The sensory thalamus and cerebral motor cortex are affected concurrently during induction of anesthesia with propofol: a case series with intracranial electroencephalogram recordings.
OBJECTIVE
Brain imaging studies suggest that loss of consciousness induced by general anesthetics is associated with impairment of thalamic function. There is, however, limited information on the time course of these changes. We recently obtained intracranial electroencephalogram (EEG) recordings from the ventroposterolateral (VPL) nucleus of the thalamus and from the motor cortex during induction of anesthesia in three patients to study the time course of the alterations of cortical and thalamic function.


METHODS
The patients were American Society of Anesthesiologists physical status I-II males aged 33-57 yr with intractable central pain caused by brachial plexus injury (patient 1 and 2) or insular infarct (patient 3). Anesthesia was induced with propofol (2.5-3.1 mg·kg(-1) over 30-45 sec) followed, after loss of consciousness, by rocuronium for tracheal intubation. The data retained for analysis are from one minute before the start of propofol to 110 sec later during ventilation of the patients' lungs before tracheal intubation. Spectral analysis was used to measure absolute EEG power. Propofol caused significant increases of cortical and thalamic power in the delta to beta frequency bands (1-30 Hz). These increases of cortical and thalamic power occurred either concomitantly or within seconds of each other. Propofol also caused a decrease in cortical and thalamic high-gamma (62-200 Hz) power that also followed a similar time course.


CONCLUSIONS
We conclude that induction of anesthesia with propofol in these patients was associated with concurrent alterations of cortical and sensory thalamic activity.
Department of Anesthesia, Montreal Neurological Institute and Hospital, McGill University, 3801 University St., Montreal, QC, H3A 2B4, Canada.
Olivier
O
Verdonck
Sean J
SJ
Reed
Jeffery
J
Hall
Jean
J
Gotman
Gilles
G
Plourde
D000328:Adult; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D004569:Electroencephalography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects* / Q000378:metabolism; D010148:Intractable Pain / Q000628:therapy; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology*; D013788:Thalamus / Q000187:drug effects* / Q000378:metabolism
D018686:Anesthetics, Intravenous; D015742:Propofol