The febrile response to mild infections in elderly hospital inpatients.

We studied 74 patients whose temperature was normal according to nurses' temperature charts and who were not on antibiotic treatment. The subjects were inpatients whose condition had deteriorated on the ward, or patients admitted the previous day in whom no diagnosis had been established. One simultaneous set of measurements was made of sublingual, rectal, axillary and proximal auditory canal temperatures. A fever was recorded in 63 of 74 patients (85%); 54 febrile patients had a raised rectal temperature, and 54 had a raised proximal auditory canal temperature; 60 patients were febrile at one or both of these sites. A further three patients had raised sublingual temperatures alone. All patients who were regarded as being definitely or probably infected were febrile at one or more sites. Eighty-one per cent of those considered to be possibly infected, and 71% of those with no clinical evidence of infection were also febrile. Rectal and proximal auditory canal temperatures can each detect fever in approximately 86% of febrile patients, sublingual temperature in 66%, and axillary temperature in 32%. Rectal temperature is clinically the most useful temperature measurement in elderly patients. We conclude that significant infections in patients in a warm environment result in a fever which often remains undetected when only sublingual temperature is measured.