Bleeding

Bleeding, also known as hemorrhage, occurs when blood escapes from the circulatory system. This happens because blood vessels have been damaged. Bleeding can be external, meaning it exits through a puncture in the skin or a natural opening like the nose, mouth, or ears. It can also be internal, where blood stays inside the body. Internal bleeding might occur in organs like the liver, kidney, or spleen. If a person loses a massive amount of blood, it is called hypovolemia. If the loss is so extreme that it causes death, the process is called exsanguination.

To manage blood loss, the body uses a process called hemostasis. Hemostasis is the method of stopping or controlling bleeding. This is a vital part of both medical surgery and first aid. The hemostatic system relies on two main components: platelets and the coagulation system. Platelets are tiny parts of the blood that form a physical plug in the damaged vessel wall. They also produce substances that trigger the creation of a blood clot. These clots work to seal the leak and prevent further loss.

Traumatic injury is a common cause of bleeding. There are many specific types of wounds. An abrasion, or graze, occurs when a foreign object moves across the skin without going deep. A laceration is an irregular wound often caused by blunt impact or tearing. A puncture wound happens when an object like a nail or knife penetrates the skin. A contusion, commonly known as a bruise, is caused by blunt trauma that damages tissue under the surface. Other injuries include incisions made by surgical tools and crushing injuries caused by extreme force.

Bleeding can also result from underlying medical conditions rather than physical trauma. This is often called medical bleeding. It can happen due to changes inside the blood vessels, such as high blood pressure. It can also happen because of changes in the vessel walls, such as an aneurysm. An aneurysm is a bulge in a vessel wall. Changes outside the vessels, like a tumor or infection, can also cause blood to escape. Some infectious diseases, such as Ebola or yellow fever, are known to cause bleeding.

Certain medications can interfere with the body's ability to achieve hemostasis. Nonsteroidal anti-inflammatory drugs, or NSAIDs, include medicines like ibuprofen and aspirin. Aspirin is a prototype for this group and works by inhibiting thromboxane. This prevents platelets from activating effectively. The effect of aspirin is irreversible and lasts about ten days until new platelets are made. Another medication, warfarin, increases bleeding risk by inhibiting Vitamin K production in the gut. The liver requires Vitamin K to produce clotting factors II, VII, IX, and X. If antibiotics kill gut bacteria that make Vitamin K, the risk of bleeding increases.

Doctors use specific classifications to measure the severity of blood loss. The American College of Surgeons uses four classes of hemorrhage. Class I involves a loss of up to 15% of total blood volume. In Class II, a person loses 15% to 30%, which may cause a rapid heartbeat or pale skin. Class III involves a loss of 30% to 40%, leading to a drop in blood pressure and worsening mental status. Class IV is the most severe, involving a loss of more than 40%. At this stage, the body's ability to compensate is exhausted, and aggressive treatment is needed to prevent death.

Bleeding can also manifest in very specific locations in the body. For example, a subconjunctival hemorrhage is a bloody eye caused by a broken vessel in the white part of the eye. This often results from straining, such as coughing or sneezing. Within the skull, an intracranial hemorrhage can occur. A cerebral hemorrhage is a specific type where bleeding happens within the brain tissue itself. Other types include subarachnoid hemorrhage, where blood enters the subarachnoid space. These different locations and types help doctors understand the exact nature of the injury or condition.