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Clonidine premedication modifies responses to adrenoceptor agonists and baroreflex sensitivity
1Department of Anesthesiology and Critical Care Medicine, Gifu University School of Medicine, Japan.
Canadian Journal of Anaesthesia = Journal Canadien D'Anesthesie
|February 18, 1999
Summary
Clonidine premedication enhances arterial pressure and heart rate responses to agonists during anesthesia. However, it impairs baroreflex sensitivity to nitroglycerin, potentially increasing hypotension risk.
Area of Science:
- Anesthesiology
- Pharmacology
- Cardiovascular Physiology
Background:
- Clonidine is an alpha-2 adrenergic agonist used for sedation and analgesia.
- Its effects on cardiovascular responses and baroreflex sensitivity during anesthesia require further elucidation.
Purpose of the Study:
- To evaluate the impact of clonidine premedication on arterial blood pressure (AP) and heart rate (HR) responses to adrenoceptor agonists.
- To assess the effect of clonidine on baroreflex sensitivity during anesthesia.
Main Methods:
- Sixty anesthetized patients were divided into two groups: one receiving clonidine premedication and a control group.
- Hemodynamic measurements, including AP and HR, were recorded after administration of phenylephrine, isoproterenol, and nitroglycerin.
- Baroreflex sensitivity was quantified using the slope of the linear regression between HR and AP changes.
Main Results:
- Clonidine significantly augmented AP responses to phenylephrine and HR responses to isoproterenol.
- No significant difference in baroreflex sensitivity was observed in response to phenylephrine.
- Baroreflex sensitivity to nitroglycerin was significantly decreased in patients who received clonidine.
Conclusions:
- Clonidine premedication may increase the risk of critical hypotension during anesthesia and surgery.
- Intravenous phenylephrine and isoproterenol can effectively restore AP and HR, respectively.
- Careful monitoring of baroreflex function is warranted in patients receiving clonidine.