M.O. Orji1, B.B. Osinaike1, S.D. Amanor-Boadu1, and A. Ugheoke2

  1. Department of Anaesthesia, College of Medicine, University of Ibadan, Ibadan, Nigeria.
  2. Department of Anaesthesia, University College Hospital, Ibadan, Nigeria.


Background: Sore throat is a common post-operative complaint which can cause significant distress and morbidity. We tested and compared the efficacy of nebulized Magnesium and Ketamine on the incidence and severity of sore throat within the first 24 hours after general anaesthesia.

Objective: To compare the incidence and severity of post-operative sore throat at 2, 4, 8, 12 and 24 hours after extubation following pre-induction administration of nebulized Magnesium and Ketamine.

Method: In this randomized controlled trial, 99 adult ASA I and II patients between the ages of 16 – 65 years were administered nebulized Ketamine 50 mg, Magnesium Sulphate 250 mg or saline for ten minutes prior to induction of general anaesthesia and orotracheal intubation. Incidence and severity of post-operative sore throat were assessed at 2, 4, 8, 12 and 24 hours post extubation.

Result: The incidence of sore throat at 4, 8, 12 and 24 hours post tracheal extubation were significantly lower in the Magnesium (18.2%, 12.1%, 0, 0; p = 0.009, 0.006, <0.0001, 0.003) and Ketamine group (24.2%, 12.1%, 6.1%, 0; p = 0.041, 0.006, 0.001, 0.003) compared with the saline group (48.5%, 42.4%, 39.4%, 24.2%). Patients also had significantly less severe sore throat at 4 and 8 hours post extubation in both Magnesium and Ketamine groups (p = 0.0 11, 0.041).

Conclusion: Pre-induction nebulization of Ketamine or Magnesium can decrease the incidence and severity of sore throat in the first 24 hours after anaesthesia.

Keywords: Nebulize, Sore throat, Magnesium, Ketamine.


Dr. M.O. Orji
Department of Anaesthesia,
College of Medicine,
University of Ibadan,
Ibadan, Nigeria


Post-operative sore throat (POST) is a common phenomenon after general anaesthesia with endotracheal intubation. It is considered as the second leading minor adverse event after post-operative nausea and vomiting.1 The incidence vary widely but reportedly as high as 49 and 69.6% in two separate studies in our sub-region.2,3 Notable risk factors for developing POST include female sex, airway instrumentation and airway surgeries.4 Mucosal injury during airway instrumentation is a recognizable pathophysiological mechanism in the literature. Endotracheal anaesthesia incorporate many manoeuvres that can cause these injuries including laryngoscopy, suctioning, endotracheal intubation and sometimes oro-/nasogastric tube passage.

Gentle airway manipulation at anaesthetic induction can minimize mucosal injury and prevent occurrence of POST. Pre-induction administration of topical/ local anti-nociceptive and anti-inflammatory agents attenuate POST by counteracting the inflammation or nociception induced by mucosal injury.5–7

The peripheral nerves in the airway subserving nociception contain N-methyl D-Aspartate receptors (NMDAR).8 Antagonists to NMDAR are considered anti-nociceptive and have been investigated for POST in the forms of gargle, lozenge and nebulization with varied outcomes.9–11 Nebulization however offers the unique advantage of even distribution over all areas exposed to instrumentation and mucosal damage while the gargle and lozenge forms are restricted to the supraglottic region with considerable inter-patient variability during administration.

Magnesium and Ketamine are commonly available NMDAR antagonists with anti-inflammatory properties. Previous studies compared these agents with placebo using varied doses and application patterns. We decided to undertake this study to test and compare the efficacies of pre-induction nebulized Magnesium and Ketamine for POST attenuation within 24 hours following general anaesthesia with endotracheal intubation.

We conducted a double blind randomized controlled trial at the University College Hospital, Ibadan over a 6 month period. Ninety-nine eligible ASA I and II patients scheduled for elective surgical procedures in supine position under general anaesthesia were recruited. Patients with recent sore throat, chronic airway disease, anticipated difficult airway or undergoing head and neck procedures were excluded. Our sample size was calculated from the presumption that the incidence of POST in our environment is 69.6%.3 To show a 50% reduction in incidence using a power of 80% with a 95% confidence interval, power analysis generated 30 patients per group.12 We added 10% of the calculated sample size to account for attrition. Following institutional ethics approval, a block randomisation using computer generated table of random numbers divided the prospective patients into equal groups of 33. Written informed consent was obtained from each patient at the preoperative review. Patients were allocated according to group to receive one of three nebulized medications: Magnesium sulphate 250mg (Group M); Ketamine 50mg (Group K) and saline. The medications were made up to 5ml volume with sterile water and delivered with a compressor nebulizer (Omron Healthcare Co. Ltd., Japan) for 10 minutes. The drugs were indistinguishable in colour and to ensure blinding, an assistant carried out the nebulization. During nebulization, patients were inclined at 450 and encouraged to simultaneously breathe through the mouth and nose.