Efficacy of Magnesium Sulfate Added to Local Anesthetic in a Transversus Abdominis Plane Block for Analgesia Following Total Abdominal Hysterectomy: A Randomized Trial

Abstract

Background: Major abdominal surgeries are associated with severe pain, which can affect respiratory and cardiac functions if insufficiently treated; this increases postoperative morbidity.

Objective: We aim at evaluating the efficacy of magnesium sulfate as an adjuvant to local anesthetic in an ultrasound-guided transversus abdominis plane (TAP) block for postoperative analgesia in total abdominal hysterectomy.

Study design: A prospective, randomized, double-blinded clinical trial.

Setting: An academic medical center.

Methods: This study is registered at https://ichgcp.net/clinical-trials-registry/NCT02930707" title="See in ClinicalTrials.gov">NCT02930707). This randomized, double-blinded clinical trial included 60 women undergoing total abdominal hysterectomy that were divided into 2 groups (30 patients per group). Group I received a TAP block with 20 mL per side of 0.25% bupivacaine plus 2 mL magnesium sulphate 10% (200 mg). Group II received a TAP block with 20 mL per side of 0.25% bupivacaine. Visual analog scale (VAS) scores, the time of the first analgesic request, total morphine consumption, and any side effects were assessed and recorded.

Results: The mean postoperative VAS score was significantly reduced in group I compared to group II in all of the time-points except after 10 hours. The mean time of the first request for rescue analgesia was significantly prolonged in group I (15.67 hrs.) compared to group II (7.33 hrs.) (P < 0.001), and the mean total morphine consumption, over the first 24 hours postoperatively, was significantly lower in group I (7.63 ± 2.93 mg) than in group II (16.20 ± 3.24 mg) (P < 0.001). No significant difference in side effects was observed.

Limitations: Sample size.

Conclusion: The addition of 200 mg of magnesium sulfate to bupivacaine in an ultrasound-guided TAP block significantly reduced postoperative opioid requirements, prolonged the duration of analgesia, and reduced the VAS score in patients who underwent abdominal hysterectomy, without significant side effects.

Key words: Magnesium sulfate, TAP block, postoperative pain, total abdominal hysterectomy.