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Epidural anesthesia, hypotension, and changes in intravascular volume
Kathrine Holte1, Nicolai B Foss, Christer Svensén
1Department of Surgical Gastroenterology, Hvidovre University Hospital, DK-2650 Hvidovre, Denmark. kathrine.holte@dadlnet.dk
Anesthesiology
|January 24, 2004
Summary
Thoracic epidural anesthesia does not alter blood volumes despite blood pressure reduction. Fluid administration dilutes plasma volume, while vasopressors do not, suggesting vasopressors may be preferable for certain patients.
Area of Science:
- Anesthesiology and Perioperative Medicine
- Cardiovascular Physiology
- Fluid and Hemodynamics
Background:
- Hypotension is a common side effect of epidural or spinal anesthesia, often treated with fluid infusions or vasopressors.
- Previous short-term studies suggested plasma volume may increase during hypotension, but long-term data are lacking.
- Understanding blood volume changes is crucial for effective hypotension management during anesthesia.
Purpose of the Study:
- To investigate the long-term effects of thoracic epidural anesthesia on plasma and erythrocyte volumes.
- To compare the impact of fluid administration versus vasopressor administration on blood volumes and hemodynamics.
- To provide evidence-based guidance for managing hypotension post-epidural anesthesia.
Main Methods:
- 12 healthy volunteers received thoracic epidural anesthesia with bupivacaine.
- Plasma and erythrocyte volumes were measured before and after anesthesia using radiolabeled tracers (125I-albumin, 51Cr-EDTA).
- Following anesthesia, subjects were randomized to receive hydroxyethyl starch (fluid) or ephedrine (vasopressor), with subsequent volume measurements and hemodynamic monitoring.
Main Results:
- Thoracic epidural anesthesia did not alter plasma or erythrocyte volumes despite decreased blood pressure.
- Fluid administration increased plasma volume, indicating dilution, while vasopressor administration did not.
- Both treatments achieved similar hemodynamic effects, but fluid administration led to a decrease in hemoglobin concentration.
Conclusions:
- Thoracic epidural anesthesia alone does not cause significant changes in blood volumes, even with reduced blood pressure.
- Fluid resuscitation primarily expands central volume, causing dilution, whereas vasopressors do not impact volume.
- Vasopressors may be a preferred choice over fluids in patients susceptible to fluid overload, such as those with cardiopulmonary conditions.