出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/04/04 17:15:28」(JST)
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| Bleeding | |
|---|---|
| Classification and external resources | |
A bleeding human finger
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| ICD-10 | R58 |
| MedlinePlus | 000045 |
| MeSH | D006470 |
Bleeding, technically known as hemorrhaging or hæmorrhaging (see American and British spelling differences), is the loss of blood escaping from the circulatory system.[1] Bleeding can occur internally, where blood leaks from blood vessels inside the body, or externally, either through a natural opening such as the mouth, nose, ear, urethra, vagina or anus, or through a break in the skin. Hypovolemia is a massive decrease in blood volume, and the complete loss of blood, causing death, is referred to as exsanguination.[2] Typically, a healthy person can endure a loss of 10–15% of the total blood volume without serious medical difficulties, and blood donation typically takes 8–10% of the donor's blood volume.[3]
Hemorrhaging is broken down into four classes by the American College of Surgeons' advanced trauma life support (ATLS).[4]
This system is basically the same as used in the staging of hypovolemic shock.
Individuals in excellent physical and cardiovascular shape may have more effective compensatory mechanisms before experiencing cardiovascular collapse. These patients may look deceptively stable, with minimal derangements in vital signs, while having poor peripheral perfusion. Elderly patients or those with chronic medical conditions may have less tolerance to blood loss, less ability to compensate, and may take medications such as betablockers that can potentially blunt the cardiovascular response. Care must be taken in the assessment of these patients.
The World Health Organization made a standardized grading scale to measure the severity of bleeding.[5]
| Grade 0 | no bleeding |
| Grade 1 | petechial bleeding; |
| Grade 2 | mild blood loss (clinically significant); |
| Grade 3 | gross blood loss, requires transfusion (severe); |
| Grade 4 | debilitating blood loss, retinal or cerebral associated with fatality |
Bleeding arises due to either traumatic injury, underlying medical condition, or a combination.
Traumatic bleeding is caused by some type of injury. There are different types of wounds which may cause traumatic bleeding. These include:
The pattern of injury, evaluation and treatment will vary with the mechanism of the injury. Blunt trauma causes injury via a shock effect; delivering energy over an area. Wounds are often not straight and unbroken skin may hide significant injury. Penetrating trauma follows the course of the injurious device. As the energy is applied in a more focused fashion, it requires less energy to cause significant injury. Any body organ, including bone and brain, can be injured and bleed. Bleeding may not be readily apparent; internal organs such as the liver, kidney and spleen may bleed into the abdominal cavity. The only apparent signs may come with blood loss. Bleeding from a bodily orifice, such as the rectum, nose, or ears may signal internal bleeding, but cannot be relied upon. Bleeding from a medical procedure also falls into this category.
'Medical bleeding' denotes hemorrhage as a result of an underlying medical condition (i.e. causes of bleeding that are not directly due to trauma). Blood can escape from blood vessels as a result of 3 basic patterns of injury:
The underlying scientific basis for blood clotting and hemostasis is discussed in detail in the articles, Coagulation, hemostasis and related articles. The discussion here is limited to the common practical aspects of blood clot formation which manifest as bleeding.
Certain medical conditions can also make patients susceptible to bleeding. These are conditions that affect the normal "hemostatic" functions of the body. Hemostasis involves several components. The main components of the hemostatic system include platelets and the coagulation system.
Platelets are small blood components that form a plug in the blood vessel wall that stops bleeding. Platelets also produce a variety of substances that stimulate the production of a blood clot. One of the most common causes of increased bleeding risk is exposure to non-steroidal anti-inflammatory drugs (or "NSAIDs"). The prototype for these drugs is aspirin, which inhibits the production of thromboxane. NSAIDs inhibit the activation of platelets, and thereby increase the risk of bleeding. The effect of aspirin is irreversible; therefore, the inhibitory effect of aspirin is present until the platelets have been replaced (about ten days). Other NSAIDs, such as "ibuprofen" (Motrin) and related drugs, are reversible and therefore, the effect on platelets is not as long-lived.
There are several named coagulation factors that interact in a complex way to form blood clots, as discussed in the article on coagulation. Deficiencies of coagulation factors are associated with clinical bleeding. For instance, deficiency of Factor VIII causes classic Hemophilia A while deficiencies of Factor IX cause "Christmas disease"(hemophilia B). Antibodies to Factor VIII can also inactivate the Factor VII and precipitate bleeding that is very difficult to control. This is a rare condition that is most likely to occur in older patients and in those with autoimmune diseases. von Willebrand disease is another common bleeding disorder. It is caused by a deficiency of or abnormal function of the "von Willebrand" factor, which is involved in platelet activation. Deficiencies in other factors, such as factor XIII or factor VII are occasionally seen, but may not be associated with severe bleeding and are not as commonly diagnosed.
In addition to NSAID-related bleeding, another common cause of bleeding is that related to the medication, warfarin ("Coumadin" and others). This medication needs to be closely monitored as the bleeding risk can be markedly increased by interactions with other medications. Warfarin acts by inhibiting the production of Vitamin K in the gut. Vitamin K is required for the production of the clotting factors, II, VII, IX, and X in the liver. One of the most common causes of warfarin-related bleeding is taking antibiotics. The gut bacteria make vitamin K and are killed by antibiotics. This decreases vitamin K levels and therefore the production of these clotting factors.
Deficiencies of platelet function may require platelet transfusion while deficiencies of clotting factors may require transfusion of either fresh frozen plasma or specific clotting factors, such as Factor VIII for patients with hemophilia.
| Condition | Prothrombin time | Partial thromboplastin time | Bleeding time | Platelet count |
|---|---|---|---|---|
| Vitamin K deficiency or warfarin | Prolonged | Normal or mildly prolonged | Unaffected | Unaffected |
| Disseminated intravascular coagulation | Prolonged | Prolonged | Prolonged | Decreased |
| Von Willebrand disease | Unaffected | Prolonged or unaffected | Prolonged | Unaffected |
| Hemophilia | Unaffected | Prolonged | Unaffected | Unaffected |
| Aspirin | Unaffected | Unaffected | Prolonged | Unaffected |
| Thrombocytopenia | Unaffected | Unaffected | Prolonged | Decreased |
| Liver failure, early | Prolonged | Unaffected | Unaffected | Unaffected |
| Liver failure, end-stage | Prolonged | Prolonged | Prolonged | Decreased |
| Uremia | Unaffected | Unaffected | Prolonged | Unaffected |
| Congenital afibrinogenemia | Prolonged | Prolonged | Prolonged | Unaffected |
| Factor V deficiency | Prolonged | Prolonged | Unaffected | Unaffected |
| Factor X deficiency as seen in amyloid purpura | Prolonged | Prolonged | Unaffected | Unaffected |
| Glanzmann's thrombasthenia | Unaffected | Unaffected | Prolonged | Unaffected |
| Bernard-Soulier syndrome | Unaffected | Unaffected | Prolonged | Decreased or unaffected |
| Factor XII deficiency | Unaffected | Prolonged | Unaffected | Unaffected |
| C1INH deficiency | Unaffected | Shortened | Unaffected | Unaffected |
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| 関連記事 | 「hemorrhagin」 |