Joosten et al. are to be congratulated on their deployment of technically complex closed-loop systems to support patients during anesthesia and surgery. The possibility of experiencing impaired neurocognitive function in association with a surgical episode is a concern to patients and those who care for them. It makes sense to establish whether changes in clinical technologies might diminish or abolish these unwelcome syndromes.

Nevertheless, we have concerns about the Primary Outcome Measure and its analysis.

On clinical trials.gov (https://clinicaltrials.gov/ct2/show/NCT03148730) the Primary Outcome Measure is “Incidence of postoperative cognitive dysfunction.” This implies a definition of postoperative cognitive dysfunction. The authors chose the Montreal Cognitive Assessment score (maximum 30), so we need to consider what a meaningful change is. Reduction by a single point is very unlikely to be clinically significant and certainly does not...

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