Effect of Magnesium Sulfate nebulisation on incidence of postoperative sorethroat; A Randomized prospective double blinded study

Sore throat is a common complication in post operative period after tracheal intubation, and one of the most common undesirable anaesthesia associated problems. The incidence of post operative sore throat (POST) has been found to be as high as 21% - 65%.The factors known for post operative sore throat include age, sex, larger tracheal tubes, cuff design, intracuff pressures, mechanical injury during laryngoscopy and intubation, continuous pressure by the inflated tracheal tube cuff on tracheal mucosa causing injury and dryness of the mucosa. The use of Nitrous oxide also increases incidence of post operative sore throat.

Thus various measures has been attempted to reduce the incidence of POST- Some among these are non pharmacological and some pharmacological. Gentle endotracheal intubation for elective surgeries in a single attempt with avoidance of inadvertent trauma to the airway accounts for minimal incidence of sore throat. Awareness and knowledge about the potential risk factors and precautions may thereby help to reduce this complication. These factors include avoidance of large endotracheal tubes, careful airway instrumentation, decreasing the number of attempts of both laryngoscopy and intubation, intubation after full relaxation of larynx, gentle oropharyngeal suctioning and extubation when the tracheal tube is fully deflated. Besides inflating the bulb of endotracheal tube to a pressure <20mmHgand regular checking of cuff pressure also reduces post operative sore throat.

Pre-emptive application of locally active analgesic and anti inflammatory agents can presumably decrease the discomfort, airway inflammation and in turn sore throat. Pharmacological measures include inhalation of beclomethasone and fluticasone, gargling with azulene sulfonate, aspirin, benzydamine hydrochloride and licorice, ketamine as gargle or nebulization, intracuff application of alkalized lignocaine and application of lignocaine spray.

It is an established fact that NMDA receptors (N- methyl D- aspartate) play a role in nociception and inflammation and these receptors are known to be present in central and peripheral nervous system.NMDA antagonists such as magnesium sulfate and ketamine work on peripheral nerve endings in the mucosal lining of the upper airway which in turn may reduce the incidence of sore throat. Moreover magnesium sulfate being an antagonist to NMDA receptors further prevents sensitization to the peripheral pain stimulus.

Various studies have used magnesium sulfate in the form of nebulization in various doses. Nebulization is considered better than other methods as it is easy to administer, smaller volume of drugs with low systemic adverse effects are delivered and better acceptance forpatients may be achieved.

With this background the present study was planned to evaluate the efficacy of preoperative magnesium sulfate nebulization to reduce the incidence of post operative sore throat in patients undergoing elective surgeries with general anaesthesia with endotracheal intubation.