Hemorrhage, commonly known as bleeding, is the loss of blood from the body’s circulatory system. The severity of any bleeding injury is determined not solely by the total amount of blood lost, but by the speed, volume, and location of that loss. A minor injury can become life-threatening if the blood loss is rapid or compromises organ function. Understanding these factors is important for recognizing the most serious types of bleeding.
Categorizing Bleeding by Source Vessel
Bleeding is classified by the type of blood vessel damaged: capillaries, veins, or arteries. Capillary bleeding is the most common type, resulting from damage to the smallest vessels near the skin’s surface. This blood loss appears as a slow ooze or trickle and usually clots quickly.
Venous bleeding occurs when a vein is damaged, carrying dark red, deoxygenated blood back toward the heart. The blood flows in a steady stream. Although under lower pressure than arterial flow, damage to a large vein can still result in a significant volume of blood loss if left uncontrolled.
Arterial bleeding is the most immediately dangerous external source of blood loss due to the high pressure within the arteries. This oxygen-rich blood is bright red and is ejected from the wound in spurts or pulses synchronized with the heartbeat. The force of the flow makes it difficult for the body to form a clot, leading to the fastest potential rate of blood loss.
The Hidden Threat of Internal Hemorrhage
Although arterial bleeding is the most dramatic external injury, internal hemorrhage often presents a greater threat because it is hidden. Bleeding into body cavities, such as the abdomen, chest, or skull, cannot be controlled externally and requires definitive medical intervention like surgery. This type of bleeding frequently results from blunt force trauma, such as a severe fall or motor vehicle accident, which can tear deep vessels and organs like the liver or spleen.
The danger of internal bleeding is compounded because symptoms can be delayed for hours or days, masking the injury’s seriousness. General signs include noticeable swelling, tightness, or hardness in the abdomen or around the injury site. More specific signs may include vomiting blood, coughing up blood, or passing dark or black blood in urine or stool. Unexplained pain that worsens or extensive, deep purple bruising (ecchymosis) also indicates blood pooling beneath the skin.
Understanding Hypovolemic Shock
The ultimate measure of bleeding severity is its ability to induce hypovolemic shock, a life-threatening condition resulting from the loss of a large volume of blood. This state is triggered when a person loses more than 20% of their total blood volume, leading to a failure of the circulatory system to deliver adequate oxygen to the tissues. The body attempts to compensate for this rapid volume depletion by prioritizing blood flow to the brain and heart.
This redirection reduces blood flow to the limbs and non-essential organs, triggering a cascade of observable symptoms. The first sign is often a rapid, weak pulse (tachycardia) as the heart attempts to pump the reduced volume faster. The victim’s skin becomes pale, cool, and clammy as blood vessels near the surface constrict to maintain core pressure.
Progressive blood loss causes breathing to become rapid and shallow. The individual may exhibit confusion, anxiety, or dizziness due to reduced oxygen delivery to the brain. As the condition advances, systolic blood pressure drops significantly, and the body produces very little or no urine. Recognizing these signs of systemic failure is important, as intervention is necessary to prevent organ damage and death.
Essential Steps for Immediate Care
The immediate action when severe bleeding is suspected, whether external or internal, is to call emergency medical services. For severe external bleeding, the priority is to stop the flow by applying firm, direct pressure to the wound using a clean cloth or sterile gauze. If the material becomes soaked, do not remove it; place additional material on top to maintain continuous pressure.
If the injury is on a limb and a bone fracture is not suspected, elevating the wound above the heart can help slow blood loss. For a person suspected of internal bleeding or hypovolemic shock, stabilization is the focus while awaiting professional help. The person should lie down and be covered with a blanket to maintain body temperature. Elevating the legs approximately twelve inches can assist in circulating blood back toward the core, but avoid this if a head, neck, or back injury is suspected.