Standardize Your Patient Warming Protocols


Preventing inadvertent perioperative hypothermia demands placing a premium on active prewarming.

I was recruited to work at New York-Presbyterian Queens Hospital and assigned the task of reducing the rate of surgical site infections among colorectal surgery patients. I immediately noticed all patients weren't being warmed preoperatively and asked OR leadership, "That's interesting, you don't prewarm patients here?" I was told, "No, they're warm." But were they? Consider these eye-opening statistics:

  • Research shows 70% of surgical patients develop inadvertent perioperative hypothermia (IPH).
  • Patients who lose just one degree or more of body heat are at increased risk for a morbid event.
  • SSIs are responsible for 40% of infections in the surgical population, and IPH is associated with an increased incidence of post-op infection.

The OR leadership's response spoke volumes, not only about how things were done at our facility back then, but also about the attitude far too many surgical staff have regarding patient warming. When it comes to maintaining normothermia, there's simply no excuse for not actively prewarming your patients.

Turning up the heat

In my quest to right the trend on SSIs, I collaborated with nursing, surgical and anesthesia leaders to develop a colon bundle for our facility. Active patient warming, which occurs throughout the entire surgical episode, is a major component of the bundle. To ensure our staff follows standardized warming protocols, I created a guideline for preventing IPH (you can access it here: Here are some of its key elements:

  • Know the risks. There are several factors that exacerbate the risk of IPH and 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 affects the body's thermoregulation.

  • Temperature monitoring. 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 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 upon 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.

Passive warming with a cotton blanket is an inefficient and ineffective way to warm patients.

Mistakes are often made with temperature maintenance. All too often, a patient gets wheeled into the OR, her 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 time out 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.

  • Pre-op warming. The only effective type of prewarming is active warming, which includes forced-air and conductive warming. It's a method 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 only takes about 20 minutes to perform, but a patient could be in the OR for 30 to 45 minutes in total. That's why our warming policy isn't based strictly on procedure time; we consider how long the patient will be in the OR. For that reason, we prewarm most patients.

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.

Passive warming with a cotton blanket also isn't an economic choice because it increases linen costs and linen inventory. Staff must dedicate time to loading blanket warming units and reapplying blankets in pre-op. That's a lot of inefficiency for no gain in clinical outcomes.

Cost is often cited as a barrier to implementation of active warming methods. To gain buy-in for active warming, consider you'll be saving money on postoperative morbidity. Warm patients wake up quicker because they metabolize anesthetics at an increased rate. They're able to fight off infection because their tissue oxygenation levels are higher. They heal better and they're more comfortable.

  • Intraop warming. Continue the warming method that was initiated in pre-op when patients enter the OR. For procedures lasting longer than 30 minutes, increase the ambient room temperature and, if appropriate, ask the surgeon to use warmed irrigation solutions. This should be an agreed upon methodology between surgery and anesthesia leaders.
  • Post-op warming. Patients can lose 0.5 ?C to 1.5 ?C of their body temperature as they recover in the PACU. Regularly monitoring the patient's temperature therefore remains imperative during the post-operative phase.
HEAT CHECK Prewarmed blankets may make your patients feel warm and comfortable, but the heat they give off lasts for only a matter of minutes and doesn't impact core body temperature.

While patients are recovering, reassess and identify IPH risk factors. Observe patients for signs and symptoms of hypothermia and continue active warming methods until the patient's minimum body temperature reaches 36 ?C.

All too often, staff in PACUs check patients' temperatures only when they arrive in the unit and right before discharge. That's not often enough if active warming has been discontinued, especially if the patient stays in the PACU for more than an hour. You really should be monitoring temperatures upon admission to the PACU, within 15 minutes of arrival and every 15 minutes thereafter for at least an hour. Temperature assessments should continue every hour until discharge or until the patient reaches an acceptable post-anesthesia recovery score and is ready to head home.

Warming trend

The only way to ensure staff's compliance with any new policy is through adequate training and education. Don't forget about informing patients about the importance of active warming protocols. A simple explanation of why pre-warming is important is an effective way to gain acceptance from the patient.

When I first came to my facility, our colorectal SSI rates were a negative outlier compared with other facilities in our state. Now, we're an outlier in the positive direction and our rates are well below the state's average. Patient warming was a big part of that reversal.

Your ultimate responsibility is to ensure patients achieve the best possible outcomes. If you don't have a standardized patient warming protocol in place that includes active prewarming, that responsibility isn't being met. OSM

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