Almost never used it in residency and still don't in practice but see everyone else - colleagues and CRNAs - almost universally sticking them on people's foreheads and charting the numbers it spews out; but I either don't see or appreciate how the anesthetic is altered by its application. I'm not aware of any hard evidence for its utility. Does it correlate with depth? Does it "prevent" awareness? Will I get sued if a pt of mine ever has awareness and i didn't use BIS? Is it just a waste of money? I feel like proprietary algorithm = snakeoil...
Let me attempt to answer your questions:
1. Hard evidence for utility- limited data to none
2. Does it correlate with depth- yes, to some degree especially with BIS readings less than 20; so, if you typically overdose your vapor it may be helpful. In addition, minimizing the use of volatile agents in sick and/or elderly patients is likely the most beneficial use of the BIS device.
3. Does it prevent awareness- yes and no. When using vapor as the main anesthetic agent BIS is inferior to ET Vapor concentration. An ET vapor MAC of 0.7 is superior to a BIS value of 40 in terms of preventing recall. That said for a pure TIVA the BIS device is the best method we have for preventing recall.
4. Lawsuits- BIS is inferior to an ET MAC of 0.7 so no you won't get sued for not using a BIS if you typically run at least 0.7 MAC of volatile agent. For TIVA cases and other cases where you MAC is less than 0.5 MAC of volatile agent I recommend the BIS device.
5. Waste of money- probably the way most people use or don't use the BIS it is a waste of money.
Finally, BIS is not "snake oil" but it has its limitations. I selectively use the BIS for my cases which means i I typically use it 10% of the time.
Examples of cases I use BIS:
1. TIVA with any muscle relaxant
2. Elderly or ASA 4 (limit the volatile agent to the minimum)
3. History of recall ( BIS plus an ET vapor concentration of at least 0.7 or higher)
4. History of Chronic Pain or taking Benzos daily