Magnesium sulphate pretreatment obtunds fentanyl-induced cough during general anaesthesia induction

Introduction: Fentanyl-induced cough is common during induction of general anaesthesia. This unpleasant cough may increase the intraocular, intracranial, and intraabdominal pressure. We hypothesised that 30 mg/kg of prophylactic intravenous magnesium sulphate is effective in obtunding 2 μg/kg fentanyl-induced cough.Methods: One hundred and forty patients scheduled for general anaesthesia, aged between 18 to 70 years old with American Society of Anesthesiologists physical status I were randomised into two groups. Group I and Group II patients received 30 mg/kg intravenous magnesium sulphate and normal saline, respectively. The solution studied was infused over 15 minutes followed by a fentanyl bolus 2 μg/kg delivered within 3 seconds. The incidence of cough and severity were documented. Mean arterial pressure and heart rate were recorded every 5 minutes during the infusion.Results: Eight patients (11.4%) had cough in Group II and one (1.4%) in Group I. Compared to Group II, the incidence and severity of cough were significantly lower in Group I (p = 0.003 and p = 0.037), respectively. There was no significant difference regarding the haemodynamic status between the two groups during the infusion of both solutions.Conclusion: During general anaesthesia induction, 30 mg/kg of intravenous magnesium sulphate effectively obtunded fentanyl-induced cough.