Comparison of Intermittent Epidural Top-up Dose Injection with Continuous Epidural Infusion of Local Anesthetics for Lower Extremity Surgery

Lee, Do Huyn; Key, Hwa Young; Han, Jeong Uk

Abstract

BACKGROUND
There are two methods of extending the duration of epidural anesthesia in prolonged lower extremity surgery; an intermittent top-up dosage injection and the continuous infusion of local anesthetics. An intermittent top-up dosage injection, at two-segment regression times in epidural anesthesia, occasionally meets with difficulty relating to the "in-time injection", and if not given in-time, tachyphylaxis can develop. In this study, the intermittent epidural top-up dose injection was compared with the continuous epidural infusion of local anesthetics for prolonged surgery. METHODS: Twenty four healthy patients, scheduled for knee joint surgery, were randomly divided into two groups. An epidural puncture was performed at the L3-4 interspace, with an initial dose of 2% lidocaine (80% of total dose) injected epidurally to both groups, and the remaining 20% of the total dose was injected 20 minute later. The intermittent top-up dosage group (n = 12) was administered with 50% of the initial dose per 1 hour. The continuous infusion group (n = 12) received 50% of initial dose per hour, from 20 minute after the initial dose injection. The blood pressure, heart rate, and the extent of sensory and motor block levels in each group were evaluated. RESULTS: There were no significant differences in the heart rates, blood pressures, levels of sensory block and degrees of motor block. However, the time to reach the T10 dermatome in the sensory block was faster in the continuous infusion than in the top-up dosage group. CONCLUSIONS: The continuous infusion method was no different from the intermittent injection of top-up dosage method in extending the duration of epidural anesthesia.