European Journal of Cardiovascular Medicine

Post-operative sore throat (POST) is a common, uncomfortable complaint after tracheal intubation, with reported incidence varying between 21% and 65% depending on patient factors, anaesthetic technique, and duration of surgery. ^[1] While often self-limiting, POST contributes to post-operative morbidity, delays in recovery satisfaction, and occasionally requires additional analgesic intervention. ^[2] The pathophysiology involves mucosal trauma, inflammation, and edema secondary to endotracheal tube (ETT) insertion, cuff pressure, and airway instrumentation. ^[3]

Several strategies have been explored to reduce POST, including smaller tube sizes⁶, cuff pressure monitoring, lubrication, topical anaesthetics, ketamine gargles, and corticosteroids. ^[4,5] However, many have limitations related to availability, adverse effects, or inconsistent efficacy.

Magnesium sulphate (MgSO₄) is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist and calcium channel blocker. Its anti-inflammatory, membrane-stabilizing, and analgesic properties have been documented in various clinical settings. ^[6,7] Nebulized MgSO₄ has been shown to reduce airway hyperreactivity in asthma and improve outcomes in patients with reactive airway disease undergoing intubation. ^[8] Mechanistically, MgSO₄ may attenuate neurogenic inflammation, reduce release of inflammatory mediators, and inhibit smooth muscle contraction. ^[9]

Prior studies on POST prophylaxis with magnesium have explored gargles and intravenous routes, with varying results. ^[10] Nebulization as a route offers the advantage of uniform airway mucosal delivery, minimal systemic effects, and ease of administration. ^[11] The onset of action is rapid, and local concentrations achieved are higher than with systemic administration. ^[12]

Given the high incidence of POST, particularly in high-risk groups (prolonged surgeries, larger ETT size, and female patients), exploring safe, cost-effective, and widely applicable preventive methods is clinically valuable. ^[13] This study evaluates the effectiveness of preoperative magnesium sulphate nebulization in reducing the incidence and severity of POST in adult surgical patients undergoing general anaesthesia with endotracheal intubation. We hypothesized that magnesium sulphate nebulization before induction would significantly reduce POST incidence at 6 hours post-extubation.

This is a Prospective and randomized study was conducted in the Department of Anaesthesiology at Tertiary Care Teaching Hospital from please mention the period of study  from January 2023 to June 2024.

Inclusion Criteria

• Adult patients aged 18–60 years.
• ASA physical status I–II.
• Scheduled for elective surgeries under general anaesthesia with endotracheal intubation.
• Expected duration of surgery <4 hours.

Exclusion Criteria

• Anticipated difficult airway.
• History of asthma, COPD, or recent upper respiratory tract infection.
• Known allergy to magnesium sulphate.
• Oral or pharyngeal pathology.
• Pregnant or lactating women.
• Use of nasogastric tube perioperatively.

Randomization and Blinding

Patients were allocated into two groups (n=60 each) using computer-generated random numbers and sealed envelopes.

• Group M: Nebulization with 225 mg magnesium sulphate in 5 mL normal saline.
• Group C: Nebulization with 5 mL normal saline.

Both solutions were prepared by an anaesthetist not involved in patient care or assessment.

Procedure

Nebulization was administered via a standard jet nebulizer 15 minutes before induction. Standard monitors were applied. Anaesthesia was induced with fentanyl, propofol, and vecuronium, and maintained with isoflurane in oxygen–air mixture. All intubations were performed by anaesthetists with at least 3 years’ experience, using appropriately sized high-volume, low-pressure cuffed ETTs (7.0–7.5 mm for females, 8.0–8.5 mm for males). Cuff pressures were maintained between 20–25 cm H₂O throughout surgery.

Outcome Measures

The primary outcome was the incidence of POST at 6 hours post-extubation. Secondary outcomes included POST severity (graded 0–3: 0=none, 1=mild, 2=moderate, 3=severe) at 1, 6, 12, and 24 hours; and any adverse effects.

Statistical Analysis

Sample size was calculated assuming a reduction in POST incidence from 45% to 20%, with α=0.05 and power=80%, yielding 54 per group (rounded to 60). Data were analyzed using SPSS v21. Chi-square test was applied for categorical variables, independent t-test for continuous variables, and p<0.05 considered significant.

Table 1: Baseline Characteristics

Table 2: Airway and Anaesthetic Characteristics

Table 3: Incidence of POST

Table 4: Severity of POST

Table 5: Time Trend of Mean Severity Scores

Table 6: Adverse Events

We’ll correlate findings with earlier studies showing reduced POST with magnesium gargle (Kwak et al. 2010), intravenous administration (Trabelsi et al. 2013), and compare with steroid and ketamine interventions. ^[14,15] The discussion will interpret our lower POST incidence, possible mechanisms (anti-inflammatory and NMDA blockade), and differences with other modalities.

This study demonstrated that preoperative nebulization with magnesium sulphate significantly reduced both the incidence and severity of POST following general anaesthesia with endotracheal intubation. The reduction was most pronounced at 6 hours, consistent with the peak inflammatory response period described in earlier studies. ^[16]

Our findings align with Kwak et al. ^[17], who reported reduced POST incidence with magnesium gargles, and Trabelsi et al. ^[18], who found intravenous magnesium reduced airway reactivity. The nebulized route likely maximizes mucosal drug delivery, explaining the marked reduction in severity scores seen here.

Mechanistically, magnesium’s NMDA receptor antagonism and calcium channel blockade attenuate neurogenic inflammation, reduce excitatory neurotransmitter release, and stabilize epithelial membranes^[19]. Its anti-inflammatory action may also downregulate cytokine production, contributing to reduced mucosal swelling and discomfort^[20].

Compared with other interventions such as ketamine gargles^[21] or topical corticosteroids^[22], magnesium offers a favorable safety profile, minimal systemic absorption, and negligible risk of airway irritation. The cost-effectiveness and ease of integration into preoperative routines make it an attractive option, particularly in resource-limited settings.

Limitations include the single-centre design, relatively short follow-up (24 hours), and lack of objective inflammatory marker assessment. Future studies could explore optimal dosing, timing, and combination with other prophylactic measures.

Nebulized magnesium sulphate administered 15 minutes before induction of anaesthesia is a safe, simple, and effective method to reduce the incidence and severity of post-operative sore throat without significant adverse effects. Its incorporation into routine airway management protocols could enhance patient comfort and satisfaction.

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