Abstract
Objective: laryngoscopy and tracheal intubation are associated with hemodynamic and cardiovascular responses consisting of increased heart rate, blood pressure and tachycardia and dysrhythmias. The alpha2-adrenoreceptor agonists such as clonidine and tizanidine have several beneficial actions during the perioperative period. They improve hemodynamic stability in response to endotracheal intubation and surgical stress. In this study we compared the effect of oral clonidine and tizanidine on hemodynamic responses after laryngoscopy in patients undergoing coronary artery bypass surgery.
Methods: Ninety patients age 30-70 years old underwent coronary artery bypass surgery with HR>50 b/min and EF>40% evaluated in this randomized double blinded study. Thizanidine 4 mg prescribed to group A, 0.2 mg clonidine to group B and placebo to group C, 90 minutes before laryngoscopy. systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and heart rate recorded before, During , 1 minute after laryngoscopy and then each 5 to 15 minutes after that.
Results: There was no significant differences in systolic blood pressure (p.value for repeated measure= 0.507), diastolic blood pressure (p.value for repeated measure=0.707) and mean arterial blood pressure (p.value for repeated measure=0.997) but there was a significant difference in heart rate (p.value for repeated measure= 0.036) between three groups. According to post_Hoc test there was a significant difference in heart rate between clonidine group and placebo group.( p.value=0.042) There was no significant differences in diabetes mellitus and hypertension, in side effects and in arrhythmia, ischemia and request for TNG, Esmolol and vasopressor between three groups.
Conclusion: According to the recent study as in clonidine and tizanidine group (specially in clonidine group) heart rate reduced significantly after laryngoscopy , no significant side effects was reported and there was no significant differences in arrhythmia and ischemia and request for TNG, Esmolol and vasopressor between three groups, tizanidine and clonidine (specially clonidine) could be recommended as useful drugs for premedication in general anesthesia in patients undergoing CABG surgery.