Implementing Safe and Effective Patient Warming


Use these tips and evidence-based practices to implement and sustain your facility’s protocol.

The sweet spot for an adult’s core body temperature throughout the perioperative experience is 36.5°C to 37.5°C, but maintaining this safe temperature range can be a challenge — and a safety concern, according to Lisa Spruce, DNP, RN, CNS-CP, CNOR, ACNS, ACNP, FAAN, director of evidence-based perioperative practice at the Association of periOperative Registered Nurses (AORN). “Patients can get cold while waiting for surgery in the pre-op area or they can be cold prior to coming to the facility for surgery,” explains Dr. Spruce. “Then, during the first 30 or 40 minutes after a patient receives anesthesia, their core temperature can drop due to the loss of the body’s behavioral response to anesthesia and the fact that anesthesia causes peripheral vasodilation that is associated with the loss of body heat.”

Patients whose core body temperature dips below 36°C are classified as developing unplanned hypothermia, which puts them at an increased risk of surgical site infection, poor wound healing, increased postop pain and increased length of stay in the PACU.

To counteract these effects, AORN recommends pre-warming the patient before surgery in its Guideline for Prevention of Hypothermia, which Dr. Spruce says is based on a solid collection of evidence. For example, the authors of five systematic reviews and nine randomized controlled trials recommend pre-warming the patient. Six clinical practice guidelines, including from the American Society of PeriAnesthesia Nurses and the National Collaborating Centre for Nursing and Supportive Care in the United Kingdom, recommend pre-warming as an intervention for preventing unplanned hypothermia.

AORN recommends pre-warming every patient with active warming — such as intravenous fluid warming, circulating water mattresses and forced-air warming devices — or a combination of active warming methods and passive insulation methods such as warmed cotton blankets.

While some form of patient warming is conducted in most outpatient surgery settings, the methods may vary. Protocols might include different warming tools, temperature measurement strategies, tracked outcome measures and communication approaches. One important difference in protocols occurs when there are procedure-specific warming strategies.

Some facilities apply warming methods according to procedure length. At Urology Surgical Center in Lincoln, Neb., all patients are given warm cotton blankets before surgery and receive warmed IV fluids. As an additional warming strategy, patients who will undergo surgeries lasting more than one hour also receive a forced-air warming blanket prior to anesthesia, according to Clinical Director Jill Hain, RN. “For surgeries less than 60 minutes, we have found we can keep the patient warm by using warmed cotton blankets and warmed IV fluids.” In the PACU, patients are given warm blankets and if they do not maintain normothermia, forced-air warming is applied. Ms. Hain adds that most procedures in her center do not exceed 60 minutes.

RISK FACTOR Pre-warming reduces the impact of anesthesia induction, which causes redistribution hypothermia when the body’s heat moves from the core to the periphery.

All patients have their peripheral temperatures monitored in the OR by a skin temperature sensor that attaches to the anesthesia machine. Temperatures are documented in the patient’s health record and communicated verbally if a patient’s temperature requires additional warming to achieve normothermia. A normothermia outcome equal to or better than 36°C within 15 minutes of arrival in the PACU is tracked for patients whose surgical procedure is longer than 60 minutes. Ms. Hain says her center is at 100% compliance for this outcome.

At Valley Surgery Center in Scottsdale, Ariz., every patient receiving general anesthesia gets a forced-air warming system blanket at the start of their stay, according to Nurse Administrator Meghan Quinn, RN. This blanket is attached to the forced-air machine once the patient is transferred to the OR table and prior to receiving anesthesia.

Throughout intraoperative care, the patient’s peripheral temperature is monitored by the anesthesia professional and documented on the anesthesia record. “If there are any issues with the temperature of the patient, anesthesia will communicate this with the OR team,” explains Ms. Quinn, noting that this communication is an important part of their standardized protocol for maintaining patient normothermia. 

Here are a few tips for implementing effective patient warming practices.

