hemolysis

Hemolysis (or haemolysis)—from the Greek αἷμα (aima, haema, hemo-) meaning "blood" and λύσις (lusis, lysis, -lysis) meaning a "loosing", "setting free" or "releasing"^[1]—is the rupturing of erythrocytes (red blood cells) and the release of their contents (hemoglobin) into surrounding fluid (e.g., blood plasma). Hemolysis may occur in vivo or in vitro (inside or outside the body).

In vivo (Inside the body)

In vivo hemolysis can be caused by a large number of medical conditions, including many Gram-positive bacteria (e.g., streptococcus, enterococcus, and staphylococcus), some parasites (e.g., malaria), some autoimmune disorders (e.g., hemolytic disease of the newborn), and some genetic disorders (e.g., sickle-cell disease or G6PD deficiency).

Streptococcus

Many species of the genus Streptococcus cause hemolysis. Streptococcal bacteria species are classified according to their hemolytic properties.

• Alpha-hemolytic species, including S. pneumoniae, S. mutans, and S. salivarius, reduce the iron in the hemoglobin (turning it dark green in culture).
• Beta-hemolytic species, including S. pyogenes and S. agalactiae, completely rupture the red blood cells (visible as a halo in culture).
• Gamma-hemolytic, or non-hemolytic, species do not cause hemolysis and rarely cause illness.

Enterococcus

The genus enterococcus includes lactic acid bacteria formerly classified as beta-hemolytic Group D in the genus streptococcus (see above), including E. faecilis (S. faecalis), E. faecium (S. faecium), E. durans (S. durans), and E. avium (S. avium).

Staphylococcus

Staphylococcus is another Gram-positive cocci. S. aureus, the most common cause of "staph" infections, is frequently beta-hemolytic.^[2]

Parasitic hemolysis

Because the feeding process of the plasmodium parasites damages red blood cells, Malaria is sometimes called "parasitic hemolysis" in medical literature.

Hemolytic disease of the newborn

Hemolytic disease of the newborn is an autoimmune disease resulting from the mother's antibodies crossing the placenta to the fetus.

Hemolytic anemia

Because in vivo hemolysis destroys the red blood cells, in uncontrolled chronic or severe cases it can lead to hemolytic anemia.

Hemolytic crisis

A hemolytic crisis, or hyperhemolytic crisis, is characterized by an accelerated rate of red blood cell destruction leading to anemia, jaundice, and reticulocytosis.^[3] Hemolytic crises are a major concern with sickle-cell disease and G6PD deficiency.

In vitro (lit. "in glass," but generally meaning outside the body)

Hemolysis of blood samples. Red blood cells without (left and middle) and with (right) hemolysis. If as little as 0.5% of the red blood cells are hemolyzed, the released hemoglobin will cause the serum or plasma to appear pale red or cherry red in color.^[4] Note that the hemolyzed sample is transparent, because there are no cells to scatter light.

In vitro hemolysis can be caused by improper technique during collection of blood specimens, by the effects of mechanical processing of blood, or by bacterial action in cultured blood specimens.

From specimen collection

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 during specimen collection can cause inaccurate laboratory test results by contaminating the surrounding plasma with the contents of hemolyzed red blood cells. For example, the concentration of potassium inside red blood cells is much higher than in the plasma and so an elevated potassium level is usually found in biochemistry tests of hemolyzed blood.

In vitro hemolysis can also occur in a blood sample because of prolonged storage or storage in incorrect conditions (i.e., too hot or too cold).

From mechanical blood processing during surgery

In some surgical procedures (especially some heart operations) where substantial blood loss is expected, machinery is used for intraoperative 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 a patient's cells must be done at a correspondingly higher speed to prevent hypotension, pH imbalance, and a number of other hemodynamic and blood level factors.

From bacteria culture

Hemolysis from streptococcus. Examples of the blood culture patterns created by (from left) alpha-, beta- and gamma-hemolytic streptococci.

Visualizing the physical appearance of hemolysis in cultured blood samples may be used as a tool to determine the species of various Gram-positive bacteria infections (e.g., streptococcus).

See also

• Hemolysin
• Glucose-6-phosphate dehydrogenase deficiency

External links

• Effects of Hemolysis on Clinical Specimens
• MeSH Hemolysis

References