Effective dose of dexmedetomidine as an adjuvant sedative to peripheral nerve blockade in elderly patients.

Abstract

The median effective dose (ED₅₀ ) of sedative dexmedetomidine adjuvant to peripheral nerve block (PNB) has not yet been verified in elderly patients. This study assessed the ED₅₀ of intravenous dexmedetomidine for sedation in elderly patients who were undergoing total knee arthroplasty (TKA) with PNB. Forty-two patients aged 65-85 years were included and stratified into two groups according to age: young-old group (aged 65-74 years) and middle-old group (aged 75-85 years). After the PNB was performed, a pre-calculated dose of dexmedetomidine was administered for 10 min. The Observer's Assessment of Alertness/Sedation scale, bispectral index score, blood pressure and heart rate were recorded. ED₅₀ values of dexmedetomidine for adequate sedation were estimated by the up-and-down method of Dixon and probit regression. The ED₅₀ of single-dose dexmedetomidine adjuvant to PNB was 0.57 μg/kg (95% confidence interval [CI], 0.47-0.65) in the young-old group and 0.38 μg/kg (95% CI, 0.28-0.46) in the middle-old group. The ED₅₀ of dexmedetomidine differed significantly between the two groups (P < 0.001). In addition, no significant adverse hemodynamic or hypoxemic effects were noted. We determined the ED₅₀ for sedation using intravenous dexmedetomidine adjuvant to PNB in elderly patients. The ED₅₀ of dexmedetomidine in the middle-old group decreased by 33% compared with that in the young-old group with a mean age difference of 11 years between the two groups.