Hypothermia, defined as core body temperature <36°C, affects 50% to 70% of surgical patients.1 Maintaining normothermia during surgery is promoted to reduce surgical wound infections, ensure normal coagulation, and expedite hospital discharge.2,3 In addition, patient temperature is now monitored by the National Hospital Inpatient Quality Measures (Centers for Medicare & Medicaid Services), The Joint Commission, and the Surgical Care Improvement Project (SCIP-Perioperative Temperature Management).
New variations of forced-air warming (FAW) blankets, such as the Bair Paws™ flex gown system (Arizant Healthcare Inc., a 3M company, 3M Infection Prevention Division, St. Paul, MN), are specifically designed to facilitate both preoperative and intraoperative warming with a single patient gown. We report a significant and unexpected complication after routine use of this FAW gown system in an adult patient undergoing ambulatory surgery.
The patient provided written informed consent for use of this material and photograph for educational purposes.
A 44-year-old, 81-kg man with a medical history of recurrent neck cancer was scheduled for a microdirect laryngoscopy with microflap biopsies and CO2 laser excision of vocal cord lesions under general anesthesia. His preoperative vital signs were within normal limits including admission temperature of 36.9°C orally. In keeping with the hospital admission and holding room protocol, the patient was dressed in the FAW gown (Bair Paws flex gown system) approximately 1 hour before the start of anesthesia. The FAW control was initiated on the medium heat setting and could be adjusted at the patient’s discretion.
The patient was transported to the operating room (OR) dressed in the FAW gown (disconnected from heat source) along with 2 cotton blankets for additional comfort and coverage. Room temperature in the OR was approximately 20.5°C. Anesthesia was induced with midazolam, fentanyl, lidocaine, and propofol, and insertion of an oral 6.0 laser-safe endotracheal tube was facilitated by a bolus of rocuronium. Anesthesia was maintained with desflurane in an air/oxygen mixture titrated commensurate with use of the CO2 laser. The patient’s body temperature was measured via a skin probe in the axilla.
The OR table was then rotated 90° to facilitate access to the mouth, positioning of surgical staff, and access to key operative equipment. In addition, the patient was supine on a padded mattress and secured to the OR table by 2 safety belts (per OR policy). One belt was fitted in a standard position over the upper thighs, and a second safety belt was placed circumferentially around the lower thorax. The warm air hose was connected to the distal port of the FAW gown in between the 2 belts.
The first recorded skin temperature was 35.6°C, which was approximately 20 minutes after induction of anesthesia. After final positioning and draping of the patient, the FAW controller was initiated at the “high” temperature setting (43°C). It remained at that setting for the duration of the 3-hour and 50-minute surgical procedure. Notably, despite the lack of any open abdominal or chest cavity during surgery and the FAW heat controller set to its maximal setting, the patient’s temperature did not increase substantially (highest recorded temperature during the duration of the operation was only 35.7°C).
Near the completion of surgery, it was noted that several surgical instruments, retractors, suction tubing, and other operative devices had been positioned on top of the FAW over the patient’s abdomen, compressing the anterior aspect of the air blanket. While preparing for tracheal extubation and on removal of the FAW gown, a very warm area of intense erythema with mottling was noted over the left flank, left lateral torso, and left upper thigh directly underneath the FAW inlet hose. Closer inspection revealed that there were small erythematous linear punctate marks on the skin that aligned with the small air hole perforations in the FAW gown (Fig. 1).
After tracheal extubation, the patient was transported to the postanesthesia care unit. His vital signs in the postanesthesia care unit remained within normal limits, and oral temperature on arrival to the unit was 36.6°C. The patient denied significant pain in the area of the truncal erythema though he confirmed a sustained warm sensation in that region. The trauma burn service was consulted and diagnosed a superficial (first degree) burn that involved 5% of the patient’s body. Within 1 hour, the erythema faded to approximately 25% to 50% of the original hue. Following recommendations of the consulting team, the patient was managed conservatively with close observation and symptomatic therapy. He was informed of the circumstance and the likely mechanism. The patient wished to return home and was discharged the same evening. By phone follow-up, the first-degree burn fully resolved over the next 24 to 48 hours. He was offered clinic follow-up, but he declined it. The patient experienced no scaring or pain afterwards and completely recovered from the incident.
