Laryngeal mask airway (LMA) has superseded endotracheal intubation for elective as well as emergency surgeries. This could be due to some of its advantages such as ease of insertion, no requirement for muscle relaxant, less invasive approach and fewer complications as compared to endotracheal intubation. Post-operative sore throat (POST) is one of the noted complications of endotracheal intubation as well as LMA insertion. Though the reported incidence of sore throat following insertion of LMAs is less as compared to endotracheal intubation,, it is still prevalent and can lead to patient dissatisfaction besides prolonging hospital stay. Variable factors such as individual differences in insertion skills and techniques, use of lubricants, cuff pressure and duration of surgery can contribute to the incidence of POST. A number of techniques have been adopted to reduce the incidence of POST such as reducing cuff pressure, lignocaine spray, application of lignocaine gel over device, lignocaine nebulisation, intravenous (IV) magnesium sulphate, ketamine gargle and nebulisation,, saline gargle, tramadol gargle, induction with propofol, preoperative IV gabapentin and use of muscle relaxant before the insertion of supraglottic airway device. Though most of the techniques are effective in reducing the severity of POST, the overall incidence is still high. The aim of this study was to compare the efficacy of 2% lignocaine viscous gargle versus ketamine gargle in reducing the incidence of POST following insertion of the classic LMA.
After obtaining Institutional Ethics Committee approval and written informed consent, the study was conducted in a tertiary care teaching hospital in India between August 2017 and January 2018. Ninety patients aged between 18 and 60 years, belonging to the American Society of Anesthesiologists Physical Status 1 or 2, scheduled for elective surgery under general anaesthesia with LMA were included in the study. Patients with anticipated airway difficulty, history of preoperative sore throat or asthma, known sensitivity to the study drug, recent intake of anti-inflammatory medication and patients with upper respiratory tract disease were excluded from the study. Patients requiring more than two attempts for LMA insertion were also excluded from the study. Patients were randomised into two groups of 45 patients each: Group L (lignocaine group) and Group K (ketamine group) using a computer-generated random number sequence. Group allocation was done using a closed envelope technique.
All patients were fasted for 6 h preoperatively and were premedicated with tablets famotidine 40 mg, metoclopramide 10 mg and alprazolam 0.5 mg orally 2 h prior to surgery. Operation theatre nursing staff who were blinded to the study prepared the solution for gargle according to the group allocated. In the preoperative area, patients were made to gargle according to the group allocation by the attending anaesthesiologist who was also blinded to the study drug being used.
All patients belonging to Group L received 30 mL of 2% lignocaine viscous undiluted as a gargle, while those belonging to Group K received 50 mg of 5% ketamine in 29 mL normal saline (total volume 30 mL). After 10 min, patients were shifted to the operating room. Standard monitoring (5-electrode electrocardiogram monitoring lead II, noninvasive blood pressure, pulse oximetry and temperature) was established and anaesthesia was induced with injections propofol 2 mg/kg, fentanyl 2 μg/kg and atracurium 0.5 μg/kg. After 3 min of mask ventilation, a reusable silicon classic LMA was placed and the cuff was inflated with 30 mL or 40 mL of air for LMA size #3 or size #4 respectively. Proper placement of the LMA was confirmed by free ingress and egress of anaesthetic gases during assisted ventilation and observation of a square wave capnograph. After confirmation of correct placement of LMA and ensuring adequate ventilation, anaesthesia was maintained with isoflurane (0.6%–1.0%) in a mixture of nitrous oxide and oxygen (50:50) using controlled ventilation through the circle system. Cuff pressure was checked every 15 min and maintained up to 60 cmH2O while ensuring that there was no leak around the cuff. Number of attempts for successful LMA insertion and any incidence of desaturation during insertion were noted. Heart rate, blood pressure and SpO2 were recorded in the intraoperative period and duration of surgery was also noted. At the end of surgery, residual neuromuscular blockade was antagonised using IV neostigmine (50 μg/kg) with IV glycopyrrolate (10 μg/kg). The LMA was removed when patient was fully awake. In the postanaesthesia care unit, all patients were questioned for POST at 0, 1, 2, 4, 6, 12, 18 and 24 h. The severity of POST was assessed using a 4-point scale and graded as follows: 0 (no POST) – no sore throat, 1 (mild) – complains of sore throat only on asking, 2 (moderate) – complains of sore throat on their own and 3 (severe) – change of voice or hoarseness associated with throat pain. Severe and moderate POST was managed with the nebulisation of normal saline.
