Sore throat (ST), a common complaint of postoperative period after tracheal intubation is being considered as a minor complication, but is a valid reason of dissatisfaction and morbidity among patient. The incidence of ST is 21–65% in patients receiving general anaesthesia (GA) with tracheal intubation. Various non pharmacological and pharmacological trials have been used for attenuating ST with no proven single modality.

The pharmacological methods used to reduce ST include use of beclomethasone gel, gargling with azulene sulphonate, ketamine, licorice, magnesium sulphate, etc. One of the most common sequelae of endotracheal intubation is post-operative sore throat (POST), as the previous studies have mentioned the prevalence of post-operative sore throat ranging from 20 to 65%. The possible etiologies mentioned in the studies were mucosal erosion, inflammation and dehydration leading onto the irritation of trachea thereby resulting in POST.

Though it is considered as a minor complication in the post-operative period but the major issue is, it leads to patient’s dissatisfaction and increases the duration of stay in the hospital.[4] Research trials have been conducted on various pharmacological and nonpharmacological measures for ameliorating POST but the success rate were varied

The various nonpharmacological measures that were tried are reducing the size of endotracheal tubes, reducing the cuff pressure to less than 20 mm Hg and minimising the attempts made for laryngoscopy and similarly the various pharmacological measures that were attempted are use of ketamine gargle, ketamine nebulisation, lignocaine spray, beclomethasone gel and magnesium sulphate gargle Among all these measures ketamine gargle or lozenges had shown the maximum success rate, but the major disadvantage is ketamine has a bitter taste because of which the risk of aspiration is high and that might lead onto serious complications.

 Because of which administration of drug through nebuliser route in the form of aerosol has become popular among anaesthetist and the patient’s acceptance was also good.[7,8] The major receptors responsible for nociception and inflammation are NMDA receptors (N-methyl D-aspartate) receptors and these receptors are present both in central and peripheral nervous system. Both magnesium and ketamine has antagonistic property towards NMDA receptors and hence it acts as anti-nociception and anti-inflammatory agent.

 Previous studies have been conducted using analgesic drug, ketamine in the form of gargles and aerosols and few studies had been done using magnesium in the form of gargles, lozenges and nebulisation and varied type of results were shown] Since very few studies had been conducted using magnesium in the form of nebulisation and not much work has been carried out in this part of the state the current study was conducted to assess the efficacy of use of magnesium sulphate nebuliser in reducing the incidence of postoperative sore throa.

Following institutional ethical committee approval and written informed consent, the prospective randomized double-blinded study was conducted in 100 cases. With the level of significance (alpha) = 0.05, and power of 80%, sample size required was 40 per group. To accommodate any exclusion, 50 patients from each group were selected.

Patients included in study were of either gender, aged between 18 and 60 years belonging to American Society of Anesthesiologist (ASA) 1 or 2 status undergoing elective surgery of approximately 2 h or more duration requiring tracheal intubation. Patients with neuromuscular disease, allergy or hypersensitivity of drugs, undergoing neck surgeries, and laparoscopic surgeries were excluded. Patients were allocated randomly to two groups, Group A and Group B. Simple randomization was done using SPSS software (IBM, SPSS Statistics 21).

All patients were kept fasting overnight and premedicated with oral alprazolam 0.5 mg and ranitidine 150 mg on night before surgery and on the morning of surgery.

Five minutes prior to the induction of anesthesia, patients in Group A were nebulized with 3 ml of normal saline and the patients in Group B were nebulized with 3 ml of 225 mg isotonic nebulized magnesium sulfate for 15 min. The solution for nebulization was administered by an anesthesiologist not associated with the management of the case. The anesthesiologist anesthetizing the case and those recording the scores were blinded to it.

In the operation theater, after connecting the patient to standard monitoring intravenous access was secured.

Anesthesia was induced with fentanyl 2 mcg/kg and thiopentone 5 mg/kg. Tracheal intubation was facilitated by atracurium 0.6 mg/kg, and the trachea intubated with soft seal cuffed sterile polyvinyl chloride tracheal tube (Portex Limited CT 21, 6JL, UK) of 7 mm inner diameter in female and 8 mm in male patients. The tracheal tube cuff was inflated with air.

The cuff pressure was checked just after intubation using handheld tracheal cuff pressure monitor (Portex Cuff Inflator/Pressure Gauge, SIMS Portex, Hythe, Kent, UK) and then every half hourly till end of surgery and maintained at 20 cm of H₂O.

Ventilation was controlled, and no nasogastric tube was inserted. Anesthesia was maintained with 66% nitrous oxide in oxygen with 1% of isoflurane and intermittent doses of atracurium and fentanyl as required. The last dose of atracurium was given 20 min prior to extubation. At the end of surgery, the muscle relaxation was reversed with a combination of neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg. The trachea was extubated after extubation criteria were met, and the patients were shifted to postanesthesia care unit.

Presence of sore throat was noted at rest and on swallowing immediately after extubation, and 2 h, 4 h, and 24 h postoperatively. In the postoperative ward, patients were also monitored for any drug-related side effects.

