Ultrasound filters fat from blood
Surgery aid could reduce post-operative
brain damage.
2 October 2002
CHARLOTTE WESTNEY
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| Blood comes out
of the filter 95% fat free. |
| © H.Jonsson |
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A new filter fires ultrasound at tiny tubes of blood
to separate out blobs of fat. The device could stop
fat getting into the brain during heart surgery, say
its Swedish developers.
On the operating table, leaking blood is sucked up
and put back into a patient. Fat from the heart, arteries
and bone marrow seeps into this blood. This fat can
accumulate in the brain, where it is thought to cause
the memory and movement impairments seen in up to two-thirds
of patients after heart surgery - around 3 per cent
suffer strokes.
The new filter squeezes blood through hair-thin channels.
Different components in the blood react to ultrasound
waves in different ways - fat is pushed to the sides
of the channels. The blood that comes out is 95 per
cent fat-free.
"We have very big hopes," for its medical use, says
Henrik Jonsson, who helped devise the filter at the
Lund Institute of Technology in Sweden. Clinical trials
are planned for next year.
Some surgeons use screen filters, but fat can pass
through the pores only to reform as larger blobs on
the other side.
The new filter "shows great promise in treating blood"
agrees Dixon Moody, who studies the post-operative impact
of fat on the brain at Wake Forest University in North
Carolina. But to be useful in the operating theatre,
he warns, it will have to process at least a litre of
blood an hour - the filter currently manages only 300
millilitres.
The team hopes to increase its capacity by running
200 channels in parallel. The final device should look
like a compact-disc case. "It's a neat contraption,"
comments Moody.
And it should have other uses. Already the filter has
separated cream from milk; it could help in water purification
and even dialysis. It will be displayed at the Technology
Fair in Ålvsjö, Sweden, next week.
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