says Dr. Silverton. "What this study demonstrates is that orthopedic patients in their 70s and those with low body mass further compounds the body to regulate its temperature. Further study is needed to look at the association between infection and hypothermia when a re-warming device is used."

Researchers theorize that it's possible the sustained increased rate of hypothermia with active re-warmer use is the result of the devices being applied in response to intraoperative hypothermia, rather than as a preventative measure. They also says it's fair to wonder whether patients with lower BMI have further impairment of their thermoregulation, with less physiologic tolerance to alteration of thermoregulatory control, which potentially affects their likelihood of experiencing intraoperative hypothermia.

Routinely warming every patient
The key to maintaining normothermia lies in actively warming patients with blankets, blowers, underbody mattresses or IV fluids, what Terry Wicks, CRNA, MHS, a staff anesthetist at Catawba Valley Medical Center in Hickory, N.C., refers to as "cost-effective and efficient solutions that assist anesthesia clinicians in preserving surgical patient thermal homeostasis."

But not every surgical facility routinely warms every patient. The question of whether to warm is usually the anesthesia provider's to answer based on such factors as the duration of the case and the type of anesthetic. He might, for example, actively warm patients undergoing general anesthesia, which can enhance hypothermia as it causes a tonic vasoconstriction of the peripheral blood vessels. He'll reserve active re-warming for regional anesthesia patients only if intraoperative hypothermia is documented or if the case is expected to last more than 60 minutes.

"If we can prevent some surgical site infections by warming patients, then we must strictly maintain normothermia during surgery," says Theresa Criscitelli, EdD, RN, CNOR, the assistant director of professional nursing practice and education at Winthrop-University Hospital in Mineola, N.Y.

SSI LINK Craig Silverton, DO, and his team of researchers at The Henry Ford Hospital, found that hypothermia is associated with an increased risk for infection in patients who undergo surgery to repair a hip fracture.

Do forced-air warming blankets increase SSIs?
Further complicating matters are the allegations that forced-air warming blankets can increase the infection risk in patients undergoing total joint replacement surgery. The allegations state that forced-air warmers stir up bacteria from the OR floor and disrupt protective laminar airflow patterns. While there's no scientific proof, the mere suggestion that forced-air warming could cause SSIs was enough for Ms. Sions to trial other warming options at Ruby Memorial Hospital, including reflective surface blankets and conductive fabric heating mattresses.

While heat loss during surgery is nearly unavoidable, you can prevent a patient from becoming hypothermic and contracting a wound infection because of it. Ms. Sions is quick to point out that hypothermia is only one of many factors that can cause an infection, and preventative measures must be multifaceted.

She says, "It's a lot of things taken together — like wiping off vials, nasal swabbing, surgical attire, skin prepping, at-home showers, antibiotic administration, how you set up the sterile field and the reuse of adhesive tape rolls — that is greater than the sum of its parts." OSM