Data were expressed as mean, and 95% confidence interval of mean. Test of normality (Kolmogorov-Smirnov, Shapiro-Wilk) was done for continuous variables (height, weight, age. Categorical data (gender) were expressed as frequency of occurrence. Comparison of continuous data between groups was done using ANOVA of means. Comparisons of categorical data between groups were done using Pearson Chi-square, continuity correction, likelihood ratio, Fisher's exact test; P < 0.05 was considered statistically significant. IBM SPSS-21 was used for statistical analysis

The age and gender wise distribution of the study subjects between the two groups are more or less equally distributed with a mean age of 37. 07 and 37.3 among group A and group B respectively with no statistical significant difference between the two groups (table 1).

The mean weight among the group A subjects was 55.8 and among group B it was 56.3 with no statistical significant difference and similarly the airway assessment made through malampatti grading showed an almost equal distribution of subjects between grade I and grade II in both the groups. Anesthesia assessment for the patients was done through ASA grading system and majority of them were in grade I and 15 – 20% were in grade II in both the groups and no statistical significant difference was observed between the groups (table 2). The vital parameters such as pulse rate, systolic and diastolic BP and the respiratory rate among the subjects in both the groups were within normal limits (table 3).

Among the duration of surgery, for majority of the subjects the duration was between 1 and 2 hrs in both the groups with a mean duration of 1.38 hrs among group A and 1.42 hrs among group B.

Only less than 5% of the surgeries in both the groups lasted for more than 3 hrs (table 4). The various type of operative procedures performed were open reduction with internal fixation, tonsillectomy, excisional biopsy, septoplasty, cholecystectomy, etc. and the distribution of these procedures between the two groups were more or less similar. The mean size of the ET tube used in normal saline group was 7.35 mm and in MgSO4 group it was 7.31 mm and no statistical significant difference was observed between the two groups. The occurrence of sore throat both at rest and during swallowing among both the groups was shown in table 5.

It was assessed and monitored during the post-operative period from 0 hr to 24 hrs.

It clearly shows that the incidence of sore throat both at rest and during swallowing is very much high among the group which used normal saline as nebuliser and it is observed that the incidence was more than 80% in the immediate post- operative period and at the end of 24 hrs the incidence was 65 – 70% both at rest and during swallowing. Among the group which used MgSo4 as nebuliser the incidence of sore throat in the immediate post-operative period was 45 – 50% and it was 0% at the end of 24% both at rest and during swallowing and a statistical significant difference was observed in the occurrence of sore throat between the two groups.

Table 1: Age and gender wise distribution of the study subjects

Table 2: Weight, Mallampatti grading of airway and ASA grading among the study subjects

Table 3: Mean and SD of the vital parameters among the study subjects

Table 4: Distribution of the study subjects based on the duration of the operative procedure

The causative mechanism for post-operative sore throat could be multiple in origin, including mechanical injury during laryngoscopy and intubation, continuous pressure by the inflated tracheal tube cuff on tracheal mucosa causing damage and dehydration of the mucosa, along with de-epithelialisation and local inflammatory damage of the mucosa. Literature pertaining to the use of nebulized magnesium sulphate for attenuation of POST is scarce. Numerous non pharmacological and pharmacological measures have been used for attenuating POST with variable success. Among the non pharmacological methods, smaller sized tracheal tubes, careful airway instrumentation, minimizing the number of laryngoscopy attempts, intubation after the full relaxation of the larynx, gentle oropharyngeal suctioning, filling the cuff with an anaesthetic gas mixture, minimizing intracuff pressures 2% jelly was used as a lubricant on the tracheal tube. The effectiveness of magnesium lozenges 30 min preoperatively was studied by Borazan et al. (15) found it effective in reducing both incidence and severity of POST in the immediate postoperative period. These results are comparable to our study results. Gupta et al(16) also assessed the efficacy of preoperative nebulization of magnesium sulphate and found that the incidence and severity of POST were reduced at rest and on swallowing at all-time points (P < 0.05). Though our study couldn’t demonstrate an effective reduction in the incidence of sore throat right after extubation at rest and swallowing, a clear advantage of a significant reduction in the incidence of sore throat on swallowing from the two hour period after extubation was observed. There was no associated risk of local or systemic toxicity as the dose used was around one-tenth of the systemically used dose for the treatment of pre-eclampsia and eclampsia and the mucosal drug absorption would not anywhere match the systemic levels of parenteral administration of the same drug similar to the conclusions of by Blitz et al. (17) who used nebulized magnesium sulphate for treatment of acute asthma.(18) The mucosal absorption although stated to be variable is also low to the level of around 10%.The drawback of our study was the absence of the measurements of serum magnesium levels making it difficult to rule out the contribution of systemic effects of magnesium. In our study, magnesium sulphate nebulisation reduced the incidence of post-operative sore throat at rest after four hours with a significant difference compared to the group which received nebulisation with normal saline. Magnesium sulphate group also had a significantly lesser incidence of post-operative sore throat on swallowing after two hours in comparison to the normal saline nebulisation group.

We conclude that, preoperative nebulization with Ketamine (50mg) statistically significantly decreased incidence and severity of postoperative sore throat, hoarseness of voice and postoperative cough compared to magnesium sulfate (500mg) nebulization. 6. Source of Funding None. 7. Conflict of Interest The authors declare no conflict of interest.

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