A randomized controlled trial to evaluate the effect of addition of epidural magnesium sulphate on the duration of postoperative analgesia in patients undergoing lower abdominal surgeries under epidural anaesthesia

Abstract

Abstract:Background: Noxious stimuli release excitatory neurotransmitters such as glutamate and aspartate, which bind to various receptors including N-methyl-D-aspartate (NMDA) receptors. Magnesium is a NMDA antagonist and has antinociceptive effects in animal and human models of pain. The addition of magnesium to postoperative epidural infusion may decrease postoperative pain and requirement of opioids.Methods: Sixty patients undergoing elective total abdominal hysterectomies were enrolled to receive either 1ml of magnesium sulfate (50 mg/ml) (Group M) or 1 ml of saline (Group C) in the epidural anaesthetic solution (9ml of 0.125% bupivacaine) for postoperative analgesia. Fentanyl 1µg/kg was given epidurally as rescue analgesia. Haemodynamic parameters, pain assessment using a visual analogue scale (VAS), and fentanyl consumption were recorded in the postoperative period.Results: There was significant difference between groups in the time to first analgesic requirement. Compared with Group C, patients in Group M received smaller doses of epidural fentanyl (P< 0.001). The cumulative fentanyl consumption in 24 h was significantly lower in Group M (119±56 mg) as compared to Group C(267.8± 92 mg)(P < 0.001). Patients in Group M had less pain as measured via VAS score in the first hour of the postoperative period (P < 0.001). The groups were similar with respect to haemodynamic and respiratory variables, sedation, pruritus, and nausea. Conclusion: Administration of magnesium to epidural local anaesthetic solution provides longer duration of postoperative analgesia and reduced postoperative fentanyl consumption without added side-effects.

Comparative evaluation of epidural bupivacaine alone and bupivacaine combined with magnesium sulfate in providing postoperative analgesia: a meta-analysis of randomized controlled trials

“…The literature search identified 4392 studies totally and 112 references from CENTRAL, 2481 references from MEDLINE (OvidSP), and 1799 studies from Embase (Ovidsp). Eleven studies fulfilled our inclusion criteria after screening [12][13][14][15][16][17][18][19][20][21][22]. The details of retrieval was shown in Fig.…”

“…Seven trials applied magnesium sulfate as a bolus followed by a continuous infusion [12][13][14][15][16][17][18], while the remaining four trials applied a bolus injection [19][20][21][22]. In eight studies enrolled participants undergoing Lower abdominal or lower limb surgeries [12,13,15,[17][18][19][20]22], with participants administered epidural anesthesia. Participants in Mohammad 2015 and Radwan 2017 underwent unilateral thoracic surgery and spine surgery respectively with general plus epidural anesthesia.…”

“…3 presents the risk of bias of the included studies. We assessed 3 of these trials as low risk of bias [12,13,16], while the remaining 8 trials as high risk of bias according to our pre-specified criteria [14,15,[17][18][19][20][21][22].…”

“…Subgroup analysis was conducted according to the administration of magnesium sulfate. Five studies administrated magnesium sulfate by bolus injection [12][13][14][15]17], and only one study by bolus followed a continuous injection [20]. We noted the time to the first request for rescue analgesics was also prolonged significantly in the magnesium sulfate group compared with the control group when the study by bolus followed a continuous injection was excluded (SMD 3.67; 95% CI [1.75, 5.58], P = 0.0002, I 2 = 97%).…”

“…The requirement for rescue analgesia was reported in five studies involving 300 participants [12,14,17,19,22]. The meta-analysis showed that the magnesium sulfate group had significantly lower consumption of rescue analgesics than the control group (SMD -2.65; 95% CI [− 4.23, − 1.06], P = 0.001, I 2 = 96%; Fig.…”