This ambulatory surgery patient sustained a 5% body surface area first-degree burn from an FAW device initially applied and operated according to manufacturer’s guidelines. Essentially the entire heat output of the FAW device was confined to this enclosed space bounded on 4 quadrants by external barriers (Fig. 2). Restricting the flow of heated air from the entire distribution of the FAW gown appears to be the mechanism of this patient’s injury.
In a simulated reconstruction of the procedure, it was surprisingly easy to create a scenario where only 1 portion of the FAW received all the heated air and the remainder of the blanket remained underinflated or uninflated (Fig. 2). Indeed, the surface of the manikin juxtaposed to this restricted area of the gown was noticeably and significantly warmer to the touch than under the area of the underinflated gown. The product label for the FAW system warns against use of the high setting in patients with low cardiac output, severe vascular disease, or poor or marginal cutaneous perfusion. Because none of these conditions were applied to our patient, we were comfortable using the high (43°C) setting on a continuous basis.
An intraoperative clue might have alerted the anesthesia team earlier to what occurred in this patient. Generally, FAW procedures should produce a linear temperature increase by approximately 0.4°C after the first hour of application.4 In our patient, despite continuous use of the warming unit set at 43°C for multiple hours, there was no significant increase in the patient’s temperature. Additional uncertainty was introduced by the necessity of using the axillary skin for temperature monitoring because of the operative procedure in the mouth. Axillary temperatures are more variable and typically lag behind core temperature sites by 2 to 3 hours due to variation in skin blood flow, air temperature, insulation, and other external factors. Thus, we were puzzled but not alarmed by the lack of increase in this patient’s axillary temperature (total increase of only 0.1°C) during surgery. Nonetheless, failure of core temperature to respond appropriately to warming interventions should alert the anesthesia professional to investigate the application, continuity, and function of all heating device(s). In addition, alternative sites for core temperature monitoring such as the bladder or rectum could be considered a more reliable and timely measure of temperature during ear-nose-throat surgery.
The FAW gown system is an important strategy to assist anesthesia professionals in maintaining perioperative normothermia. This strategy invokes presurgical warming for 1 hour before the start of anesthesia to mitigate the effects of vasodilation produced by opioids, IV anesthetics, and inhaled anesthetic gases that inhibit the tonic vasoconstriction of peripheral skin.5 Without presurgical warming, blood flows from the warmer core to the cooler periphery, accounting for a large and rapid 1°C to 1.5°C decrease in core temperature during the first hour of anesthesia.6 Prewarming helps maintain core temperature after the induction of anesthesia.
While FAW devices are generally considered to be simple, cost effective, and safe, as shown in this case as well as other reports of thermal burns, they have the potential to produce patient injury.7–11 Intraoperatively, pediatric patients sustained injuries secondary to obstructed flow of an FAW.7,8 In these cases, the infants had the FAW placed around their bodies during their operation. Postoperatively, they too developed first-degree burns. Misuse of FAW devices including “hosing” or blowing heated air directly onto the patient’s skin without attaching the machine to the manufacturer’s blanket is a recognized cause of injury to patients.9 This can be especially dangerous in patients with compromised circulation such as those with diabetes or heart disease.10,11
To prevent future burns from FAW devices in our ORs, perioperative staff have modified positioning protocols to ensure all safety straps are secured underneath the FAW blankets. Furthermore, surgical instruments are secured on stands or OR tables and not placed on top of the warming gowns or patients. Lastly, anesthesia professionals should be wary of an uncharacteristic lack of response to FAW devices, particularly when using the high-heat setting and when using axillary temperature as a surrogate for core temperature. OR personnel must be vigilant to check the function of the warming device itself, as well as to ensure free inflow and egress of air from FAW gowns and blankets.
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