Attenuating the Pressor Response to Laryngoscopy and Endotracheal Intubation in Controlled Hypertensives: The Effect of Combining Lidocaine and Magnesium Sulphate.

Background: Laryngoscopy and intubation result in a pressor response which may be deleterious especially in hypertensives, resulting in potentially harmful effects. Many drugs have been used to attenuate this undesirable pressor response to laryngoscopy and intubation in hypertensives; amongst them are magnesium alone in different doses or in combination with lidocaine. However, drug combinations have been found to be more effective than single drug therapy.

Objective: This study compared the different doses of magnesium sulphate and its combination with lidocaine for the attenuation of the pressor response.

Methods: A prospective, randomized, double-blinded study. Nighty-six controlled hypertensives (ASA physical status II) scheduled for elective surgery under general anaesthesia and who required endotracheal intubation were recruited and randomized into either Group I (they received 30mg/kg of IV MgSO4 plus 1.5mg/kg of 2% lidocaine) or Groups II and III who received 30mg/kg and 40mg/kg of IV MgSO4 alone, respectively. The outcome was the change in the systolic blood pressure (SBP) from the baseline following administration of study medication and after laryngoscopy and endotracheal intubation. The side effects of study medication and changes in serum magnesium level prior to and after 30 minutes of administering study medication were documented.

Results: The post-intubation SBP was attenuated in patients in groups I and III only. However, five patients in group III had hypotension. Serum magnesium levels were higher than their respective baseline values in all the groups.

Conclusion: The combination of 1.5 mg/kg of 2% lidocaine and 30 mg/kg of MgSO4 is more effective than 30 mg/kg of MgSO4 alone and even MgSO4at the higher dose of 40 mg/kg.