Effect of melatonin on postoperative cognitive function in elderly patients submitted to transurethral resection of the prostate under spinal anesthesia.

Background: Hospitalization for Transurethral Prostate Resection (TURP) involves circadian rhythm disturbance - a possible cause of Postoperative Neurocognitive Disorder (POCD) in elderly patients. This study investigated whether melatonin ameliorated this effect.

Methods: A double-blind, randomized clinical trial used a battery of neuropsychological tests to evaluate cognitive performance of 118 patients aged ≥ 60, before TURP with spinal anesthesia, and at 21- and 180-days PO. Patients received 10 mg of melatonin, or a placebo, on the night before surgery and 1-, 2- and 3-days PO. Delayed neurocognitive recovery in the two groups at 21 days PO was compared using the Chi-Squared test; individual performances in each test at each date were compared using the General Mixed Model. Results with p < 0.05 were considered significant.

Results: Pre-surgery, both groups had significant cognitive deficits. Delayed cognitive recovery at 21 days PO was the same in both. There were no cases of POCD at 180 days. The melatonin group performed better in the delayed-recall FOME, which assesses memory, and in the Digit Span test, which assesses attention and cognitive flexibility. Unexpectedly, global neurocognitive performance was improved at 180 PO in both groups.

Conclusions: Melatonin had no statistical effect on POCD, but a selective beneficial effect was observed in two cognitive areas. The high prevalence of preoperative cognitive impairment may be related to the lower urinary tract symptoms which were reasons for the surgery; the unexpected improvement of cognitive performance in all patients at 180 days PO may reflect alleviation of these symptoms.