Automated blood-flow monitoring may help prevent brain damage
10 September 2007
Researchers from the Johns Hopkins Children’s Center
in the US and Cambridge University in England have designed a system to
track potentially dangerous changes in blood flow to the brain in real time.
It shows promise for preventing brain damage and death in children with head
Healthy brains regulate blood flow and oxygen levels during
drops and spikes in blood pressure, but injured brains may lose this
fail-safe mechanism, leading to oxygen starvation and permanent brain
Although monitors have long been able to track blood pressure and
blood flow to the brain, the Hopkins–Cambridge team created a system that
for the first time precisely determines the 'breakpoint' at which the brain
begins to lose its ability to cope with changes in blood pressure.
software does this by gauging minute shifts in blood pressure and
oxygenation every 60 seconds and alerting doctors when they approach
|Dr. Ken Brady, critical care specialist at the
Johns Hopkins Children's Center, tracks blood-flow changes as they
are displayed on a monitor by a patient's bedside.
Photo credit: Keith Weller, Johns Hopkins Medical Institutions.
“More tests are needed, but we have demonstrated the value of gathering
much more detailed information over time about what safe levels of pressure
and oxygen are in children,” says Ken Brady, MD, a critical-care specialist
at the Children’s Center who led the study.
“Despite our ability to
monitor pressure and oxygen levels, we have desperately needed more
information about what are optimal levels for damage prevention in
children,” Brady says. “Not knowing that is much like flying a plane in a
fog, but this new software is helping us map safe terrain and danger zones
in blood pressure.”
Using software developed by two Cambridge scientists, Hopkins doctors fed
data into a computer from two staples of the paediatric intensive care unit
— an old-fashioned arterial blood pressure monitor and an oxygen meter that
uses beams of infrared light to estimate oxygen saturation in the brain.
The software essentially makes these two devices talk to each other,
researchers explain, showing in a continuous stream the interplay between
blood pressure and oxygen levels, whether the brain is coping with pressure
changes, and more importantly, what blood pressure range is conducive to
“This intricate interplay between oxygenation and blood flow was the
big unknown in what is indeed a simple equation, and now we’ve pinpointed
the level where arterial blood pressure needs to be in order to promote
healing in the injured brain,” Brady says.
In traumatic brain injuries,
some brain damage occurs on impact, but much damage and indeed many deaths
occur in the critical two-to-five-day window following the injury, a
critical time when brain function must be monitored to ward off damage. This
is when and where the new system will be most useful, researchers say.
technique could be also used in premature babies, who are particularly prone
to ischemic strokes and bleeding in the brain because of their brains’
immature self-regulatory mechanisms and their fragile blood vessels.
report on the research, including results of preliminary testing in baby
pigs, will appear in the October issue of Stroke.
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