Abstract: Abstract Objective To observe the effect of a variety of dexmedetomidine on circulatory and cognitive functions in elderly patients undergoing hip orthopedic surgery. Methods A total of 120 cases for hip orthopedic surgery, aged over 65 years old and recruited from 06/2013 to 09/2014, were administered intravenously dexmedetomidin -e after epidural anesthesia. Based on the various doses of dexmedetomidine, the patients were randomly and averagely divided into 3 groups, including group A of 0.2 μg?h-1?kg-1, group B of 0.4 μg?h-1?kg-1, and group C of 0.6 μg?h-1?kg-1, with 40 cases in each group. The heart rate (HR)，mean arteria1 pressure (MAP), and pulse oxygen saturation (SpO2) were recorded at 6 time points, including the time of admission to the operating room(T0), 10 min (T1), 20 min (T2) after drug administration, the time of drug withdrawal (T3), 10 min after drug withdrawal (T4) and the terminal time of surgery (T5), respectively. Cognitive function was evaluated by mini-mental state examination (MMSE) at the time points of 24 hours before surgery (t1), 12 hours (t2), 24 hours (t3), and 72 hours (t4) after surgery. Results there was no significant difference of the general status among the 3 group (P > 0. 05). A significant decrease in MAP and HR at T2 and T3 time point was observed in group C compared to that in group A or group B (P < 0.05). There was no significant difference in MMSE at time point t0 among the three groups (P > 0.05). However, compared to that in group A or group C, MMSE increased significantly at time point t2, t3 in group B (P< 0.05). In addition, compared to group A or group C, the patients in group B exhibited lower incidence of postoperative cognitive function disorder(POCD) (P<0.05)。 Conclusion Continuous intravenous pumping of Dexmedetomidine can be used in elderly patient undergoing hip orthopedic surgery with the dose of 0.4 μg?h-1?kg-1 safely, with less interference to circulatory and cognitive function in perioperative period.

Key words: anesthesia, epidural, cognition disorder, postoperative period, aged, Dexmedetomidine