Electrocardiographic changes during continuous intravenous application of bupivacaine in neonatal pigs.

BACKGROUND It is controversial as to whether T-wave elevation is caused by local anaesthetics, epinephrine, or their combination. It has been shown that T-elevation after intravascular injection of a small bupivacaine test dose is caused by epinephrine and not by bupivacaine. The aim of this study was to investigate ECG changes with higher doses of i.v. bupivacaine. METHODS Thirty neonatal pigs were anaesthetized with sevoflurane and their tracheas intubated and artificially ventilated. Under steady-state conditions, bupivacaine was continuously infused (flow rate 3.2 ml kg(-1) min(-1)) by a syringe infusion pump through a central venous catheter. Group 1 received bupivacaine 0.125%, Group 2 bupivacaine 0.5%. The ECG was continuously printed and subsequently analysed for alterations in heart rate, ventricular de- and repolarization, and arrhythmias at 1.25, 2.5, and 5 mg kg(-1) bupivacaine infused. RESULTS Sinus rhythm persisted in all pigs. Heart rate decreased progressively in both groups, but this was significantly more pronounced in Group 1. T-wave elevation occurred in 40% and 0% (Groups 1 and 2) at 1.25 mg kg(-1), in 80% and 0% at 2.5 mg kg(-1), and in 93% and 80% at 5 mg kg(-1) bupivacaine infused. There were significant differences between the two groups at 1.25 and 2.5 mg kg(-1) infused. CONCLUSIONS Higher doses of i.v. infused bupivacaine can cause T-elevation. With slower injection technique, T-elevation can already be detected at lower bupivacaine doses administered.