Wang C, et al. - Herein, researchers investigated the median effective dose (ED₅₀) of intravenous dexmedetomidine for sedation in elderly patients who were undergoing total knee arthroplasty (TKA) with peripheral nerve block (PNB). In the young-old group and in the middle-old group, the identified ED₅₀ of single-dose dexmedetomidine adjuvant to PNB was 0.57 μg/kg and 0.38 μg/kg, respectively. Furthermore, relative to the young-old group, ED₅₀ of dexmedetomidine in the middle-old group decreased by 33% with a mean age difference of 11 years between the two groups.