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Epidural anesthesia increases apparent leg temperature and decreases the shivering threshold
T H Emerick1, M Ozaki, D I Sessler
1Department of Anesthesia, University of California, San Francisco.
Anesthesiology
|August 1, 1994
Summary
Epidural anesthesia lowers the shivering threshold by increasing the apparent leg temperature, not the actual temperature. This finding explains why patients feel cold and shiver at higher core temperatures during regional anesthesia.
Area of Science:
- Physiology
- Anesthesiology
Background:
- Regional anesthesia, such as epidural and spinal anesthesia, lowers the shivering threshold.
- The exact reason for this impaired thermoregulation is not fully understood.
- A proposed mechanism involves altered peripheral thermal signaling affecting central thermoregulatory responses.
Purpose of the Study:
- To investigate the mechanism by which regional anesthesia affects thermoregulation.
- To test the hypothesis that increased apparent leg temperature contributes to hypothermia tolerance during epidural anesthesia.
- To quantify the contribution of leg temperature to the shivering threshold.
Main Methods:
- Six female participants were studied under four conditions: varying leg-skin temperatures and epidural anesthesia.
- Core hypothermia was induced via central venous infusion of cold fluid.
- Linear regression analyzed the relationship between shivering thresholds and leg temperatures to determine apparent temperature during epidural anesthesia.
Main Results:
- A strong linear correlation was found between shivering threshold and leg-skin temperature (r2 = 0.94).
- Leg-skin temperature contributed approximately 11% to the shivering threshold.
- During epidural anesthesia, apparent leg-skin temperature was ~4°C higher than actual leg-skin temperature.
Conclusions:
- Regional anesthesia, specifically epidural anesthesia, reduces the shivering threshold.
- This effect is attributed to an increased apparent leg temperature, not an actual increase.
- The findings suggest that altered thermal perception due to conduction block is a key factor in thermoregulatory impairment during regional anesthesia.