Research Article

Effect of IV Infusion of Magnesium Sulfate on Postoperative Pain after Spinal Anesthesia: A Prospective Randomized Trial


Background: The current study attempts to evaluate the effect of intravenous (IV) infusion of magnesium sulfate during spinal anesthesia on postoperative pain and postoperative analgesic requirements in lower limb surgeries.
Methods: In this double blind, randomized controlled study, 60 patients undergoing elective lower limb surgeries, were selected and randomly divided into two groups. Group I received isotonic saline and group II was administered magnesium sulfate 50 mg Kg-1 IV for 15 min and then 15 mg Kg-1 h-1 by continuous IV infusion till the end of surgery or 2 hours, whichever was earlier. Ramsay sedation scores, VAS scores for pain, time of first administration of rescue analgesic and total analgesic requirement were noted in both the groups.
Results: Statistically significant difference was observed in the VAS score between the two groups at 1st, 2nd, 3rd, 6th, 9th and 12th hour intervals; with VAS scores being lower in the magnesium group (p<0.05). The mean time of first rescue analgesic requirement in control group was 144.00 mins, while in magnesium group was 246.00 mins (p<0.05). The total rescue analgesic requirement was found to be 251.67 mg and 181.67 mg at the end of 24 hours, in control and magnesium groups, respectively (p<0.05).
Conclusion: This study demonstrates statistically significant lowering of postoperative VAS scores, delayed need of postoperative analgesia and reduced total postoperative analgesic requirement in patients receiving intraoperative IV magnesium sulfate compared to the control group. Magnesium sulfate did not cause sedation or any other significant adverse effect in the doses used in the study.

