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Thermal balance and tremor patterns during epidural anesthesia.
J M Hynson1, D I Sessler, B Glosten
1Department of Anesthesia, University of California, San Francisco 94143-0648.
Anesthesiology
|April 1, 1991
Summary
Central hypothermia during epidural anesthesia is primarily caused by body heat redistribution, not excessive environmental heat loss. Shivering observed is normal thermoregulation, potentially blunted by blocked cold signals.
Area of Science:
- Anesthesiology
- Physiology
- Thermoregulation
Background:
- Central hypothermia is a known complication of epidural anesthesia.
- The exact cause of this hypothermia remains unclear.
Purpose of the Study:
- To investigate the primary cause of central hypothermia within the first hour of lumbar epidural anesthesia.
- To differentiate between excessive heat loss and internal heat redistribution as the cause.
- To characterize the nature of tremor observed during epidural anesthesia.
Main Methods:
- Studied five healthy volunteers before and after epidural anesthesia induction.
- Measured cutaneous heat loss using thermal flux transducers and oxygen consumption for heat production.
- Compared tremor patterns during epidural anesthesia with shivering induced by iced saline infusion.
Main Results:
- During the first hour of epidural blockade, tympanic membrane temperature decreased by 1.1°C, while average skin temperature increased.
- Cutaneous heat loss increased by 16%, but metabolic heat production increased even more.
- Tremor patterns during epidural anesthesia resembled normal shivering, with no abnormal EMG activity detected.
Conclusions:
- Central hypothermia during early epidural anesthesia results primarily from the redistribution of body heat from central to peripheral tissues.
- The observed tremor is likely normal thermoregulatory shivering, potentially with delayed onset or reduced intensity due to blocked cold signals.