Massive Blood transfusion

Massive Transfusion is usually defined as the need to transfuse from one to two times the patient's normal blood volume. In a "normal" adult, this is the equivalent of 10-20 units. Potential complications from this include coagulopathy, citrate toxicity, hypothermia, acid-base disturbances and changes in serum potassium concentration.
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Coagulopathy is common with massive transfusion. The most common cause of bleeding following a large volume transfusion is dilutional thrombocytopenia. This should be suspected and treated first before moving on to factor deficiencies as the cause of coagulopathy.
Citrate toxicity results when the citrate in the transfused blood begins to bind calcium in the patient's body. Clinically significant hypocalcemia does not usually occur unless the rate of transfusion exceeds one unit every five minutes or so. Citrate metabolism is primarily hepatic - so hepatic disease or dysfunction can cause this effect to be more pronounced. Treatment is with intravenous calcium administration - but identification of the problem requires a high index of suspicion.
Hypothermia should not occur on a regular basis. Massive transfusion is an absolute indication for the warming of all blood and fluid to body temperature as it is being given.
Acid-Base balance can be seen after massive transfusion. The most common abnormality is a metabolic alkalosis. Patients may initially be acidotic because the blood load itself is acidic and there may be a prevailing lactic acidosis from hypoperfusion. However, once normal perfusion is restored, any metabolic acidosis resolves and the citrate and lactate are then converted to bicarbonate in the liver.
Serum potassium can rise as blood is given. The potassium concentration in stored blood increases steadily with time. The amount of potassium is typically less than 4 milliequivalents per unit - so you can see that large amounts of blood at a high rate of delivery is required to raise serum levels of potassium.
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Infectious Agents can be passed along with blood transfusion as well.
o Hepatitis
o AIDS
o Other viral agents (CMV, EBV, HTLV)
o Parasites and bacteria
Hepatitis has been an ongoing problem. Until recently, the incidence of hepatitis following transfusion was as high as 10% with the overwhelming majority of these infections caused by hepatitis C. Now that this virus is identified and tested for, the risk is decreased. Currently the risk from transfusion is estimated to be in the range of 1:1,000,000 for hepatitis A, 1:30,000 - 250,000 for hepatitis B and 1:30,000 - 150,000 for hepatitis C.
AIDS is a feared disease but the actual risk is quite low. All blood is tested for the anti-HIV-1 antibody which is a marker for infectivity. Unfortunately, there is a 6-8 week period required for a person to develop the antibody after they are infected with HIV and therefore infectious units can go undetected. The current risk for HIV infection due to transfusion is estimated to be 1:200,000 to 2,000,000.
CMV and EBV are usually the cause of only asymptomatic infection or mild systemic illness. Unfortunately, some of these people become asymptomatic carriers of the viruses and the white blood cells in blood units are capable of transmitting either virus. Immunocompromised and immunosuppressed patients are particularly susceptible to CMV and should receive CMV negative units only.
Human T cell Lymphocytic Viruses (HTLV-1 responsible for tropical spastic paresis and HTLV-II) are leukemia and lymphoma retro-viruses that have been reported to be transmitted via transfusion. Screening is done for these, but again those in the window before antibodies are made can be missed. Current risk is estimated at 1:250,000 - 2,000,000.
Parvovirus B19 has been reported to be transmitted by factor concentrates and occurs in approximately 1:10,000 transfusions. It is associated with aplastic anemia and liver failure, especially inimmunologically compromised children.
Parasitic diseases reported to be transmitted via blood transfusion include malaria, toxoplasmosis, and Chagas' disease. Fortunately, such cases are rare and the prevalence of these diseases is very low in the United States. Therefore, these are of very little concern in this country.
Both gram-positive and gram-negative bacteria can rarely contaminate blood transfusions. To avoid the possibility of significant bacterial contamination, blood should be administered over a period of shorter than four hours.