The Impact of Single Low Dose IV Magnesium Sulphate Adjuvant to Ultrasound Guided Transverses Abdominis Plain Block for Control of Postcesarean Pain

Abstract

Objective: The aim of this study is to determine the role of preoperative low dose intravenous MgSO4 when given adjuvant to ultrasound guided transversus abdominis plane (TAP) block in augmenting postcesarean analgesic effects and reducing opioid requirements during the first 24 hours. Subjects and Methods: In this prospective, randomized double blind study, a total of sixty full term pregnant women were recruited for the study underwent caesarean section. Thirty patients were assigned to MgSO4 group (A) and another thirty to placebo group (B). Participants in group (A) received 50 mg/kg MgSO4 in 100 ml isotonic saline intravenous (IV) over 20 minutes prior to induction of general anesthesia by 30 minutes while participants in group (B) received 100 ml isotonic saline (placebo) by the same route and over the same duration as control. Results: Visual Analogue Scale (VAS) was analysed within 24 hours postoperatively. The mean pain score at 6 and 12 hours postoperatively was significantly lower in MgSO4 group compared to control group (40.4 ± 5.12 vs 53.6 ± 4.92; 26.1 ± 3.01 vs 35.5 ± 3.98 respectively, p = 0.012, 0.005). Comparing both groups regarding the mean time interval of first rescue analgesia (morphine sulphate) requested by the patients, it was longer in MgSO4 group compared to control group. The total dose of rescue analgesia consumed during 24 hours was analysed and it was significantly higher in control group compared to MgSO4 group (10.1 ± 0.95 vs 6.2 ± 0.87, p = 0.001). Conclusion: We concluded that preoperative low doses (50 mg/Kg) of MgSO4 with general anesthesia combined with ultrasound guided TAP block offer longer postoperative pain free periods thus reducing total opioid consumption. In addition to the safety of the drug to the mother and fetus so we recommend IV MgSO4 as an adjuvant therapy with TAP block.