The effects of neostigmine on postoperative cognitive function and inflammatory factors in elderly patients - a randomized trial

Background: Postoperative cognitive dysfunction is a common postoperative complication in elderly patients. In elderly patients, the decline of organ function and neuromuscular junction function make them more sensitive to muscle relaxants. They are more likely to experience residual muscle relaxation after surgery, which may cause various adverse events. Neostigmine, a commonly used muscle relaxant antagonist, can reduce the expression of inflammatory factors, thereby reducing the pro-inflammatory response and neurodegeneration of the cerebral cortex and hippocampus after surgery. The study aimed at observing the effect of different doses of neostigmine on postoperative cognitive function and peripheral inflammatory factors in elderly patients.

Methods: One hundred thirty-two elderly patients who underwent a radical section of gastrointestinal cancer at First Affiliated Hospital of Dalian Medical University were divided into neostigmine and saline groups at a 2:1 ratio. Neostigmine was intravenously injected in the post-anesthesia care unit (PACU) according to the train-of-four ratio (TOFR) T4/T1. When TOFR was ≤0.5, 0.04 mg/kg neostigmine was administered, whereas when TOFR was > 0.5, 0.02 mg/kg neostigmine was injected. The main observation indexes were cognitive function, interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and interleukin 6 (IL-6) in peripheral blood at the different times before and after the surgery. Secondary observation indicators include the number of atropine injection, extubating time, PACU residence time, incidence of hypoxemia, hypercapnia, and postoperative nausea and vomiting in PACU, time of exhaustion, and length of hospitalization.

Results: The extubating and PACU times in 0.04 mg/kg and 0.02 mg/kg groups were significantly shorter than those in the control group (P < 0.001). The incidence of early postoperative cognitive decline in 0.04 mg/kg and 0.02 mg/kg groups was 10 and 15.7%, respectively, which were significantly lower than those in the control group (P = 0.013).

Conclusion: In elderly patients, 0.02-0.04 mg/kg neostigmine could significantly reduce the incidence of early postoperative cognitive decline without affecting peripheral inflammatory factors.

Trial registration: Trial registration: Chinese Clinical Trial Registry, ChiCTR2000031739. Registered 8 April 2020 - Retrospectively registered, http://www.medresman.org.cn .

Keywords: Cholinergic anti-inflammatory pathway; Cognitive impairment; Elderly patients; Neostigmine; Pro-inflammatory factors.