Sample size was calculated based on the findings of a previous study done by Rudra et al. They showed that the incidence of POST was reduced up to 40% in the 1st hour after using ketamine gargle. We hypothesised that lignocaine viscous gargle would reduce the occurrence of POST to 20%. A total of 34 patients needed to be enrolled in each group to achieve a power of 90% with a Type 1 error of <0.05. We included 45 patients in each group to compensate for attrition. A list of computer-generated random numbers was created for group allocation. Statistical analysis was done using SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). All data were analysed for normal distribution using the Shapiro–Wilk test. Categorical data were analysed using the Chi-square test or Fisher's exact test as appropriate. Normally distributed parametric data were analysed using Student's t-test. All tests were two tailed; P < 0.05 was considered to be statistically significant.
Demographic data such as age, weight, height, duration of surgery and number of attempts of LMA insertion were comparable between the groups [Table 1]. In our study, the incidence of POST at 0 h was 17.5% in Group L and 40% in Group K. The incidence as well as severity of POST [Table 2] was significantly less in Group L as compared to Group K [Figure 1]. In Group L, 17.5% patients had mild grade of POST, while the remaining 82.5% had no complaints. In Group K, 15% had moderate grade, 25% had mild grade and 60% of patients had no complaints of POST [Figure 1]. Similarly, the severity of POST in the subsequent evaluations at 1, 2, 4, 6, 12, 18 and 24 h after surgery was significantly less in the lignocaine group as compared to the ketamine group. After 4 h, all patients had recovered from POST in the lignocaine group, while patients in the ketamine group took longer time (18 h) to recover completely from POST.
POST is one of the most common complaints following general anaesthesia. It was recently ranked as the eighth most important problem of the current clinical anaesthesiology by American anaesthesiologists. The LMA has now become the airway of choice in a large number of situations in perioperative medicine, thereby avoiding many situations of unnecessary endotracheal intubation. While easy insertion technique and lesser complications associated with LMA have reduced the incidence of POST, they have not completely eliminated the problem. POST caused by LMA has been attributed to insertion method and techniques, number of attempts, experience of the anaesthesiologist and LMA cuff pressure.
Various methods have been tried to prevent POST, but none of them have been completely effective. Although application of lignocaine jelly to the LMA cuff is one of the commonly adopted techniques to reduce the incidence of POST, results are not promising. Therefore, we used lignocaine viscous gargle in the place of lubricants to assess the effectiveness in reducing POST. In our study, the incidence of POST was 17.5% in lignocaine group and 40% in ketamine group, and the difference was statistically significant.
Preoperative use of lignocaine to prevent post-extubation cough has been in use for years. Tanaka et al. and Soltani and Aghadavoudi have used lignocaine as topical application over the cuff and IV injection respectively and showed that it is effective in reducing both the incidence and severity of POST. We chose lignocaine viscous gargle over the above method because this method is much safer than IV injection and more effective in anaesthetising the oral cavity, oropharynx and hypopharynx as compared to lubrication of cuff which anaesthetises only the soft palate. Many studies reporting the topical anti-inflammatory effect of ketamine after nasal, oral and rectal administration have suggested that local use of this drug is both effective and conceivable.,, Canbay et al. have shown that ketamine gargle significantly reduces the incidence and severity of POST after endotracheal intubation.
Our study demonstrated that 2% lignocaine viscous gargle before the insertion of classic LMA significantly reduces the incidence and severity of POST as compared to ketamine gargle. In our study, though patients in both the groups complained of POST in the early postoperative period, the severity was significantly less in the lignocaine gargle group as compare to ketamine gargle group. The Cochrane Database of Systematic Reviews also showed that topical lignocaine is very effective in reducing the incidence of POST. Lignocaine spray over the endotracheal tube has been reported to be very effective in preventing the incidence of POST. Shetty et al. have compared ketamine gargle with lignocaine gargle before endotracheal intubation and showed that ketamine is more effective in reducing POST after endotracheal intubation. In contrast, our study showed that lignocaine gargle is more effective than ketamine gargle. This could be because we used 2% lignocaine viscous solution which is specifically meant for gargling, whereas Shetty et al. used 2% lignocaine meant for IV use.
In our study, the incidence of POST in the lignocaine viscous gargle group was limited to the immediate postoperative period (<3 h) as compared to ketamine gargle where it was reported for a period of up to 12 h in the postoperative period.
POST after LMA insertion is common and essential steps should be taken to avoid it. We conclude that gargling with 2% lignocaine viscous solution effectively reduces the incidence as well as severity of POST without any adverse reactions.
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