Abstract

Background Postoperative delirium (POD) in elderly patients is a common and serious complication after surgery with an unclear pathogenesis at the molecular level. Perioperative untargeted high-throughput proteomic profiling may provide insights into underlying mechanistic molecular patterns and help identify patients at high risk, guiding preventative and therapeutic measures.

Methods This study is a monocentric substudy of the European BioCog project, a prospective multicentre observational study involving elderly patients aged ≥65 undergoing elective surgery. Patients with preexisting cognitive impairment (Mini-Mental State Examination score ≤23) were excluded. POD was assessed twice daily for up to seven days using the Nursing Delirium Screening Scale (Nu-DESC) and the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU), along with patient chart reviews. Proteomic profiling was conducted using high-throughput liquid chromatography mass spectrometry on sequential pre- and postoperative plasma samples. Data were analysed using a matched case-control design, employing both cross-sectional and longitudinal approaches, along with pathway enrichment analysis as a functional approach.

Results A total of 226 highly abundant proteins were investigated in 168 patients (50% POD incidence). Multiple pathways, particularly those involved in the activation of the innate immune response and the complement system, were associated with POD in both cross-sectional and longitudinal analyses. Butyrylcholinesterase showed the most robust regulation, with preoperative downregulation and postoperative upregulation in patients with POD, while further downregulated in those without POD. Enzyme activity showed significant decrease in both groups. Additionally, a set of eight preoperative proteins distinguished between patients with and without POD with 86% sensitivity and 79% specificity.

Conclusion Untargeted high-throughput proteomics is a feasible approach to characterize pathways involved in POD pathogenesis. This case-control study identified a protein signature associated with POD, emphasizing the need for larger cohorts to confirm these observations and improve the mechanistic understanding of POD.

Highlights

The complex pathophysiology of postoperative delirium is poorly understood

High-throughput proteomics uncovered distinct regulated features in delirium patients

Enrichment analysis showed differential regulation of pathways in multiple domains

Logistic regression separates delirium patients using 8 proteins with 86% sensitivity

Competing Interest Statement

Mario Lamping: The author declares that there are no conflicts of interest within the study submitted. Maria Heinrich: Maria Heinrich is a participant in the BIH Charite Digital Clinician Scientist Programme funded by the Charite Universitaetsmedizin Berlin and the Berlin Institue of Health at Charite (BIH). Vadim Farztdinov: The author declares that there are no conflicts of interest within the study submitted. Clarissa von Haefen: The author declares that there are no conflicts of interest within the study submitted. Jayanth Sreekanth: The author declares that there are no conflicts of interest within the study submitted. Michael Muelleder: The author declares that there are no conflicts of interest within the study submitted. Markus Ralser: The author declares that there are no conflicts of interest within the study submitted. Georg Winterer: The author declares that there are no conflicts of interest within the study submitted. Outside the submitted manuscript GW reports to be the CEO of PI Solutions GmbH and PI Health Solutions GmbH as well as the CEO/President of PharmaImage Biomarker Solutions GmbH/Inc. Claudia D. Spies: The author declares that there are conflicts of interest within the study submitted (public grants from the Will Foundation - AVD 137017, 01.01.2024 - 31.12.2025 and the EU - 602461, 01.02.2024 - 30.01.2019). Outside the submitted manuscript CDS reports grants from The European Commission Horizont Europa, German Federal Joint Committee (Gemeinsamer Bundesausschuss GBA), German Federal Ministry of Education and Research (BMBF), Philips Electronics Nederland BV, Max Planck Society, Sintetica GmbH, Dr. F. Koehler Chemie GmbH, Georg Thieme Verlag, German Federal Ministry for Economic Affairs and Climate Action (BMWI), European Society of Anesthesiology and Intensive Care, Stifterverband (non profit society promoting science and education), Charite internal university grants, Einstein Foundation Berlin, German Aerospace Center (Deutsches Zentrum fuer Luft und Raumfahrt e.V. DLR) and German Research Society (Deutsche Forschungsgemeinschaft) during the conduct of the study. In addition, CDS has different patents and an unpaid leadership or fiduciary role in association of the Scientific Medical Societies in Germany (AMWF), German Research Foundation (Deutsche Forschungsgemeinschaft), German National Academy of Sciences Leopoldina (Deutsche Akademie der Naturforscher Leopoldina e. V.), Berlin Medical Society (Berliner Medizinische Gesellschaft), ESICM European Society of Intensive Care Medicine, ESAIC European Society of Anaesthesiology and Intensive Care, German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft fuer Anaesthesiologie und Intensivmedizin DGAI), German Interdisciplinary Association for Intensive Care and Emergency Medicine (Deutsche Interdisziplinaere Vereinigung fuer Intensiv und Notfallmedizin DIVI) and German Sepsis Foundation (Deutsche Sepsis Stiftung). CDS has participated on Data Safety Board or Advisory boards for Prothor, Takeda Pharmaceutical Company Limited and Lynx Health Science GmbH.

