Die zentralnervösen exzitatorischen Effekte von Ketamin werden durch den Zusatz von Midazolam verringert

S(+)-ketamine attenuates increase in electroencephalograph activity and amplitude height of sensory-evoked potentials during rapid opioid detoxification

Anesthesia-assisted opioid detoxification offers an opportunity for patients who have undergone unsuccessful conventional detoxifications. Little is known of excitatory effects taking place in the central nervous system during this procedure. Because acute withdrawal is accompanied by N-methyl-d-aspartic acid (NMDA)-receptor activation we tested whether the administration of the nonspecific N-methyl-d-aspartic acid antagonist S(+)-ketamine results in a reduction of hyperactivity in the central nervous system. Thirty-one patients with a long history of opioid abuse were acutely withdrawn with naltrexone during propofol/clonidine anesthesia and mechanical ventilation. Electroencephalogram (EEG) power spectra as well as median nerve-evoked somatosensory potentials (SSEP) were determined at the following times: evening before detoxification (control), steady-state propofol/clonidine-anesthesia, 30 min after naltrexone administration, and 5 min and 60 min after additional S(+)-ketamine (1.5 mg/kg). Compared to steady-state anesthesia, naltrexone induced a decrease by 270% in the low delta (0.5-3 Hz) and an increase by 110% in the fast beta (13-30 Hz) domain of the EEG with only minor changes in the theta-(3-7 Hz) and alpha-(7-13 Hz) band. Simultaneously, mean amplitude of the late N(100) peak of the SSEP increased from 3.3 muV to 10.5 muV. The changes could be attenuated by the additional administration of S(+)-ketamine, 5 min and 60 min after injection. Cardiovascular changes were not a reliable index for monitoring acute withdrawal symptoms and determining termination of rapid opioid detoxification. In this regard, EEG power spectra and SSEP were more consistent and clinically useful variables. S(+)-ketamine is a valuable adjunct in the anesthetic regimen, since it attenuates hyperactivity of the central nervous system during rapid opioid detoxification.

Increase in delta- and beta-wave activity of the EEG during rapid opiate detoxification (ROD)-reversal by administration of the non-specific NMDA-antagonist S+ ketamine-

Little is known on effects taking place in the CNS during rapid opioid detoxification (ROD) while the patient is under anesthesia. We therefore measured EEG-power spectra in the beta, alpha, Theta, and delta-band in 36 patients undergoing ROD. Measurements were taken before, during steady-state anesthesia and following administration of the antagonist naltrexone. In addition, the non-specific NMDA-antagonist S+ ketamine was given for reduction of CNS-hyperexcitation, while the efficacy of this adjunct was determined using EEG power spectra analysis. Compared to steady-state anesthesia, EEG power spectra were characterized by a marked decrease of power by 251% in the delta (0.5-3 Hz) and an increase by 209% in the beta- (13-30 Hz) domain when withdrawal was induced with naltrexone. Subsequent administration of S+-ketamine induced a reversal of acute abstinence-related EEG power changes: compared to anesthesia with naltrexone on board, power in the EEG increased by 65% in the delta- and decreased by 723% in the beta-band. While sympathetically induced hemodynamic alterations in anesthesia-assisted opioid detoxification can be attenuated by the alpha2-agonist clonidine and sedation, central nervous sensory activation can be attenuated by the administration of S+-ketamine (1.5 mg/kg). Since EEG alterations during acute withdrawal with naltrexone can be controlled by the non-specific NMDA-antagonist S+-ketamine, this latter presents a useful adjunct during ROD management.

Low-dose midazolam antagonizes cerebral metabolic stimulation by ketamine in the pig

In order to test the hypothesis that low-dose midazolam reduces excitatory cerebral symptoms by attenuating ketamine-induced increases in the cerebral metabolic rate for oxygen (CMRO2), we compared the cerebral effects of a combination of an anesthetic dose of ketamine hydrochloride (10.0 mg.kg-1 i.v.) and a subanaesthetic dose of midazolam maleate (0.25 mg.kg-1 i.v., n = 6; or 0.10 mg.kg-1 i.v., n = 6) with results recently obtained with ketamine (10.0 mg.kg-1 i.v.) in normoventilated pigs anaesthetized with fentanyl, nitrous oxide and pancuronium. Cerebral blood flow (CBF) was measured with the intra-arterial 133Xe clearance technique, and CMRo2 was calculated from CBF and the cerebral arteriovenous oxygen content difference (CaVO2). The CMRO2 did not increase significantly. In contrast, the maximal increase in cerebral CaVo2 (by 56-59% at 10 min; P < 0.01) was similar to that induced by ketamine, since CBF was more depressed (by 35-45% at 1 min: P < 0.001) by ketamine-midazolam than by ketamine only. Midazolam was found to increase CVR (P < 0.01) and further depress CBF (P < 0.01), and to antagonize the ketamine-induced increase in CMRO2 (P < 0.05). Ketamine-induced effects on mean arterial pressure (MAP) and spectral electroencephalographic (EEG) voltage were not significantly altered by midazolam. The pharmacokinetics of ketamine, as measured during an 80-min period, were not affected by the concomitant administration of midazolam. We propose that a ketamine-midazolam combination comprising a low-dose fraction (1/100-1/40) of midazolam is superior to ketamine alone for anaesthetic use.