hemolysis, destruction of red blood cells in the bloodstream. Although new red blood cells, or erythrocytes, are continuously created and old ones destroyed, an excessive rate of destruction sometimes occurs. The dead cells, in sufficiently large numbers, overwhelm the organ that destroys them, the spleen, so that serum pigments resulting from hemoglobin breakdown appear in the blood serum. Jaundice is caused by overloading the liver with pigment. Large-scale destruction of red blood cells, from any of a variety of causes, results in anemia. Rh disease, or erythroblastosis fetalis, is a hemolytic disease of newborns caused by an immune reaction between fetal red blood cells and maternal antibodies to them. Some hemolytic conditions, e.g., those in which red blood cells are fragile and rupture easily, are treated by removal of the spleen to slow cell breakdown or by administration of steroids. Autoimmune hemolytic conditions result from splenomegaly. The spleen not only sequesters red blood cells, but produces antibodies against the body's red blood cells. This is a potentially lethal condition that occurs more often in women than men.

Hemolysis (or haemolysis)—from the Greek Hemo-, Greek Αἷμα meaning blood, -lysis, meaning to break open—is the breaking open of red blood cells and the release of hemoglobin into the surrounding fluid (plasma, in vivo).

In vivo hemolysis

In vivo hemolysis, which can be caused by a large number of conditions, can lead to anemia.

Anemias caused by in vivo hemolysis are collectively called hemolytic anemias.

In vitro hemolysis

In vitro hemolysis can be an important unwanted effect in medical tests and can cause inaccurate results, because the contents of hemolysed red blood cells are included with the plasma. The concentration of potassium inside red blood cells is much higher than in the plasma and so an elevated potassium is usually found in biochemistry tests of hemolysed blood. If as little as 0.5% of the red blood cells are lysed the serum will have a visually obvious pinkish colour, due to hemoglobin.

Most causes of in vitro hemolysis are related to specimen collection. Difficult collections, unsecure line connections, contamination, and incorrect needle size, as well as improper tube mixing and incorrectly filled tubes are all frequent causes of hemolysis. Excessive suction can cause the red blood cells to be literally smashed on their way through the hypodermic needle owing to turbulence and physical forces. Such hemolysis is more likely to occur when a patient's veins are difficult to find or when they collapse when blood is removed by a syringe or a modern vacuum tube. Experience and proper technique are key for any phlebotomist or nurse to prevent hemolysis. In vitro hemolysis can also occur in a blood sample owing prolonged storage or storage in incorrect conditions (ie too hot, too cold).

Hemolysis due to mechanical blood processing during surgery

In some surgical procedures (especially some heart operations) where substantial blood loss is expected, machinery is used for intra-operative blood salvage. A centrifuge process takes blood from the patient, washes the red blood cells with normal saline, and returns them to the patient's blood circulation. Hemolysis may occur if the centrifuge rotates too quickly (generally greater than 500 rpm)—essentially this is hemolysis occurring outside of the body. Unfortunately, increased hemolysis occurs with massive amounts of sudden blood loss, because the process of returning patient's cells must be done at a correspondingly higher speed to prevent hypotension, pH imbalance, and a number of other hemodynamic & blood level factors.

Hemolysis in microbiology

Hemolytic patterns of the various Gram positive cocci; Streptococci are differentiated by hemolysis of red blood cells on blood agar (BA) plates.

• Alpha hemolysis is shown by a greenish halo around the colony and is the result of hemoglobin oxidation to methaemoglobin in red blood cells.
• Beta hemolysis is shown by a clear halo around the colony and is produced by complete hemolysis of the red blood cells.
• Gamma hemolysis is shown as no hemolysis or discoloration of the blood.

See also

• Hemolysin

External links

• Effects of Hemolysis on Clinical Specimens