Exhaled volatile organic compounds, phospho-tau and postoperative delirium

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Postoperative delirium (POD) is common, especially in elderly patients. Patients with Alzheimer’s disease (AD) or AD-related dementias (ADRD) have a higher risk of delirium. Patients with delirium have a higher chance to develop AD and ADRD. It has been shown that AD-related biomarkers, such as phospho-tau and neurofilament light, in the blood are associated with POD. However, these tests take time and are expensive to perform. Harvesting blood carries a minor risk. Patients with AD and POD have metabolic dysfunction. Studies have shown that there are differences in the volatile organic compounds (VOCs) in the exhaled gases between AD patients and healthy controls. Whether this situation exists between patients with POD and non-POD is not known. Evaluating exhaled VOCs is no-invasive and can be done at bed site with our equipment. We hypothesize that patients with POD have a unique pattern of exhaled VOCs and that this pattern is associated with AD-related biomarkers in the blood. To address these hypotheses, we will recruit 150 patients with spine surgery who are 65 years or older. Their exhaled gases will be analyzed by using advanced portable gas chromatography. Their blood will be used to analyze tau, phospho-tau, neurofilament light and amyloid beta peptides. The POD incidence and severity will be assessed. The VOC and blood biomarker results of patients with POD will be compared with those of patients without POD. The predicting values of VOCs and AD-related biomarkers for POD will be determined. These studies will for the first time determine whether a no-invasive and quick analysis of exhaled VOCs can be used to predict POD. The identified VOCs that contribute to the different patterns between patients with and without POD will indicate metabolic pathways that are dysfunctional. The analysis of the correlation between exhaled VOCs and AD-related biomarkers in the blood may reveal possible relationship between AD-like neuropathology and exhaled VOCs. Thus, this project may provide initial evidence for the role of VOCs in POD and AD-related neuropathology.