Influence of S-Ketamine, at low Doses, on the Electroencephalogram - BIS Suppression Rate: A Randomized Clinical Trial

Objective: To evaluate the influence of low doses of S-ketamine, during total intravenous anesthesia, on the suppression rate (SR) induced during total intravenous anesthesia (TIVA) by deepening the anesthetic plane. Methods: A triple-blind clinical trial was conducted with 20 patients who underwent elective operations under general anesthesia, randomly allocated into two groups, CG (control: 0.9% saline) and CGS (s-ketamine: 0.2 mg.kg-1). Each group was assessed at M0 (immediately before pre-oxygenation), M1 (3 minutes after SR stabilization) and M2 (3 minutes after infusion of s-ketamine or 0.9% saline). Bispectral index (BIS), electromyography, and SR were recorded at each moment. Results: There were no statistically significant changes regarding BIS and EMG from M1 to M2. There was also no indication of a significant difference between the average SR values concerning the factors group and moment, jointly (p=0.499), and separately (G1 and G2, p=0.812 and p=0.923). Conclusions: Low doses of s-ketamine were insufficient to determine changes in SR values, validating this important electroencephalographic parameter. Significance: The study findings reinforce that low doses of s-ketamine do not invalidate the SR values