HYPOTHERMIA is common during extensive and prolonged surgery such as a liver transplantation (OLT). Hypothermia can cause or exacerbate preexisting coagulation abnormalities and myocardial dysfunction. 1,2Efforts to prevent hypothermia during OLT and other major operations have largely employed active warming devices utilizing forced-air warming. A new device, the Allon System with the ThermoWrap garment (MTRE Advanced Technologies Ltd., Centerville, OH), circulates warmed water through a special garment to prevent hypothermia. We report the case of pressure/burn injury secondary to the use of this device.

Case Report

A 67-yr-old woman with end-stage liver disease secondary to primary biliary cirrhosis presented to the operating room for OLT. Preoperative dietary assessment had noted significant muscle wasting and a poor nutritional status. Laboratory analysis revealed a serum albumin level of 2.9 g/dl (normal range, 3.4–4.8 g/dl). The patient's skin was noted to be intact at her admission physical examination.

In the operating room, the patient was placed on a prewarmed ThermoWrap garment (MTRE Advanced Technologies Ltd.) per the manufacturer's directions and under the supervision of a MTRE representative. Before it was used, the ThermoWrap garment was checked by the institutional bioengineering department and was approved for operating room use. General anesthesia was induced, with fentanyl, midazolam, propofol, and succinylcholine. After induction, the usual percutaneous catheters were placed for the surgery. The warming blanket was then wrapped around the the patient's legs with the adjustable Velcro. The ThermoWrap garment is designed to cover the legs, torso, and arms with the use of Velcro attachments. Because of the nature of the surgical procedure, the arms and torso were not wrapped. The temperature sensor for the warming system was placed in the esophagus. Surgery then proceeded. The intraoperative course was unremarkable, with a time of 6.5 h in the operating room. There were approximately 15 min of hypotension during the procedure (defined as less than 70% baseline systolic pressure). There was no evidence of warmer malfunction. The patient's temperature was 36.3°C at the end of the case. The patient was then transferred to the cart without the warming garment and taken to the intensive care unit for postoperative care, where she was extubated 8 h later. The next day, the patient reported back pain in both the thoracic and sacral areas. Examination revealed a several-centimeter area over the mid-sacrum and a similarly sized area on the mid-upper thorax, which was erythematous and blistered in the pattern of the warming blanket and consistent with second-degree burns in the opinion of the attending surgeon (figs. 1 and 2). These and the associated pain resolved over the next few days, and she was discharged on postoperative day 9. The patient visited the transplant clinic on postoperative days 12 and 20; examination during both visits revealed continued appropriate healing of the affected areas.

Fig. 1. Photograph showing skin injury at the mid-sacrum and mid-upper thorax.

Fig. 1. Photograph showing skin injury at the mid-sacrum and mid-upper thorax.

Fig. 2. Photograph showing mid-upper thorax skin injury.

Fig. 2. Photograph showing mid-upper thorax skin injury.


The Food and Drug Administration-approved Allon System employs the ThermoWrap blanket, body temperature sensors, and a microprocessor that controls the heating unit. The ThermoWrap garment can be wrapped around the extremities and torso, thus allowing for a greater surface area for heat transfer and more efficient temperature regulation. The ThermoWrap blanket is filled with water; temperature is regulated via  a microprocessor that receives feedback from up to three temperature sensors. The sensors can be utilized to measure rectal, esophageal, and skin temperatures. Feedback from the sensors adjusts the temperature of the water circulating through the garment.

The warmed, circulating water has been used to maintain body temperature intraoperatively in both children and adults. 3,4A small study in patients undergoing OLT found this technology to be safe and effective in maintaining core temperature. 5To date there have been no previous reports of injury associated with the use of warmed circulating water technology. Our patient had several risk factors that may have predisposed her to skin injury, including age, poor nutritional status, low serum albumin level, and prolonged surgery 6,7; however, these characteristics are not infrequent in patients who undergo OLT or other major surgical procedures. Whether the injury was primarily due to pressure, heat, or a combination of these two factors is difficult to discern. Because the patient complained of burning pain on her back soon after she was able to effectively communicate with her caregivers, the primary injury was most likely a burn. MTRE Advanced Technologies Ltd. was notified of this patient-related injury.

Despite the existence of some data affirming its effectiveness, clinicians planning to use the Allon System or any system that employs circulating warmed fluid for prolonged procedures should first consider this potential risk.


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