| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[1] Anaesthetics and sedatives: World Health Organisation. WHO model prescribing information: Drugs used in anaesthesia, 1994. https://apps.who.int/medicinedocs/en/d/Jh2929e/2.html