April 1, 2021

Understanding risk factors and standardized temperature monitoring are also essential in preventing hypothermia.

A surgical leader's ultimate responsibility is to ensure patients achieve the best possible outcomes. A standardized patient warming protocol that includes active prewarming is a critical part of meeting that responsibility. Anita Volpe, DNP, APRN, director of surgical outcomes, research and education for the department of surgery at New York-Presbyterian Queens Hospital in Flushing, discusses how facilities of all types can roll out and monitor effective patient warming initiatives.

What is the most important aspect of preoperative patient warming?

The only effective type of prewarming is active warming, which includes forced-air and conductive methods. Active warming is recommended by professional associations such as ASPAN, AORN, ASA and IHI. Our guideline requires active prewarming for a minimum of 30 minutes for patients scheduled to undergo procedures lasting 30 minutes or more.

But that time frame can be deceiving. Take a simple lipoma removal. The procedure takes only about 20 minutes to perform, but a patient could be in the OR for 30 to 45 minutes in total. Despite active warming's clear benefits, plenty of surgical facilities still give patients a warmed blanket in pre-op and consider that acceptable. It's not. Cotton blankets might make patients feel warm and comfortable, but research shows the heat they give off lasts for only about 10 minutes, and does not impact core body temperature.

What patients are most at risk for inadvertent perioperative hypothermia (IPH)?

Several factors exacerbate the risk of IPH. Preventing it starts with the patient assessment. Staff need to be aware of hypothermia's risk factors (note them in your warming policy) and pay extra attention to patients who exhibit them. Pediatric patients and geriatric patients are most at risk. People with a low BMI (17 or below) and patients on psychotropics, antidepressants and thyroid supplements are also susceptible.

Procedure type and anesthesia technique also play a role. For example, patients undergoing procedures requiring placement of a pneumatic tourniquet are more at risk for IPH. Those who receive spinal anesthesia or regional blocks are at double the risk because the blocks impact the sympathetic vasoconstrictor and vasodilator systems, which affect the body's thermoregulation.

How should facilities monitor patients' temperatures during the perioperative process?

Standardized temperature monitoring methods should be explicitly spelled out in your warming policy. You might have noticed some staff members take oral temperature readings and others opt for an axillary measurement — perhaps for the same patient. These methods simply aren't equitable and are an inconsistent method of temperature-taking that could impact the effectiveness of your warming practices.

It's essential to get buy-in for a standardized monitoring method by including it in your guidelines. For example: "Tympanic measurement is our standard. We'll use it pre-op, intra-op and post-op." If your facility decides on a different standard, that's fine. Pick one and stick with it. If you're unable to use that method due to the patient's health status or procedure type, have a designated backup method in place.

What's the most common mistake facilities make with patient warming?

Mistakes are often made with temperature maintenance. All too often, a patient gets wheeled into the OR, their temperature gets recorded and staff think, "36.4°C, great. The patient's warm." Then what happens? They spend time positioning and prepping the patient and conducting the pre-procedure timeout without actively warming the patient. By the time the surgeon is ready to make the incision, the patient's temperature has dropped.

That's potentially problematic because general anesthetics cause vasodilation, especially during the first hour after induction, letting the body's core heat flow to the extremities. Prewarming and active warming in the OR builds up a patient's temperature reserve to lessen anesthesia's impact on core body temperature.

Inexpensive reflective blankets maintain normothermia in conjunction with traditional active warming methods.

A 115-bed major medical center in the southwest U.S. that included a Level III trauma unit had a numbers problem: 30% of the incentives it received from CMS were directly connected to patient satisfaction, but surveys showed that 33% of its patients were unsatisfied with their thermal comfort.

The facility studied over a six-month time period whether an inexpensive solution — space blankets — could be an effective pre- and post-operative replacement for its traditional warming measures in conjunction with active intraoperative warming methods. The disposable reflective blankets, used for survival purposes, cost approximately $1 per case, according to the facility's study.

Patients arrived at least two hours before a procedure and were given a single unwarmed cotton blanket. The intervention was the simple addition of a $1 space blanket that was placed under the cotton one. The space blanket traveled with patients for use at every stop before and after the OR. Every patient in the facility's same-day surgery units received space blankets in the pre-op bays, a pre-op holding area and the PACU.

The result was a 14% increase in patients' thermal comfort satisfaction ratings. Patients who responded to surveys said things like: "I am basically a cold person, but loved the space blankets and this has been the only time I've had surgery where I can say I was actually warm in the recovery room"; "The silver cover blankets kept me warm. They can be a little noisy when you move"; and "Silver blankets are great. Keep using them."

The study's authors say rural surgery centers, as well as smaller surgery centers on tight budgets, could particularly benefit from this inexpensive yet effective way to maintain normothermia in patients. While the study didn't include an economic analysis, the authors said the practice would likely reduce a facility's linen costs while freeing staff from the burden of repeatedly stocking and distributing multiple cotton blankets.

Finding the right option to fit each patient

Too many patients experience some form of unplanned perioperative hypothermia in which their core body temperature drops below 96.8° F during surgery. A drop in core body temperature can lead to adverse patient outcomes such as myocardial events, infections, poor incision healing, postoperative pain and increased blood loss.

The Association of perioperative Registered Nurses (AORN) issued the latest update to the "Guideline for Prevention of Hypothermia." It provides new evidence supporting more detailed recommendations to improve hypothermia prevention, according to Byron Burlingame, MS, BSN, RN, CNOR, AORN's senior perioperative practice specialist and author of the guideline updates that were published in AORN's online Facility Reference Center on July 1, 2019.

