Abstract
Visual and computerized methods were used to analyze the effects of intravenously injected narcotic analgesics on the EEG of dogs implanted with cortical and subcortical electrodes. The drugs were morphine (1.6 mg/kg), fentanyl (0.004 mg/kg), sufentanil (0.0004 mg/kg), and a new potent and very short‐acting compound under clinical trial in anaesthesia, alfentanil (0.04, 0.16 and 0.63 mg/kg). All compounds increased the amplitude of the EEG, decreased the frequency of the EEG, and produced spindle‐like bursts of biphasic waves. These bursts were more frequent and of a higher amplitude following alfentanil than after the other compounds. A computerized on‐line power spectral analysis was applied to three derivations (frontal‐occipital cortex, dorsal hippocampus, amygdala). The power of the total band width (0–40 Hz) increased following all narcotic analgesics. The duration of this increase was coincident with the period of loss of righting. Spectral analysis of various frequency bands revealed significant differences between the compounds, specifically with regard to fentanyl and alfentanil as compared to morphine and sufentanil. Sleep‐wake patterns of the night following injection of alfentanil were studied. This compound did not produce significant post‐drug effects.