Effect of clonidine on the target dose of propofol: bispectral index evaluation

Abstract

Background: The increasing evidence associating general anaesthetics with neurotoxicity and post-operative cognitive disturbances, mainly with deeper levels of anaesthetics, has led to more frequent use of adjuvants. This study aimed to analyse the effect of clonidine on the target dose of propofol in total intravenous anaesthesia. Methods: A randomised, double-blind clinical trial was performed in a large hospital located in the southern region of Ceará, Brazil. Fifty-one patients from the anaesthesia outpatient clinic were enrolled. Patients were divided into two groups: one group received 100 mL of 0.9% sterile saline, and the other group received 100 mL of 0.9% sterile saline with clonidine at a dose of 3 µg/kg. A target-controlled infusion pump was used to administer propofol, following the modified Marsh pharmacokinetic model and aiming for a bispectral index (BIS) score of approximately 40 for intubation and 45 for anaesthesia maintenance. The anaesthesiologist was informed which group the patient belonged to after completion of surgery and data recording. Results: The chi-squared test was used to evaluate the distribution of the samples with respect to gender, and the Student’s t-test was used to evaluate the parametric variables. There was no statistically significant difference between the samples. A significant difference was observed in the target dose of propofol between the two groups during the maintenance and awakening phases, but not at the time of intubation. Conclusions: Clonidine pre-operatively administered at a dose of 3 µg/kg significantly reduced the target dose of propofol needed to maintain adequate levels of anaesthesia as measured by BIS