Perioperative Medicine  |   July 2020
Magnesium and Bladder Discomfort after Transurethral Resection of Bladder Tumor: A Randomized, Double-blind, Placebo-controlled Study
Author Notes
  • From the Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea (J.-Y.P.. D.-H.K., J.Y., J.-H.H., Y.-K.K.); and the Department of Urology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea (J.H.H.).
  • Submitted for publication November 5, 2019. Accepted for publication March 17, 2020. Published online first on April 16, 2020.
    Submitted for publication November 5, 2019. Accepted for publication March 17, 2020. Published online first on April 16, 2020.×
  • Address correspondence to Dr. Kim: Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea. kyk@amc.seoul.kr. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Clinical Science / Renal and Urinary Systems / Electrolyte Balance
Perioperative Medicine   |   July 2020
Magnesium and Bladder Discomfort after Transurethral Resection of Bladder Tumor: A Randomized, Double-blind, Placebo-controlled Study
Anesthesiology 7 2020, Vol.133, 64-77. doi:https://doi.org/10.1097/ALN.0000000000003309
Anesthesiology 7 2020, Vol.133, 64-77. doi:https://doi.org/10.1097/ALN.0000000000003309
Abstract

Background: Catheter-related bladder discomfort occurs because of involuntary contractions of the bladder smooth muscle after urinary catheterization. Magnesium is associated with smooth muscle relaxation. This study hypothesized that among patients having transurethral resection of bladder tumor, magnesium will reduce the incidence of postoperative moderate-to-severe catheter-related bladder discomfort.

Methods: In this double-blind, randomized study, patients were randomly allocated to the magnesium group (n = 60) or the control group (n = 60). In magnesium group, a 50 mg/kg loading dose of intravenous magnesium sulfate was administered for 15 min, followed by an intravenous infusion of 15 mg · kg−1 · h−1 during the intraoperative period. Patients in the control group similarly received normal saline. The primary outcome was the incidence of catheter-related bladder discomfort above a moderate grade at 0 h postoperatively. None, mild, moderate, and severe catheter-related bladder discomfort at 1, 2, and 6 h postoperatively, patient satisfaction, and magnesium-related adverse effects were also assessed.

Results: The incidence of catheter-related bladder discomfort above a moderate grade at 0 h postoperatively was significantly lower in the magnesium group than in the control group (13 [22%] vs. 46 [77%]; P < 0.001; relative risk = 0.283; 95% CI, 0.171 to 0.467; absolute risk reduction = 0.55; number needed to treat = 2); similar results were observed for catheter-related bladder discomfort above a moderate grade at 1 and 2 h postoperatively (5 [8%] vs. 17 [28%]; P = 0.005; relative risk = 0.294; 95% CI, 0.116 to 0.746; and 1 [2%] vs. 14 [23%]; P < 0.001; relative risk = 0.071; 95% CI, 0.010 to 0.526, respectively). Patient satisfaction on a scale from 1 to 7 was significantly higher in the magnesium group than in the control group (5.1 ± 0.8 vs. 3.5 ± 1.0; P < 0.001; 95% CI, 1.281 to 1.919). Magnesium-related adverse effects were not significantly different between groups.

Conclusions: Magnesium reduced the incidence of catheter-related bladder discomfort above a moderate grade and increased patient satisfaction among patients having transurethral resection of bladder tumor.

Editor’s Perspective:

What We Already Know about This Topic:

  • Catheter-related bladder discomfort results from involuntary muscle contraction

  • Magnesium relaxes smooth muscle and may therefore relieve bladder discomfort

What This Article Tells Us That Is New:

  • In a randomized trial of 120 patients recovering from transurethral resection of bladder tumor, intravenous magnesium substantially reduced discomfort with a number needed to treat of only 2

  • Intravenous magnesium is a simple and inexpensive way to reduce bladder discomfort