Effects of ketamine or dexmedetomidine on postoperative cognitive dysfunction after cataract surgery: A randomized controlled trial

BACKGROUND AND AIMS: Ketamine and dexmedet omidine have neuroprotective effects that may reduce the occurrence of postoperative cognitive dysfunction (POCD) when they are used by intravenous infusion in geriatric patients scheduled for cataract extraction. METHODS: Ninety patients aged 65-85 years old, ASA physical status II and III, and scheduled for cataract extraction under peribulbar block were randomly distributed equally among three groups: control group, in which patients received normal saline; ketamine group, in which patients received 0.3 mg/kg/h of ketamine; and dexmedetomidine group, in which patients received 0.5 µg/kg/h of dexmedetomidine. Medications were administrated by intravenous infusion and started 10 min before the surgery and continued throughout the duration of surgery. The analysed parameters included the incidence of POCD (primary outcome) through composite score of neuropsychological testing at one week and 3 months after surgery, postoperative pain score, postoperative sedation score, changes in haemodynamic parameters, changes in intraocular pressure, and incidence of complications. RESULTS: In comparison with control group, ketamine and dexmedetomidine groups exhibited a significant decline in number of patients who developed POCD (P < 0.0001), a decrease in the postoperative pain score 4 h after surgery (P = 0.038), and an increase in the postoperative Ramsay sedation Score (P = 0.0002, 0.0003, and 0.011), without significant changes in the vital parameters, intraocular tension, or incidence of complications. Ketamine and dexmedetomidine groups were comparable. CONCLUSION: Intravenous administration of ketamine or dexmedetomidine in elderly patients undergoing cataract surgery under peribulbar anesthesia significantly decreases the incidence of POCD.