To the Editor
We read with great interest the recent article by Shin et al. which concluded that dexmedetomidine shows a lower incidence of postoperative delirium compared to propofol sedation in healthy older adults undergoing lower limb surgery during spinal anesthesia, which included patients aged greater than 65 with an American Society of Anesthesiologists (ASA) Physical Status I or II. Although we applaud the efforts of the group to establish consensus on the mode of sedation for this cohort, we would like to highlight some additional considerations.
Additional baseline characteristics associated with delirium were not explored in this study, e.g., frailty, nutrition, education level, depression, and a past history of delirium. A recent systematic review and meta-analysis of more than 41 studies has identified frailty as the strongest risk factor for the development of delirium after major surgery, with its strength of association with delirium incidence only exceeded by a history of delirium (odds ratio of 6.4 and 4.1, respectively). This compares to an odds ratio of 2.2 and 1.7, respectively, for the factors of age and ASA status. Estimates for the prevalence of frailty in all age ranges in the surgical population range between 4.1 and 50.3% highlighting the vulnerability of this patient group when considering the surgical patient cohort. Although this study suggests that dexmedetomidine has a delirium-sparing effect compared to propofol in the healthy older patient, the frail patient has not been included. The results of this trial may not reflect the risks of sedation with dexmedetomidine in this patient cohort.