Blood transfusion is a therapeutic procedure widely utilized across various clinical disciplines. It plays a critical role in improving patient conditions, enhancing treatment efficacy, and reducing mortality rates.
Types of Blood Transfusions
Classification Based on Blood Source
Blood transfusion can be categorized into autologous transfusion and allogeneic transfusion.
Autologous Transfusion
Autologous transfusion involves the reinfusion of a patient's own blood, which has been pre-collected or recovered from blood loss. There are three forms of autologous transfusion:
- Acute Normovolemic Hemodilution (ANH): To minimize surgical blood cell loss, a certain amount of blood is collected from the patient before surgery, while crystalloids and colloids are infused to maintain blood dilution. The collected blood is reinfused in the later stages of surgery.
- Predeposit Autologous Transfusion: The patient's blood is stored in advance for future use when needed.
- Intraoperative or Postoperative Blood Salvage: Blood lost during trauma, surgery, or the postoperative period is collected using blood salvage equipment and safely reinfused into the patient.
Indications for Autologous Transfusion:
- Patients scheduled for elective surgery requiring predictable transfusion needs without preoperative anemia.
- Pregnant women needing to avoid allogeneic transfusion during delivery.
- Patients with a history of severe reactions to allogeneic transfusion.
- Individuals with rare blood types or those who have experienced difficulty in blood crossmatching.
- Individuals in remote areas with limited blood supply who may require transfusions.
- Healthy individuals storing autologous blood for emergency use.
Contraindications for Autologous Transfusion:
- Patients suspected of having sepsis or receiving antibiotic therapy.
- Patients with abnormal liver or kidney function.
- Patients suffering from severe heart or lung diseases.
- Anemic, actively bleeding, or hypotensive patients.
- Patients who experienced syncope or loss of consciousness within 12 hours post-donation.
- Patients for whom blood collection might trigger or exacerbate their own underlying diseases.
Advantages of Autologous Transfusion:
- Avoidance of transfusion-transmitted infections.
- Prevention of alloimmune reactions and potential errors associated with allogeneic transfusion.
- Conservation of blood supplies, helping to ease the demand-supply imbalance.
Allogeneic Transfusion
Allogeneic transfusion refers to the infusion of blood or blood components from donors, with matching blood types, into the patient. This is typically referred to as "blood transfusion" in general practice. The subsequent sections of this chapter mainly focus on allogeneic transfusion, as it is widely applicable to various clinical scenarios requiring blood transfusion.
Classification Based on Blood Components
Blood transfusion can be divided into whole blood transfusion or component transfusion.
Whole Blood Transfusion
Whole blood transfusion refers to the infusion of a fixed quantity of blood containing all components, either from autologous or allogeneic sources. Whole blood products include fresh blood and stored blood. This approach aims to replenish red blood cells and plasma for the patient. However, stored whole blood contains minimal or negligible platelets and granulocytes due to degradation over time, and certain coagulation factors may also diminish. Given considerations of efficacy and blood conservation, whole blood transfusion is not generally advocated as a routine practice.
Component Blood Transfusion
Component transfusion refers to the isolation or apheresis of specific blood components from suitable donors, delivered for targeted therapeutic purposes. Component blood products include red blood cells (such as packed red blood cells, washed red blood cells, frozen red blood cells, or red cell suspensions), platelets, concentrated granulocyte suspensions, plasma, cryoprecipitate, and various plasma derivatives (e.g., albumin, globulin, fibrinogen, Factor VIII, prothrombin complex). The approach prioritizes high therapeutic specificity, efficacy, and blood conservation, marking the future direction of transfusion medicine development.
Classification Based on Transfusion Methods
Transfusion may adopt unconventional methods to address specific clinical needs, such as pressurized transfusion, oxygenated transfusion, or exchange transfusion.
Pressurized Transfusion
Pressurized transfusion aims to address acute severe bleeding by rapidly infusing blood using physical methods, such as gentle compression of the blood bag, elevating the bag to increase vertical distance, or applying syringe pressure.
Oxygenated Transfusion
Oxygenated transfusion provides red blood cells that have been externally oxygenated to improve hypoxia in patients with anemia complicated by acute respiratory distress syndrome. This process requires that oxygenation avoids contamination or damage to the red blood cells prior to intravenous administration.
