A randomised, double-blind, comparative study of preoperative magnesium sulphate versus zinc sulphate gargle for prevention of postoperative sore throat following endotracheal intubation.

BACKGROUND AND AIMS: Magnesium sulphate and zinc sulphate have been reported to attenuate postoperative sore throat (POST). The study aims to compare the effect of preoperative magnesium sulphate and zinc sulphate gargle on the incidence and severity of POST following endotracheal intubation within 24 h.

METHODS: After ethics committee approval, 132 patients were randomly allocated to three groups (M, Z and D). Fifteen minutes before laryngoscopy and tracheal intubation, patients assigned to groups M and Z received a solution for gargle containing magnesium sulphate 20 mg/kg and zinc sulphate containing 40 mg of elemental zinc dissolved in 20 ml of 5% dextrose solution, respectively. Group D received 20 ml of 5% dextrose solution. Incidence and severity of POST (4-point score: Grade 0- no sore throat, Grade 1- mild sore throat, Grade 2- moderate sore throat, Grade 3- severe sore throat) was assessed for 24 h after extubation. Statistica, Version 8.0 (StatSoft, Inc., Tulsa, Oklahoma, USA) was used for analysing the data.

RESULTS: The lowest incidence of POST in group M was 13.6% (95% confidence interval [CI] 3.5-23.7) compared to 0% in group Z, whereas the highest incidence recorded in group M was 25% (95% CI 12.2-37.7) in contrast to 13.6% (95% CI 3.5-23.7) in group Z during the first 24 h after operation. It was observed that the incidence of mild POST (POST score 1) was significantly lower ( P < 0.05) in group Z compared to group M in the first 4 h postoperatively.

CONCLUSION: Zinc sulphate gargle before laryngoscopy and tracheal intubation is more effective for reducing the incidence of POST than magnesium sulphate gargle.