Bupivacaine inhibits baroreflex control of heart rate in conscious rats.

Abstract

BACKGROUND:

Because exposure to intravenously administered bupivacaine may alter cardiovascular reflexes, the authors examined bupivacaine actions on baroreflex control of heart rate in conscious rats.

METHODS:

Baroreflex sensitivity (pulse interval vs. systolic blood pressure in ms/mmHg) was determined before, and 1.5 and 15.0 min after rapid intravenous administration of bupivacaine (0.5, 1.0, and 2.0 mg/kg) using heart rate changes evoked by intravenously administered phenylephrine or nitroprusside. The actions on the sympathetic and parasympathetic autonomic divisions of the baroreflex were tested in the presence of a muscarinic antagonist methyl atropine and a beta-adrenergic antagonist atenolol.

RESULTS:

Within seconds of injection of bupivacaine, mean arterial pressure increased and heart rate decreased in a dose-dependent manner. Baroreflex sensitivity was unaltered after administration of 0.5 mg/kg bupivacaine. In addition, 1 mg/kg bupivacaine at 1.5 min depressed phenylephrine-evoked reflex bradycardia (0.776 +/- 0.325 vs. 0.543 +/- 0.282 ms/mmHg, P < 0.05) but had no effect on nitroprusside-induced tachycardia. Bupivacaine (2 mg/kg), however, depressed reflex bradycardia and tachycardia (phenylephrine, 0.751 +/- 0.318 vs. 0.451 +/- 0.265; nitroprusside, 0.839 +/- 0.256 vs. 0.564 +/- 0.19 ms/mmHg, P < 0.05). Baroreflex sensitivity returned to prebupivacaine levels by 15 min. Bupivacaine (2 mg/kg), in the presence of atenolol, depressed baroreflex sensitivity (phenylephrine, 0.633 +/- 0.204 vs. 0.277 +/- 0.282; nitroprusside, 0.653 +/- 0.142 vs. 0.320 +/- 0.299 ms/mmHg, P < 0.05). In contrast, bupivacaine did not alter baroreflex sensitivity in the presence of methyl atropine.

CONCLUSIONS:

Bupivacaine, in clinically relevant concentrations, inhibits baroreflex control of heart rate in conscious rats. This inhibition appears to involve primarily vagal components of the baroreflex-heart rate pathways.

• Authors: K S Chang, D R Morrow, K Kuzume, M C Andresen
• Journal: Anesthesiology (Anesthesiology) Vol. 92 Issue 1 Pg. 197-207 (Jan 2000) ISSN: 0003-3022 [Print] United States
• PMID: 10638917 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Anesthetics, Local
• Antihypertensive Agents
• Cardiotonic Agents
• Nitroprusside
• Phenylephrine
• Atenolol
• Bupivacaine

Topics

• Anesthetics, Local (administration & dosage, pharmacology)
• Animals
• Antihypertensive Agents (pharmacology)
• Atenolol (pharmacology)
• Blood Pressure (drug effects)
• Bupivacaine (administration & dosage, pharmacology)
• Cardiotonic Agents (antagonists & inhibitors, pharmacology)
• Dose-Response Relationship, Drug
• Electrocardiography
• Heart Rate (drug effects)
• Injections, Intravenous
• Male
• Nitroprusside (pharmacology)
• Phenylephrine (antagonists & inhibitors, pharmacology)
• Pressoreceptors (drug effects)
• Rats
• Rats, Sprague-Dawley