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Blood – Part 4

Blood – Part 4. Bleeding Disorders. The most common causes of abnormal bleeding are: Platelet deficiency Known as thrombocytopenia Deficits of some of the clotting factors M ight result from impaired liver function or certain genetic disorders. Thrombocytopenia.

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Blood – Part 4

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  1. Blood – Part 4

  2. Bleeding Disorders • The most common causes of abnormal bleeding are: • Platelet deficiency • Known as thrombocytopenia • Deficits of some of the clotting factors • Might result from impaired liver function or certain genetic disorders

  3. Thrombocytopenia • Thrombocytopenia – Results from an insufficient number of circulating platelets. • Even normal movements cause spontaneous bleeding from small blood vessels. • This is evidenced by many small purplish blotches called petechiae on the skin. • Can arise from any condition that suppresses myeloid tissue such as: • Bone marrow cancer • Radiation • Certain drugs

  4. Impaired Liver Function • When the liver is unable to synthesize its usual supply of clotting factors, abnormal and often severe bleeding episodes occur. • If vitamin K (needed by the liver to produce clotting factors) is deficient, the problem is easily corrected with supplements. • When liver function is severely impaired (as in hepatitis and cirrhosis) only whole blood transfusions are helpful.

  5. Hemophilia • Hemophilia – The term applies to several different hereditary bleeding disorders that result from a lack of any of the factors needed for clotting. • Commonly called “bleeder’s disease.”

  6. Hemophilia: Signs and Symptoms • Hemophilias have similar signs and symptoms that begin early in life: • Minor tissue trauma results in prolonged bleeding and can be life threatening. • Repeated bleeding into joints causes them to become disabled and painful.

  7. Hemophilia: Treatment • When a bleeding episode occurs hemophiliacs are given either: • A transfusion of fresh plasma • Injections of the purified clotting factor they lack • Hemophiliacs are completely dependent on these therapies.

  8. Loss of Blood Volume • The body can compensate for a loss of blood volume up to a certain limit. • Losses of 15-30% lead to pallor and weakness. • Losses of over 30% cause severe shock, which can be fatal.

  9. Blood Transfusions • Are routinely given to replace substantial blood loss and to treat severe anemia and thrombocytopenia. • Blood banks mix the collected blood with an anticoagulant to prevent blood clotting. • The treated blood can be stored for about 35 days until needed.

  10. Human Blood Groups • People have different blood groups and transfusing incompatible or mismatched blood can be fatal. • The plasma membranes of RBCs bear genetically determined proteins (antigens), which identify each person as unique. • An antigen is a substance that the body recognizes as foreign. • Antigens stimulates the immune system to release antibodies or use other means to mount a defense against it. • Most antigens are viruses or bacteria.

  11. Human Blood Groups • Each of us tolerates our own antigens. • One person’s RBC proteins will be recognized as foreign if transfused into another person with different RBC antigens. • Antibodies are “recognizers.” • Present in the plasma • Attach to RBCs bearing surface antigens different from those on the patient’s (blood recipient’s) RBCs.

  12. Agglutination • Binding of the antibodies causes the RBCs to clump, a phenomenon called agglutination. • Leads to the clogging of small blood vessels throughout the body. • During the next few hours, the foreign RBCs are lysed (ruptured) and their hemoglobin is released into the bloodstream.

  13. Transfusion Reactions • Most Devastating Consequence: The freed hemoglobin molecules may block the kidney tubules and cause kidney failure. • If kidney shutdown does not occur, then the reaction will probably not be fatal. • The transfused blood is unable to deliver the increased oxygen-carrying capacity hoped for. • Can cause fever, chills, nausea, and vomiting.

  14. Treatment of Transfusion Reactions • Treatment is aimed at preventing kidney damage by: • Infusing alkaline fluids to dilute and dissolve the hemoglobin • Diuretics to flush it out of the body in urine

  15. RBC Antigens • There are over 30 RBC antigens in humans, allowing each person’s blood cells to be classified into different blood groups. • However, it is the antigens of the ABO and Rh blood groups that cause the most vigorous transfusion reactions.

  16. ABO Blood Groups • ABO Blood Groups – Based on which of two antigens, type A or type B, the person inherits. • Type O Blood: Absence of both antigens. • Type AB Blood: Presence of both antigens. • Type A Blood: Presence of type A antigen. • Type B Blood: Presence of type B antigen.

  17. ABO Blood Groups • Antibodies are formed during infancy against the ABO antigens NOT present on your own RBCs. • A baby with neither the A nor the B antigen (group O) forms both anti-A and anti-B antibodies. • A baby with type A antigens (Group A) forms anti-B antibodies and so on…

  18. Rh Blood Groups • Named because one of the eight Rh antigens was originally identified in Rhesus monkeys. • Later the same antigen was discovered in human beings. • Most Americans are Rh+ (Rh positive), meaning that their RBCs carry the Rh antigen.

  19. Rh Blood Groups • Anti-Rh antibodies are NOT automatically formed and present in the blood of Rh- . • If an Rh- person receives Rh+ blood, shortly after the transfusion his/her immune system becomes sensitized and begins producing anti-Rh+ antibodies against the foreign blood type. • Hemolysis (rupture of RBCs) does not occur with the first transfusion because it takes time for the body to react and start making antibodies. • But the second and every time thereafter, a typical transfusion reaction occurs.

  20. Rh-Related Problem in Pregnancy • An important Rh-related problem occurs in pregnant Rh- women who are carrying Rh+ babies. • The first such pregnancy usually results in the delivery of a healthy baby.

  21. Rh-Related Problem in Pregnancy • Because the mother is sensitized by Rh+ antigens that have passed through her bloodstream, she will form anti-Rh+ antibodies unless treated with RhoGAM shortly after giving birth. • RhoGAM is an immune serum that prevents this sensitization and her subsequent immune response.

  22. Rh-Related Problem in Pregnancy • If the Rh- mother is not treated with RhoGAM and becomes pregnant a second time with a Rh+ baby, her antibodies will cross through the placenta and destroy the baby’s RBCs. • The baby will be anemic and becomes hypoxic. • Brain damage and even death may occur unless fetal transfusions are done before birth to provide more RBCs for O2 transport.

  23. Blood Typing • The importance of determining the blood group of both the donor and the recipient BEFORE blood is transfused is glaringly obvious. • Blood typing involves testing the blood by mixing it with two different types of immune serum- • Anti-A • Anti-B • Typing for Rh factors is done in the same manner as ABO blood typing.

  24. Blood Typing • Type A Blood: • Agglutination occurs only when mixed with the anti-A serum • Type B Blood: • Agglutination occurs only when mixed with anti-B serum • Type AB Blood: • Agglutination occurs when mixed with both the anti-A serum and the anti-B serum. • Type O Blood: • No agglutination occurs when mixed with either serum.

  25. Blood Typing • Since it is critical that blood groups be compatible, crossmatching is done. • Cross matching involves testing for agglutination of donor RBCs by the recipient serum, and of the recipient’s RBCs by the donor serum. • Type AB: Can receive any type of blood • Type O: Universal donor

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