Using the Eye as a Window to the Brain
In June, three MCIRCC multidisciplinary research teams received Prolonged Field Care Research Awards from the Department of Defense’s Combat Casualty Care Research Program (CCCRP). These awards call for the development of next-generation diagnostics, monitoring, resuscitation and stabilization methods for prolonged field care (PFC) and prolonged damage control resuscitation (pDCR). In the coming months, we will profile each of these teams and their innovative research.
When first responders are faced with the challenge of caring for a patient with a traumatic brain injury (TBI), whether that be in the Emergency Room, out in the field, or on the front lines, two dilemmas usually come to mind: what is the extent of their initial injury, and are there any secondary injuries underway?
Unfortunately, the current available technologies make answering such questions difficult. This includes gauging a patient’s intracranial pressure (ICP) or evaluating the presence of any additional brain edema or ischemia at the scene. Current technologies use invasive processes that require special training and can often lead to complications such as infection or additional injury.
“Having non-invasive technologies to measure ICP and provide information about blood volume and flow into the brain would accelerate decision making and improve a patient’s outcomes dramatically,” said Hakam Tiba, MD, MS, the PI for the study.
Approximately 20% of TBI patients will suffer a serious decline in their condition during the first 72 hours (the window for PFC) due to increased pressure in the brain, reduced brain blood flow, and subsequent inflammation and ischemia leading to devastating and lasting secondary injuries, disabilities, and even death.
Dr. Tiba and his team are working to develop non-invasive methods using electrical bioimpedance and ultrasound in a novel manner that will not only evaluate ICP but also monitor cerebrovascular autoregulation (CAR), one of the most important neuroprotective processes of the brain. CAR reflects the brain’s blood vessels’ ability to relax and contract to compensate for changes in blood pressure and maintain a steady flow of blood. If CAR is impaired, severe secondary brain injury occurs.
To do this, Dr. Tiba and his co-investigators will use non-invasive bioimpedance to evaluate the cerebral blood volume (CBV), and use this to determine whether CAR is intact. Bioimpedance is an electrical property of tissues, that describes the degree to which the tissues resist an externally applied electrical current and which is heavily influenced by blood.
A small electrical current will be administered through the eyelid using a wearable device. The team discovered that electrical current is very efficiently carried into the brain through the eyes as opposed to passing the current through the scalp. The current will flow into the brain, and the device will detect the tissue’s resistance to the current. This gives clinicians information about CBV and CAR, allowing them to better evaluate and manage any secondary injury to the brain. In addition, the device will be able to collect additional information such as respiratory variation and heart rate, giving physicians further insight into a patient’s status.
Simultaneously, Dr. Tiba and his colleagues will be developing a computer image analysis algorithm capable of automating the analysis of the optic nerve sheath (ONS) obtained by ultrasound of the eye. This will allow responders to non-invasively evaluate ICP on-site.
Using a portable ultrasound, first responders will be able to measure the diameter of the ONS and gain information about ICP. To develop this algorithm, the team will record images of the ONS using ultrasound and compare the algorithm prediction with expert evaluations.
With these two technologies working in tandem, Dr. Tiba and his team believe they will be able to significantly accelerate the decision-making process and improve patient outcome thanks to early detection of secondary brain injury.
Once these technologies are developed and validated, the team plans to license the technology to an industry partner. The project is expected to take three years, consisting of two animal models and a clinical study enrolling 100-150 patients and 60 test animals.
Dr. Tiba is working with MCIRCC’s Executive Director, Kevin Ward, MD from the Departments of Emergency Medicine and Biomedical Engineering on this project along with several other MCIRCC members, including Hasan Alam, MD (Department of Surgery), Craig Williamson, MD (Department of Neurosurgery), and Venkatakrishna Rajajee, MBBS (Department of Neurosurgery). This interdisciplinary team of experts brings knowledge of trauma, emergency critical care, and combat casualty care, as well as engineering, physiology, and noninvasive monitoring.