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Epidural anaesthesia attenuates the catecholamine response to hypoventilation
R A Stevens1, P J Lineberry, T J Arcario
1Department of Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814.
Canadian Journal of Anaesthesia = Journal Canadien D'Anesthesie
|November 1, 1990
Summary
High epidural blocks with lidocaine in dogs significantly reduced the stress hormone response to hypoventilation. However, the sympathetic nervous system block was not complete, as indicated by persistent baseline levels of norepinephrine and epinephrine.
Area of Science:
- Anesthesiology
- Neuroscience
- Pharmacology
Background:
- The sympathetic nervous system plays a crucial role in the physiological response to stress, including hypoventilation.
- Catecholamines, such as norepinephrine and epinephrine, are key mediators of the sympathetic response.
- Understanding how anesthetic techniques modulate these responses is vital for patient safety.
Purpose of the Study:
- To investigate the effect of a high epidural block using lidocaine on the catecholamine response to hypoventilation in dogs.
- To assess the completeness of the sympathetic efferent block achieved by the epidural administration of lidocaine.
Main Methods:
- Six unanesthetized dogs received intravenous sufentanil, and their catecholamine levels were measured.
- A high epidural block was induced using 8-10 ml of 2% lidocaine.
- Plasma norepinephrine and epinephrine levels were measured before and after the epidural block and sufentanil administration.
- Intravenous lidocaine infusions were administered to assess their effect on catecholamine levels.
Main Results:
- Sufentanil alone significantly increased plasma norepinephrine and epinephrine levels.
- The high epidural block with lidocaine reduced plasma norepinephrine and epinephrine to approximately 50% of baseline levels.
- Subsequent sufentanil administration after the epidural block raised catecholamine levels back to near baseline.
- Intravenous lidocaine did not significantly alter plasma catecholamine levels within the tested range.
Conclusions:
- A high epidural block with 2% lidocaine attenuates the catecholamine response to hypoventilation in dogs.
- The findings suggest that the efferent sympathetic block achieved by a high epidural block is incomplete.
- Further research may be needed to optimize epidural techniques for complete sympathetic blockade.