Correlation Between Noninvasive Blood Vessel Functionality Parameters and Cerebral Hemodynamics in Neurocritical Care Patients

For this research, the investigators will strategically position two noninvasive sensors on the patients' foreheads, specifically over the temporal region. It is imperative that the skin in this area is accessible, free from hair or any underlying wounds beneath the sensor. These sensors are specifically designed to gather crucial data on cerebral oxygen saturation (StO2) and blood volume index (BVI). As per FDA recommendations, should the monitoring extend beyond 6 hours, it is advisable to replace the sensor adhesive to ensure optimal functionality and accuracy. The collected information will be transmitted to the investigators' monitoring system, equipped with preinstalled software that offers real-time insights into several key parameters:

• Regional Tissue Oxygen Saturation (StO2): This parameter provides data on regional hemoglobin oxygen saturation in the cerebral tissue beneath the sensor. It is captured using our cerebral oximetry sensors and offers critical insights into tissue oxygenation.
• Blood Volume Index (BVI): BVI provides information on the regional blood-to-tissue volume ratio in the cerebral tissue beneath the sensor, again captured using our cerebral oximetry sensors. BVI is instrumental in understanding blood volume dynamics in the brain.
• Mean Arterial Pressure (MAP) and Systolic Blood Pressure (SBP): Real-time MAP and SBP data will be pulled from the Philips patient monitor, providing a comprehensive overview of the patient's circulatory status.
• Intracranial Pressure (ICP): Similar to MAP and SBP, real-time ICP data will also be pulled from the Philips patient monitor, offering valuable insights into intracranial dynamics.
• Vasodilation/Constriction Index (VDC): VDC is a derived parameter from BVI, signifying the relative change in blood vessel cross-sectional area. An increase indicates vessel dilation, while a decrease indicates vessel constriction. This index offers insights into cerebral vessel reactivity.
• Vascular Resistance Index (VR): VR is a derived parameter from BVI, indicating the percent change in blood vessel resistance based on the Hagen-Poiseuille formula. VR helps assess the resistance to blood flow within cerebral vessels.
• Volume Reactivity Index (VRx): VRx is a real-time moving Pearson Correlation Coefficient between Blood Volume Index (BVI) derived from our Cerebral Oximetry sensors and MAP. This parameter is derived from Pressure Reactivity Index (PRx), making VRx a non-invasive alternative to the invasive PRx. VRx is used to assess autoregulation.

Inclusion criteria

Subjects who meet all the following inclusion criteria may be included:

• Adults (> 18 years of age);
• Able and willing to provide written informed consent for participation by self or legally authorized representatives.
• Clinical diagnosis of traumatic brain injury (TBI), brain hemorrhage, brain tumor, neurotrauma (including closed head injuries, penetrating head injuries, or other forms of neurotrauma), hemorrhage (intracerebral or subarachnoid), or stroke.
• Continuous Blood Pressure Monitoring: Patients must have continuous blood pressure monitoring in place during the study period, obtained from an arterial line. This criterion ensures that we have real-time data on mean arterial pressure (MAP) and systolic pressure (SBP).
• Intracranial Pressure (ICP) Monitoring: Patients must have intracranial pressure (ICP) monitoring in place during the study period. This criterion ensures that we can assess the correlation between our blood vessel functionality parameters (VDC, VR, and VRx) and ICP, a key indicator of intracranial dynamics.

Exclusion criteria

• Subjects who meet any of the following exclusion criteria will be excluded:
• Expected to be at increased risk due to study participation (e.g. due to hemodynamic instability), in the medical opinion of an investigator;
• Pregnant as determined per site standard practice;
• Previously participated in this study, or are enrolled in another research study that could be expected to interfere with participation, in the opinion of the investigator;
• Require or are anticipated to require emergent medical care in which study participation may reasonably delay his/her medical care or increase risk or unfavorable outcome, in the opinion of the investigator;
• Allergy to adhesive tape;
• Ongoing photodynamic therapy.