Effects of epidural anesthesia on thermal sensation.
OBJECTIVE
Epidural anesthesia decreases the core temperatures triggering vasoconstriction and shivering, presumably by increasing apparent (as opposed to actual) lower-body temperature. We therefore tested the hypothesis that epidural anesthesia also increases the overall perception of warmth.


METHODS
We studied 8 volunteers in a randomized, cross-over protocol separated by at least 48 hours. On one day, epidural anesthesia was induced to a T11 sensory level; the other day was a control without anesthesia. Core temperature and upper-body skin temperatures (33 degrees C) were kept constant throughout. Lower-body skin temperature was set in a random order to 31 degrees C, 32 degrees C, 33 degrees C, 34 degrees C, 35 degrees C, and 36 degrees C and maintained by circulating water and forced air. At each temperature, the volunteers rated their thermal sensation with a visual analog scale (0 = cold, 100 = hot). Core temperature was 36.8 +/- 0.1 degrees C on the control day and 36.7 +/- 0.1 degrees C on the epidural day.


RESULTS
Scores for thermal sensation on the epidural day were near 47 mm at each lower-body skin temperature. On the control day, visual analog scores at a lower-body skin temperature of 31 degrees C were 16 +/- 10 mm and increased linearly to 61 +/- 6 mm at 36 degrees C. Control thermal sensation scores thus equaled those during epidural anesthesia when lower-body skin temperature was near 34 degrees C.


CONCLUSIONS
Thermal sensation with and without epidural anesthesia was comparable at a lower-body temperature near 34 degrees C, which is a normal leg skin temperature. This suggests that autonomic and behavioral thermoregulatory consequences of epidural anesthesia differ-or that the current explanation for reduced vasoconstriction and shivering thresholds during epidural anesthesia is incorrect.
Rajek
A
A
Department of Anesthesia and Perioperative Care, University of California, San Francisco, California, USA.
Greif
R
R
Sessler
D I
DI
D000328:Adult; D000767:Anesthesia, Epidural; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D018592:Cross-Over Studies; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D010101:Oxygen Consumption / Q000187:drug effects; D012881:Skin Temperature / Q000502:physiology; D013697:Thermosensing / Q000187:drug effects*