Hemolysis
Hemolysis is the premature breakdown of red blood cells (RBCs), occurring when their outer membranes rupture and release their contents into the surrounding fluid. This process can take place either within the body (in-vivo) or outside of it (in-vitro), such as during blood sampling or storage. Hemolysis is often identifiable through changes in the color of the fluid and can be confirmed via laboratory tests. In-vivo hemolysis can be triggered by various factors, including infections, immune reactions, tumors, and certain medications, leading to conditions like hemolytic anemia. This anemia can be classified as extrinsic, caused by external factors that lead to the destruction of healthy RBCs, or intrinsic, stemming from inherent defects in the blood cells themselves. In-vitro hemolysis may occur due to mishandling during blood collection or processing, as well as due to patient conditions before the draw. Understanding hemolysis is crucial for diagnosing and managing related health issues effectively.
Hemolysis
Hemolysis refers to the premature breakdown of red blood cells (RBCs). It occurs when the outer membrane of the cells ruptures, releasing the components of the RBCs into the fluid around them. The presence of hemolysis can be detected by the color of the surrounding fluid and through laboratory tests. It can occur either within the body of the organism (in-vivo) or after the blood is outside of the animal (in-vitro), such as in a blood sample or in donated blood.
Red Blood Cell Components and Function
Although blood appears to be a homogenous, or uniform, fluid, it is composed of plasma, platelets, white blood cells, and red blood cells. Each component has a specific function. The largest portion—about 40 to 45 percent—of the volume of blood is made up of red blood cells, also known as erythrocytes. These RBCs contain the protein hemoglobin, which is what makes blood red.
Red blood cells carry oxygen from the lungs to the rest of the body, where cells use it to generate energy. The byproduct of this energy production, carbon dioxide, is then carried away by the red blood cells and taken to the lungs, where it is expelled during the breathing process. The exact percentage of RBCs in an individual's blood is known as the hematocrit level.
In-Vivo Hemolysis
Red blood cells within a living body are normally viable for from 110 to 120 days before they naturally break down and are filtered out of the blood stream through the spleen. New cells to replace them are manufactured in the bone marrow. Normally, the bone marrow can keep up with the need. However, several conditions can cause red blood cells to break down prematurely, including infections; immune reactions; tumors; leukemia; lymphoma; chemical sources such as medications, toxins or poisons; and treatments that remove the blood from the body and return it, such as hemodialysis and heart-lung bypass machinery. The bone marrow may not be able to manufacture new RBCs quickly enough and the hematocrit level may drop.
This altered level of red blood cells can result in a condition known as hemolytic anemia. The two forms of this anemia are extrinsic and intrinsic.
Extrinsic anemia, also known as autoimmune hemolytic anemia, happens when something causes the spleen to capture and destroy healthy RBCs along with the worn out ones it normally removes from the circulatory system. This type is caused by infections, cancer, autoimmune disorders, and side effects from medication. A number of medications, ranging from over-the-counter pain relievers including acetaminophen and ibuprofen to antibiotics and medications such as quinine and rifampin, can cause drug-induced extrinsic anemia.
This type of anemia can also result when a patient receives a blood transfusion of a different blood type than their own; the body sees the foreign blood as an invader and releases antibodies to destroy the blood cells. This sometimes happens in newborns when the mother and baby have incompatible blood types, especially during second pregnancies; the mother may have developed antibodies to other blood types during her first pregnancy, and these antibodies can be passed on to the infant, causing hemolysis and anemia.
Extrinsic anemia can occur in people of all ages and is curable. It can be treated by blood transfusions, corticosteroid medications, and intravenous administration of immunoglobulin. As a last result, the spleen may be surgically removed to prevent the premature destruction of the red blood cells.
Intrinsic anemia is the result of blood cells that are defective because of an illness such as sickle cell anemia, in which the cells are misshapen, or thalassemia, in which the body produces an abnormal form of hemoglobin. Sickle cell hemolytic anemia is inherited and is more common in people of African American descent. It can be treated and its symptoms—which include pain and increased infection risk—can be minimized, but the condition can be fatal. A patient with thalassemia produces fewer red blood cells than normal. This condition can also be managed and sometimes needs no treatment.
In-Vitro Hemolysis
Hemolysis can also occur once the blood is removed from the body, either because of the effects of a condition the patient has or because of the way the blood is removed or handled after removal.
Knowing the amount of intact red blood cells a patient has as determined by the hematocrit reading is an important diagnostic tool for physicians. However, blood samples can sometimes be inadvertently damaged, especially when blood is drawn hurriedly, such as in an emergency room. A number of things can damage the blood cells and cause them to rupture, including working too fast when drawing the blood or transferring it to a vial, shaking the collected blood too vigorously, or even allowing insufficient time for the alcohol used as a skin disinfectant to dry before proceeding. The patient's condition at the time of the blood draw can also be a factor in hemolysis; a dehydrated patient, or one with an infection or illness that is attacking the blood cells, might be more prone to having the cells rupture after a blood draw.
Hemolysis can also happen in stored blood that has been prepared for infusions. Red blood cells can normally be stored for 42 days before use, but a number of factors have been shown to increase the rate of hemolysis in collected blood. These include the addition of too much anticoagulant factor to keep the blood fluid, delays between collection and processing, and even the size and type of bag used to store the blood.
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