IN positioning for cervical spinal surgery, it is common to place a bolstering device to help support and position the operative site, specifically the anterior aspect of the neck. Ordinarily a 10‐lb leather‐bound sandbag or a liter bag of intravenous fluid is used for this purpose. During a lengthy surgery, warmed intravenous fluid bags also have been used to treat hypothermia. The purpose of the following two case reports is to promulgate a strong awareness of a hazard in using warmed intravenous fluid bags in such circumstances.
A 53‐yr‐old man was taken to surgery on January 6, 1996 for resection of cervical osteophytes via the anterior approach. The patient was placed in the supine position, and a liter bag of intravenous fluid was used to position his head in an extended posture. The intravenous fluid bag was obtained from the blanket warmer (set at 114 [degree sign]F) for patient comfort. It was wrapped in a towel and placed between the scapulate at the upper thoracic and lower cervical region of his back. The surgery proceeded without complication in the ensuing 1.5 h.
After the procedure the patient reported severe pain in the upper thoracic region. Inspection of this site revealed “islands” of second‐ and third‐degree burns overlying the spine and the scapulae (Figure 1
). Plastic surgery consultation was obtained, and successful debridement and skin grafting was accomplished in subsequent days. The patient healed satisfactory without functional impairment.
On January 1, 1992 a 44‐yr‐old woman, in preparation for a lumbar laminectomy, was placed on the operating room Table i
n the knee‐chest position. The procedure required 4.5 h. During this time, progressive hypothermia developed that was resistant to standard warming measures, such as heated inspiratory gasses, warm intravenous fluids, and warming blankets. For this reason, warmed intravenous bags were taken from the blanket warmer and placed in the axillary areas.
After operation the patient was noted to have sustained burns in the regions of the inner arm and upper lateral chest, including the breasts bilaterally (Figure 2
, Figure 3
). Debridement and grafting were subsequently conducted to care for the second‐ and third‐degree burns. The patient healed without functional impairment.
Burns secondary to “warmed” supporting and bolstering devices in anesthetized patients have been reported. Kokate et al. 
performed an animal study wherein a disc‐shaped pressure device generating 100 mmHg pressure was applied for 5 h at different positions on the dorsal surface of the animal. The pressure device contained a heating element, which allowed the effects of the applied pressure at temperatures of 25, 35, 40, and 45 [degree sign]C to be studied. Table 1
outlines the histopathologic observations at various tissue levels for the fixed pressure device at the temperatures noted during a 5‐h period. There was increasing tissue damage between 35 and 45 [degree sign]C; at 25 [degree sign]C tissues remained free of injury. At 35 [degree sign]C, muscle damage deep to the epidermis and dermis predominated, whereas at 40 [degree sign]C there was a mixture of epidermal necrosis and moderate muscle damage. At 45 [degree sign]C, full epidermal necrosis with moderate dermal and severe muscle damage was observed.
Salisbury reported that a temperature even less than 44 [degree sign]C results in tissue death if exposure is prolonged. 
Between 44 and 51 [degree sign]C the rate of cell destruction doubles with each increased temperature degree. Thus, the higher the temperature with constant pressure and time the more likely and deeper will be the burn depth.
Wounds from hypothermic animals during the same conditions were compared with those of normothermic animals. No difference was identified indicating that generalized hypothermia is not protective. However, Iaizzo et al. 
showed that decreasing tissue temperatures to less than 30 [degree sign]C minimizes tissue damage, which would normally result from an applied pressure of 100 mmHg for durations of 5 h or more. A mechanism by which this phenomena occurs was offered by Morris and Field, 
who identified a difference between heating time and injury in normal and ischemic tissue. These results were interpreted in terms of a decreased tissue pH.
The frequent need for bolstering and supporting devices during surgical procedures makes the contour‐forming aspect of a liter bag of intravenous fluid ideal for certain body regions. Such containers are also readily available in the operating theater. Raising its temperature, however, to more than room temperature for protection from the risk of hypothermia or for patient comfort is unsound practice. Litigation involving patients undergoing surgery who sustained burns as a result of either designed warming devices or other heated devices used for patient positioning and bolstering have been reviewed by Cheney et al. 
Burns from either of these two sources represented 1% of a total of 3,000 medico‐legal claims studied. In their review, intravenous fluid bags specifically used as warming devices represented 64% of the burn claims, compared with 19% of the claims when the intravenous fluid bag was used strictly for body positioning and bolstering.
Hypothermia during surgical procedures is best prevented using equipment designed for such purposes. The factors affecting the genesis of such lesions include temperature magnitude, points of bony prominence, duration of pressure‐temperature exposure, skin protection, and patient weight. This time‐temperature‐pressure relation is critical in the development and depth of a burn.
Therefore, we can appreciate how a bag of intravenous fluid warmed nominally and placed in contact with skin and under pressure for a few hours can produce severe burns. In the first patient described, the significant temperature and pressure of the warm fluid bag produced by the bulk of the patient and the scapular spinous process protuberances accelerated the thermal damage. In the second patient, the thin skin of the inner arm, axilla, and ribs in a similar temperature‐pressure environment were contributing factors in the production of a severe thermal burn.
Two cases were presented wherein minimally invasive warming of a patient during surgery resulted in significant thermal burns. Given the potential for thermal injury, warmed bags should not be used as bolsters or warming devices during surgical procedures. Because of the potentially protracted contact time under some pressure, even a bag minimally warm to the touch can cause a full‐thickness thermal burn. All health‐care providers managing anesthesia and postanesthesia care should be made aware of this risk, and department procedures should be modified appropriately.
1. Kokate JY, Leland KJ, Held AM, Hansen GL, Kveen GL, Johnson BA, Wilke MS, Sparrow EM, Iaizzo PA: Temperature-modulated pressure ulcers: A porcine model. Arch Phys Med Rehabil 1995; 76:666-73
2. McCarthy JG, May JW, Littler JW: Burns, Plastic Surgery. Philadelphia, WB Saunders, 1990, pp 787-813
3. Iaizzo PA, Kveen GL, Kokate JY, Leland KJ, Hansen GL, Sparrow EM: Prevention of pressure ulcers by focal cooling: Histological assessment in a porcine model. Wounds: A Compendium of Clinical Research and Practice 1995; 7:161-9
4. Morris CC, Field SB: The relationship between heating time and temperature for rat tail necrosis with and without occlusion of the blood supply. Int J Radiat Biol 1985; 47:41-8
5. Cheney FW, Posner KL, Caplan RA, Gild WM: Burns from warming devices in anesthesia: A closed claims analysis. Anesthesia 1994; 80:806-10
© 1999 American Society of Anesthesiologists, Inc.