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Methylene Blue for Prevention of Perioperative Neurocognitive Disorders: Mechanisms and Recent Clinical Evidence
Yu Wu1, Jinbao Wang1, Xiaojian Wan2
1Department of Anesthesiology, Bethune International Peace Hospital, Shijiazhuang, People's Republic of China.
Insights
Methylene blue (MB) shows promise in preventing perioperative neurocognitive disorders (PND) in elderly surgical patients by protecting mitochondria and reducing inflammation. Clinical trials indicate MB significantly lowers the incidence of postoperative delirium (POD).
Area of Science:
- Neuroscience
- Pharmacology
- Geriatric Medicine
Background:
- Perioperative neurocognitive disorders (PND), including postoperative delirium (POD) and delayed neurocognitive recovery (dNCR), impact 15-40% of elderly surgical patients.
- PND is linked to long-term cognitive decline and increased mortality, with no current universal pharmacological prevention.
- Methylene blue (MB), a mitochondrial-targeting agent, is a potential neuroprotectant for PND.
Purpose of the Study:
- To review the neuroprotective mechanisms of MB.
- To evaluate clinical evidence for MB's efficacy in preventing PND in elderly surgical patients.
Main Methods:
- Comprehensive narrative review of preclinical and clinical studies.
- Focus on mechanistic pathways and randomized controlled trial (RCT) evidence.
- Emphasis on MB's role in perioperative neuroprotection.
Main Results:
- MB protects neurons via mitochondrial electron transport, Nrf2 activation, reduced neuroinflammation, inhibited tau aggregation, and blood-brain barrier preservation.
- A single intraoperative IV dose of MB (2 mg/kg) significantly reduced POD incidence from 24% to 7% in elderly patients (NNT=6).
- Biomarkers showed reduced neuronal injury (S100β) and systemic inflammation post-MB.
Conclusions:
- MB offers a mechanism-based approach targeting PND pathophysiology.
- Further large-scale RCTs are needed to confirm MB's role and optimize dosing for high-risk populations.
Background:
Perioperative neurocognitive disorders (PND), encompassing postoperative delirium (POD) and delayed neurocognitive recovery (dNCR), affect 15-40% of elderly surgical patients and are associated with accelerated long-term cognitive decline and increased mortality. Currently, no pharmacological agent is universally accepted for PND prevention. Methylene blue (MB), a phenothiazine derivative with unique mitochondrial redox properties, has emerged as a promising multimodal neuroprotectant.
Objective:
This review synthesizes evidence supporting MB's neuroprotective mechanisms and evaluates emerging clinical data regarding its efficacy as a preventive strategy for PND in elderly surgical patients.
Methods:
We conducted a comprehensive narrative review of preclinical and clinical studies investigating MB's role in perioperative neuroprotection, with particular emphasis on mechanistic pathways and randomized controlled trial evidence.
Results:
MB exerts neuroprotection through multiple convergent mechanisms: functioning as an alternative electron carrier in the mitochondrial electron transport chain, activating the Nrf2/antioxidant response element (ARE) pathway, suppressing microglia-mediated neuroinflammation, inhibiting tau protein aggregation, and preserving blood-brain barrier integrity. Recent randomized controlled trials demonstrate that single-dose intraoperative intravenous MB (2 mg/kg) significantly reduces POD incidence (from 24% to 7%, number needed to treat = 6) in elderly patients undergoing major non-cardiac surgery. Biomarker studies confirm attenuated neuronal injury (reduced serum S100β) and decreased systemic inflammation following MB administration.
Conclusion:
MB represents a mechanism-based therapeutic strategy targeting the mitochondrial and inflammatory core of PND pathophysiology. Large-scale, multicenter randomized controlled trials with extended neurocognitive follow-up are warranted to establish MB's definitive role in perioperative neuroprotection and to optimize dosing protocols for high-risk populations.