Create consistency. Standardization is a key factor in making sure a patient warming protocol is practiced the same way for every patient, acknowledges Ms. Quinn. To shape her facility’s patient warming protocol, she worked with a team of nurses, physicians, surgical techs and anesthesia care professionals to draft a policy and procedure that includes each representative’s role in patient warming practices. Ms. Quinn stresses the importance of including anesthesia professionals in this work because they play a big part in patient warming and temperature monitoring.

Document and assess. As with any new protocol, Ms. Hain suggests having a clear plan for how a patient warming protocol will be completed and documented. Every patient warming encounter is documented in the patient’s chart to show all warming steps have been completed. She also runs a quarterly report for procedures lasting more than 60 minutes, evaluates these patients’ PACU temperatures at or below normothermia and uses a spreadsheet to track outcomes data according to the name of the anesthesia professional who was in the room for the surgery.

Talk about best practices. One important way to increase long-term sustainability of patient warming is to share the benefits of it with staff, according to Ms. Hain. “If the team realizes that this is not just something else to chart but something that ensures patients will have a better, happier stay, nurses will be on board,” she says.

Reviewing recommendations in the AORN Guideline for Prevention of Hypothermia is one way to help teams realize all the benefits of warming, including patient satisfaction and improved surgical outcomes. Dr. Spruce highlights a few recommendations from the guideline to discuss as a team. Select the temperature measurement site and method in collaboration with the perioperative team based on the requirements of the procedure, anesthesia type, anesthesia delivery method, accessibility of the body site for measurement and invasiveness of the method. Use the same site and method of temperature measurement throughout the perioperative phases when clinically feasible.

When hypothermia is identified before surgery, preoperative staff should initiate interventions to normalize the patient’s core body temperature before the patient is transferred to the operating room, if possible.

AORN’s guideline also includes a few important reminders for the team. Don’t take a patient’s word that they are warm because research has shown that a patient may confirm thermal comfort but actually be hypothermic. Know that 80% of the time, redistribution of body heat from the core to the periphery is the reason for a drop in body temperature during the first hour after general anesthesia is initiated and can cause a patient’s core temperature to drop by 0.9°C to 2.7°C.

Remember that a patient who is hypothermic as they recover from anesthesia will shiver as a natural response and this can negatively impact their recovery because shivering may increase surgical site pain, intracranial pressure and oxygen consumption. OSM 

Evidence to Support Pre-Op Patient Warming

Take time to share the evidence-based practices behind patient warming with your team. Here are a few sources to get started:

• AORN Guideline for Prevention of Hypothermia in the 2022 edition of Guidelines for Perioperative Practice. 
• The Management of Inadvertent Perioperative Hypothermia in Adults, NICE Clinical Guidelines No. 65, 2016. 
• ASPAN’s evidence-based clinical practice guideline for the promotion of perioperative normothermia: second edition, 2010. 
• A Compendium of Strategies to Prevent Healthcare-Associated Infections in Acute Care Hospitals: 
2014 Updates.
• The Centers for Disease Control and Prevention guideline for the prevention of surgical site infection, 2017. 

Randomized Controlled Trials
• Smith CE, Sidhu RS, Lucas L, Mehta D, Pinchak AC. Should patients undergoing ambulatory surgery with general anesthesia be actively warmed? Internet J Anesthesiol. 2007;12(1). 
• Erdling A, Johansson A. Core temperature—the intraoperative difference between esophageal versus nasopharyngeal temperatures and the impact of prewarming, age, and weight: a randomized clinical trial. AANA J. 2015;83(2):99-105. 
• Sato H, Yamakage M, Okuyama K, et al. Urinary bladder and oesophageal temperatures correlate better in patients with high rather than low urinary flow rates during non-cardiac surgery. Eur J Anaesthesiol. 2008;25(10):805–809. 
• Salazar F, Donate M, Boget T, et al. Intraoperative warming and post-operative cognitive dysfunction after total knee replacement. Acta Anaesthesiol Scand. 2011;55(2):216-222. 

Carina Stanton

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