Correspondence  |   April 2018
In Reply
Author Notes
  • University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
  • (Accepted for publication December 21, 2017.)
    (Accepted for publication December 21, 2017.)×
Article Information
Correspondence   |   April 2018
In Reply
Anesthesiology 4 2018, Vol.128, 857-858. doi:10.1097/ALN.0000000000002101
Anesthesiology 4 2018, Vol.128, 857-858. doi:10.1097/ALN.0000000000002101
We appreciate the interest of Liu et al. in our article.1  This offers the opportunity to put more emphasis on the role of sedation level, displayed by the parameter bispectral index, on analgesic monitoring. As Liu et al. pointed out, the patients’ Bispectral Index (BIS) values in the study were lower than recommended values during surgical procedures. As they assumed in their letter, these low values are caused by the initial bolus of propofol for induction of general anesthesia and successful placement of the laryngeal mask. Persistence of low BIS values with a standard dosage of propofol of 4 to 5 mg · kg–1 · h–1 is not unusual when considering that patients were in a stimulus-reduced dark and silent room. The aim of our study was to compare the detection of nociceptive stimuli on different analgesic levels but on the same level of sedation, and accordingly the BIS values were low throughout the whole intervention period. We agree that tetanic stimulation obviously was not sufficient to provoke electrocortical activation in the sense of “arousal” from deep sedation. This is exactly our point: The nociceptive stimulus provoked a significant change in analgesic indices and pupil dilation, but not in BIS values. Furthermore, the extent of the change in analgesic indices and pupil dilation was diminished by an increase of opioid administration (fig. 2).1  Thus, the Analgesia Nociception Index and Surgical Pleth Index as well as the pupil diameter are proven to reflect the analgesic level. BIS in contrast did not correlate at all with the application of a nociceptive stimulus. Consequently, BIS does not display the analgesic level. Other authors’ findings support our conclusion that BIS monitoring is unable to detect and predict stimulation response.2,3 
First Page Preview
First page PDF preview
First page PDF preview ×
View Large