Chapter 107. Transfusion Biology and Therapy (Part 8) ppsx

Chapter 107. Transfusion Biology and Therapy (Part 8) Nonimmunologic Reactions Fluid Overload Blood components are excellent volume expanders, and transfusion may quickly lead to volume overload. Monitoring the rate and volume of the transfusion and using a diuretic can minimize this problem. Hypothermia Refrigerated (4°C) or frozen (–18°C or below) blood components can result in hypothermia when rapidly infused. Cardiac dysrhythmias can result from exposing the sinoatrial node to cold fluid. Use of an in-line warmer will prevent this complication. Electrolyte Toxicity RBC leakage during storage increases the concentration of potassium in the unit. Neonates and patients in renal failure are at risk for hyperkalemia. Preventive measures, such as using fresh or washed RBCs, are warranted for neonatal transfusions because this complication can be fatal. Citrate, commonly used to anticoagulate blood components, chelates calcium and thereby inhibits the coagulation cascade. Hypocalcemia, manifested by circumoral numbness and/or tingling sensation of the fingers and toes, may result from multiple rapid transfusions. Because citrate is quickly metabolized to bicarbonate, calcium infusion is seldom required in this setting. If calcium or any other intravenous infusion is necessary, it must be given through a separate line. Iron Overload Each unit of RBCs contains 200–250 mg of iron. Symptoms and signs of iron overload affecting endocrine, hepatic, and cardiac function are common after 100 units of RBCs have been transfused (total-body iron load of 20 g). Preventing this complication by using alternative therapies (e.g., erythropoietin) and judicious transfusion is preferable and cost effective. Deferoxamine and other chelating agents are available, but the response is often suboptimal. Hypotensive Reactions Transient hypotension may be noted among transfused patients who take angiotensin-converting enzyme (ACE) inhibitors. Since blood products contain bradykinin that is normally degraded by ACE, patients on ACE inhibitors may have increased bradykinin levels that cause hypotension. The blood pressure typically returns to normal without intervention. Immunomodulation Transfusion of allogeneic blood is immunosuppressive. Multiply transfused renal transplant recipients are less likely to reject the graft, and transfusion may result in poorer outcomes in cancer patients and increase the risk of infections. Transfusion-related immunomodulation is thought to be mediated by transfused leukocytes. Leukocyte-depleted cellular products may cause less immunosuppression, though controlled data have not been obtained and are unlikely to be obtained as the blood supply becomes universally leukocyte- depleted. Infectious Complications Nucleic acid amplification testing (NAT) began in 1999 to screen donated blood for the presence of HIV and hepatitis C virus (HCV) RNA. Since 2003 NAT has been used to detect West Nile virus (WNV) RNA in donated blood. Viral Infections Hepatitis C Virus Blood donations are tested for antibodies to HCV and HCV RNA. Fewer than 200 HCV RNA-positive, antibody-negative donors have been found. The risk of acquiring HCV through transfusion is now calculated to be approximately 1 in 2,000,000 units. Infection with HCV may be asymptomatic or lead to chronic active hepatitis, cirrhosis, and liver failure. Human Immunodeficiency Virus Type 1 Donated blood is tested for antibodies to HIV-1, HIV-1 p24 antigen, and HIV RNA using NAT. Approximately a dozen seronegative donors have been shown to harbor HIV RNA. The risk of HIV-1 infection per transfusion episode is 1 in 2 million. Antibodies to HIV-2 are also measured in donated blood. No cases of HIV-2 infection have been reported in the United States since 1992. Hepatitis B Virus Donated blood is screened for HBV using assays for hepatitis B surface antigen (HbsAg). NAT testing is not practical because of slow viral replication and lower levels of viremia. The risk of transfusion-associated HBV infection is 1 in 63,000 units, twentyfold greater than for HCV. Vaccination of individuals who require long-term transfusion therapy can prevent this complication. . Chapter 107. Transfusion Biology and Therapy (Part 8) Nonimmunologic Reactions Fluid Overload Blood components are excellent volume expanders, and transfusion may quickly. calcium and thereby inhibits the coagulation cascade. Hypocalcemia, manifested by circumoral numbness and/ or tingling sensation of the fingers and toes, may result from multiple rapid transfusions complication by using alternative therapies (e.g., erythropoietin) and judicious transfusion is preferable and cost effective. Deferoxamine and other chelating agents are available, but the response