The Use Of Leeches In Modern Therapeutic — страница 3

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al.1996). A. hydrophila plays an important role in the ability of the leeches to digest blood, by supplying proteolytic enzymes to the leech (Daane et al. 1997). This bacterium, a gram negative rod, can cause infection in patients at ratios varying from 0% to 20% within twenty-four hours to ten days after leech use, resulting in complications from minor would infection to the possibility of extensive tissue loss or damage (Daane et al. 1997). Antibiotics effective in fighting wound infection are penicillans, cephalosporins, tetracyclines and aminoglycosides (Haycox et al.1995). Although leeches are not natural virus carriers, they can transmit viruses, such as hepatitis B, to humans if infected (Daane et al. 1997). In order to eliminate the risk of the transmission of these

viruses, leeches are only reused if a method of filleting is applied to drain the ingested blood for emergency reuse. In most situations, the leeches are disposed of by placing them in a container of alcohol and then discarding with infectious waste (Daane et al. 1997). Other complications that can arise due to medicinal leech therapy is the possibility of extensive blood loss, where blood transfusions may be necessary (Daane et al. 1997). Transfusions are often required because of anticoagulation and the continuous flow of blood from the leeches feeding site (Daane et al. 1997). Also, allergic reactions to leeches have been reported (from the chemical constituents in the leech saliva), but allergic reactions to the common medicinal leech, H. medicinalis, is extremely rare (Daane

et al. 1997). Proper precautions and care should be used in handling leeches to reduce the risks of infection in patients (See Table 3). The risk of infection may be decreased by first dipping the leeches in 0.02% chlorhexidine hydrochloride solution for ten to fifteen seconds before applying the leech to the wound (Haycox et al.1995). Also, the administration of antibiotics to the patient before leech application has been proven to reduce the risks of infection (Haycox et al. 1995). Leeches are also the source of the most potent anticoagulant found in nature, hirudin, the gene for which has now been cloned, and leech saliva may suppress the spread of tumors (Lent et al. 1988). Another chemical found in leech saliva is calin, which prevents platelets from attaching to collagen

and forming plugs (Godfrey 1997). A new development from the Southern Illinois University is the “mechanical leech”. This leech consists of a suction chamber with continuous heparin infusions, attached at a full-thickness punch biopsy site (Daane et al. 1997). The new “mechanical leech” has proved to be superior to the medicinal leech in restoring blood flow in congested replanted tissue in rats. Perhaps the “mechanical leech” will take over the 3500 year old role of the medicinal leech in reconstructive surgery, opening new doors in the field of medical technology and render the ancient medicinal practice of using real leeches obsolete. Despite the risk of wound infection and complications that can arise from medicinal leech therapy, most patients accept the use of

leeches when presented with a clear explanation of the benefits (Daane et al. 1997). The survival rate for major replanted parts or revascularizations using leeches is about 85%, and the success rate for tissue transfers is about 95% (Varghese et al. 1996). Leeches increase the success of these operations by removing excess blood, which prevents the tissues from dying while the capillaries regrow (Lent 1990). Therefore, the ancient practice of leech therapy is still considered to be a well-accepted medical technique used in replantation and reconstructive procedures. Table 1: Anticoagulants and related inhibitors from leeches (Eldor et al. 1996). Table 2: Inhibitors of platelet aggregation from leeches (Eldor et al. 1996). Table 3: Guidelines for the administration of leeches

(Daane et al. 1997). Figure 1: A single leech bite, consisting of a set of three incisions, one from each jaw (approximately 1mm). This bite was made in parafilm on a 37|C surface, a method for assessing leech hunger. However, leeches make similar wounds in the skin of their prey, and both kinds of bites resemble the Mercedes-Benz logo (Lent 1990). Figure 2: Ventral view of a dissected leech head shows the animal’s nervous system and feeding organs (Lent et al.1988). Figure 3: Feeding cycle of the medicinal leech alternated between hunger and satiation. The hunger phase consists of two subphases, appetite and ingestion. During the appetitive phase the leech swims toward wave sources. Once it finds a warm blooded host, it will feed for half an hour, consuming up to nine times