Bispectral index monitoring: appreciated but does not affect drug dosing and hypnotic levels

Abstract

Background: Bispectral index (BIS) has been associated with benefits from less-deep anesthesia as well as preventing awareness, albeit not at the same time. We investigated how increasing experience from BIS in clinical practice affect the hypnotic level, drug consumption, as well as subjective opinions on this monitoring.

Methods: Eight certified registered nurse anesthetists (CRNAs) with previous experience from 88 (46-121) BIS monitored cases anesthetized 80 cases with concealed BIS, followed by 80 cases with available BIS. Additional education and training was followed by yet another 160 patients randomized to open or blindly recorded BIS. BIS levels, anesthetic gas consumption, fentanyl use, and subjective opinions on utility and reliability were investigated.

Results: After gaining initial experience from BIS monitoring, the fraction of time with BIS levels of 40-60 did not deteriorate in cases with concealed monitoring and no further improvement was found in subsequent cases with available data from the BIS monitoring, not even after additional training and encouragement to adhere to the 40-60 interval. Compared with the first experience from BIS monitoring the subjective opinions on utility had increased from 33 to 78 mm (100 mm visual analog scales) (P<0.0001).

Conclusion: Although BIS became considerably appreciated, growing experience and repeated education had no impact on drug dosing and BIS levels.