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

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.

Inclusion criteria

• Greater than 18 years of age
• American Society of Anesthesiologists Class I-II
• Supraglottic Airway Device usage duration < 2 hours

Exclusion criteria

• History of upper respiratory tract infection, sore throat, dysphonia, or dysphagia in the past 2 weeks
• Morbidly obese (body mass index >35 kg/m2)
• Increased risk of regurgitation or aspiration (eg. symptomatic gastro-oesophageal reflux, hiatus hernia)
• Pregnant or nursing
• Known allergies to study drug
• More than one attempt at Supraglottic Airway Device insertion or use of adjuncts during insertion
• Insertion/presence of a gastric tube
• Expected airway difficulties or conversion to endotracheal tube