Letters to the Editor: Letters & Announcements
To the Editor:
The volunteer study by Messner et al. (1) confirmed what has previously been reported regarding the confounding effect of electromyographic activity on the Bispectral Index value (2,3). However, it is unclear how these authors concluded that because decreased electromyographic activity leads to a reduced Bispectral Index value “awareness in totally paralyzed patients cannot be excluded.” Although this article elicited two subsequent Letters to the Editor (4,5), it is interesting that no one commented on the possible ethical question of administering muscle relaxants to unanesthetized (awake) volunteers.
Paul F. White, PhD, MD, FANZCA
Professor and Holder of the Margaret Milam McDermott Distinguished Chair in Anesthesiology
University of Texas Southwestern Medical Center at Dallas
1. Messner M, Beese U, Romstock J, et al. The bispectral index declines during neuromuscular block in fully awake persons. Anesth Analg 2003;97:488–91.
2. Bruhn J, Bouillon TW, Shafer SL. Electromyographic activity falsely elevates the bispectral index. Anesthesiology 2000;92:1485–7.
3. Vivien B, Di Maria S, Ouattara A, et al. Overestimation of bispectral index in sedated intensive care unit-patients revealed by administration of muscle relaxant. Anesthesiology 2003;99:9–17.
4. Seubert CN, Mahla ME. Bispectral index decline caused by neuromuscular blockade. Anesth Analg 2004;98:871.
5. Bruder N, Velley L, Rey M. A low voltage EEG signal may give low bispectral index values. Anesth Analg 2004;98:873.