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Effects of epidural anesthesia on splanchnic capacitance
Q H Hogan1, A Stadnicka, J P Kampine
1Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
Advances in Pharmacology (San Diego, Calif.)
|January 1, 1994
Summary
Epidural anesthesia affects splanchnic venous capacitance by causing vasodilation and interrupting sympathetic nerve activity. The response varies with anesthetic dose and block location, influencing circulatory control.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
Background:
- Splanchnic veins are crucial for regulating circulatory capacitance.
- The impact of epidural anesthesia on splanchnic venous capacitance was previously unexamined.
Purpose of the Study:
- To investigate the effects of epidural anesthesia on splanchnic venous capacitance in a rabbit model.
- To elucidate the mechanisms underlying these effects, particularly sympathetic nerve activity.
Main Methods:
- Utilized a rabbit model with direct measurements of mesenteric vein diameter and sympathetic efferent nerve activity.
- Administered epidural lidocaine at varying doses and intramuscular lidocaine.
- Performed regional blocks to isolate the effects of thoracic and lumbar epidural anesthesia.
Main Results:
- Epidural anesthesia induced hypotension, mesenteric venodilatation, and sympathetic interruption.
- Responses were dose-dependent and prolonged with higher epidural doses.
- Thoracic epidural blocks mimicked effects of extensive blocks, while lumbar blocks caused venoconstriction and increased sympathetic activity.
Conclusions:
- Epidural anesthesia significantly alters splanchnic venous capacitance.
- The observed effects result from a balance between sympathetic activation due to hypotension and sympathetic blockade of splanchnic fibers.
- Understanding these mechanisms is vital for managing circulatory dynamics during anesthesia.