Effects of low‐dose ketamine on neuropathic pain: An electroencephalogram–electrooculogram/behavioral study

Abstract

The aim of the present study was to clarify the neurophysiological changes associated with analgesic and behavioral effects of low-dose ketamine HCl in patients suffering from chronic neuropathic pain. Ten in-patients with neuropathic pain participated in this single-blind, placebo-controlled study after giving written informed consent. Following intravenous injections of a saline solution (placebo), three bolus injections of 5 mg ketamine HCl were administered at 5 min intervals. Changes in pain perception were assessed using a numerical rating scale for pain. Behavioral changes, including psychotomimetic effects, were assessed using the Brief Psychiatric Rating Scale (BPRS). Electroencephalograms (EEG) and electrooculograms (EOG) were recorded continuously throughout the testing period. One minute EEG and closed-eye eye movements were quantified. The effects of ketamine were evaluated by comparing the neurophysiological and behavioral parameters obtained from the placebo and ketamine trials. Pain reduction was significantly correlated with ketamine-induced changes in hallucinatory behavior and excitement as measured by the BPRS. Ketamine injections caused a significant decrease in the EEGa amplitude without an accompanying reduction in EEG frequency. The EEGa amplitude reduction at the right central electrode was significantly related to subjective pain relief. Subanesthetic doses of ketamine significantly decreased rapid eye movements, but did not initiate slow eye movements. In conclusion, the present EEG-EOG/behavioral results indicate that ketamine-induced failure of neural integration between cortical-subcortical regions induces psychotic symptoms and alters pain perception on neuropathic pain.

Resting-state electroencephalography and magnetoencephalography as biomarkers of chronic pain: a systematic review

“…Finally, 76 studies were included. 1,[5][6][7][8]10,11,15,16,[18][19][20][21][22][23][24][25][26][27][30][31][32][33]35,[37][38][39][40][41][42][43][44][45][46][47][48][49]51,56,59,60,63,[66][67][68][69][74][75][76]79,80,82,[89]…”

Ketamine Pharmacology: An Update (Pharmacodynamics and Molecular Aspects, Recent Findings)

“…Ketamine modifies electroencephalogram (EEG) differently from other anesthetic drugs. The most typical EEG aspect is the diminution of alpha rhythm amplitude (even its abolition) without modification of its frequency and the appearance of theta waves, without a measurable relationship with the depth of narcosis . Moreover, ketamine does not decrease the amplitude of mid‐latency auditory evoked potentials or somatosensory evoked potentials .…”

Alcohol, toxins, and medications as a cause of sleep dysfunction

“…Ketamine's use as an anesthetic in humans has been associated primarily with reports of excessive dreaming. These results suggest that ketamine produced a conscious state that was neither alert nor drowsy (Oga et al, 2002). In a study of awake EEG recordings in patients with neuropathic pain, subanesthetic doses of ketamine caused a significant decrease in alpha-wave amplitude without increasing the absolute amplitude of slow-wave activity (Rangaswamy et al, 2004).…”