Elsevier

Journal of Clinical Anesthesia

Volume 34, November 2016, Pages 379-384
Journal of Clinical Anesthesia

Original Contribution
Magnesium sulfate improves postoperative analgesia in laparoscopic gynecologic surgeries: a double-blind randomized controlled trial,☆☆

https://doi.org/10.1016/j.jclinane.2016.05.006Get rights and content

Highlights

  • Intravenous magnesium sulfate reduced morphine consumption similar to ketorolac.

  • Magnesium sulfate reduced morphine consumption, not nausea and vomiting (PONV).

  • Magnesium sulfate reduced pain intensity similar to intravenous ketorolac.

Abstract

Study objective

The aim of this study is to compare the analgesic effect of intravenous infusion of magnesium sulfate to ketorolac during laparoscopic surgeries.

Design

Double-blind randomized controlled trial.

Setting

University-affiliated teaching hospital.

Patients

Sixty women submitted to laparoscopic gynecologic oncology surgeries.

Interventions

Intravenous ketorolac 30 mg in bolus followed by saline infusion (group K), intravenous magnesium sulfate 20 mg/kg in bolus followed by magnesium 2 mg kg 1 h 1 (group M) or intravenous saline solution 20 mL in bolus followed by saline infusion during the entire procedure (group S).

Measurements

Postoperative pain, nausea, vomiting, sedation, opioid consumption, time to first dose of analgesic.

Main results

Magnesium sulfate reduced opioid consumption compared with placebo in the postoperative, but not in the intraoperative, period. Nausea, not vomiting, was reduced in ketorolac but not in the magnesium group. Pain intensity was higher in placebo than in the other 2 groups during all periods of observation. In the first 60 minutes, pain intensity was lower in the magnesium than in the ketorolac or the placebo group.

Conclusion

Intraoperative magnesium sulfate improves postoperative pain control, acting as an opioid-sparing adjuvant, and is similar to ketorolac 30 mg administered in the beginning of surgery.

Introduction

Magnesium is an important ion in the body and has key roles in several physiological processes. It has been reported to potentiate lidocaine [1], induce analgesia during spinal anesthesia [2], [3], improve morphine analgesia in animals [4]and humans [5], and reduce postoperative morphine consumption [6], [7]. Several trials with different doses, routes, and methods of administration of magnesium have been reported, some with conflicting results [8], [9], [10], [11], [12].

The analgesic effect of nonsteroidal anti-inflammatory drugs (NSAIDs), on the other hand, is well documented. Nonsteroidal anti-inflammatory drugs alleviate postoperative pain by inhibiting cyclooxygenases-1 and cyclooxygenases-2 with subsequent reduction of prostanoids [13] and induction of analgesia. However, some gastrointestinal (GI), renal, and cardiovascular adverse effects prevent the use of these drugs [14].

The search for alternatives to NSAIDs as analgesics leads us to investigate magnesium sulfate, an inexpensive, safe, and easy-to-use drug that can be administered by intravenous route during the perioperative period. Few studies compared magnesium sulfate to NSAIDs [15], [16].

The objective of this study is to quantify the effect of intraoperative magnesium sulfate in postoperative pain and compare these effects with saline and NSAIDs.

Section snippets

Materials and methods

After approval from the local ethics committee, written informed consent was obtained from all patients (CEP 003/11). Sixty American Society of Anesthesiologists (ASA) I-II patients undergoing laparoscopic gynecologic oncology surgeries were enrolled in this study. Exclusion criteria were as follows: chronic pain, cardiovascular, hepatic or renal disease, neuromuscular disease, diabetes, drug or alcohol abuse, obesity, patients treated with calcium channel blockers or magnesium, allergy, or

Results

One hundred twenty patients were eligible for the study, but 60 did not meet the inclusion criteria. The remaining 60 were allocated in the 3 groups, 20 patients per group. Two patients were excluded from each group due to conversion to open surgery, resulting in 18 patients in each group for analysis (Fig. 1).

Most patients were classified as ASA II and were scheduled for laparoscopic hysterectomy (Table 1). There was no difference in age, weight, time to hospital discharge, surgery, and

Discussion

The major finding of this study is that intravenous magnesium sulfate infused during anesthesia significantly reduced postoperative morphine consumption and pain scores, similar to ketorolac tromethamine. There were no reports of hemodynamic instability related to the study protocol or any additive complications. Despite reducing morphine consumption, the incidence of adverse effects was not different among groups, which is in accordance to previous reports [7], [19], [20].

The beneficial

Acknowledgments

The authors thank Dr Alexandre Slullitel for reviewing the text and the Anesthesia team from the Cancer Institute of the State of Sao Paulo for helping us to conclude the study.

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    Conflicts of interest: The authors declare no conflicts of interest.

    ☆☆

    Funding: No funds provided.

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