ABSTRACT
Objective To study the median effective doses (ED50) of dexmedetomidine to induce adequate sedation in elderly patients undergoing epidural anaesthesia. Methods Seventy-five elderly patients undergoing lower extremity operation under epidural anesthesia were selected, and the patients were divided into 5 groups according to the random digits table method with 15 cases each: D1 group (dexmedetomidine 0.2 μg/kg), D2 group (dexmedetomidine 0.4 μg/kg), D3 group (dexmedetomidine 0.6 μg/kg), D4 group (dexmedetomidine 0.8μg/kg) and D5 group (dexmedetomidine 1.0μg/kg). After 20 min of dexmedetomidine injection, adequate sedation was defines as observer′s assessment of alertness/sedation score (OAA/S score) ≤ 3 scores. The ED50 and 95% effective dose (ED95) of dexmedetomidine and 95% CI in elderly patients undergoing epidural anaesthesia were calculated by probit regression method. The changes of mean arterial pressure (MAP), heart rate, pulse oxygen saturation (SpO2) and OAA/S score among 5 groups were compared. The incidences of adverse effects such as hypotension, bradycardia, hypoxemia and excessive sedation were compared. Results The ED50 in elderly patients was 0.36 μg/kg (95% CI 0.27 - 0.44 μg/kg); the ED95 was 0.94 μg/kg (95% CI 0.71 - 1.62 μg/kg). After dexmedetomidine injection, the MBP, heart rate, SpO2 and OAA/S scores in 5 groups were decreased, but in the D4 group and D5 group the decreases were more significant. The incidences of hypotension, bradycardia and excessive sedation in D1 group, D2 group and D3 group were significantly lower than those in D4 group and D5 group:2/15, 5/15 and 8/15 vs. 14/15 and 15/15;1/15, 6/15, 7/15 vs. 13/15 and 14/15;0, 0 and 1/15 vs. 5/15 and 7/15, the incidences of hypoxemia in D1 group, D2 group and D3 group were significantly lower than those in D5 group: 0, 0 and 0 vs. 3/15 and 4/15, and there were statistical differences (P0.05). Conclusions The ED50 of dexmedetomidine in elderly patients undergoing epidural anaesthesia is 0.36μg/kg, (CI 0.27-0.44μg/kg). The incidences of adverse effects are increased when single-dose dexmedetomidine is more than 0.8μg/kg.