Effectiveness of resistive heating compared with passive warming in treating hypothermia associated with minor trauma: A randomized trial

Objectives: To determine the occurrence of hypothermia in patients with min or trauma, to test the hypotheses that resistive heating during transport i s effective treatment for hypothermia and that this treatment reduces patie nts' thermal discomfort, pain, and fear, and to evaluate the accuracy of or al temperatures obtained at the scene of injury. Patients and Methods: In December 1999 and January 2000, 100 patients with minor trauma were randomly assigned to passive warming or resistive heating . All patients were covered with a carbon-fiber resistive warming blanket a nd a wool blanket, but the warming blanket was activated only in those assi gned to resistive heating. Core (tympanic membrane) and oral temperatures, heart rate, pain, fear, and overall satisfaction of patients were compared between the 2 groups on arrival at a hospital, Results: Hypothermia was noted in 80 patients at the time of rescue. Mean i nitial core temperatures were 35.4 degreesC (95% confidence interval [CI], 35.2 degreesC-35.6 degreesC) in the patients who received passive warming a nd 35.3 degreesC (95% CI, 35.1 degreesC-35.5 degreesC) in those who receive d resistive heating. From the time of rescue until arrival at the hospital, mean core temperature decreased 0.4 degreesC/h (95% CI, 0.3 degreesC/h-0.5 degreesC/h) with passive warming, whereas it increased 0.8 degreesC/h (95% CI, 0.7 degreesC/h-0.9 degreesC/h) with resistive heating. Oral and tympan ic membrane temperatures were similar. Mean heart rate decreased 23 beats/m in in those assigned to resistive heating but remained unchanged in those a ssigned to passive warming. Patients in the resistive heating group felt wa rmer, had less pain and anxiety, and overall were more satisfied with their care. Conclusions: Oral temperatures are sufficiently accurate for field use, Hyp othermia is common even in persons with minor trauma. Resistive heating dur ing transport augments thermal comfort, increases core temperature, reduces pain and anxiety, and improves overall patient satisfaction.