Santosh Kesari, MD, PhD, FANA, FAAN, Chair and Professor Department of Translational Neurosciences and Neurotherapeutics, John Wayne Cancer Institute and Pacific Neuroscience Institute at Providence Saint John’s Health Center discusses a research project using patients with shunts here on Earth to better understand and eventually help improve astronaut vision loss upon returning from space.
Tell us a little bit about the project.
Dr. Kesari: This project is in collaboration with NASA thru an NSBRI grant with Dr. Brandon Macias of NASA-JSC KBRwyle. The goal is to study the effects of pressure on the brain and understand the symptoms, such as visual loss, that astronauts may develop. The goal is to see if we can reverse symptoms of increased intracranial pressure that occurs when astronauts are in space by pulling venous blood to the legs.
Tell us how you do that here on Earth?
Dr. Kesari: The pressure in the brain is affected by many things; for instance, when we’re lying down, the pressure is different than when you’re standing up. The body auto regulates itself to prevent massive fluctuations in the pressure. An example would be feeling a sense of pressure when you cough or strain, it’s because the pressure goes up transiently. The goal of the study on Earth is to examine the changes of pressure in the brain with various maneuvers. Mainly, what we’re doing is placing a cuff on patients’ thighs, (like a arm blood pressure cuff, but much lower cuff pressures) and it squeezes it at a certain pressure. That pressure prevents the blood flow from the legs to the abdomen and that affects the pressure in brain. What we’re doing in patients that have Ommaya or ventriculoperitoneal shunts, we measure pressure in real time when we place a catheter, or a needle, into the Ommaya. We then monitor the pressure in real time in different positions and as we compress the thigh cuffs.
That’s how Karen is participating?
Dr. Kesari: Yes, exactly. She has a shunt, and what we’re doing is measuring the pressure in real time by hooking the shunt to an external pressure monitor. At the same time, we’re having her sit up, lie flat, put her head down, and then checking the pressures. We are also trying to prevent the pressure changes with a thigh cuff by keeping venous blood in the legs (venous blood can affect ICP),
You adjust the pressure by making the cuff tighter or looser?
Dr. Kesari: Exactly. By raising the pressure of the cuff and changing the blood flow from the legs back to the body, it affects the pressure in the brain. What we’re trying to understand is what type of forces will affect the changes in the brain, and how do we understand that process. We can then use that process to prevent increased pressure in the brain that causes neurological symptoms, including visual problems.
Is it something that’s happening in space right now, the eye problem?
Dr. Kesari: Yes, this is a known problem that occurs, especially with long space flight. This is why NASA wants to develop counter measures to prevent it from happening. Whether it’s a physical process, such as using a thigh cuff at a certain pressure or times of the day, we would like to prevent the long term consequences of pressure changes in space.
What have you found so far?
Dr. Kesari: Well, we are in the early stage of this study. But we can easily monitor the pressure in these patients and show a correlation with the pressure cuff and the pressure in the brain. We also look at the pressure in the eye and the pressure in the jugular veins. Within three to four hours, we do many measurements with these patients in different positions. We’re receiving a lot of data from each participant about the effects of thigh cuff pressures, and the various types of data from the venous pressure, to the eye pressure, and to the brain pressure.
Does Karen come in multiple times or just one time for all these measurements?
Dr. Kesari: At this point, the study is just a one-time test of measuring pressure over several hours in different positions.
How long would the turnaround be from findings to NASA actually putting something into work?
Dr. Kesari: Even though we spent several hours with each patient gathering all the data, we’re still analyzing it because it’s real time data collected in the span of three to four hours. We’re still going through the data and trying to tweak out different factors and correlating different measurements with each other.
Even NASA being this amazing technological behemoth, could the answer be as simple as squeezing a thigh?
Dr. Kesari: Well, it’s amazing. I think that we have to be creative, we have to have a simple solution for long space flight. A more complicated or invasive solution is not going to be feasible. It’s basic physiology. We’ve known as medical students that venous pressure can affect pressure in the spinal column. We are using what we know from an understanding of how spinal fluids flow; the pressure in the brain is affected by position and by various blood flow processes.
Karen had said she is happy to participate and help give back, is there something that is beneficial to her participating in the study as well?
Dr. Kesari: We explained that to all of our patients that there may not be any benefit to them direclty, but they wanted to help. Not only to identify the problems they had, but also, to help astronauts that are in flight. But interestingly, another patient who underwent the same procedures found out that she benefited clinically from the pressure cuff. She was having chronic headaches and noted that when she wore the cuff thighs, she felt tremendously better. Even though that was not the intent of the study, she actually felt better. We’re using that information and using various other cuffs and stockings to improve her quality of life and improve her symptoms of pressure problems in her brain.
Do we know that the reactions and the results that you get here on Earth are going to translate to orbit?
Dr. Kesari: The result is step one of many different steps in the future. We decided to do a study at a hospital because it created a unique advantage; we had easy access to the patients. These are patients that already have Ommaya or shunt for other reasons, but we could invasively measure brain pressure as part of their standard procedures that we were planning to do anyway.
To be a part of it they have to have a shunt? Why couldn’t I participate in the study?
Dr. Kesari: Well in fact normal patients can participate. We would have to do a spinal tap and do it a different way. So that’s a little bit more invasive and certainly we offer that to patients as well but it was easier to get patients who already have a shunt where it’s a much smaller, easier procedure.
The shunt goes through the spine to the leg?
Dr. Kesari: Most of the patients have what’s called a ventriculoperitoneal (VP) shunt. From the skull, there’s a little reservoir and then a catheter that goes into the belly, and there’s also shunt adjuster which we can turn on and off. We can also reset the baseline pressure before we start the procedure.
What is an Ommaya?
Dr. Kesari: Ommaya is a reservoir like a port for patient’s getting chemotherapy in the vein, but it’s in the brain ventricles where the spinal fluid is made.
What haven’t I asked you about the study that is important to include.
Dr. Kesari: The study highlights translational medicine: we are seeing fundamental human physiology and the fine tuning that our body does on a second by second basis to adjust pressure in the brain as we move, cough, strain, etc. We see the results in real time as the patients move in different positions. We see the pressure going up and down as they cough, and as we do the therapeutic maneuver by putting pressure on the thigh we can see the pressure changes. I think it’s amazing how we can adjust human physiology, human brain pressure, by affecting blood flow from the leg to the body.
END OF INTERVIEW
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