Influence of Ketamine on Early Postoperative Cognitive Function After Orthopedic Surgery in Elderly Patients

Postoperative cognitive dysfunction (POCD) is a serious and frequent complication after surgery, especially in elderly patients. Ketamine is an N-methyl D-aspartic acid receptor antagonist with demonstrated neuroprotective effects. An intravenous bolus of a sub-anesthetic dose (0.5 mg/kg) of ketamine can reduce postoperative delirium (POD) and POCD after cardiac surgery. But, the influence of ketamine on early POCD after non-cardiac surgery is unclear.

The current study aimed to evaluate the influence of ketamine on early postoperative cognitive function after orthopedic surgery in elderly patients.

Fifty six elderly patients (> 60-years-old), scheduled for elective orthopedic surgery during general anesthesia (duration of anesthesia > two hours) were enrolled. Patients received intravenous bolus, a total of 3 mL mixed with 0.9% normal saline and 0.5 mg/kg ketamine (K group) or 3 mL of 0.9% normal saline (N group). Three neurocognitive function tests (mini-mental status examination, trail-making test, digit substitution test), and c-reactive protein (CRP) concentration were determined before surgery and on postoperative day one (POD 1) and postoperative day six (POD 6).

The two groups had similar demographic characteristics except for the gender. Surgical and anesthetic data were not significantly different. A statistically significant difference was observed in comparison of trail-making test score. Trail-making test score increased more in the N group (52.5 points) than the K group (13 points) at POD 1 (P = 0.047) compared with baseline scores. There were no significant differences in the mini-mental status examination, digit substitution test and CRP concentration at POD 1 and POD 6 between the two groups. POCD (the two Z-scores in more than two tests or the combined Z-score was 1.96 or more) was present in one patient (4%) in the K group at POD 6 (P = 0.98).

The incidence of POCD was not significantly influenced by a bolus dose of ketamine (0.5 mg/kg) after orthopedic surgery in elderly patients. There were no negative effects of ketamine on early POCD.