Efficacy of Magnesium Sulphate as an Adjunct to Ropivacaine in Local Infiltration for Postoperative Pain Following Lower Segment Caesarean Section

Abstract

Introduction: Intravenous and peri-articular magnesium has been shown to reduce perioperative analgesic consumption. With this background, subcutaneous infiltration was hypothesized to potentiate the subcutaneous infiltration of local anaesthetic agent. Aim: To comparatively evaluate the efficacy of magnesium sulphate as an adjunct to ropivacaine in local infiltration for postoperative pain following lower segment cesarean section. Materials and Methods: Sixty parturients undergoing cesarean delivery were randomized to either group A or B in a double blinded manner. After uterine and muscle closure but before skin closure, Group A was administered local subcutaneous wound infiltration of Injection (Inj) ropivacaine 0.75% 150 milligram (mg) or 20 millilitres(ml) whereas, group B patients were given a local subcutaneous wound infiltration of Inj magnesium sulphate 750 mg (1.5 ml of Inj 50% Magnesium sulphate) added to Inj ropivacaine 0.75% (18.5 ml) making a total volume of 20 ml. In postoperative period, Heart rate (HR), Mean Arterial Pressure (MAP), Visual Analogue Score (VAS), supplemental analgesic consumption and timing of each subsequent analgesic was noted for the initial 24 hours. Results: There was no difference in the timings for the requirement of first Intravenous (IV) rescue analgesic among both the groups (p=0.279). However, the need for 2nd and 3rd doses of rescue analgesics was significantly later in group B and the difference was statistically significant with p-value of 0.034 and 0.031 respectively. The number of patients who were administered 2nd, 3rd and 4th doses of rescue analgesics was significantly greater in group A as compared to group B. None of the patients in group B needed more than 4 doses of rescue analgesia while in group A, 5 patients were administered a rescue analgesic for 5th time. The cumulative analgesic requirement in the initial 24 hours was also greater in group A as compared to group B and the difference was statistically significant (p =0.01). The incidence of adverse effects was similar in both the groups. Conclusion: Subcutaneous infiltration of magnesium along with local anaesthetic prolongs the analgesic efficacy of local anaesthetic and is not associated with any significant adverse effects.

Keywords

• cesarean pain
• local anaesthetic infiltration
• subcutaneous infiltration
• wound infiltration