Benzydamine Hydrochloride and Post-operative Sore Throat

Postoperative sore throat (POST) after laryngeal mask airway (LMA) insertion is common, with reported incidences being as high as 40 - 60%. This is in spite of ongoing efforts to address this pertinent issue, including utilization of updated iterations of LMA devices, reduction of LMA cuff pressure, etc.. POST is an independent predictor of patient dissatisfaction following general anaesthesia and should be investigated further.

The cause of POST is multifactorial, with various mechanisms at play. A significant cause of POST is mechanical injury to the airway mucosa during airway instrumentation, leading to mucosal injury and inflammation. While the application of topical lidocaine on airway mucosa after surgery for analgesic relief may seem to be a possible solution, this may however, increase the risk of aspiration due to diminished cough reflex and swallowing ability. On the other hand, mouth gargles with analgesics may not provide immediate relief for POST as they require much cooperation from the patient that proves to be challenging in the immediate postoperative period.

The Difflam Forte Anti-Inflammatory Throat Spray is an over-the-counter medication indicated for temporary relief of painful mouth and throat conditions. It contains benzydamine hydrochloride (BH) 3 mg/mL, a non-steroidal anti-inflammatory agent (NSAID), and is recommended for adults to spray 2 to 4 times to the affected throat every 1.5 to 3 hours as needed. The effectiveness of benzydramine on alleviating sore throat has been well established in modern medicine. However, a spray formulation of this medication has not been utilized for this purpose yet. With the spray formulation, patient cooperation will not be required for effective delivery of BH medication - a critical factor in view of patient drowsiness post operation.

• Benzydamine Hydrochloride (Drug), also known as benzydamine hydrochloride 3 mg/mL, Difflam Forte Anti-Inflammatory Throat Spray: The Difflam Forte Anti-Inflammatory Throat Spray (iNova Pharmaceuticals Pte Ltd, Singapore) is an over-the-counter medication indicated for temporary relief of painful mouth and throat conditions. It contains benzydamine hydrochloride (BH) 3 mg/mL, a non-steroidal anti-inflammatory agent (NSAID), and is recommended for adults to spray 2 to 4 times to the affected throat every 1.5 to 3 hours as needed.

Primary outcomes

• Postoperative sore throat [1 day; from the immediate and 4 hours postoperative recovery period]: Presence of postoperative sore throat (POST) during the immediate and 4 hours postoperative recovery period. At these two time points patients will be asked whether they have sore throat; and answering 'yes' will be considered as 'POST present'.

Secondary outcomes

• Postoperative pain score [1 day; from the immediate and 4 hours postoperative recovery period]: Pain score during the immediate and 4 hours postoperative recovery period after intervention (Visual analog scale 0-10) will be asked, with zero being no pain, and 10 being the worst pain possible.
• Side effects [1 day; from the immediate and 4 hours postoperative recovery period]: Presence of side effects during the immediate and 4 hours postoperative recovery period. At these two time points patients will be asked whether they have burning and/or stinging, dry mouth, cough, local numbness; and answering 'yes' will be considered as 'burning and/or stinging, dry mouth, cough, local numbness present'.

Sex: Female, ages: 21 Years to 80 Years

Inclusion Criteria:

1. American Society of Anaesthesiologists (ASA) physical status 1-2
2. Female patients having laryngeal mask airway (LMA) for airway management for surgery in KKH;
3. BMI < 40 kg/m2.

Exclusion Criteria:

1. Pregnant;
2. Pre-existing sore throat, or history of upper respiratory tract infection/ abnormalities, hypertension, chronic pain or anti-inflammatory drugs and antihypertensive treatment;
3. Allergies to benzydamine hydrochloride;
4. Symptomatic hiatus hernia;
5. Severe gastroesophageal reflux disease;
6. Contraindications to the use of LMA.

• Ban Leong Sng, Principal investigator, KK Women's and Children's Hospital