[1] Raja SN, Carr DB, Cohen M, Finnerup NB, Flor H, Gibson S, et al. The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises. Pain. 2020; 161(9):1976-82.
[2] Syal K, Chandel A. Comparison of the post-operative analgesic effect of paravertebral block, pectoral nerve block and local infiltration in patients undergoing modified radical mastectomy: A randomised double-blind trial. Indian J Anaesth. 2017; 61(8):643-8.
[3] Tobe M, Suto T, Saito S. The history and progress of local anesthesia: multiple approaches to elongate the action. J Anesth. 2018; 32(4):632-636.
[4] Schoenmakers KP, Wegener JT, Stienstra R. Effect of local anesthetic volume (15 vs 40 mL) on the duration of ultrasound-guided single shot axillary brachial plexus block: a prospective randomized, observer-blinded trial. RegAnesth Pain Med. 2012; 37(3):242-7.
[5] Scott DB, Lee A, Fagan D, Bowler GMR, Bloomfield P, Lundh R. Acute toxicity of ropivacaine compared with that of bupivacaine. Anesth Analg. 1989; 69(5):563-9.
[6] Ilfeld BM. Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg. 2011; 113(4):904-25.
[7] Forget P. Opioid-free anaesthesia. Why and how? A contextual analysis. Anaesth Crit Care Pain Med. 2019; 38(2):169-172.
[8] Altıparmak B, Çelebi N, Canbay Ö, Toker MK, Kılıçarslan B, Aypar Ü. Effect of magnesium sulfate on anesthesia depth, awareness incidence, and postoperative pain scores in obstetric patients. A double-blind randomized controlled trial. Saudi Med J. 2018; 39(6):579-585.
[9] Taheri A, Haryalchi K, Mansour Ghanaie M, Habibi Arejan N. Effect of low-dose (single-dose) magnesium sulfate on postoperative analgesia in hysterectomy patients receiving balanced general anesthesia. Anesthesiol Res Pract. 2015; 2015:306145.
[10] Haryalchi K, Abedinzade M, Khanaki K, Mansour Ghanaie M, Mohammad Zadeh F. Whether preventive low dose magnesium sulfate infusion has an influence on postoperative pain perception and the level of serum beta-endorphin throughout the total abdominal hysterectomy. Rev Esp Anestesiol Reanim. 2017; 64(7):384-390.
[11] Kiran S, Gupta R, Verma D. Evaluation of a single-dose of intravenous magnesium sulfate for prevention of postoperative pain after inguinal surgery. Indian J Anaesth. 2011; 55(1):31-5.
[12] Ghaffaripour S, Mahmoudi H, Eghbal H, Rahimi A. The Effect of Intravenous Magnesium Sulfate on Post-Operative Analgesia During Laminectomy. Cureus. 2016; 8(6):e626.
[13] Ko SH, Lim HR, Kim DC, Han YJ, Choe H, Song HS. Magnesium sulfate does not reduce postoperative analgesic requirements. Anaesthesiology. 2001; 95(3):640-6.
[14] Dabbagh A, Elyasi H, Razavi SS, Fathi M, Rajaei S. Intravenous magnesium sulfate for post-operative pain in patients undergoing lower limb orthopedic surgery. Acta Anaesth. 2009; 53(8):1088-91.
[15] Hwang JY, Na HS, Jeon YT, Ro YJ, Kim CS, Do SH. IV infusion of magnesium sulfate during spinal anesthesia improves postoperative analgesia. Br J Anaesth. 2010; 104(1):89-93.
[16] Faith Kahraman and Ahmet Eroglu. The Effect of intravenous magnesium sulfate infusion on sensory spinal block and postoperative pain score in abdominal hysterectomy. Biomed Res Int. 2014; 2014:236024.
[17] White P F. The changing role of Non Opioid analgesic techniques in the management of postoperative pain. Anesth Analg. 2005; 101:S5-22.
[18] Scholz J. Mechanisms of chronic pain. Mol Pain. 2014;10(Suppl 1):O15.
[19] Woolf CJ, Thompson SWN. The induction and maintenance of central sensitization is dependent on N-methyl -D- aspartic acid receptor activation: implications for the treatment of post -injury pain and hypersensitivity states. Pain. 1991; 44(3):293-99.
[20] Feria M, Abad F, Sanchez A, Abreu P. Magnesium sulfate injected subcutaneously suppresses autotomy in peripherally deafferented rats. Pain. 1993; 53(3):287-89.
[21] Iseri LT, French JH. Magnesium: nature’s physiologic calcium blocker. Am Heart J. 1984; 108(1):188-93.
[22] Kaur H, Jhand HK, Baghla N, Chaudhry D, Singh A, Kaur R. Analgesic effect of magnesium sulfate as an adjuvant to ropivacaine in pectoral nerve block. Bali J Anaesthesiol. 2020; 4:156-60.
[23] Agrawal A, Agrawal PS, Agrawal S. Effect of continuous magnesium sulfate infusion on spinal block characteristics: A prospective study. Saudi J Anaesth. 2014; 8:78-82.
[24] Kumar M, Dayal N, Rautela RS, Sethi AK. Effect of intravenous magnesium sulfate on postoperative pain following spinal anesthesia. A randomized double blind controlled study. Middle East J Anaesthesiol. 2013; 22(3):251-6.
[25] Olapour A, Goushe MR, Soltanzadeh M, Soltani F, Mohtadi AR, Nezamabadi V. Comparison of intravenous magnesium and placebo administration on postoperative pain and analgesic consumption during spinal anesthesia for inguinal hernia repair. JPSI. 2013; 2(3):16-19.
[26] Tramer MR, Glynn CJ. An evaluation of a single dose of magnesium to supplement analgesia after ambulatory surgery: randomized controlled trial. Anesth Analg. 2007; 104(6):1374–79.
IssueVol 7 No 4 (2021): Autumn QRcode
SectionResearch Article(s)
Magnesium Sulfate Postoperative pain Spinal Anesthesia VAS Score

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How to Cite
Singhal S, Bharti D, Yadav S, Hayaran N. Effect of IV Infusion of Magnesium Sulfate on Postoperative Pain after Spinal Anesthesia: A Prospective Randomized Trial. Arch Anesth & Crit Care. 2021;7(4):209-215.