The Influence of Age on Sensitivity to Dexmedetomidine Sedation During Spinal Anesthesia in Lower Limb Orthopedic Surgery.

To investigate the influence of age on sensitivity to dexmedetomidine sedation in adult patients, we selected 79 patients scheduled for lower limb orthopedic surgery under spinal anesthesia to identify the dexmedetomidine ED50 for adequate sedation among different age groups. After a spinal anesthetic was placed, a dose of dexmedetomidine determined by the Dixon up-and-down method was administered over 15 minutes. The ED50 in the elderly group was lower than in the other 2 groups (elderly: 0.88 +/- 0.07; middle aged: 1.16 +/- 0.08; young: 1.21 +/- 0.06 mu g/kg; both P<.001). There was no difference between the young and middle-aged groups (P=.160).