We're impressed by the original research studies published in AJN because of their rigor, relevance, and readability. We were especially interested in “The Effects of Active Warming on Patient Temperature and Pain After Total Knee Arthroplasty” (May) because of the nurse's key role in maintaining postoperative normothermia and because of our own recent study in this area1 and our study (in process) about optimal blanket-warming cabinet temperatures.
The authors state that the temperature of the blanket-warming cupboard wasn't monitored. We wonder, however, at what temperature the cupboard was set. Low cupboard settings (<150°F) produce lukewarm blankets and lower skin temperatures and lower ratings of thermal comfort compared with higher cupboard settings.2-3
We are pleased that the authors measured “thermal comfort,” because little research has been done on this important variable, and agree with the belief that thermal comfort is “integral to a patient's perception of well-being,” as stated in the article.
Based on our own recent study of perioperative hypothermia,1 we caution against using the patient's thermal comfort rating as predictive of core temperature. In our study, we asked patients on arrival to the postanesthesia care unit whether they felt “too hot,” “too cold,” or “just right.” We found that the patient's thermal comfort response did not accurately reflect hypothermia as measured by core (bladder) temperature.
Elizabeth H. Winslow, PhD, RN, FAAN
Patricia A. Kelly, DNP, APRN, CNS, AOCN
Authors Ember E. Benson, Diana E. McMillan, and Bill Ong respond: The readers are correct in noting that the warming cupboard temperature wasn't monitored. We don't know at what temperature the cupboards were set, because various models within the research facility were used, some of which didn't have an indicator displaying the set temperature or the actual temperature. Temperature variations were likely to occur because of real clinical factors, such as the addition of room-temperature blankets, the door opening, and the length of time before the blanket was applied to the patient.
We weren't attempting to predict patients' core temperature using their response to thermal comfort. Rather, we assessed for hypothermia using oral temperature readings, and we measured how satisfied patients were with the thermal comfort provided by the warming methods during the perioperative period and whether this affected their pain.
A previous study found that the application of warmth (via forced air blankets) provides patients with a positive feeling of comfort and reduced anxiety.1 Furthermore, some research suggests a link between anxiety and pain2; providing “anxiety reducing strategies,”3 such as warmth, may ultimately affect postoperative pain.
We are encouraged that perioperative hypothermia is garnering greater interest, as we believe the subject is of critical importance and worthy of more study.
1. Winslow EH, et al. Unplanned perioperative hypothermia and agreement between oral, temporal artery, and bladder temperatures in adult major surgery patients J Perianesth Nurs. 2012;27(3):165–80
2. Bujdoso PJ. Blanket warming: comfort and safety AORN J. 2009;89(4):717–22
3. Sutton LT, et al. The use of warmed cotton blankets on patients following surgery: a safe practice for promoting patient comfort [ASPAN conference abstract] J Perianesth Nurs. 2011;26(3):201–2
References For Author Response
1. Fossum S, et al. A comparison study on the effects of prewarming patients in the outpatient surgery setting J Perianesth Nurs. 2001;16(3):187–94
2. Vaughn F, et al. Does preoperative anxiety level predict postoperative pain? AORN J. 2007;85(3):589–604
3. Feeney SL. The relationship between pain and negative affect in older adults: anxiety as a predictor of pain J Anxiety Disord. 2004;18(6):733–44