IMPORTANCE Failure to rescue causes significant morbidity and mortality in the surgical population. Human error is often the underlying cause of failure to rescue. Human error can be reduced by the use of cognitive aids.OBJECTIVES To test the effectiveness of cognitive aids on adherence to best practice in the management of deteriorating postoperative surgical ward patients. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial in a simulation setting. Surgical teams consisted of 1 surgeon and 2 nurses from a surgical ward from 4 different hospitals in Amsterdam, the Netherlands. Data were analyzed between February 2, 2017, and December 18, 2018.INTERVENTIONS The teams were randomized to manage 3 simulated deteriorating patient scenarios with or without the use of cognitive aids. MAIN OUTCOMES AND MEASURESThe primary outcome of the study was failure to adhere to best practice, expressed as the percentage of omitted critical management steps. The secondary outcome of the study was the perceived usability of the cognitive aids. RESULTSOf the total participants, 93 were women and 51 were men. Twenty-five surgical teams performed 75 patient scenarios with cognitive aids, and 25 teams performed 75 patient scenarios without cognitive aids. Using the cognitive aids resulted in a reduction of omitted critical management steps from 33% to 10%, which is a 70% (P < .001) reduction. This effect remained significant (odds ratio, 0.63; 95% CI, −0.228 to −0.061; P = .001) in a multivariate analysis. Overall usability (scale of 0-10) of the cognitive aids was scored at a median of 8.7 (interquartile range, 8-9). CONCLUSIONS AND RELEVANCEFailure to comply with best practice management of postoperative complications is associated with worse outcomes. In this simulation study, adherence to best practice in the management of postoperative complications improves significantly by the use of cognitive aids. Cognitive aids for deteriorating surgical patients therefore have the potential to reduce failure to rescue and improve patient outcome.