There has been some observational evidence that a greater depth of anesthesia, as measured by BIS, may be associated with an increase in post-operative mortality. In particular the association of the "triple low state" (low BIS, low volatile-ET, low MAP) with post-operative mortality is worrying.
Completion of the Balanced Anaesthesia Study Group’s large RCT looking at this issue however brings us as close to a final word as we may expect. Short et al. (2019) showed no difference in 1-year mortality for older patients undergoing major surgery, whether they received a deep (BIS target 35) or light (BIS target 50) general anaesthetic.
It is likely that earlier observational studies were showing the consequences of intraoperative hypotension resulting from anaesthetic depth, rather than anaesthetic depth itself.summary
An extensive collection of research debunking a range of myths and misconceptions regarding the way we use neuromuscular blocking drugs.
- Myth 1: Modern relaxants are so reliable and predictable that monitoring is unnecessary.
- Myth 2: Post-op residual paralysis is neither common or important.
- Myth 3: Post-op residual paralysis is easy to identify.
- Myth 4: Sugammadex makes residual paralysis a non-issue. (it might, but only if it is routinely available and used!)
- Myth 5: Using propofol and remifentanil we can avoid relaxants for intubation all together.
- Myth 6: Neuromuscular blockade has no effect on BIS.
And bonus myth: deep relaxation is necessary for improving surgical access during laparoscopy.summary
...and 1 more note