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Wednesday, 5 June, 2002, 18:05 GMT 19:05 UK
Eye scan warns of internal bleeding
Emergency patient
Blood vessels at the back of the eye could help doctors
Doctors may have developed a simple method of spotting whether patients arriving at hospital have dangerous internal bleeding.

The new test checks the concentration of oxygen in the eye, which, they say, gives a reliable clue to the state of the patient.

Accident and emergency specialists can find it hard to identify patients who are bleeding internally.

Very often, the first clue is a drop in blood pressure - by which time the patient can be hard to save.

A slowly rising pulse may also be a clue - but pain and shock can also increase it.

The tester, developed by researchers at a company in Princeton, US, measures the amount of oxygen in blood vessels leaving the eye.

Laser light

It is completely non-invasive - using a low-powered laser fired into the eye's retina.

Blood rich in oxygen absorbs a different amount of laser-light compared with oxygen-free blood.

The device records how much light bounces back off the blood vessel, and a computer works out oxygen saturation from this.

Doctors can already easily check the oxygen saturation of other blood vessels, but this device will be more useful, says its inventor.

This is because eye tissues always try to absorb a constant amount of oxygen.

Hard to spot

If there is less oxygen available - or there are subtle changes in blood pressure which might indicate an internal bleed, the eye is still likely to strip away the same amount of oxygen from the blood.

This means there will be an instant drop in blood oxygen levels in the veins of the eye.

Mr John Heyworth, president of the British Association of Accident and Emergency Medicine, said that internal bleeding was very difficult to spot.

"You only see a drop in blood pressure once they've lost 25% to 30% of their blood.

"The blood pressure then drops through the floor, and by that time, they are very sick."

The research is reported in New Scientist magazine.

See also:

27 May 00 | Health
14 Oct 00 | Health
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