A Comparison of Propofol- and Dexmedetomidine-induced Electroencephalogram Dynamics Using Spectral and Coherence Analysis

Background: Electroencephalogram patterns observed during sedation with dexmedetomidine appear similar to those observed during general anesthesia with propofol. This is evident with the occurrence of slow (0.1 to 1 Hz), delta (1 to 4 Hz), propofol-induced alpha (8 to 12 Hz), and dexmedetomidine-induced spindle (12 to 16 Hz) oscillations. However, these drugs have different molecular mechanisms and behavioral properties and are likely accompanied by distinguishing neural circuit dynamics. Methods: The authors measured 64-channel electroencephalogram under dexmedetomidine (n = 9) and propofol (n = 8) in healthy volunteers, 18 to 36 yr of age. The authors administered dexmedetomidine with a 1-mu g/kg loading bolus over 10 min, followed by a 0.7 mu g kg(-1) h(-1) infusion. For propofol, the authors used a computer-controlled infusion to target the effect-site concentration gradually from 0 to 5 g/ml. Volunteers listened to auditory stimuli and responded by button press to determine unconsciousness. The authors analyzed the electroencephalogram using multitaper spectral and coherence analysis. Results: Dexmedetomidine was characterized by spindles with maximum power and coherence at approximately 13 Hz (mean SD; power, -10.8 +/- 3.6 dB; coherence, 0.8 +/- 0.08), whereas propofol was characterized with frontal alpha oscillations with peak frequency at approximately 11 Hz (power, 1.1 +/- 4.5 dB; coherence, 0.9 +/- 0.05). Notably, slow oscillation power during a general anesthetic state under propofol (power, 13.2 +/- 2.4 dB) was much larger than during sedative states under both propofol (power, -2.5 +/- 3.5 dB) and dexmedetomidine (power, -0.4 +/- 3.1 dB). Conclusion: The results indicate that dexmedetomidine and propofol place patients into different brain states and suggest that propofol enables a deeper state of unconsciousness by inducing large-amplitude slow oscillations that produce prolonged states of neuronal silence.