Newly Published
Correspondence  |   July 2020
Impact of Closed-loop Anesthesia on Cognitive Function: Comment
Author Notes
  • University of Plymouth, Plymouth, United Kingdom (J.R.S.). robert.sneyd@pms.ac.uk
  • Accepted for publication June 19, 2020.
    Accepted for publication June 19, 2020.×
Article Information
Correspondence
Correspondence   |   July 2020
Impact of Closed-loop Anesthesia on Cognitive Function: Comment
Anesthesiology Newly Published on July 14, 2020. doi:https://doi.org/10.1097/ALN.0000000000003468
Anesthesiology Newly Published on July 14, 2020. doi:https://doi.org/10.1097/ALN.0000000000003468
Joosten et al. are to be congratulated on their deployment of technically complex closed-loop systems to support patients during anesthesia and surgery.1  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 represent a reduction of more than 1 SD less than normative published data.2  A decline of two points? Five points? Falling from more than 26 to less than 26? Each patient either does or does not have postoperative cognitive dysfunction and the incidence would be the proportion of patients with the condition in each of the two treatment groups; then we can compare the incidence after control and closed-loop treatments.