Inadvertent
hypothermia occurs frequently at typical ambient operating room (OR) temperatures, especially in elderly patients receiving
general anesthesia. The aims of the current study were to 1) determine the incidence and magnitude of core
hypothermia in an unusually warm OR environment, and 2) to assess age-related differences in perioperative thermoregulatory responses under these circumstances. Forty patients receiving
general anesthesia for
orthopedic surgical procedures (20 younger patients, 20-40 yr old) and (20 older patients, 60-75 yr old) were enrolled. Mean ambient temperature in the
ORs was 25.8 degrees +/- 0.2 degrees C. Core temperature, vasoconstriction, and shivering were compared in the younger and older age groups. Mean core temperature on admission to the postanesthesia care unit was not significantly different in the younger (36.7 degrees +/- 0.1 degrees C) and older (36.4 degrees +/- 0.1 degrees C) age groups. Only 10% of patients (n = 4, 1 younger, 3 older) were admitted with a core temperature <36.0 degrees C. Only 2% of patients (n = 1, older group) had a core temperature <35.5 degrees C. This very mild degree of
hypothermia was associated with postoperative vasoconstriction in 80% of the younger and 55% of the older patients (P = 0.18). Postoperative shivering occurred in 40% of the younger patients and in 10% of the older patients (P = 0.06). In summary, an ambient OR temperature near 26 degrees
C (79 degrees F) is effective in preventing core
hypothermia during
general anesthesia regardless of patient age. Even very mild postoperative
hypothermia may initiate thermoregulatory responses.
IMPLICATIONS: By increasing ambient temperature in the operating room to 26 degrees
C (79 degrees F), the incidence of core
hypothermia can be dramatically reduced in both younger and older patients.