Does Strepsils® With Lignocaine Lozenges Reduce Post Operative Sore Throat Due To Supraglottic Airway Devices

The primary objective of this study is to assess the effect of preoperative administration of oral Strepsils® with added Lignocaine lozenges on the incidence of postoperative sore throat (POST) after general anaesthesia using a Supraglottic Airway Device (SAD). Patients undergoing surgery with general anaesthesia will require ventilation of their lungs with either a flexible tube placed beyond the voice box called an endotracheal tube (ETT) or a tube placed above the voice box called a Supraglottic Airway Device. This tube helps oxygenate the patient and delivers anaesthetic gas to the lungs. The procedure is invasive and uncomfortable, and one of the most common complaints is a sore and inflamed throat after the tube is taken out. This is termed postoperative sore throat (POST). The incidence of POST after SAD is comparable with the ETT and though many studies have focused on ETT, few have examined the SAD. After written informed consent is received in pre-op, a sealed and coded envelope with either the Strepsils lozenges or the placebo lozenges will be given to the patient to be administered orally, with the instruction to dissolve the lozenge by sucking on it 45 minutes prior to surgery. Upon completion of surgery and emergence from general anaesthesia, the patient will be assessed regarding the incidence and severity of sore throat, difficulty in swallowing and difficulty in speaking by the investigator using an interview format. The severity of these symptoms will be graded on a 4-point scale ranging from 0 to 3; 0 being no symptoms, 1 being mild symptoms, 2 being moderate symptoms, and 3 being severe symptoms. This evaluation will be performed at 30 minutes and 24 hours post removal of SAD.

The incidence of postoperative sore throat (POST) has been reported up to 62% following general anaesthesia with varying severity from mild to severe. It is among the top undesirable events experienced by patients after anaesthesia. The supraglottic airway device (SAD) is commonly used as an airway device during the delivery of general anaesthesia. The incidence of POST after SAD use has been documented of up to 49% and is comparable with the incidence of up to 45% when using an endotracheal tube (ETT). Many studies have been evaluating the occurrence of POST with the use of an ETT but studies investigating POST and the use of SAD are limited. A recent study comparing sore throat following three SADs (LMA™ Unique, LMA™ Supreme and I-gel®) found that the incidence of POST was not significantly different between any of them. There are various drugs being extensively investigated to reduce the incidence and severity of POST such as Lignocaine, Dexamethasone, NSAIDs, Liquorice and NMDA receptor antagonists \[1\]. A Cochrane review on the use of Lignocaine for endotracheal intubation concluded that Lignocaine applied topically or administered systemically resulted in reduced risk and severity of POST. Amylmetacresol and Dichlorobenzyl Alcohol, the active ingredient in the standard preparation of Strepsils® lozenges has been shown to reduce the intensity of sore throat in non-anaesthetised subjects, including one study involving Strepsils® Max Plus lozenges which additionally contains Lignocaine, a local anaesthetic agent. Currently studies that evaluated POST after endotracheal intubation using the standard preparation of Strepsils® (without Lignocaine) have reported a reduction in the incidence and severity of POST. The effect of Strepsils® Max Plus (with Lignocaine) lozenges on POST and particularly due to SAD is not known and is the basis of this study. It is the investigator's hypothesis that Strepsils® with added Lignocaine will reduce the incidence and severity of POST based on existing studies that showed the individual and combined beneficial effect of both substances. The goal of this study is to identify a simple, safe, and inexpensive perioperative intervention to reduce the incidence and severity of post operative sore throat due to supraglottic airway devices. Eligible participants include adult patients scheduled to undergo elective surgery under general anaesthesia using a supraglottic airway device. This study is a prospective, randomised, double-blinded study involving 60 subjects and they will assessed on the incidence and severity of sore throat, dysphagia and dysphonia at 30 minutes and 24 hours after removal of the supraglottic airway device using an interview format. Outcomes from this study can be extended to patients who will be receiving general anaesthesia using a supraglottic airway device in the future.