LAUSR

(Accepted for publication May 7, 2018.) Electroencephalogram and Anesthetics To the Editor: I was intrigued by the article by Warnaby et al., who reported that electroencephalographic slow-wave activity saturation is observed for both intravenous and volatile anesthetics.1 Furthermore, they found that opiates reduced the concentration of anesthetic at which slow-wave saturation was observed. In contrast, they reported that muscle relaxants did not alter the anesthetic concentration at which electroencephalographic slow-wave saturation occurred. Their results may lead to the erroneous conclusion that muscle relaxants do not alter the electroencephalographic effects of anesthetics. By comparison, our own study in dogs demonstrated that pancuronium neuromuscular blockade potentiated electroencephalographic burst suppression elicited by isoflurane.2 This effect on electroencephalography was reversed by the administration of neostigmine. Furthermore, the description of electroencephalographic burst suppression by Warnaby et al. as an “artefactual disturbance” greatly obscures this issue. Most certainly, electroencephalographic burst suppression is not an artefactual disturbance, as multiple reports confirm that dose-dependent electroencephalographic burst suppression is elicited by a wide variety of anesthetic agents of diverse chemical structure.3 For all of these anesthetics, electroencephalographic burst suppression is associated with a dose-related decrease in cerebral metabolic rate. Indeed, altered electroencephalographic burst suppression in elderly patients confirms the accepted principal of age-related shifts in the pharmacodynamics of volatile anesthesia.4,5 It should also be noted that in their clinical study, Warnaby et al. failed to control for dose, A conserved behavioral state barrier impedes transitions between anesthetic-induced unconsciousness and wakefulness: evidence for neural inertia. PLoS One 2010; 5: e11903