Bringing the
patients to their 'dry weight,' the weight, at which their fluid levels are
optimized, is one of the important goals of dialysis. However, determining the
dry weight is highly challenging and doctors use physical signs and
trial-and-error over multiple dialysis sessions to estimate it.
Presently in
the US, there are about half a million people on dialysis; however, there
is no easy, reliable way to measure hydration levels in these patients. The
methods currently used are invasive, unreliable or subjective. Hypervolemia or
fluid overload is assessed by doctors by way of physical signs like examining
the size of the jugular vein, pressing on the skin or probing the ankles where
water might pool.
Hydration Sensor Device
A research
team from MIT and Massachusetts General Hospital has now developed a portable
sensor device to accurately measure patients' hydration levels using a technique
called nuclear magnetic resonance (NMR) relaxometry.
This device, in addition to helping dialysis patients, could also
benefit those with congestive heart failure, athletes and elderly
who may be prone to dehydration. The device uses the same technology that
the
magnetic resonance
imaging (MRI) scanners use, but provides information faster and at a
lower cost as there is no imaging involved.
Dr. Michael
Cima, Professor of Engineering in MIT's Department of Materials Science and
Engineering and a member of MIT's Koch Institute for Integrative Cancer
Research, is the senior author of the study.
"There's a tremendous need across many different patient populations to
know whether they have too much water or too little water. This is a way we
could measure directly, in every patient, how close they are to a normal
hydration state," says Dr. Cima.
The paper
appears in the issue of
Science
Translational Medicine and the lead author is Dr. Lina Colucci, a former
graduate student in health sciences and technology. Matthew Li - a graduate
student from MIT; Kristin Corapi, Andrew Allegretti, and Herbert Lin -
Nephrologists from MGH; Xavier Vela Parada - MGH research fellow; Dennis
Ausiello - MGH Chief of Medicine; and Matthew Rosen - Assistant Professor in
Radiology at Harvard Medical School are the other authors.
New Approach
Dr. Cima
began working on the project around 10 years ago when he realized that the need
for an accurate, noninvasive way to measure hydration was highly significant. A
new approach based on NMR was chosen by the MIT team. In T2 Biosystems, a
company Dr. Cima had previously launched, small NMR devices were used to
diagnose bacterial infections by analyzing blood samples of patients. Dr. Cima
came up with the idea of using such devices to measure water content in tissue.
A few years
ago, the team got a grant from the MIT-MGH Strategic Partnership to
conduct a small clinical trial for monitoring
hydration. Patients with end-stage renal disease
who were on dialysis regularly and healthy controls were studied. The MIT-MGH
team was able to show that more accurate information on dry weight could be
provided by quantitative NMR, which works by measuring T2 relaxation time, a
property of hydrogen atoms. Both the environment and quantity of hydrogen atoms
present could be measured by the T2 signal.
"The beauty of magnetic resonance compared to
other modalities for assessing hydration is that the magnetic resonance signal
comes exclusively from hydrogen atoms. And most of the hydrogen atoms in the
human body are found in water molecules," says Dr. Colucci
Fluid volume
in patients before and after they underwent dialysis was measured by the
research team using the device.
The results exhibit that this technique has the
potential to tell apart healthy patients from those requiring dialysis right
after the first measurement. Additionally, the measurement could also show the
dialysis patients correctly moving closer to a normal hydration state during
the course of their treatment. The Way Forward
Additional
clinical trials with dialysis patients are being planned by the research team.
Dialysis, which currently costs the US more than $40 billion per year, is
expected to be one of the biggest applications for this technology.
Monitoring
of this kind could also benefit around 5 million other people in the country
with congestive heart failure.
"The water retention issues of congestive heart
failure patients are very significant," Dr. Cima says.
"Our sensor may offer the possibility of a
direct measure of how close they are to a normal fluid state. This is important
because identifying fluid accumulation early has been shown to reduce
hospitalization, but right now there are no ways to quantify low-level fluid
accumulation in the body. Our technology could potentially be used at home as a
way for the care team to get that early warning," he added.
While studying the healthy controls, the
research team incidentally also found that
the
device could detect dehydration. This feature could benefit in monitoring
the elderly who frequently become dehydrated as with age their sense of thirst
would have lessened. Similarly, athletes participating in marathons or other
endurance events could also use the device to check hydration.
The research
team also planned
for future clinical trials to test their technology's
potential to detect dehydration.
Reference : - Hydration sensor could improve dialysis - (http://news.mit.edu/2019/hydration-sensor-dialysis-0724)
Source: Medindia
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