A prospective, randomized, double blind, placebo controlled study between pre operative magnesium sulfate and zinc sulfate gargle for prevention of post operative sore throat following endotracheal intubation.

Background: Theantiinflammatory and antinociceptive properties of magnesium by inhibiting calcium entry into the cell and N-methyl-D-aspartate-type(NMDA) glutamate receptors may have a potential role in reducing postoperative sore throat (POST).[1] Several studies also demonstratedefficacy of magnesium sulfate to reduce incidence and severity of POST.[2,3]

On the other hand, recent studies with topical zinc has shown thatit directly activates receptors that promote epithelial repair and high dose oforal zinc sulfate decreases the intensity of mucositis, xerostomia and pain inindividuals undergoing chemotherapy or radiotherapy treatments.[4,5] Recentlyin 2018, one study has observed significant reduction in the incidence andseverity of POST compared to placebo when zinc sulfate lozenges were usedpreoperatively before endotracheal intubation.[6]

Thus, in the present study wehave compared the incidence and severity of post operative sore throatfollowing endotracheal intubation in patient undergoing laparoscopiccholecystectomy after pre operative magnesium sulfate and zinc sulfate gargle.

Methodology: After obtaining permission fromInstitutional Ethics Committee and written informed consent from patients, 132adult patients who met inclusion and exclusion criteria will be randomlyallocated to three equal groups (n = 44 in each group) using computergenerated random number list.

Patients inGroup A will receive magnesium sulfate solution 20mg/kg dissolved into 20 ml of 5% dextrose solution, group B will receive zincsulfate 170 mg dissolved into 20 ml of 5% dextrose solution , group C willreceive 20 ml of 5% dextrose.

Patientswill be asked to gurgle slowly with the solution as per allotment of the groupand drug for 30 sec, 15 min before induction of anesthesia. The solution forgargle will be wrapped in colored nontransparent glasses to ensure blinding.The anesthesiologist distributing the solution for gargling will be unaware ofthe constituent of the drug and allotment of the group and similarly residentdoctors keeping records of different parameters will also be unaware of thegroup allotment.

Tracheawill be intubated with a soft seal cuffed sterile polyvinyl chloride ETT with astandard cuff and an internal diameter of 7 mm for women and 8 mm for men.Laryngoscopy and tracheal intubation will be performed by an experiencedanesthesiologist after ensuring maximum neuromuscular blocking effect asassessed by train‑of‑four (TOF) guard. Tracheal tube cuffwill be inflated with sterile water until no air leakage could be heard with apeak airway pressure at 20 cm H2O. Those patients who required morethan one attempt for passage of the tube will be excluded from the study.

Thepatients will be interviewed in a standard fashion by an anesthesiologist(blinded investigator) who is unaware of the group allocation. On arrival inthe postanesthesia care unit (0 h), and then at half hourly interval for 2hours POST will be graded on a four point scale(0–3).[25] After 2 hour POST score will be assessed at 4 hr, 6 hr,12 hr and 24 hr after extubation. Vital signs, oxygen saturation (SpO2),visual analogue score and sedation score will be recorded at the same time.

Resultswill be analyzed by unpaired Student’s t-test for parametric data andMann-Whitney U-test for nonparametric data when two groups will be compared.One-way ANOVA for parametric data and Kruskal-Wallis test for nonparametricdata will be used while comparing three groups. Fisher’s exact test and Chi-squaretest will be used for categorical data as appropriate. P < 0.05 willbe considered statistically significant. All statistical tests will be done by"STATISTICA" version 9 (StatSoft, Inc. Tulsa, OK, USA).

Expectedoutcome: We expect that both of the drugs will reduce thePOST following laryngoscopy and endotracheal intubation but which one issuperior will only be known after the completion of study.

References:

1)Fawcett WJ, Haxby EJ, Male DA. Magnesium: Physiology and pharmacology. Br JAnaesth 1999; 83:302–20.

2. Borazan H,Kececioglu A, Okesli S, Otelcioglu S. Oral Magnesium Lozenge ReducesPostoperative Sore Throat: A Randomized, Prospective, Placebo-controlled Study.  Anesthesiology2012;117(3):512-518.

3. Teymourian H,Mohajerani SA, Farahbod A. Magnesium and Ketamine Gargle and Postoperative SoreThroat. Anesth Pain Med.2015;5(3):e22367.

4. Arbabi-kalatiF, Arbabi-kalati F, Deghatipour M, Ansari Moghadam A. Evaluation of theefficacy of zinc sulfate in the prevention of chemotherapy-induced mucositis: adouble-blind randomized clinical trial. Arch Iran Med. 2012 Jul;15(7):413-7.

5. Sharir H,Zinger A, Nevo A, Sekler I, Hershfinkel M. Zinc released from injured cells isacting via the Zn2+-sensing receptor, ZnR, to trigger signaling leading toepithelial repair. J Biol Chem. 2010 Aug 20;285(34):26097-106.

6. Farhang B, Grondin L. TheEffect of Zinc Lozenge on Postoperative Sore Throat: A Prospective Randomized,Double-Blinded, Placebo-Controlled Study. Anesth Analg 2018; 126(1):78–83.