Efficiency of donepezil in elderly patients undergoing orthopaedic surgery due to underlying post-operative cognitive dysfunction: study protocol for a multicentre randomised controlled trial

Influence of Neostigmine on Early Postoperative Cognitive Dysfunction in Older Adult Patients Undergoing Noncardiac Surgery: A Double-Blind, Placebo-Controlled, Randomized Controlled Trial

BACKGROUND

The goal of this study was to investigate the efficacy of neostigmine on postoperative cognitive dysfunction (POCD) and determine its effect on systematic markers of oxidative stress in older patients.

METHODS

This double-blind placebo-controlled trial enrolled 118 elderly patients (≥65 years) undergoing noncardiac surgeries who were allocated to a neostigmine treatment group (0.04 mg/kg) or a placebo control group (normal saline) postoperatively. POCD was diagnosed if the Z -scores for the mini-mental state examination and the Montreal Cognitive Assessment were both ≤-1.96. Postoperative serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), and brain-derived neurotrophic factor (BDNF) were also compared. Multivariable regression analysis with dose adjustment of atropine was used to demonstrate the influence of neostigmine on the incidence of POCD.

RESULTS

Patients receiving neostigmine had a significantly reduced incidence of POCD compared to patients who were treated with placebo on the first day after surgery (-22%, 95% confidence interval [CI], -37 to -7), but not on the third (8%, 95% CI, -4 to 20) or seventh day after surgery (3%, 95% CI, -7 to 13). Postoperative plasma MDA levels were significantly lower ( P = .016), but SOD and BDNF levels were increased ( P = .036 and .013, respectively) in the neostigmine group compared to the control group on the first day after surgery.

CONCLUSIONS

Neostigmine reduced POCD on the first day after noncardiac surgery in older patients. Neostigmine treatment inhibited oxidative stress and increased serum BDNF levels. There was no significant influence of neostigmine on POCD on the third or seventh day after surgery. The clinical influence of neostigmine on POCD should be further investigated.

Donepezil inhibits neuromuscular junctional acetylcholinesterase and enhances synaptic transmission and function in isolated skeletal muscle

BACKGROUND AND PURPOSE

Donepezil, a piperidine inhibitor of acetylcholinesterase (AChE) prescribed for treatment of Alzheimer's disease, has adverse neuromuscular effects in humans, including requirement for higher concentrations of non-depolarising neuromuscular blockers during surgery. Here, we examined the effects of donepezil on synaptic transmission at neuromuscular junctions (NMJs) in isolated nerve-muscle preparations from mice.

EXPERIMENTAL APPROACH

We measured effects of therapeutic concentrations of donepezil (10 nM to 1 μM) on AChE enzymic activity, muscle force responses to repetitive stimulation, and spontaneous and evoked endplate potentials (EPPs) recorded intracellularly from flexor digitorum brevis muscles from CD01 or C57BlWldS mice.

KEY RESULTS

Donepezil inhibited muscle AChE with an approximate IC50 of 30 nM. Tetanic stimulation in sub-micromolar concentrations of donepezil prolonged post-tetanic muscle contractions. Preliminary Fluo4-imaging indicated an association of these contractions with an increase and slow decay of intracellular Ca2+ transients at motor endplates. Donepezil prolonged spontaneous miniature EPP (MEPP) decay time constants by about 65% and extended evoked EPP duration almost threefold. The mean frequency of spontaneous MEPPs was unaffected but the incidence of 'giant' MEPPs (gMEPPs), some exceeding 10 mV in amplitude, was increased. Neither mean MEPP amplitude (excluding gMEPPs), mean EPP amplitude, quantal content or synaptic depression during repetitive stimulation were significantly altered by concentrations of donepezil up to 1 μM.

CONCLUSION AND IMPLICATIONS

Adverse neuromuscular signs associated with donepezil therapy, including relative insensitivity to neuromuscular blockers, are probably due to inhibition of AChE at NMJs, prolonging the action of ACh on postsynaptic nicotinic acetylcholine receptors but without substantively impairing evoked ACh release.