A mechanical leech has been invented to replace the thirsty worms used widely in modern medicine to prevent blood-clotting after severed fingers and limbs are reattached. The little device is based on a vacuum pump and unlike leeches will be sterile, inexhaustible, and, most important, not slimy.
Michael Conforti is one of the University of Wisconsin team involved and says the artificial bloodsucker consists of a glass shell that fits over the skin and a vacuum to draw off blood. A slender rotating probe pierces the skin and infuses a mixture of the anticoagulant heparin and polyvinyl alcohol to keep the blood flowing. The device will be submitted for FDA approval.
Photo: Jeff Miller
Real leeches are used by surgeons because arteries are easier to reestablish than the more fragile veins. This means a reattached finger often swells up with blood, which coagulates, clots and prevents the finger grafting properly.
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The leeches inject a bit of saliva containing their own anticoagulant hirudin and then feed. The process is generally painless but both patients and pharmacists are often psychologically repelled by the idea of touching the slimy creatures.
Gut bacteria
Up to 20 per cent of patients treated with real leeches develop infections caused by Aeromonas hydrophila, bacteria that live in the leech’s gut. These infections can be treated with antibiotics, but Conforti says that his device would be sterile.
And while leeches stop feeding when sated, their mechanical counterparts will go on removing blood for as long as needed. Finally, the mechanical leech’s probe can be adjusted to go deep into the tissue if clotted blood collected there- real leeches just attach to the surface and suck.
But Ara Der Marderosian, a scientist at the University of the Sciences in Philadelphia, is sceptical about the new device: “Leeches are cheap, easy to use, and if you need more blood removed, you just put on another leech,” he says.