Exchange Transfusion
Exchange transfusion is indicated when abnormal substances (e.g., anticoagulants, hemolysins, bilirubin, M proteins, exogenous toxins) in the plasma exceed the patient’s physiological elimination capacity. Plasma exchange can involve the removal of 2,000–3,000 mL of the patient’s plasma (in adults) using apheresis equipment, with simultaneous replacement using normal donor plasma (or potentially one-fourth the volume in crystalloid solution). Plasma exchange is often performed daily over consecutive days and is the preferred approach for conditions such as thrombotic thrombocytopenic purpura (TTP) or hemolytic uremic syndrome (HUS). Neonatal hemolysis may also warrant exchange transfusion treatment.
Conventional Transfusion
Conventional transfusion, by contrast, includes transfusion of blood or blood components via standard methods without pressurization, oxygenation, or exchange.
Indications for Blood Transfusion
Blood transfusion serves different therapeutic purposes depending on the specific treatment goals, leading to various indications.
Replacement Therapy
This constitutes the earliest and most common clinical use of blood transfusion. Indications include primary or secondary deficiencies in blood components (both cellular and plasma elements), such as various types of anemia, thrombocytopenia, coagulation factor deficiencies (e.g., hemophilia), hypoalbuminemia, hypotransferrinemia, and hypogammaglobulinemia. When these components decrease beyond a critical threshold, the body cannot compensate, leading to impaired organ function or even life-threatening conditions. In such cases, a “replacement” blood transfusion is employed to replenish the missing components as per the principle of "replacing what is deficient."
Immunotherapy
Since the 1980s, it has been recognized that immune-mediated conditions associated with antibody-induced tissue damage—such as primary immune thrombocytopenia, autoimmune hemolytic anemia, and immune-related pancytopenia—can benefit from intravenous immunoglobulin therapy.
Additionally, leukemia patients undergoing allogeneic hematopoietic stem cell transplantation may receive donor lymphocyte infusions (DLI) at regular intervals, which facilitate the donor lymphocytes in targeting and eliminating residual recipient leukemia cells.
Exchange Therapy
When an excess of specific blood components (e.g., M protein, bilirubin, or urea nitrogen) or the presence of abnormal substances (e.g., hemolysins, toxins) disrupts homeostasis and poses a life-threatening risk, exchange transfusion therapy is applied. This involves the simultaneous removal of abnormal or excess components while infusing replacement components. Such therapy is a temporary, symptomatic intervention designed to address urgent needs but should be combined with etiological treatments for improved outcomes.
Transplantation Therapy
Broadly defined, recipients of hematopoietic stem cell transplantation (stemming from allogeneic or autologous sources such as bone marrow or peripheral blood) are essentially undergoing a “component transfusion” under special conditions after completing preparative regimens such as chemotherapy and/or radiotherapy.
Adverse Reactions to Blood Transfusion
Adverse reactions to blood transfusion refer to new abnormal manifestations or diseases arising in a recipient during or after transfusion, with these reactions broadly classified into hemolytic and non-hemolytic categories.
Hemolytic Reactions
Hemolytic reactions occur when transfused red blood cells or the recipient's own red blood cells are excessively destroyed during or after transfusion. These reactions account for only 0.1% of all transfusion reactions; however, when they occur, they carry high mortality rates. Hemolytic reactions can be classified as acute or chronic. Pre-transfusion screening for irregular antibodies (those other than anti-A, anti-B, or anti-AB, such as antibodies from the Rh or P blood group systems) significantly reduces the incidence of hemolysis.
Acute Hemolytic Reaction
Acute hemolysis occurs within minutes to hours during or after transfusion. Symptoms may include high fever, chills, palpitations, shortness of breath, back or lumbar pain, hemoglobinuria, or even anuria, as well as signs of acute renal failure and disseminated intravascular coagulation (DIC). Severe reactions can result in death. Laboratory findings indicate intravascular hemolysis. Causes of this type of hemolysis include the following:
- Blood type incompatibility between donor and recipient (e.g., ABO or Rh mismatches, or mismatches among rare subtypes).
- Improper blood storage, transportation, or handling.
- Presence of hemolytic diseases in the recipient.
Management includes prompt and comprehensive measures, such as termination of the transfusion, administration of high-dose corticosteroids, urine alkalization, diuresis, maintenance of blood volume and electrolyte balance, correction of hypotension, and prevention of renal failure and DIC. In some cases, dialysis, plasma exchange, or exchange transfusion may be necessary.
