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Cool surgical tables, frigid ORs, paper-thin gowns: It's no wonder patients are at risk of hypothermia throughout the perioperative process. But did you know that a drop in average core body temperature of 1.9 ?C could triple surgical site infection risks? Maintaining normothermia isn't just about scoring big on patient satisfaction surveys — it has a major impact on your infection prevention efforts.
On the rise
For years, my hospital's post-op infection rate crept upward until in 2006 it eclipsed our acceptable range of 0.4 percent to 0.8 percent of cases performed. We formed a Surgical Site Infection Prevention (SSIP) task force to drill down to the root cause of the infections. The task force confirmed that caregivers prepped surgical sites using electric clippers instead of razors, and that they administered the appropriate antibiotics 60 minutes before procedure start times and discontinued them within the first 24 hours after surgery. Those infection prevention practices checked out.
Next, we decided to audit patients' temperatures in PACU, thinking that'd be the best way to determine how well our intraoperative warming interventions were working. We wanted to see if post-op hypothermia affected our infection rates, as clinical research has shown that it can.
Turns out we had some work to do before reaching any meaningful conclusions: A scant 47 percent of patients had their temperature taken and recorded after surgery. That figure needed to improve, as did our temperature auditing if we wanted an accurate assessment of how well we warmed patients.
Constantly remind staff about measuring post-op temperatures and recognize those who lead the charge. We singled out nurses who remembered to measure and record patients' temperatures by placing gold stars next to their names on a publicly displayed poster. It took 7 months before our staff doubled its temperature recording compliance rate, finally cracking the 90 percent goal we established from the start.
We set the lowest acceptable post-op temperature at 36 ?C, but ideally want readings in PACU to reach 37 ?C. Our initial review of post-op temps — before we instituted heating interventions — included 388 patients, almost half of whom were below the 36 ?C minimum threshold, ranging from 35.1 ?C to 35.7 ?C.
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How Does Hypothermia Increase Infection Risks? |
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Beyond concerns over patients' post-op comfort and increased risks of myocardial injury, intraoperative hypothermia is also a cause of increased surgical site infections. Minor deviations in core temperature cause the body to initiate thermoregulatory defenses. Vasoconstriction and shivering are the body's autonomic responses that normally act to preserve and regain heat when exposed to cold. Anesthesia usually results in vasodilatation and a cessation of the normal shivering mechanism; this, coupled with cold operating rooms, blood loss, and cold intravenous fluids can result in significant reductions in patient body temperatures. The body's principle defense against surgical pathogens is oxidative killing by bloodborne neutrophils. Hypothermia triggers constriction of blood vessels, decreases blood flow to tissues and decreases oxygenation of the surgical wound tissues. In this way, hypothermia allows bacteria a more favorable environment in which to take hold and multiply. Hypothermia also slows down the production of superoxide radicals, thus diminishing the oxidative action of neutrophils. SSIs are thought to be more likely to take hold during prolonged hypothermic surgical events, and begin demonstrating signs and symptoms within several hours after completion of surgery. They have become a hot topic not only because of the direct negative effect on wound healing, but because they can lead to prolonged and expensive hospital stays. — Adam Dorin, MD, MBA Dr. Dorin ([email protected]) is an anesthesiologist and partner with Anesthesia Service Medical Group and medical director of the RiverView MD Facility and Spa in San Diego, Calif. |
On the hot seat
So what factors caused patients' temperatures to drop below our target temperature and the acceptable minimum threshold? We looked at numerous possibilities to find out, including:
- Patient age. The risk of hypothermia was loosely correlated with patients' ages up to 50-plus years. For patients older than 55 years of age, however, we failed to discover a positive link to hypothermia risks.
- Anesthesia type. We compared cases involving spinal and general anesthesia, noting median post-op temperatures of 35.6 ?C and 36.2 ?C, respectively. That's a significant difference.
- Surgery type. A procedure's duration didn't seem to affect hypothermia rates. However, patients undergoing ENT procedures had higher median temperatures than patients undergoing joint replacement surgery. Laparoscopic procedures didn't have a positive correlation to hypothermia risks.
