• Oluwaseun Akeju, Kara J Pavone, M Brandon Westover, Rafael Vazquez, Michael J Prerau, Priscilla G Harrell, Katharine E Hartnack, James Rhee, Aaron L Sampson, Kathleen Habeeb, Lei Gao, Gao Lei, Eric T Pierce, John L Walsh, Emery N Brown, and Patrick L Purdon.
• From the Department of Anesthesia, Critical Care, and Pain Medicine (O.A., K.J.P., R.V., M.J.P., P.G.H., K.E.H., J.R., A.L.S., G.L., E.T.P., J.L.W., E.N.B., P.L.P.) and Department of Neurology (M.B.W.), Massachusetts General Hospital, Boston, Massachusetts; Clinical Research Center, Massachusetts General Hospital, Boston, Massachusetts (K.H.); Harvard Medical School, Boston, Massachusetts (O.A., M.B.W., R.V., M.J.P., P.G.H., J.R., G.L., E.T.P., J.L.W., E.N.B., P.L.P.); Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, Massachusetts (E.N.B., P.L.P.); Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts (E.N.B.); and Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts (E.N.B.).
• Anesthesiology. 2014 Nov 1; 121 (5): 978-89.

BackgroundElectroencephalogram 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.MethodsThe 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-µg/kg loading bolus over 10 min, followed by a 0.7 µg kg h infusion. For propofol, the authors used a computer-controlled infusion to target the effect-site concentration gradually from 0 to 5 μg/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.ResultsDexmedetomidine 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).ConclusionThe 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.

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