During medieval Europe, doctors were called "leeches" because they used leeches to treat many ailments. Today, leech therapy is generally used to prevent venous congestion after surgery, primarily reconstructive surgery involving the reattachment of limbs, digits, and skin flaps.
After surgery, blood flows from the heart and lungs through the arteries, providing much needed oxygen and nutrients to keep the tissue alive. The blood then flows back to the heart and lungs through the veins carrying back waste products.
When a reattachment is performed, arteries and large veins are reconnected but many small veins are not. Small veins will eventually reconnect on their own in three to seven days but until then, blood may not be able to return as fast as it should . It will begin to pool, causing the area to swell. The buildup of blood compresses the arteries and prevents fresh blood from entering the attachment. Without fresh blood, the attachment will not survive.
With leech therapy, leeches are placed over the affected area to suck out the excess blood, relieving the pressure on the arteries.
The saliva from the leech contains hirudin, a potent anticoagulant that prevents the blood from clotting. After the leech consumes enough blood, usually 5-15 ml (several times its body weight), it removes itself from the body. Because of this anticoagulant, the area will continue to bleed from the injection site, up to 50 ml, for 24-48 hours.
Leech saliva also acts as a vasodilator. When veins are dilated, blood flow is improved. Another benefit of leech therapy after surgery is relieving pain. When a leech bites into the skin, they release a biochemical that will numb the site.
When a leech is attached to the skin, it will feed for 30 minutes to 6 hours. More than one treatment may be needed before the small veins reconnect.
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