Evaluation of the effect of magnesium sulphate vs. clonidine as adjunct to epidural bupivacaine

Abstract

For treatment of intra and postoperative pain, no drug has yet been identified that specifically inhibits nociception without associated side effects. Magnesium has antinociceptive effects in animal and human models of pain. The current prospective randomised double-blind study was undertaken to establish the effect of addition of magnesium or clonidine, as adjuvant, to epidural bupivacaine in lower abdominal and lower limb surgeries. A total of 90 American Society of Anesthesiology (ASA) grade I and II patients undergoing lower abdominal and lower limb surgeries were enrolled to receive either magnesium sulphate (Group B) or clonidine (Group C) along with epidural bupivacaine for surgical anaesthesia. All patients received 19 ml of epidural bupivacaine 0.5% along with 50 mg magnesium in group B, 150 mcg clonidine in Group C, whereas in control group (Group A), patients received same volume of normal saline. Onset time, heart rate, blood pressure, duration of analgesia, pain assessment by visual analogue score (VAS) and adverse effects were recorded. Onset of anaesthesia was rapid in magnesium group (Group B). In group C there was prolongation of duration of anaesthesia and sedation with lower VAS score, but the incidence of shivering was higher. The groups were similar with respect to haemodynamic variables, nausea and vomiting. The current study establishes magnesium sulphate as a predictable and safe adjunct to epidural bupivacaine for rapid onset of anaesthesia and clonidine for prolonged duration of anaesthesia with sedation.

Keywords: Bupivacaine; clonidine; epidural anaesthesia; magnesium sulphate.

Figure 1

Patient characteristics in the three groups. Data are given as mean (SD)

Figure 2

Systolic arterial blood pressures (SAP) in the operative period. There were no significant differences between groups. Data are given as mean (SD)

Figure 3

Intergroup comparison of intensity of operative pain as measured using a VAS at different time intervals. The difference in intensity of operative pain between groups was statistically significant at 45 minutes (P < 0.05) by using two-way repeated-measures analysis of variance (ANOVA). Data are given as mean (SD)