Intraoperative magnesium sulfate is not associated with improved pain control after urologic procedures

To evaluate effects of intraoperative magnesium sulfate infusion on pain control and analgesic use in the postanesthesia care unit (PACU).

This is a retrospective review of patients undergoing robot-assisted radical prostatectomy (RARP) and endoscopic procedures of the bladder, prostate, and urethra from 2/2021 to 12/2021. Patients receiving Mg infusion (Mg group) received an intravenous 2-g bolus of Mg at anesthesia induction, followed by infusion of 1 g/h until procedure end. Outcomes were compared with patients who underwent similar procedures during this timeframe without Mg (Control). Endpoints were use of anticholinergic (AC) and belladonna and opium suppositories (BO), maximum pain score, and morphine milligram equivalents (MME) in PACU.

There were 182 patients, with 89 (48.9%) patients in the Mg group and 93 (51.1%) in the Control. Significantly, fewer patients in the Mg group were given AC/BO in PACU (9.0% vs. 21.7%, p = 0.02), with odds of using AC/BO which was 0.36 (95% CI 0.14, 0.83). No differences were found in pain score (p = 0.62) or MME administration (p = 0.94). In subgroup univariate analysis, only those who underwent bladder procedures had a significant difference in use of AC/BO (9.5% vs. 30.2%; p = 0.02). Across all surgeries, Mg infusion was associated with decreased use of AC/BO in the PACU (OR 0.34, p = 0.02); however, stratifying by procedure type did not find a difference in AC/BO use postoperatively.

Intravenous infusion of magnesium was found to decrease use of AC/BO in the PACU; however, this significance was lost after multivariable analysis stratifying by procedure type.