Evaluation of the electroencephalogram in awake, sedated, and anesthetized dogs

Sedation and anesthesia alter the raw electroencephalogram (EEG). Interpretation of the EEG is facilitated by measuring the patient state index (PSI), visual inspection of density spectral arrays (DSA), and power density analysis of the delta (0.1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), and beta plus gamma (12–40 Hz) frequency bands. Baseline data were recorded in six male intact Beagles before sedation with intravenous acepromazine (0.03 mg/kg) and hydromorphone (0.1 mg/kg). Anesthesia was induced and maintained for five minutes with intravenous propofol (1.5 mg/kg over five seconds followed by 12 mg/kg/h). Additional propofol (0.5–1.0 mg/kg and up to 16.7 mg/kg/h) was administered within this time frame if the PSI was above 50. The effects of sedation and anesthesia were evaluated with a mixed-effect model followed by Dunnett's test (alpha = 0.05). The average baseline PSI (95% confidence interval) was 93.0 (91.4–94.6) and decreased on sedation [88.7 (86.0–91.3); p = 0.039] and anesthesia [44.5 (40.8–48.2); p