Antihemorrhagic agents used in medicine have various mechanisms of action:
- Systemic drugs work by inhibiting fibrinolysis or promoting coagulation.
- Locally-acting hemostatic agents work by causing vasoconstriction or promoting platelet aggregation.
Topical hemostatic agents have been gaining popularity for use in emergency bleeding control, especially in military medicine. They are available in two forms—as a granular powder poured on wounds, or embedded in a dressing.
Microfibrillar collagen hemostat (MCH) is a topical agent composed of resorbable microfibrillar collagen. It attracts platelets and allows for the formation of a blood clot when it comes into contact with blood. Unlike the hemostatic clamp, no mechanical action is involved. The surgeon presses the MCH against a bleeding site, and the collagen attracts and helps with the clotting process to eventually stop bleeding.
The practical application for MCH is different from that of the hemostatic clamp.
Chitosan hemostats are topical agents composed of chitosan and its salts. Chitosan bonds with platelets and red blood cells to form a gel-like clot which seals a bleeding vessel. Unlike other hemostat technologies its action does not require the normal hemostatic pathway and therefore continues to function even when anticoagulants like heparin are present.
Chitosan is used in some emergency hemostats which are designed to stop traumatic life-threatening bleeding. Their use is well established in many military and trauma units.
Styptics cause hemostasis by contracting blood vessels.
A common delivery system for this is a styptic or hemostatic pencil (not to be confused with a caustic pencil). This is a short stick of medication, usually anhydrous aluminium sulfate, potassium alum (both are types of alum) or titanium dioxide which is applied directly to the bleeding site. The high ionic strength promotes flocculation of the blood, and the astringent chemical causes local vasoconstriction. Before safety razors were invented, it was a standard part of a shaving kit and was used to seal shaving cuts. Some people continue to use styptic pencils for minor skin wounds from safety or electric razors.
Styptic powder is used in the veterinary trade to stop bleeding from nails that are clipped too closely. This powder is generally used on animals, such as dogs, cats, rabbits, and birds, where the vein is found in the center of the nail.
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