Canadian Journal of Anesthesia, Vol 21, 57-67, Copyright © 1974 by Canadian Anesthesiologists' Society

An Experimental Study of the Mechanism of Action of Ketamine on the Central Nervous System

¹ Department of Anaesthesia, Faculty of Medicine, University of British Columbia

The present study of the mechanism of action of ketamine on the central nervous system was carried out by the use of chronically implanted chemitrodes in a wide variety of C.N.S. sites in the cat.

Systemic injections of ketamine were found to stimulate all parts of the C.N.S. studied, directly or indirectly, producing a characteristic pattern of high voltage, slow frequency spike discharges alternating with low voltage, fast frequency desynchronized activity. This differs from Corrsen's original observations of selective action and his concept of dissociative anaesthesia.

Anterior, posterior and lateral hypothalamic injections produced varying degrees of sedation and analgesia associated with cortical spike discharges; globus pallidus injections produced catatonia; lateral geniculate body injections produced restlessness which was intensified by stimulation with light flashes; BSRF injections produced restlessness and even convulsions; and injections into the frontal cortex, the various other nuclei of the thalamus, hippocampus and amygdala did not produce any consistent response.

An explanation of the various manifestations of ketamine anaesthesia is proposed, based on these observations. We believe that the unconsciousness produced is secondary to the induced cortical EEG seizures. This suggests the need for caution in the use of ketamine in convulsive disorders and in your patients with a developing central nervous system.