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Clinical Uses of Leeches
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The first clinical use of medicinal leeches (Hirudo medicinalis) occurred approximately 2500 years ago. This small invertebrate is particularly valuable for plastic and reconstructive surgery since it can produce a small bleeding wound that mimics a venous circulation in an area of compromised tissue. The leech produces a number of important substances which contribute to the special property of the bite, including an anticoagulant, a local vasodilator and local anaesthetic. These substances allow continued bleeding normally up to 10 hours after the animal has detached. The leeches main therapeutic benefits are not derived from the average 5mls of blood removed during biting (although this may provide dramatic relief at first), but from the fact that each bite wound continues to ooze up to 150mls of blood for 10 or more hours. The goal then is to produce a minimally adequate venous outflow from the tissue by adjusting the number of bite wounds to suit the clinical situation. Research indicates that after about 3 to 5 days, new vessel ingrowth around flap margins develops sufficiently to restore effective venous drainage. Therefore, it is important that treatment is not terminated too soon, but rather, continued over a period of time to avoid failure. The property of the leech bite wound to continue bleeding, with encouragement, for 10 or more hours is related to pharmacologically active secretions (not the anticoagulant alone) introduced by the leech bite. It has not been found possible to simulate this effect by introducing conventional anticoagulants, such as heparin, into small stab wounds in skin. As with most medical/surgical procedures, a patient's attitude towards the use of leeches depends largely on the physician's skill in clearly explaining the process. It may help to mention that this age-old procedure is quite painless mainly because the area to be treated is usually denervated and the leech produces its own anaesthetic. In most cases patient receptiveness is excellent. Indicators For Therapeutic Use Of Leeches 1. Plastic and Reconstructive Surgery. Leeches are generally useful on any skin flap or other tissue suffering from impaired venous circulation. It is prudent that a true venous congestion be diagnosed before using leeches since they will not be helpful in cases of insufficient arterial inflow. Note, also, that insufficient arterial supply could lead to infection from any source, including leeches. The following criteria may help in diagnosing a true venous problem in a flap:- a. Skin colour dusky or bluish. b. Capillary return bruskier than normal (note that areas of fixed colouration are beyond salvage). c. Pinprick response. Bleeding should be rapid and dark d. History. Known problems with veins at operation, either in the pedile or at the site of a micro-vascular anastomosis. 2. Oedema. Increasingly leeches are being used to treat severely oedematous patients.
Sawyer, R.T. (1986)."Leech Biology & Behaviour". 3 volumes, Oxford University Press, Oxford. Munro, R., Hechtel,F.O.P.and Sawyer,R.T. 1989. Sustained bleeding after a leech bite in the apparent absence of hirudin. Thrombosis and Haemostasis 61(3):366-369 Munro, R.,Powell-Jones, C. and Sawyer,R.T. 1991. Calin - a platelet adhesion inhibitor from the saliva of the medicinal leech. Blood coagulation and Fibrinolysis 2: 179-184 Rao, P.,Bailie F.B., Bailey,B.N. 1985. Leechmania in microsurgery. The Practitioner 229: 901-904
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