Observational StudyPerioperative Cerebrovascular Autoregulation Monitoring in Neurosurgical Patients

One of the challenges in pediatric anesthesiology is to ensure adequate cerebral perfusion pressure to prevent cerebral ischemia or hyperemia from pressure-passive perfusion. However, there is no optimal tool for longitudinally monitoring cerebral perfusion under general anesthesia (GA). In addition, the safe limits of blood pressure that maintains adequate cerebral perfusion in infants and children are not clear. Furthermore, patients with neurological impairments may have impaired cerebral auto-regulation (CA) function which may associated with functional outcomes. To address the critical public health issues associated with the safe use of general anesthesia in during neurosurgery, monitoring cerebral perfusion and oxygenation continuously during the peri-operative period.

The investigators have pioneered a novel technology, diffuse correlation spectroscopy (DCS), to optically measure cerebral blood flow (CBF) non-invasively and demonstrated that it is safe and practical as a bedside CBF monitor in the NICU. Blood flow is distinct from blood oxygenation, but both are important for brain health. Clinical near infrared spectroscopy (NIRS) devices are available to monitor oxygenation by light absorption, but CBF must be monitored by light scattering, which is only available with research DCS devices. While the physical principles of the methods are different, the sensors for both techniques are very similar. The investigators have therefore combined DCS with advanced frequency-domain NIRS (FDNIRS) in a single device to simultaneously monitor cerebral tissue oxygen saturation (cStO2), blood volume (CBV), CBF and oxygen metabolism (CMRO2), which cannot be monitored with existing clinical devices. The investigators have previously shown that these measures are far more sensitive than cStO2 alone in several infant brain pathologies. In this study, the investigators aim to test the feasibility of integrating the FDNIRS-DCS technology into perioperative monitoring to study cerebral hemodynamics and oxygen metabolism continuously in children during general anesthesia and surgery. Additionally, the investigators will determine how anesthesia-related events affect cerebral hemodynamic instability and how anesthetic level correlates with CA functions in children.