Leeches, new and improved

After being discounted as quackery for almost a century, leeches have arrived back on the medical scene as powerful aids to treat venous congestion following surgery (Today’s Chemist at Work, Oct 2001, pp 47–48). Unfortunately, leeches come with a host of limitations that curb their usefulness, including a restricted feeding capacity (1–5 mL per blood meal), a shallow reach into the skin (only to the first network of surface blood vessels), and a lack of sterility that can cause bacterial infections.

Diagram of mechanical leech.

Recently, Michael Conforti and other research scientists from the University of Wisconsin and the William S. Middleton Veterans Administration Hospital, both in Madison, developed a mechanical leech to solve these problems. The prototype consists of a small Teflon cone that sits under a surgical incision made in the skin; a stainless steel tube that delivers a heparinized saline solution, which irrigates the wound and keeps blood flowing; and a patient interface unit that sits above these parts, controlling the irrigant flow and providing mechanical agitation to increase anticoagulation. The Teflon cone and stainless steel tube are presterilized and disposable, carrying no risk of infection.

The mechanical leech can reach deeper into the skin to access a larger network of blood vessels. It is also insatiable—the current model consistently collects about 10 mL of blood per hour.

However, it is not without drawbacks. According to Conforti, a real leech has two possible advantages over its mechanical counterpart: size and cost. Conforti’s group is currently working to shrink the 1.5 × 2 cm patient interface unit so it can fit into the tiniest places needing therapy for venous congestion. Although a price has not been named, Conforti expects the disposable parts to run in the hundreds of dollars and the patient interface unit to cost thousands. The cost might well be worth it—because real leech therapy can cost $350 per day, says Conforti, a mechanical leech would pay for itself in just a few uses.