Introduction: The growing number of learners implies that all of them cannot play an active role during high-fidelity scenarios. Studies suggest a positive educational value when learners are observers only, but it remains uncertain whether learning outcomes might be improved by using an observer tool (OT).
Methods: Eighty-nine anesthesia residents were randomized to use an OT (n = 44, OT+; based on a cognitive aid) or not (n = 45, OT-) when not role-playing.