- Ambient temps. AORN recommends keeping OR thermostats set between 68 ?F and 73 ?F to help regulate patients' core temperatures. The ambient temperature in my hospital's surgical suites fluctuated between 62 ?F and 81 ?F, well outside the low and high ends of AORN's recommended range. Surprisingly, that didn't seem to affect patients' core temperatures; we found no correlation between OR temperatures and occurrences of hypothermia.
The answer lies with your anesthesia providers
We were somewhat surprised to discover that a case's primary anesthesia provider was a statistically significant predictor of a patient's post-op core temperature. While we needed to review a larger subset of procedures to identify individual providers who needed to improve their temperature monitoring and warming interventions, our task force was able to conclude that working with anesthesia providers is key to maintaining normothermia throughout the surgical process.
Sure, monitoring patients' temps is the responsibility of every caregiver from pre-op to PACU, but it's the anesthesia providers who shoulder the load in the OR. During our investigation, the SSIP task force discovered that some providers were more proactive than others in their patient warming interventions and the frequency of intra-op temperature monitoring. When we showed providers the data collected by our task force and explained the importance of their roles in the fight against SSIs, they were more than happy to work with our surgical team to maintain normothermia. In fact, we noticed a significant improvement in our ability to meet post-op target temperatures after notifying anesthesia providers of our patient-warming goals.
Learn from our experience; discuss patient warming with each of your anesthesia providers. Remind them of the impact that normothermia has on preventing SSIs. Ask them to be diligent in their monitoring of patients' temperatures. Aim to keep 90 percent to 95 percent of patients warm before, during and after procedures. Try to maintain median patient temperatures of 37 ?C throughout surgery. Conduct regular post-op temperature audits of each case, link the temperatures to the case's anesthesia provider, chart their performances and keep them updated on their abilities to maintain normothermia.
Also work with your providers to set a minimum temperature threshold in the OR and ask that they step up their warming interventions whenever a patient's temperature dips below that number. (Our providers now use forced-air warmers whenever temperatures drop below 35.5 ?C.) Wrap warmed blankets around patients in pre-op, and use warming devices to heat IV fluids and insufflation gases. The higher you're able to get patients' core temperatures before they head into surgery, the better your chances of maintaining normothermia throughout the procedure.
A warming trend
The monthly monitoring system we initially implemented to record patients' post-op temperatures is still in place, letting us continue to assess the optimal surgical conditions that promote normothermia. Maintaining normothermia should be routine for all procedures. Warm patients to keep them comfortable, and more importantly, safe throughout surgery. OSM
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4 Ways to Avoid Unplanned Hypothermia |
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AORN recommends that you understand why hypothermia occurs in surgical patients and the preventative steps you can take to maintain a patient's core temperature. Here's a quick review. 1. Know the risks. All anesthetized patients are at risk of hypothermia, but certain factors put a greater emphasis on your need to monitor pre-, intra- and post-op core temperatures. Pay particular attention to older patients, those with low body weight or metabolic disorders and patients taking antipsychotics or antidepressants. Open cavity surgery, blood infusion and the use of irrigation solutions can also drop a patient's core temperature. 2. Set a baseline. Take patients' core temperature readings during pre-op assessments. That baseline reading alerts you to pre-existing hypothermia or lets you avoid overheating already warm patients. Continue to monitor a patient's temperature throughout surgery and in PACU, intervening when needed with patient warming devices whenever you notice drops in core temperatures. 3. Preheat. Start heating interventions 15 minutes prior to surgery. While patients' perceptions of being cold are not accurate measures of hypothermia risk, warming their skin and peripheral tissue before anesthesia induction helps prevent redistribution hypothermia. 4. Stay warm. Keeping patients normothermic throughout surgery reduces negative outcomes. Forced-air warming is a clinically proven technique for preventing hypothermia. Warming IV fluids is an effective intervention when more than 2L/hr of fluid is administered (delivering less fluid than that has little impact on hypothermia risks). Heating irrigation fluid helps maintain normothermia, but should be employed in conjunction with forced-air warming techniques. IV and irrigation fluids should be warmed to normal body temperature (98.6 ?F). — Daniel Cook Source: Recommended practices for the prevention of unplanned perioperative hypothermia. AORN J. 2007;85(5):972-988. |
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