Dictionary:

hemolysis

  (hĭ-mŏl'ĭ-sĭs, hē'mə-lī'sĭs)

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The destruction or dissolution of red blood cells, with subsequent release of hemoglobin.

The breakdown of red blood cells and the release of hemoglobin that occurs normally at the end of the life span of a red blood cell.

Rupture of erythrocytes with release of hemoglobin.
In a transfusion reaction or in alloimmune hemolytic anemia antibody mediated lysis of red blood cells involves triggering of the complement cascade. Red blood cells also clump together. The agglutinated cells become trapped in the smaller vessels or are phagocytosed and eventually disintegrate.
Some microbes form substances called hemolysins that have the specific action of destroying red blood cells; beta-hemolytic streptococci are an example.
Intravenous administration of a hypotonic solution or plain distilled water will cause the red cells to fill with fluid until their membranes rupture and the cells are destroyed.
Wherever either in vitro or in vivo IgG or IgM antibodies are bound to red blood cell antigens in the presence of complement, the complement cascade is triggered the final products of which include enzymes that result in holes being ‘punched’ in the wall of the red blood cell, allowing hemoglobin to escape and which is observed as lysis.
Snake venoms and certain plant substances may cause hemolysis. A great variety of chemical agents can lead to destruction of erythrocytes if there is exposure to a sufficiently high concentration of the substance. These chemical hemolytics include copper.
A disorder of the immune response in which antibodies are made to ‘self’ red blood cell antigens resulting in the lysis of the cells. See also autoimmune hemolytic anemia.

• alpha (α) h. — a characteristic of some bacteria, especially streptococci, manifested by a zone of greenish coloration of cleared agar around a colony of the bacteria on a blood–agar plate. Note that α-hemolysis of staphylococci causes complete lysis. See also streptococcus.
• beta (β) h. — complete hemolysis of sheep and ox erythrocytes by bacteria in culture media. Note that β-hemolysin of staphylococci causes incomplete hemolysis.
• blood transfusion h. — see transfusion reaction.
• differential h. — a technique for identification of chimerism, e.g. freemartin calves. Antisera against a single blood group causes only partial hemolysis of the blood composed of two cell populations with different blood cell antigens.
• double h. — two types of hemolysis produced on blood agar by alpha and beta lysins found in Staphylococcus aureus and S. intermedius.
• extravascular h. — the hemolysis which occurs when fragments of erythrocytes and the majority of aged erythrocytes are phagocytosed directly by the cells of the mononuclear phagocytic system.
• h. fever — the rise in body temperature which accompanies each hemolytic incidence of significant size.
• fragmentation h. — see microangiopathic anemia.
• h. inhibition test — a serological test used in the diagnosis of Corynebacterium pseudotuberculosis infection.
• intravascular h. — disruption of red blood cells occurs while they are within blood vessels.
• microangiopathic h. — fragmentation hemolysis often associated with microvascular injury, as in disseminated intravascular coagulation, and resulting from a primary disease.
• target h. — see double hemolysis (above).

This article is about medical aspects of hemolysis. For hemolysis in the culture of microorgranisms, see Hemolysis (microbiology).

Hemolysis. Red blood cells with (right) and without (left and middle) hemolysis.

Hemolysis (or haemolysis)—from the Latin 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

Main article: Hemolytic anemia

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 serum. The concentration of potassium inside red blood cells is much higher than in the serum 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.

In vitro hemolysis can occur in a blood sample owing prolonged storage or storage in incorrect conditions (ie too hot, too cold). Hemolysis can also occur at the time of venipuncture, but it is uncommon when the venipuncture is straightforward and the phlebotomist is experienced. 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.

Hemolysis due to mechanical blood processing during surgery

In some surgical procedures (esp. 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

Hemolyses of streptococci. (from left) Alpha, beta and gamma

Main article: Hemolysis (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 reduction 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

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