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Bleeding, technically known as hemorrhaging or haemorrhaging (see American and British spelling differences) is the loss of blood or blood escape 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 vagina, mouth, nose, ear or anus, or through a break in the skin. The complete loss of blood is referred to as exsanguination,[2] and desanguination is a massive blood loss. 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]



By blood loss

Hemorrhaging is broken down into four classes by the American College of Surgeons' Advanced Trauma Life Support (ATLS).[4]

  • Class I Hemorrhage involves up to 15% of blood volume. There is typically no change in vital signs and fluid resuscitation is not usually necessary.
  • Class II Hemorrhage involves 15-30% of total blood volume. A patient is often tachycardic (rapid heart beat) with a narrowing of the difference between the systolic and diastolic blood pressures. The body attempts to compensate with peripheral vasoconstriction. Skin may start to look pale and be cool to the touch. The patient may exhibit slight changes in behavior. Volume resuscitation with crystalloids (Saline solution or Lactated Ringer's solution) is all that is typically required. Blood transfusion is not typically required.
  • Class III Hemorrhage involves loss of 30-40% of circulating blood volume. The patient's blood pressure drops, the heart rate increases, peripheral hypoperfusion (shock), such as capillary refill worsens, and the mental status worsens. Fluid resuscitation with crystalloid and blood transfusion are usually necessary.
  • Class IV Hemorrhage involves loss of >40% of circulating blood volume. The limit of the body's compensation is reached and aggressive resuscitation is required to prevent death.

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