I was surprised to read in the report of Ueyama et al.  1the erroneous statement, “A muscle relaxant itself does not have an effect on electroencephalogram.” We described an increase in duration of electroencephalography isoelectric interval during burst suppression after the administration of pancuronium in dogs anesthetized with isoflurane.2This effect was then reversed by antagonism of neuromuscular blockade with neostigmine. The failure of Ueyama et al.  1to control for neuromuscular blockade in their study of pregnant patients may present a confounding variable.

Mount Sinai Medical Center, New York, New York. arthur.schwartz@mountsinai.org

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