NASGBI Project Grant
Defining novel biomarkers of dysautoregulation after subarachnoid haemorrhage using non-invasive optical techniques
Dr Martin Smith
Acute brain injury, including various forms of stroke, is responsible for a large loss of productive life years because of high rates of death and disability. Whilst some of this poor outcome is related to the initial injury, subsequent changes in the injured brain worsen the outcome even in patients who receive optimal management. Cerebral autoregulation describes a process that in health allows the brain to maintain a constant supply of blood despite changes in blood pressure and other physiological variables. This protective mechanism can be impaired or absent after brain injury, rendering the brain liable to further (secondary) damage because of either too low or too high brain blood flow. Conventional methods of assessing cerebral autoregulation are either intermittent or involve the use of invasive probes implanted into the brain and are therefore not widely applicable. Near infrared spectroscopy (NIRS) is a non-invasive technique that uses near infrared light, which when applied to the scalp will penetrate into the brain, to monitor changes in brain blood flow and metabolism.
Because it is entirely non-invasive and can make continuous measurements over several regions of the brain simultaneously, it is an ideal technique to monitor the injured brain. Emerging evidence suggests NIRS signals can be analysed alongside blood pressure to indicate the efficiency of cerebral autoregulation. We believe that novel and more complex analysis of these NIRS signals will identify more robust markers of cerebral autoregulation
than those currently in use.
We have previously collected NIRS data in patients with subarachnoid haemorrhage, a severe form of stroke. We will apply several advanced analysis techniques to the NIRS data to identify specific changes, often called biomarkers, which are associated with impaired autoregulation. In this way we hope to identify clinically relevant biomarkers that can be used to guide patient management. We will use the results of this study to design subsequent studies in patients where we will use the newly identified biomarkers to guide treatment and determine whether this improves outcome.
