Science News

Mechanical Leeches Helping Surgeons

Here's something slimey. Real leeches are used by surgeons because arteries are easier to re-connect than the more fragile veins, making it easier for blood to get into the tissue than to get out. This means a reattached finger often swells up with blood, which coagulates, clots and prevents the finger grafting properly. Leeches can be useful because they inject a bit of saliva containing their own anticoagulant, called hirudin, and then feed off the excess blood which helps to keep a constant supply of fresh blood flowing into the tissues. The process is painless but patients and doctors often dislike the idea of touching the slimy creatures. Help is at hand in the form of a newly invented mechanical leech. The little device is based on a vacuum pump and unlike leeches will be sterile, and will not get tired or full up ! 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 mechanical leech has certain advantages too. 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....

18th May 2002