Comparison of Three Different Doses of Dexmedetomidine for Attenuation of the Pressor Response to Laryngoscopy and Intubation by Assessment of Haemodynamic Parameters and Plasma Catecholamine Levels Under Bi-spectral Index Guided Anaesthesia - A Randomised Double Blind Controlled Study.

Abstract

Objective: Dexmedetomidine has been studied for attenuation of laryngoscopy and intubation response with varied results, however the depth of anaesthesia and plasma catecholamine levels have not been measured. Considering the lacunae, this study was planned with three doses of dexmedetomidine: 0.5, 0.75 and 1 μg kg^-1 under bi-spectral index monitoring and plasma catecholamine assessment.

Methods: One hundred sixty-eight consenting adult patients of either sex were divided into 3 groups (56 each) to receive I/V dexmedetomidine 0.5, 0.75 or 1 μg kg^-1 prior to induction. A baseline sample of catecholamines was taken and study drug was infused over 10 minutes. Thereafter, standard anaesthesia induction followed and haemodynamic parameters were noted at designated time intervals. Another sample of catecholamines was drawn at 3 minutes after intubation. The primary outcome was to compare the change in heart rate and systolic blood pressure. Secondary outcomes included: change in catecholamine levels, sedation scores, propofol dose and adverse events.

Results: All doses of dexmedetomidine successfully obtunded the haemodynamic response; however, no significant difference was seen on inter-group comparison (P >0.05). A significant fall in nor-adrenaline values compared with baseline was noted in all groups, without any significant difference among groups for both catecholamines. Sedation scores reduced from baseline in all groups without any difference on inter- group comparison. Statistically significant reduction in propofol requirement and higher incidence of bradycardia with 1 μg kg^-1 (P=0.014) were observed.

Conclusion: 0.5 μg kg^-1 of dexmedetomidine can be used for pressor response attenuation as the incidence of bradycardia was higher with 1 μg kg^-1 and 0.75 μg kg^-1 had no added advantage.