For most, feeling cold is uncomfortable. Feeling cold is commonly experienced during frigid winter months or when spiking a fever. Despite the discomfort, core body temperature nearly always remains normal.
Unfortunately, during surgery, core body temperature can become dangerously low with far greater consequences than discomfort. When under anesthesia, the patient’s thermoregulatory system loses its ability to control core temperature. This means a surgical patient’s temperature is a much more significant vital sign than some realize. It can — and should be — closely tracked and managed to help ensure patients stay within the normothermic temperature zone between 36.0 and 37.5 C.
Because of the effect of anesthesia, patients do not experience thermal discomfort during surgery, nor can their body respond normally to changes in core temperature. As the potentially harmful effects of hypothermia may not immediately manifest in patients, clinicians may forgo robust monitoring of core temperature.
This gap can lead to unintended hypothermia (a potentially deadly, yet largely preventable condition for those undergoing surgeries involving anesthesia). Patients who are hypothermic when leaving the operating room are more likely to experience postsurgical complications such as bleeding, surgical site infections, prolonged drug effects, and longer PACU times. Depending on the baseline core temperature, as little as a 0.5°C drop in core body temperature can result in unintended hypothermia.
So why isn’t core temperature being rigorously tracked when every degree matters?
With more than 30 years of normothermia management research and innovation, we at 3M have learned there can be a variety of contributing factors — from inefficient product use to educational gaps — depending on the facility and surgery type, including the misconception that patients undergoing short-duration surgeries do not need temperature monitoring or warming.
There’s also a common perception that temperature monitoring products in the marketplace do not fit a facility’s specific needs, such as: the ability to consistently monitor and record temperature; a single device that follows the patient through the perioperative journey; and having a reliable, noninvasive device for regional anesthesia and awake patients.
Other challenges arise because of clinicians who are unaware of their facility’s unintended surgical hypothermia rates or if their rate is above average, a considerable variability in accurate temperature monitoring techniques, and a misunderstanding of the importance of monitoring core vs. surface temperatures.
Let’s take a walk through the stages of a patient’s perioperative journey to examine how to overcome these key patient temperature monitoring hurdles and to raise monitoring’s significance in surgical outcomes.
Stage 1: Preoperative
Patient temperature monitoring and management should begin in the preoperative or holding room because temperature is impossible to manage when it isn’t accurately measured. Monitoring at this stage will determine if the patient’s thermoregulatory system is normal and the patient is ready for surgery.
Temperatures outside the normothermic zone could be a sign that a patient is sick, has an infection or has developed another condition that might make them ineligible for surgery, so knowing actual core temperature beforehand is critically important.
It’s essential to note that not all temperature monitoring devices measure with the same level of accuracy. Clinicians should select a device that measures core body temperature and is able to travel with the patient to monitor temperature consistently in all three stages of the patient’s surgical journey.
Core body, as opposed to surface temperature, is more valuable because it is the most relevant indicator of the body’s overall thermal condition. Moreover, as body temperature decreases so too does the accuracy of surface temperature monitors such as skin sensor probes, liquid crystal displays, and temporal artery scanners.
Temperature monitoring needs to be as accurate as possible right from the start to help prevent the potentially costly and dangerous consequences of hypo- and hyperthermia.
The reliability of temperatures recorded when multiple modalities are used throughout the perioperative journey is poor because each method and personal technique of the clinician has a different measurement accuracy. Using a single monitoring device for the entire perioperative period reduces the variability associated with human factors and different instrument accuracies. Long-term measurement accuracy is important because adverse outcomes are related to the duration of hypothermia.
Stage 2: Intraoperative
Because of the effect anesthesia has on the thermoregulatory system, intraoperative temperature monitoring is essential to help detect hypo- or hyperthermia. While very rare, life-threatening hyperthermia as a result of malignant hyperthermia (MH) develops rapidly. Continuous temperature monitoring substantially improves survival when MH occurs.
Hypothermia is the most common thermal consequence of anesthesia and can affect as many as 50 percent of surgical patients. However, in the absence of core temperature monitoring, there is no way to determine the existence or severity of hypothermia during anesthesia.
Clinicians have the power to reduce unintended hypothermia rates by prewarming their surgical patients. Prewarming will build up a reserve of warm blood in the periphery to result in a less severe decrease in core temperature. That way as the effects of anesthesia begin to cause redistribution, the blood affected by prewarming will circulate back through the body (a redistribution of heat) and help maintain the patient’s overall body temperature.
