Neurocognitive dysfunction after cardiac surgery is a well-recognized complication that affects about 50% of patients at discharge. The brain is the organ most susceptible to damage from inadequate perfusion during cardiopulmonary bypass (CPB, i.e. heart-lung machine), but it is also the organ least monitored during surgery, due to the absence of a feasible modality for monitoring intraoperative cerebral perfusion. The broad aim of this project is to adapt near-infrared spectroscopic (NIRS) tomography to intraoperative monitoring. NIRS tomography provides real-time measures of the temporal and spatial cerebral perfusion, with spatial resolution comparable to functional MRI, but with significantly better temporal resolution. In addition to analysis of data within a conventional reductionistic framework (oxyhemoglobin, deoxyhemoglobin, and total hemoglobin considered separately), a novel contrast-enhancement method, based on resolving each form of hemoglobin into six categories that are sensitive to induced oxygen debt, will be applied to further refine spatial and temporal features of cerebral perfusion patterns. The ultimate goal of this project is to identify intraoperative biomarkers of subsequent neurocognitive dysfunction at a reversible stage. A minimum of 50 cardiac surgical patients, and 25 patients undergoing open chest surgery not involving CPB (control group), will be recruited for this project. They will undergo a standard battery of neurocognitive tests before and after surgery. Intraoperative NIRS imaging of cerebral perfusion will be performed and analyzed to identify areas of hypoxia, as well as the duration and magnitude of hypoxic stress. Comparison will be made to neurocognitive test results, as well as to records of intraoperative maneuvers by surgeons, anesthesiologists, and perfusionists, to determine which of these co-vary with the hypoxic events and are predictive of subsequent neurological deficit. Identified events will be studied to determine whether common features exist within the affected subject group that is suggestive of appropriate countermeasures during surgery to reverse or forestall cerebral malperfusion. Results from these studies will provide a basis for discerning an evidence-based cerebral protection protocol during cardiac surgery. Furthermore, improved intraoperative management decisions can be made, based on real-time NIRS imaging, to alert clinicians to culprit signature patterns of hypoperfusion and to assess the effectiveness of rescue maneuvers.
Neurocognitive dysfunction is a common complication after cardiac surgery. This project aims to utilize near- infrared optical tomography to monitor cerebral perfusion in intraoperative settings. The information gathered will help surgeons and anesthesiologists manage patients appropriately to prevent neurological complications.
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