Leeches back to relieve pain

Apr 13 2004

The leech was indispensable in 19th Century medicine for bloodletting, a practice believed to be a cure for anything from headaches to gout. Leeching was largely abandoned as medical science advanced, only occasionally being called upon to treat bruising and black eyes. However, the medicinal leech is making a comeback in modern medicine thanks in part to the work of Dr. Roy Sawyer, an American scientist who established the world's first leech farm. Based at Hendy near Swansea, South Wales, Biopharm is home to over 50,000 leeches which are supplied to hospitals and research laboratories around the world.

Thousands of patients owe the successful reattachment of body parts to miraculous technological advances in plastic and reconstructive surgery; at least some of these operations might have failed if leeches had not been reintroduced into the operating room. The appendages reattached include fingers, hands, toes, legs, ears, noses and scalps.

The pioneering use of leeches in modern plastic and reconstructive surgery can be attributed to two Slovenian surgeons, M. Derganc and F. Zdravic from Ljubljana who published a paper in the British Journal of Plastic Surgery in 1960 describing leech-assisted tissue flap surgery (in which a flap of skin is freed or rotated from an adjacent body area to cover a defect or injury). These surgeons credit their own use of leeches to a Parisian surgeon, one Philippe-Frédéric, who reported in 1836 that he had used leeches to restore circulation following reconstruction of a nose.

The rationale behind the use of leeches in surgical procedures is fairly straightforward; nonetheless, it is subject to misunderstanding, even by clinicians. The key to success is the exploitation of a unique property of the leech bite, namely, the creation of a puncture wound that bleeds literally for hours. The leech's saliva contains substances that anaesthetise the wound area, dilate the blood vessels to increase blood flow, and prevent the blood from clotting.

Microsurgeons today are adept at reattaching severed body parts, such as fingers. They usually have little trouble attaching the two ends of the arteries, because arteries are thick-walled and relatively easy to suture. The veins, however, are thin-walled and especially difficult to suture, particularly if the tissue is badly damaged. All too often the surgeon can get blood to flow in the reattached arteries but not veins. With the venous circulation severely compromised, the blood going to the reattached finger becomes congested, or stagnant; the reattached portion turns blue and lifeless and is at serious risk of being lost. It is precisely in such cases that leeches are summoned.