Mechanical leech

Related Terms

Blood-letting, hirudin, Hirudo medicinalis, hirudotherapy, mechanical leech, medicinal leech therapy, phlebotomy, Rob Sawyer.

Background

Leech therapy is the use of leeches in the treatment of medical conditions. Leeches are carnivorous or bloodsucking aquatic or terrestrial worms typically having two "suckers," one at each end. The back end suction cup helps the leech to ambulate on dry surfaces, and to attach to its host; the front-end suction cup also contains the mouth with three sharp jaws that leave a Y-shaped bite. The medicinal leech lives in clean waters. Leeches swim free in the water, with an undulating motion. When attached to its host for feeding, the leech remains in place for 30 minutes to 6 hours or more, as it fills with blood. During feeding,leeches can suck 5-15mL of blood, which is several times its own body weight.
The first medical use of leeches is thought to have taken place in ancient India in 1000 BC. The ancient Indians used leeches to treat a wide range of conditions including headaches, ear infections and hemorrhoids. In pre-scientific medicine, the medicinal leech was used to remove blood from a patient as part of a process to "balance the humors" that, according to Hippocrates, must be kept in balance in order for the human body to function properly. The four humors of ancient medical philosophy were blood, phlegm, black bile, and yellow bile. According to this theory, any sickness that caused the subject's skin to become red (e.g. fever and inflammation), must have arisen from too much blood in the body. Similarly, any person whose behavior was strident and sanguine, meaning animated, was thought to be suffering from an excess of blood. By the mid-1800s, the demand for leeches in Europe was so large that the exporter in Germany shipped over 30 million leeches a year.
Leeches (Hirudo medicinalis) historically used to remove "bad blood," are now used extensively by reconstructive surgeons needing to remove stagnant blood from a flap or reattached limb. When the venous blood does not return to the heart, it pools in the wounded area, increasing pressure and preventing fresh arterial blood from entering the area with oxygen and nutrients. The venous blood must be removed and the pressure must be reduced in order to save the flap or limb. The leech is able to do this exceptionally well, because its saliva contains biochemicals including vasodilators, anticoagulants, and anesthetics.
Perhaps the best-known advocate of medical leeches today is Roy Sawyer, an American researcher. Several decades ago, he noted the potential benefits of leech therapy and started one of the world's first modern leech farms. Today, the company BioPharm, which is based in Britain, provides tens of thousands of leeches every year to hospitals in dozens of countries.
In 2001, the mechanical leech was developed, in part by Nadine Connor, a University of Wisconsin at Madison scientist. The device, which looks a little like a small bottle attached to a suction cup, delivers an anti-clotting drug, similar to that in a leech's saliva, to damaged tissue and then gently sucks out as much blood as needed. Unlike real leeches, the mechanical version is insatiable and can remove as much blood as doctors think is necessary.

Theory / Evidence

The benefits of leech therapy are due, in large part, to the anticoagulant effects ("blood thinning"), vasodilatory effects, and anesthetic effects of the biochemicals contained in leech saliva, as well as the physical effects of blood letting (phlebotomy). Hirudin, a potent anticoagulant in leech saliva, inhibits the conversion of fibrinogen to fibrin, preventing blood from clotting. Indeed, a wound may continue to bleed for many hours after the leech has already detached due to the anticoagulant effect of hirudin. Many recently developed prescription drugs used for similar conditions were designed based on the mechanism of action of leeches.
Leeches are used to assist in the reattachment of severed body parts such as fingers, hands, toes, legs, ears and noses. Leeches are used to help with venous insufficiency when there is sufficient arterial flow when reattaching severed body parts.
Today leeches are also used to drain blood from swollen faces, limbs and digits (fingers and toes) after reconstructive surgery. They are especially useful when reattaching small body parts that have many small blood vessels. Leeches are used to prevent the clotting of blood in these small veins. Leeches are gently placed in the area needed by a qualified healthcare provider, and allowed to attach and engorge for the next 6-12 hours, after which they will release. The entire course of treatment may require one to 6 treatments or more, depending upon the goals and rate of response.
The leech will withdraw approximately 5mL (one teaspoon) of blood. Further therapeutic benefit of leech therapy comes after the leech is removed, during which up to 50mL of blood will continue to ooze, for up to 48 hours. More leeches attached to the site will result in the removal of more blood. After 3-7 days, the veins have usually reconnected themselves such that the blood is no longer pooling in the limb. Normal color and pressure should return to the area, as arterial blood circulates easily in the damaged zone. By that time, the wound will be able to heal, without further phlebotomy (removing blood).
Evidence: In 1998, Bapat et al. investigated the use of medicinal leeches in the treatment of complicated varicose veins and found that medicinal leeches aided ulcer healing and could be used as an adjunct in the management of complicated varicose veins due to their blood sucking ability. In a randomized controlled trial in 2003, Michalsen et al. found that medicinal leech therapy was effective in relieving symptoms in patients with osteoarthritis of the knee. Based on clinical use, the leech may also be of value in those performing microsurgery who are faced with the difficulties of reattaching minute veins.

Author information

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Ardehali B, Hand K, Nduka C, et al. Delayed leech-borne infection with Aeromonas hydrophilia in escharotic flap wound. J Plast Reconstr Aesthet Surg. 2006;59(1):94-5.
Bapat RD, Acharya BS, Juvekar S et al. Leech therapy for complicated varicose veins. Indian J Med Res 1998 Jun; 107:281-4.
Beer AM, Fey S, Ciborovius J, Knorr M. [Drug exanthema in connection with trimethoprim and sulfamethoxazole treatment, triggered by leech therapy] Forsch Komplementarmed Klass Naturheilkd. 2005 Feb;12(1):32-6.
BioPharm. 4 June 2006.
Michalsen A, Klotz S, Ludtke R, et al. Effectiveness of leech therapy in osteoarthritis of the knee. Annals of Internal Medicine. 2003 Nov; 139(9):724-30.
Nature: Bloody Suckers. 1 June 2006.
Ouderkirk JP, Bekhor D, Turett GS, Murali R. Aeromonas meningitis complicating medicinal leech therapy. Clin Infect Dis. 2004 Feb 15;38(4):e36-7.

Technique

The application of leeches to the patient is relatively simple, but does require application by a qualified healthcare professional. As few as one, or as many as six or more leeches may be required for a wound, depending upon its size and its clinical response. The greatest number of leeches should be applied by the healthcare provider to the area of maximal venous congestion.
The patient's skin is typically cleaned thoroughly with soap and water, and then rinsed with distilled, non-chlorinated water. A gauze barrier around the area intended for the leech is used to prevent the leech from wandering away from the site where its attachment is desired.
Once the leech is attached, it will likely remain safely in place until fully distended. The site should be checked continuously to insure that the leech has not moved. The leech will let go of the patient (host) when it is finished (usually within an hour).
If the leech is reluctant to bite, it might be necessary to entice it with a tiny droplet of blood, drawn from the wound site with a needle prick.