Abstract: Objective To investigate the effect of different doses of dexmedetomidine (Dex) on early postoperative cognitive
dysfunction in elderly patients undergoing laparoscopic surgery for colorectal cancer. Methods Eighty ASAI-III elderly
patients (over 65 years) were randomized equally into 4 groups including a control group without dexmedetomidine and 3
dexmedetomidine groups (groups D1, D2, and D3) with loading dexmedetomidine doses of 0.2, 0.5, and 0.8 μg/kg and
maintenance doses of 0.2, 0.5, and 0.8 μg·kg-1 ·h-1, respectively. Dex was discontinued 30 min before the end of surgery. The
time of operation, adverse reactions, time from the end of surgery to spontaneous breathing recovery (TR), time from
spontaneous breathing recovery to opening eyes (TO), and time from opening eyes to extubation (TE) were recorded.
Mini-Mental State (MMSE) test was used to assess the cognitive function 1 day before and at 1 day and 3 days after the
operation. Results The incidence of postoperative cognitive dysfunction (POCD) was significantly lower in groups D2 and D3
than in the control group and group D1 (P<0.05). The incidences of hypotension and bradycardia were the highest in group D3
(P<0.05), which also had longer significantly TO and TE than the other 3 groups (P<0.05). Conclusion Dexmedetomidine with a
loading dose of 0.5 μg/kg followed by maintenance doses of 0.5 and 0.8 μg·kg-1·h-1 (preferentially 0.5 μg·kg-1·h-1) can reduce
the incidence of POCD in elderly patients undergoing laparoscopic surgery for colorectal cancer.