Proactively warming patients before anesthesia is administered will help increase the likelihood that patient temperature won’t dip into dangerous zones. Continuously monitoring temperature intraoperatively will help manage heat preservation and warming therapy during the procedure.
Clinicians need access to a device that’s compatible with the type of anesthesia the surgery requires. Invasive and reliable temperature probes such as esophageal, bladder, and nasopharyngeal can be used during general anesthesia.
However, patients undergoing neuraxial anesthesia or monitored anesthesia care (MAC), can only tolerate less-invasive yet less-reliable tympanic or skin surface probes. It’s relatively well-known that invasive devices measuring core temperature are reliable and accurate, but clinicians may be less aware that a reliable and noninvasive zero-heat-flux thermometry option also exists.
Also, some patients undergoing regional or neuraxial anesthesia may perceive thermal comfort despite having substantial hypothermia. It’s important to remember that even though the patient is awake and can communicate their perception of comfort, they are still under the effects of anesthesia and a patient’s self-described thermal comfort level is not a reliable indicator of normothermia during neuraxial anesthesia or regional blocks.
The only reliable way to know what a patient’s temperature is for sure is to use a core temperature monitoring device, even with shorter procedures or those utilizing regional anesthesia.
Stage 3: Postoperative
As mentioned previously, using a single device throughout the perioperative journey is better for consistently and accurately providing temperature readouts. And that’s no less true postoperatively.
As patients enter the PACU, clinicians can immediately assess their patient’s current temperature and determine whether that patient should be warmed for comfort or clinical necessity. Consistency and accuracy afforded by a single device used throughout the perioperative journey can help give clinicians confidence that when their patients leave the PACU they are truly normothermic, a requirement for discharge, and have a lower chance of experiencing surgical complications associated with hypothermia.
These core temperature monitoring recommendations will help facilities meet today’s practice guidelines. These best practices can also help Ambulatory Surgery Centers (ASCs) comply with new normothermia quality measure reporting requirements, like the ASC-13: Normothermia Outcome, which was effective January 1, 2018. It’s a pay-for-reporting, quality data program that requires ambulatory surgical centers to report specific quality measures to receive a yearly update to annual payment rates.
11 ASC-13 recommends that patients undergoing general, spinal, or epidural anesthesia for an hour or more must maintain normothermic body temperatures throughout the duration of anesthesia and must be normothermic within 15 minutes of arrival into the PACU.12 Data reporting directly of these patients’ temperature status is required by CMS.
When patient temperature is closely monitored and measured as accurately as possible, clinicians will have an easier time knowing what needs to be done to maintain a patient’s normothermic zone. They’ll know if a patient is trending towards hypothermia and would be able to respond more quickly, before his or her temperature exceeds either end of the spectrum.
The more accurate temperature reporting is today, the more effective normothermia management becomes, and the less likely a facility will be to lose some of its reimbursement down the road or risk a lower patient satisfaction level.
Keeping patients normothermic isn’t simply important to stay compliant with practice guidelines and recommendations, but to lower the patient’s risk of negative surgical outcomes associated with unintended hypothermia.
Clinicians have the incredibly important task of maintaining patient temperature within the safe and critical normothermic zone, as anything under 36.0°C is considered hypothermic.
To be successful, facilities should supply clinicians with a temperature monitoring system that’s compatible with surgeries using any type of anesthesia, can accurately record core body temperature, and follows the patient throughout the perioperative journey. When used properly, temperature monitoring systems that meet these criteria will help fill those gaps, decrease the possibility of clinician technique inconsistencies, and help increase the likelihood that patients remain normothermic.
If you are unsure of your facility’s temperature monitoring method’s accuracy, consider a formal temperature review. 3M offers free temperature auditing tools to help track success and compliance with warming guidelines.
Facilities that know of potential gaps and understand the root causes of unintended hypothermia can work towards building a stronger and more effective temperature monitoring process.
Al Van Duren is the global director of scientific affairs and education in 3M’s Infection Prevention Division. He has a master’s degree in physiology from the University of Minnesota and holds 26 patents for warming, pulmonary, and thermometry devices.
A version of this article appeared in the January/February 2018 issue of Surgical Products.