Dexmedetomidine is known to be administered for sedation safely even in a very elderly patient. The purpose of this study was to determine the effect of age on clinically optimal dose of dexmedetomidine for sedation.

We enrolled 50 patients ASA class I and II, scheduled for lower extremity surgery that need. They were classified into a young group (n = 26), aged below 75 and an old group (n = 24), aged above 75. Dexmedetomidine was continuously infused 0.5 µg/kg within 10 min, followed by maintenance at a dose of 0.5 µg/kg/min, initially. The next dose was selected using the Dixon’s up-and-down method.

The cED50 of dexmedetomidine required to maintain optimal sedation level in young and old group were 0.50 and 0.48 µg/kg, respectively. With isotonic regression, cED95 of dexmedetomidine was 0.71 µg/kg (95% confidence intervals 0.57-1.06 µg/kg) and 0.58 µg/kg (95% confidence intervals 0.51-0.67 µg/kg). There were no significant differences in cED50 (P = 0.21), recovery variables, or incidence of side effects between the two groups.

Clinically optimal dose of dexmedetomidine was not affected to the age during sedation.