Intraoperative MgSO4 infusion protects oxygenation and lung mechanics in COPD patients during general anesthesia. A randomized clinical trial.

Ahmed, Abeer; Sayed, Ahmed H; Elkholy, Jehan; Elshal, Sahar; Badwy, Abdelrahman; Abdelhamid, Bassant; Ollaek, Mohamed

BACKGROUND The purpose of this study was to examine the effects of an intraoperative MgSO4 infusion on arterial oxygenation and lung mechanics in patients with moderate COPD undergoing cancer larynx surgery under general anesthesia (GA). Our primary outcome was arterial oxygenation determined by the PaO2 and PaO2 /FiO2 . The secondary outcomes were lung mechanics (peak airway pressure, airway plateau pressure, dead space, lung compliance, airway resistance) and postoperative complications. METHODS In this randomized controlled double blinded trial, 40 patients with an ASA classifications II and/or III who were diagnosed with moderate COPD and who were scheduled for cancer larynx surgery under GA were randomly allocated into two equal groups, the target (Mg-group) and control group (C-group). In the Mg-group, 30 mg/kg of 10% MgSO4 solution was administered intravenously for over 20 min as the loading dose, followed by the continuous infusion of 10 mg/kg/hr. In the C-group, the same loading and maintenance infusion rates were administered using 0.9% saline. RESULTS Unlike the C-group (baseline "T0" to post-infusion "T1" interval 294±97 vs 238±71 mmHg respectively, p=0.04 ±SD), the Mg-group exhibited preserved intraoperative PaO2 (T0 to T1 interval 271±89 vs 257±53 mmHg respectively, p=0.54 ±SD) and PaO2 /FiO2 (C-group T0 to T1 interval 404±81 vs 349±84, p=0.04 and Mg- group 394±91 vs 379±95, p=0.61, respectively), and these effects were modest. Further, compared to the C-group, the Mg-group exhibited lower airway resistance, dead space, airway plateau pressure, and peak airway pressure, and higher dynamic compliance. The postoperative PaO2 and PaO2 /FiO2 were higher in the Mg-group compared to the C-group. CONCLUSIONS Intraoperative infusion of MgSO4 in patients with moderate COPD undergoing laryngectomy surgery under GA produces mild perioperative protective effects on both arterial oxygenation and lung mechanics.