blood transfusion

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Blood transfusion is the process of transferring blood or blood-based products from one person into the circulatory system of another. Blood transfusions can be life-saving in some situations, such as massive blood loss due to trauma , or can be used to replace blood lost during surgery . Blood transfusions may also be used to treat a severe anaemia caused by a blood disease . People suffering from hemophilia or sickle-cell disease may require frequent blood transfusions.


ANEMIAS Anemia occur s because of : lack of red blood cell formation increased red blood cell destruction blood loss an association with a primary disease deficiences in nutrition Anemia s can be divided on three essential categories depending on red blood cells appearance : normocytic anemias e.g. aplastic anemia m icrocytic anemia e.g. iron deficiency, sickle cell anemia. m acrocytic anemias e.g. acute hemorrhage, intravascular hemolytic anemia (megalobalstic anemias commonly caused by B 12 and/or f olate deficiency.




HISTORY The science of blood transfusion dates to the first decade of the 19th century , with the discovery of distinct blood types leading to the practice of mixing some blood from the donor and the receiver before the transfusion.



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Blood group A If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma. Blood group B If you belong to the blood group B, you have B antigens on the surface of your red blood cells and A antibodies in your blood plasma .

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Blood group AB If you belong to the blood group AB, you have both A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma. Blood group 0 If you belong to the blood group 0 (null), you have neither A or B antigens on the surface of your red blood cells but you have both A and B antibodies in your blood plasma .


Rh FACTOR Many people also have a so called Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.


Rh FACTOR This can induce varying degrees of anemia in the foetus, with hiperbilirubinemia, organ malfunction, etc. Bilirubin deposition in the cerebral basal ganglia ( kernicterus )can lead to severe mental damage. Severe cases of this disease were mortal. P revention started in the 60's and nowadays Rh negative pregnant women receive immunoglobulin doses at several moments during pregnancy and after childbirth if the baby is Rh positive. Besides, women in fertile age are never transfused Rh positive blood. Thus, HDN due to Rh antibodies has practically disappeared in developed countries.


BLOOD TYPES IN THE USA O positive - 38% O negative - 7 % A positive - 34% A negative - 6% B positive - 9% B negative - 2% AB positive - 3% AB negative - 1%


WHO CAN DONATE BLOOD? To donate blood, the American Red Cross requires that people be at least 17 years old and weigh more than 110 pounds. Donors must be in good health and will be screened for certain medical conditions, such as anemia. Donors who meet these requirements can give blood every 56 days. People who meet the eligibility requirements will need to give their medical history and pass a physical exam before donating. The medical history includes questions that help blood bank staff decide if there's a risk that donors might have an infection that could be transmitted in their blood.


BLOOD TRANSFUSIONS Blood can only be administered intravenously . It therefore requires the insertion of a cannula of suitable caliber. Before the blood is administered, the personal details of the patient are matched with the blood to be transfused, to minimize risk of transfusion reactions. A unit (up to 500 ml) is typically administered over 4 hours. In patients at risk of congestive heart failure , many doctors administer diuretics to prevent fluid overload. Antihistamines are sometimes given before the transfusion to prevent a transfusion reaction.


BLOOD DONATION In emergencies, there are certain exceptions to the rule that the donor's blood type must match the recipient's exactly: Blood type O negative is the only type of blood that people of all other blood types can receive. This is helpful in emergency situations when the patient needs a transfusion but their blood type is unknown. Because of this, O negative donors are called "universal donors ." People who have type AB blood are called " universal recipients " because they can safely receive any type of blood.


BLOOD TRANSFUSIONS Blood transfusions can be grouped into two main types depending on their source: Homologous transfusions , or transfusions using the stored blood of others. Autologous transfusions , or transfusions using one's own stored blood.


BLOOD DONATION Blood is most commonly donated as whole blood by inserting a catheter into a vein and collecting it in a plastic bag (mixed with anticoagulant ) via gravity . Collected blood is then separated into components to make the best use of it. Aside from red blood cells , plasma , and platelets , the resulting blood component products also include albumin protein , clotting factor concentrates, cryoprecipitate , fibrinogen concentrate, and immunoglobulins ( antibodies ). Red cells, plasma and platelets can also be donated individually via a more complex process called apheresis .


COMPLICATIONS AND RISK Bruise of the needle site- 23 % Sore arm- 10 % Fatigue- 8 % Vasovagal symptoms- 5% Hematoma at the needle site- 2 % Sensory changes in the arm used for donation ( pain, numbness)-1 %


TRANSFUSION REACTION There are risks associated with receiving a blood transfusion, and these must be balanced against the benefit which is expected. The most common adverse reaction to a blood transfusion is a febrile non-hemolytic transfusion reaction , which consists of a fever which resolves on its own and causes no lasting problems or side effects. Hemolytic reactions include chills, headache, backache, dyspnea , cyanosis, chest pain, tachycardia and hypotension .


RISKS ASSOCIATED WITH BLOOD TRANSFUSION Transmission of viral infection –hepatitis B, hepatitis C, HIV Anaphylactic reactions Acute hemolytic reactions Volume overload Iron overload


BLOOD SUBSTITUTES As of mid- 2006 , there are no clinically utilized oxygen-carrying blood substitutes for humans; however, there are widely available non-blood volume expanders and other blood-saving techniques. These are helping doctors and surgeons avoid the risks of disease transmission and immune suppression, address the chronic blood donor shortage, and others who have religious objections to receiving transfused blood. A number of blood substitutes are currently in the clinical evaluation stage. Most attempts to find a suitable alternative to blood thus far have concentrated on cell-free hemoglobin solutions.

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