A recent study (Kelly et al., 2013) published in the Journal of PeriAnesthesia Nursing asserts that warming blankets in cabinets set to 200°F (93°C) are safe for clinical use. ECRI Institute disagrees with the paper's finding and continues to recommend that blanket warming cabinet settings be limited to 130°F (54°C). Our continuing recommendation is based on our in-hospital investigations of multiple cases of patient burns resulting from blankets that were in cabinets set to greater than 130°F. In all of these incidents, the blankets were either rolled or left folded when applied to the patients. We do not believe there is a risk of burns when blankets that have been warmed to higher temperatures (e.g., 150°F) are fully unfolded and then applied to patients. However, we maintain our 130°F temperature setting recommendation—even for unfolded blanket use—because there is no way to reliably prevent folded or rolled blankets from being applied to patients. Furthermore, warming blankets are sometimes applied to patients who are insensate or are otherwise unable to respond if the blanket is too warm.
ECRI Institute has reviewed the literature, including the Kelly study, and continues to recommend a maximum temperature setting of 130°F. Our warming cabinet temperature setting recommendation is based on investigations of incidents at three different institutions in which we concluded burns were caused by blankets heated in warming cabinets set to higher than 130°F. The burns took place over a period of 10 years. They included burn accidents involving multiple patients at two institutions and a single patient burn at another institution. These burns, some that were second degree with blistering, occurred to insensate patients (e.g., sedated, under anesthesia) when folded or rolled blankets were applied to the patient, and, in some instances, placed under the patient.
The Kelly paper examined only blankets that were applied in a single or double layer to healthy, conscious volunteers. It did not examine the possible adverse effect of folded or rolled hot blankets placed on or under the patient. Thus, while rare, we believe that there is a risk of burns to patients from blankets taken from the warming cabinets with temperatures set above 130°F. We consider a burn likelihood to be very low for a blanket at 130°F, and judge that as the temperature is increased, the risk of burn can significantly increase. Further, it is not reasonable to expect that folded or rolled blankets heated above 130°F will never be placed on a patient by hospital staff. Therefore, our recommendation assumes that the warmed blankets will at times be applied folded or to patients who will not be able to respond if the blanket is too hot.
It is important to understand that blankets, even when heated to higher than 130°F, cannot actively warm a hypothermic patient. The physics of heat transfer and thermodynamics of patient warming tell us that hot blankets are incapable of actively increasing the patient's core temperature; therefore, this should not be a reason to use hotter blankets. Active warming methods such as forced air warming technologies are more effective at warming patients and are more appropriate if post-operative hypothermia is a significant concern. Passive warming with blankets can only reduce patient heat loss as metabolic processes help the patient to warm from within.