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 MgSO 4 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 MgSO 4 group (A) and another thirty to placebo group (B). Participants in group (A) received 50 mg/kg MgSO 4 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 MgSO 4 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 MgSO 4 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 MgSO 4 group (10.1 ± 0.95 vs 6.2 ± 0.87, p = 0.001). Conclusion: We concluded that preoperative low doses (50 mg/Kg) of MgSO 4 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 MgSO 4 as an adjuvant therapy with TAP block.

Intravenous Magnesium Sulphate for Analgesia after Caesarean Section: A Systematic Review

“…However, Mireskanadari et al [ 21 ] reported lower VAS scores in the intervention group at one, six, and 12 hours ( p < 0.05), but not at 24 hours [ 21 ]. Similarly, Elrahman and Youssry [ 20 ] reported lower VAS scores at six and twelve hours in magnesium patients ( p < 0.05), but not at two or at 24 hours. Two trials, Paech et al [ 11 ] and Helmy et al [ 23 ], measured VAS scores at comparable values to the placebo-control group at several time points.…”

“…The seven subsequently included trials ( Table 2 ) encompassed a total of 530 patients, 260 of whom received intravenous magnesium sulphate preoperatively. Four trials administered magnesium concurrently with general anaesthesia [ 20 – 23 ] (240 patients: 110 receiving magnesium sulphate) while the other three were with neuraxial anaesthesia [ 11 , 24 , 25 ] (290 patients: 150 receiving magnesium sulphate).…”

“…One study used a standard dose of 6 grams as a bolus [ 24 ] which would likely be the highest dose-to-weight studied. 50 mg/kg was the most commonly studied bolus dose, with four trials assessing a group with this dose [ 11 , 20 – 22 ]. Of those with postoperative infusion protocols, two groups received a standard 2 g/hr infusion [ 11 , 24 ], one group received 1 g/hr [ 11 ] and one group received a weight-based infusion of 10 mg/kg/hr for 24 hours [ 25 ].…”

“…The effect of magnesium on prolonging time to first rescue analgesia varied in significance between trials. Three of the five found significant prolongation compared with control, p < 0.01 [ 20 , 24 , 25 ]. The remaining two found IV magnesium comparable with IV placebo [ 11 , 23 ].…”

“…Total analgesic requirement in the immediate 24 hours post caesarean was measured in six of the seven trials. Intravenous magnesium resulted in significantly less analgesic consumption than placebo in four of the six, p < 0.01 [ 20 – 22 , 25 ]. Likewise, Elgebaly et al [ 24 ] did not measure total analgesic consumption, though did measure and reveal significantly lower frequency of analgesic intake in their magnesium group (2.5) compared to control (3.0; p < 0.01) [ 24 ] in the first 24 hours post caesarean, which may be a comparable outcome.…”