Use of the NMDA antagonist magnesium sulfate during monitored anesthesia care for shockwave lithotripsy

Abstract

Purpose: To assess whether intravenous magnesium sulfate infusion affects analgesic requirements during monitored anesthesia care (MAC) for shockwave lithotripsy (SWL). Patients and Methods: Fifty patients in ASA class I or II undergoing SWL with MAC were randomized into two groups. Induction of MAC was produced by bolus doses of midazolam 0.03 mg/kg(-1) and fentanyl 0.5 mu g/kg(-1) followed by intravenous infusion of midazolam 0.015 to 0.06 mg/kg(-1)/hr(-1) with fentanyl supplementation 0.2 mu g/kg(-1). In addition, group I patients received magnesium sulfate 30 mg/kg(-1) intravenously as a bolus dose followed by a continuous infusion of 10 mg/kg(-1) /hr(-1) beginning 15 minutes before induction of sedation. The midazolam infusion rate and additional fentanyl doses were adjusted by verbal analog scale (VAS) measurements, observer assessment sedation score (OAA/S), and achieving a target bispectral index (BIS) in a range of 70 to 90. At the end of SWL, the total midazolam and total fentanyl consumptions were recorded, and the serum magnesium concentration was measured. Results: Magnesium caused significant decreases in the total consumption of midazolam (P = 0.001) and fentanyl (P = 0.001). The VAS values at the 15th, 20th, and 25th minute in group I were significantly lower than in group II. In group I, hemodynamic and arterial oxygen parameters were better than in group II. Conclusion: A magnesium bolus and infusion can be utilized to reduce analgesic requirements under MAC during SWL.