Chronic Hemolytic Reaction
Also known as delayed hemolytic transfusion reaction, this type typically presents several days after transfusion with symptoms such as jaundice and an increase in reticulocyte count. It commonly occurs in cases of rare blood type incompatibility or when a first transfusion induces sensitization and production of alloantibodies, which subsequently lead to alloimmune hemolysis during subsequent transfusions from the same donor. Management is generally similar to that for acute hemolytic reactions.
Non-Hemolytic Adverse Reactions
Fever
Non-hemolytic febrile reactions are the most common type of transfusion reactions, with an incidence exceeding 40%. These reactions are characterized by fever and rigors during transfusion. Temporarily interrupting the transfusion is effective, with antipyretic analgesics or corticosteroids often resolving symptoms. The causes include:
- Pyrogens present in the blood products, which may include drugs, various organic or inorganic impurities, bacterial or viral pyrogens, or endogenous pyrogens released from leukocyte lysis during the recipient's immune response.
- The formation of alloantibodies against leukocytes and/or platelets after repeated transfusions.
Prevention commonly involves filtering transfused blood to remove pyrogens, leukocytes, and their fragments. The use of leukocyte reduction filters significantly reduces the incidence of non-hemolytic febrile reactions.
Allergic Reactions
During or after transfusion, recipients may experience symptoms such as urticaria or angioedema. Severe cases may involve generalized rash, laryngeal edema, bronchospasm, or even anaphylactic shock. Causes for allergic reactions include IgA alloimmunization, hypersensitivity to foreign antigens, and differences in the antigenicity of IgG heavy chains among individuals. Some cases of allergic reactions are observed in individuals with congenital IgA deficiency. Management typically involves slowing or stopping the transfusion, implementing antiallergic treatment, using antispasmodic therapy for bronchospasm, performing a tracheotomy in cases of severe respiratory distress caused by laryngeal edema, and administering anti-shock treatment for circulatory failure.
Transmission of Infectious Diseases
Transfusion-transmitted infections include various types of viral hepatitis, acquired immunodeficiency syndrome (AIDS), cytomegalovirus infection, syphilis, malaria, and infections from other potential pathogens in contaminated blood. Preventative measures focus on ensuring the qualification of blood donors and maintaining aseptic conditions during blood collection, storage, transportation, quality inspection, and transfusion.
Transfusion-Related Acute Lung Injury (TRALI)
TRALI is a severe adverse reaction caused by human leukocyte antigen (HLA) antibodies or neutrophil-specific antibodies in donor plasma, leading to the aggregation and activation of neutrophils in the recipient's pulmonary vasculature. This results in damage to pulmonary capillary endothelium and interstitial pulmonary edema. TRALI has a high mortality rate. Symptom management and supportive treatment are critical, with corticosteroids administered at the earliest possible stage. Close monitoring of vital signs is essential for these patients.
Platelet Transfusion Refractoriness (PTR)
PTR not only increases transfusion costs but also diminishes the efficacy of platelet transfusion, directly impacting patient health. The causes of PTR are diverse: factors such as the frequency and volume of transfusions, organ transplantation, and pregnancy can stimulate the production of platelet antibodies, leading to PTR. Repeated transfusions are the primary cause of this condition. Patients positive for platelet antibodies are more prone to PTR. Detection of platelet antibodies in patients undergoing repeated transfusions is crucial for guiding subsequent matched transfusions.
Other Reactions
These include transfusion-associated circulatory overload (TACO) and transfusion-related dyspnea. Repeated transfusions or red blood cell infusions can result in iron overload in recipients. Repeated allogeneic transfusions can lead to the production of alloantibodies against blood cells (e.g., platelets, leukocytes), resulting in ineffective transfusions, fever, allergic reactions, or even hemolytic reactions. Transfusion of fresh whole blood rich in leukocytes may cause transfusion-associated graft-versus-host disease (TA-GVHD). Large volumes of citrated (anticoagulated) blood or plasma transfusions may chelate free calcium in the recipient's plasma, exacerbating bleeding if calcium supplementation is inadequate. Large-volume transfusions of stored blood may also result in acid-base imbalances, citrate toxicity, or hyperkalemia, which require attention.