Bleeding, known as a hemorrhage or simply blood loss, is blood escaping from the circulatory system from damaged blood vessels.
Hypovolemia is a massive decrease in blood volume, and death by excessive loss of blood is referred to as exsanguination. Typically, a healthy person can endure a loss of 10-15% of the total blood volume without serious medical difficulties (blood donation typically takes 8-10% of the donor's blood volume).
The stopping or controlling of bleeding is called hemostasis and is an important part of both first aid and surgery.
Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vagina or anus, or through a wound in the skin.
"Medical bleeding" denotes hemorrhage as a result of an underlying medical condition (causes that are not directly due to trauma). Blood can escape from blood vessels as a result of:
1. Intravascular changes — changes of the blood within vessels (↑ blood pressure, ↓ clotting factors).
2. Intramural changes — changes arising within the walls of blood vessels (aneurysms, dissections, vasculitis).
3. Extravascular changes — changes arising outside blood vessels (H pylori infection, brain abscess, brain tumor).
The following is the World Health Organization's scale to measure the severity of bleeding.
• 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 malfunction associated with fatality
Massive hemorrhage can be identified by blood loss:
• exceeding circulating blood volume within a 24-hour period,
• 50% of circulating blood volume within a 3-hour period,
• exceeding 150 ml/min, or
• blood loss that necessitates plasma and platelet transfusion.
• Individuals in excellent physical and cardiovascular shape may have more effective compensatory mechanisms before experiencing cardiovascular collapse; they may look deceptively stable, with minimal variability 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 beta blockers that can potentially lessen the cardiovascular response.
See reference for more information.
Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on May 16, 2020