"The biggest barrier to preventing perioperative hypothermia is not having the best option that fits the patient," says Burlingame. He notes that patient size, co-morbidities and the projected duration of the procedure can uniquely influence hypothermia risk.

The updated guideline puts more detailed focus on preoperative selection of patient warming methods based on patient factors, procedure, operative position, location of IV access and warming device constraints. Identifying the patient's specific needs is also discussed in the update in order to maintain a safe core body temperature prior to anesthesia induction.

Implementing the Updates

AORN recommends that every patient receive some form of hypothermia prevention, one major change to practice in the guideline update that impacts every surgical patient. "This major change in practice requires team collaboration when choosing the best method," Burlingame stresses.

He offers important ways for teams to implement this and other updates for preventing hypothermia during surgery into practice:

Assess every patient preoperatively – This is to determine the best method of hypothermia prevention, including active warming, passive warming or a combination of the two. "If your first choice is not available then use a second choice. Frequently, the best intervention is to use a combination of methods," Burlingame says.

Monitor the patient throughout intraoperative care – Anesthesia exposure is associated with 80% of heat loss in surgical patients. This is why it's important to implement active warming methods on hand, as these are the only methods that counter the effects of anesthesia. If the patient is not pre-warmed prior to arrival, the active warming device should be started as soon as possible when the patient arrives and prior to induction of anesthesia, Burlingame recommends. "The challenge is that many people may wait until everything is done to turn on and apply a warming device, which often requires catching up to maintain normothermia," he says.

Continue to manage patient core body temperature after surgery – A postoperative focus on achieving patient normothermia should continue in postoperative care until the patient's temperature is stabilized. "If the same temperature monitoring method used in intraoperative care is not used in postop care, it is recommended to use a different method," explains Burlingame.

Additionally, to help rally your team around ramping up hypothermia prevention practices, Burlingame suggests looking to the purpose statement in the guideline update, which lists the complications related to the patient becoming hypothermic in addition to the improvements in patient satisfaction scores when the patient is warmed.

He also points to evidence-based rationale cited throughout the update for actions to prevent hypothermia. "With so much good evidence out there to support perioperative hypothermia prevention, there are patients still sent to the OR with no hypothermic measures instituted – perioperative nurses have the power to change this," says Burlingame.

The latest version of "Guideline for the Prevention of Hypothermia" can be accessed in AORN's Facility Reference Center under Guidelines, Hypothermia.

Researchers discover a reduced risk ratio for SSIs in patients.

Some might believe keeping surgical patients warm, and their core body temperature above 36°C, simply is about their comfort and overall satisfaction. However, the science says that maintaining normothermia is also vital to a patient's safety. A recent systematic review and meta-analysis of nine studies and 3,627 patients that examined the efficacy of perioperative warming interventions on rates of surgical site infections (SSIs) confirms that safety should be the overriding goal and result of patient warming.

The study, published last year, focused specifically on occurrences of SSIs after procedures while examining rehabilitative length of stay, attributable SSI-related mortality and incidence of readmittance.

The study found warming interventions produced positive effects after introduction of perioperative hypothermia prevention. Eight of the nine studies linked warming procedures with reduced SSI occurrence, with the lone dissenting study exhibiting marginally insignificant strength of association between the factors. SSI risk decreased by approximately 66% in patients who received warmed and humidified CO₂. For non-warmed individuals, SSI risk increased 221% per degree below 35°C, a common clinical point of reference for perioperative hypothermic states.

With the increasing availability of data regarding warming interventions and sustained interest in improving patient surgical outcomes, maintaining normothermia should play an increasingly prominent role across surgery. Because the method is highly practical, relatively inexpensive and easily implementable, it should be quite simple to fit into your episode of care routine.

Administrators indicate when, why and how they warm

In Outpatient Surgery's most recent patient warming survey, 420 administrators at HOPDs and ASCs informed us about their practices and protocols for keeping patients normothermic and comfortable. Here's a quick synopsis of the data the survey generated:

• 64% always warm patients, while just 4% never do.
• The most popular warming devices are prewarmed cotton blankets (82%) and forced-air warming systems (81%).
• When asked about the considerations that factor into why they warm patients, the most popular answer was simply, "We warm all patients" (61%). The other most frequently cited reasons were duration of surgery (53%), type of surgical procedure (44%), ambient OR temperature (43%) and type of anesthesia (39%).
• Among respondents who cited "type of anesthesia" as a reason for warming, 88% warm when administering general anesthesia using inhalational agents, 63% warm when administering moderate to deep sedation using IV agents, 33% warm when administering light sedation using IV agents and 27% warm when administering regional anesthesia with sedation.
• When applied, warming is generally used throughout the entire perioperative process: preoperatively (75%), intraoperatively (88%) and postoperatively (76%).
• In terms of the length of preoperative warming, there was a nearly clean split in terms of variability: 33% warm for less than 30 minutes, 34% warm for exactly 30 minutes and 22% warm for more than 30 minutes.
• When asked about the clinical and operational benefits of warming patients, administrators coalesced around making patients comfortable and preventing shivering (95%), hypothermia prevention (84%), reduced recovery times (63%) and surgical site infection prevention (58%).
• The leading choice among mechanisms for monitoring and recording patient temperatures was temporal and ear sensors (57%), followed by a noninvasive core temperature monitoring system (20%), esophageal temperature probe (16%) and a digital oral option (7%).

The numbers are clear: For a variety of reasons, and through a variety of methods, devices and techniques, patient warming is increasingly seen as a critical component in the perioperative process.