Thank you for your interest in our article.1Schwartz et al.  2reported that pancuronium increased the duration of isoelectricity produced by isoflurane during burst suppression in experiments with canines. When a burst and suppression pattern was observed in a clinical situation, the anesthetic level was considered too deep. Contrary to this, Ge et al.  3reported that vecuronium did not alter the bispectral index during isoflurane anesthesia. Grief et al.  4also showed that mivacurium did not affect the bispectral index value during propofol anesthesia. In these reports, the index (BIhxin Ge et al.  3and bispectral index in Grief et al.  4) was approximately 40–50, which indicated the usual clinical level of anesthesia. The authors analyzed many electroencephalograms and concluded that vecuronium did not change electroencephalographic waveforms or derivatives during sevoflurane/opioid anesthesia in the usual clinical settings. The authors speculated that the phenomenon that Schwartz AE et al.  2observed was specific for pancuronium or in a deep anesthetic level.

It is well known that contamination of electromyograms may falsely increase electroencephalographic derivatives, and administration of a neuromuscular blocker restores them. In our study, the level of electromyograms was kept adequately low, thereby making the possibility that muscle afferents might alter the level of consciousness unlikely. The authors believe that muscle relaxants would not affect our results.

*Osaka University Graduate School of Medicine, Osaka, Japan.

Ueyama H, Hagihira S, Takashina M, Nakae A, Mashimo T: Pregnancy does not enhance volatile anesthetic sensitivity on the brain: An electroencephalographic analysis study. Anesthesiology 2010; 113:577–84
Schwartz AE, Navedo AT, Berman MF: Pancuronium increases the duration of electroencephalogram burst suppression in dogs anesthetized with isoflurane. Anesthesiology 1992; 77:686–90
Ge SJ, Zhuang XL, He RH, Wang YT, Zhang X: Neuromuscular block with vecuronium reduces the rapidly extracted auditory evoked potentials index during steady state anesthesia. Anaesthesia 2003; 50:1017–22
Grief R, Greenwald S, Schweitzer E, Laciny S, Rajek A, Caldwell J, Sessler DI: Muscle relaxation does not alter hypnotic level during propofol anesthesia. Anesth Analg 2002; 94:604–8