Electrophysiologic cardiac effects of the new local anesthetic IQB-9302 and of bupivacaine in the anesthetised dog.

BACKGROUND Local anesthetics are not free from potentially fatal complications. Therefore every new local anesthetic should be tested to demonstrate a lower, or at least similar, degree of toxicity over clinically used analogs. Most toxic effects from local anesthetics affect the cardiac electrophysiologic function, so the aim of this study was to characterize the electrophysiologic effects of a new long-acting local anesthetic (IQB-9302, Ciprocaine), and compare them with those of bupivacaine in the anesthetized dog. METHODS Eight Beagle dogs received three increasing infusion doses of either IQB-9302 or bupivacaine. Under isoflurane anesthesia, dogs were instrumented to monitor cardiovascular (cardiac output, arterial and venous blood pressures) and cardiac electrophysiologic data (sinus and atrioventricular (AV) node function, atrial, nodal and ventricular conduction times, and refractoriness). RESULTS Only the highest dose of both drugs induced hemodynamic or electrophysiologic alterations: cardiac output and heart rate were reduced while blood pressures remained unchanged. Atrial and intranodal conduction times and atrial refractoriness increased similarly with both anesthetics, but to a slightly lesser extent with IQB-9302. Significant increases in His-Purkinje and intraventricular conduction times were the most severe noxious effects and occurred only with large doses of either drug. IQB-9302 was slightly less toxic than bupivacaine and, unlike this latter drug, potentially fatal arrhythmias were not induced. CONCLUSION IQB-9302 has hemodynamic and cardiac electrophysiologic effects similar to those caused by bupivacaine. Nevertheless, slightly less toxic effects were derived from IQB-9302 administration than with bupivacaine, and, unlike the latter, the former might be less proarrhytmogenic. The new long-acting local anesthetic IQB-9302 may offer clinical advantages compared with bupivacaine.