Grant: Discovery Horizons

Cardiac surgery is a life-saving operation but carries a high-risk of brain injury. Today, 3-6% of the 40,000/year patients undergoing heart surgery in Canada will suffer from serious brain injury, mainly caused by inadequate blood flow to the brain (cerebral ischemia) resulting from the operation. Unfortunately, there is currently no noninvasive neuromonitor that can reliably detect adult cerebral ischemia in cardiac surgery. We previously developed a safe near-infrared spectroscopy (NIRS) technique that can detect cerebral ischemia in neonates by monitoring the redox state of cytochrome-c-oxidase (oxCCO) - a transmembrane protein in the mitochondria that is highly sensitive to cerebral ischemia. Such a portable device would be ideal for neuromonitoring; however, extending the technique to adults remains an unmet challenge because of their thick skull. Our objective is to develop a NIRS technique that can noninvasively monitor oxCCO in the adult brain and demonstrate the feasibility of acquiring these measurements in patients undergoing heart surgery. We will build a time-resolved NIRS device that can measure deep-tissue absorption at several dozens of wavelengths, as required for oxCCO measurement. Short pulses of light (picosecond in duration) will be sent into tissue and the time-of-flight of the photons will be precisely measured using advanced quantum detection. We will select photons that arrive at the detector long after the laser pulse, as they travelled deep in the head and have a high probability of probing the brain. This is important because the noninvasive optical probes will be placed on the skin and light must travel through the scalp and thick (10 mm) adult skull before reaching the brain. To meet the stringent technical requirements of the device, inform its design, and validate it, we have assembled an interdisciplinary team with expertise in biomedical device development, quantum sensing, and clinical applications of novel technologies to improve patient outcome. To train Canada’s future scientific workforce, three graduate students will be recruited, using current best practices in EDI, and trained to develop, validate, and use the device in the clinic. This proposal will lead to the development of a technique that could reduce the incidence of heart surgery related brain injuries and make this common surgical operation safer for the 1 million people who undergo it around the world every year.