Clinical Protocols

https://pubmed.ncbi.nlm.nih.gov/29398565/

Funding Statement

This study was supported by the Will Foundation (AnaeVPostDelir - 137017, 01.01.2024 - 31.12.2025) and is a secondary analysis of the BioCog (Biomarker Development for Postoperative Cognitive Impairment in the Elderly) study (EU602461 01.02.2014 - 31.01.2019, Seventh Framework Programme FP7/2007-2013).

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was approved by the ethics committee of the Charite-Universitaetsmedizin Berlin under the reference numbers EA2/092/14 and 14-469.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

List of AbbreviationsABCAmmonium BicarbonateAChAcetylcholineADLActivities of Daily LivingAPCSSerum Amyloid P ComponentAPOA4Apolipoprotein A-IVAPOFApolipoprotein FASA PSAmerican Society of Anaesthesiologists Physical StatusAUCArea Under the CurveB2MBeta-2-MicroglobulinBBBBlood-Brain BarrierBCHEButyrylcholinesteraseBMIBody Mass IndexC18orf63Chromosome 18 Open Reading Frame 63C1RComplement Component 1, R SubcomponentC2Complement Component 2C3Complement Component 3C4Complement Component 4C5Complement Component 5CAM-ICUConfusion Assessment Method for the Intensive Care UnitCCICharlson Comorbidity IndexCFHR2Complement Factor H-Related Protein 2CFHR4Complement Factor H-Related Protein 4ChECholinesteraseCNDP1Carnosine Dipeptidase 1CRPC-Reactive ProteinCSFCerebrospinal FluidCST3Cystatin CDE0non-POD patientsDE1POD patientsDIA-NNData-Independent Acquisition Neural NetworksSWATHSequential Window Acquisition of All Theoretical Mass SpectraDoADuration of AnaesthesiaDSM-5Diagnostic and Statistical Manual of Mental Disorders, 5th EditionEEGElectroencephalogramELISAEnzyme-Linked Immunosorbent AssayF5Factor VFBLN1Fibulin 1FCFold ChangeFCGBPFc Fragment of IgG Binding ProteinFCGRFc Gamma ReceptorFCERIFc Epsilon Receptor IFDRFalse Discovery RateFGAFibrinogen Alpha ChainGOGene OntologyGOBPGene Ontology Biological ProcessGPX3Glutathione Peroxidase 3GSEAGene Set Enrichment AnalysisHBHaemoglobinHBA1Haemoglobin Subunit Alpha 1HBDHaemoglobin Subunit DeltaHT-LCMSHigh-Throughput Liquid Chromatography-Mass SpectrometryIGF-1Insulin-Like Growth Factor 1IGF2Insulin-Like Growth Factor 2IGFALSInsulin-Like Growth Factor Binding Protein, Acid-Labile SubunitIGFBPsInsulin-Like Growth Factor Binding ProteinsIGHVImmunoglobulin Heavy VariableIGKVImmunoglobulin Kappa VariableILInterleukiniNOSinducible nitric oxide synthaseLBPLipopolysaccharide-Binding ProteinLPALipoprotein(a)LRLogistic RegressionLYZLysozymeMADMedian Absolute DeviationMASP1Mannose-Associated Serine Protease 1MBL2Mannose-Binding Lectin 2MMSEMini-Mental State ExaminationMNAMini Nutritional AssessmentMST1Macrophage Stimulating 1NCDNeurocognitive DisorderNESNormalised Enrichment ScoreNu-DESCNursing Delirium Screening ScalePCAPrincipal Component AnalysisPGLYRP2Peptidoglycan Recognition Protein 2PLMPanel Linear ModelPOCDPostoperative Cognitive DysfunctionPODPostoperative DeliriumppmParts Per MillionPROZProtein ZQSOX1Quiescin Sulfhydryl Oxidase 1ROSReactive Oxygen SpeciesS100A9S100 Calcium-Binding Protein A9S100BS100 Calcium-Binding Protein BSAA1Serum Amyloid A1SDStandard DeviationSELLL-SelectinSERPIND1Serpin Family D Member 1SWATHSequential Window Acquisition of All Theoretical Mass SpectraT0Preoperative Time Point 0 (Baseline)T1Postoperative Time Point 1 (Day 1)TFRCTransferrin ReceptorTMSB4XThymosin Beta-4 X-LinkedTNF-ɑTumor Necrosis Factor-AlphaVTNVitronectin