[Cardiac toxicity of bupivacaine and diazepam. Experimental study in the anesthetized dog].

The use of diazepam has been suggested for the treatment of convulsions resulting from accidental high plasma levels of local anaesthetics. However, it has been reported that this drug may increase the cardiac effects of bupivacaine in dogs. The present study aimed to assess the effects of diazepam on the electrophysiological signs of a high-dose intravenous bolus of bupivacaine in fourteen dogs, divided into two groups, and anaesthetized with thiopentone and ventilated. All the animals were given a bolus dose of 4 mg.kg-1 bupivacaine. Immediately afterwards, group I (n = 7) received 0.8 ml.kg-1 normal saline solution and group II (n = 7) was given 4 mg.kg-1 diazepam over 1 min. The parameters measured on lead II of the electrocardiogram were: cycle length (R-R interval), QRS length (QRS) and QT interval corrected for heart rate (cQT). Intranodal (AH) and His-Purkinje (HV) conduction times were measured with recording bipolar stimulation electrodes (USCI 6F). Mean aortic pressure (Pao) was measured via a femoral arterial line. In the two groups, the parameters were recorded before and 2, 5, 10 and 15 min after the bupivacaine bolus. Arterial blood samples for measurement of bupivacaine and diazepam serum levels were obtained before and 3, 15 and 30 min after the bupivacaine bolus. There was no significant difference between the two groups in the electrophysiological or haemodynamic parameters at any time. However, the increase in HV and QRS length was a little higher in group I than in group II.(ABSTRACT TRUNCATED AT 250 WORDS)