The effect of magnesium sulfate on sore throat following surgery in patients undergoing general anesthesia

Postoperative sore throat (POST), hoarseness of voice, and cough are common and undesirable complaints in patients receiving general anesthesia following endotracheal intubation. Magnesium (Mg) acts as antagonist at N-methyl-Daspartate (NMDA) receptor and thought to be involved in the management of pain. Furthermore, the presence of NMDA receptors on peripheral cells has been identified. The purpose of this study was to evaluate whether gargling of magnesium sulfate solution reduces postoperative sore throat (POST), hoarseness of voice, and cough. One-hundred seventy patients undergoing elective lumbar laminectomyand percutaneous nephrolithotomy (PCNL), were allocated randomly into two equal groups of control (gargling with placebo) and magnesium sulfate solution. Both groups gargled for 30 seconds 30 minutes prior to induction of anesthesia. The incidence of sore throat, hoarseness of voice, and cough at 0, 2, 4 and 24 hours postoperatively, was assessed. The incidence of postoperative sore throat at 0, 2, 4, 24 hours postoperatively, was higher in control group (25-44.7% versus 4.7-20%; p<0.0001). Although the incidence of postoperative hoarseness and cough was higher among control group (6.5-16.5% versus 1.2-8.2% for hoarseness,and 2.4-9.4% versus 5.9-14.1% for cough); no significant statistically difference was found between two groups except for postoperative hoarseness at 24 hour (p=0.01). Gargling with 10cc of Mg sulfate solution 20%, 20 minutes before induction of anesthesia reduces the incidence of postoperative sore throat, significantly. Hoarseness is also decreased at 24 hour postoperatively, but is not effective to reduce the incidence of cough after surgery.