USMLE Guide: Transfusion Medicine

Introduction

Transfusion Medicine is a branch of medicine that focuses on the safe and effective use of blood and blood products. It involves the collection, testing, processing, storage, and administration of blood components to patients. This guide aims to provide an overview of important concepts related to Transfusion Medicine for the United States Medical Licensing Examination (USMLE).

Blood Components

Blood can be separated into various components, each with specific functions and indications for transfusion:

1. Red Blood Cells (RBCs):

   • Indications: Anemia, acute blood loss, chronic transfusion support.
   • Testing: Blood type, compatibility testing, infectious disease screening.
   • Storage: Typically stored at 1-6°C for up to 42 days.
   • Administration: Transfused through a filter with normal saline or RBC-specific additive solutions.

2. Platelets:

   • Indications: Thrombocytopenia, platelet dysfunction, bleeding disorders.
   • Testing: Compatibility testing, infectious disease screening.
   • Storage: Stored at room temperature with constant agitation for up to 5-7 days.
   • Administration: Transfused through a filter with normal saline or platelet-specific additive solutions.

3. Fresh Frozen Plasma (FFP):

   • Indications: Coagulation factor deficiency, bleeding due to multiple coagulation factor deficiencies, plasma exchange.
   • Testing: Compatibility testing, infectious disease screening.
   • Storage: Stored at -18°C or colder for up to 1 year.
   • Administration: Thawed before transfusion, typically using a water bath.

4. Cryoprecipitate:

   • Indications: Fibrinogen deficiency, von Willebrand disease, factor XIII deficiency.
   • Testing: Compatibility testing, infectious disease screening.
   • Storage: Stored at -18°C or colder for up to 1 year.
   • Administration: Thawed before transfusion, typically using a water bath.

Transfusion Reactions

During blood transfusions, various adverse reactions can occur. It is important to recognize and manage them promptly:

1. Acute Hemolytic Transfusion Reaction (AHTR):

   • Presentation: Fever, chills, flank pain, hemoglobinuria, hypotension.
   • Cause: ABO incompatibility.
   • Management: Stop the transfusion immediately, provide supportive care, and treat complications.

2. Febrile Non-Hemolytic Transfusion Reaction (FNHTR):

   • Presentation: Fever, chills, headache, flushing.
   • Cause: Patient antibodies reacting to donor leukocytes or platelets.
   • Management: Stop the transfusion, administer antipyretics, and consider leukocyte-reduced products in future transfusions.

3. Allergic Transfusion Reaction:

   • Presentation: Urticaria, pruritus, flushing, wheezing, hypotension.
   • Cause: Patient antibodies reacting to donor plasma proteins.
   • Management: Stop the transfusion, administer antihistamines, and provide supportive care.

4. Transfusion-Related Acute Lung Injury (TRALI):

   • Presentation: Acute respiratory distress, hypoxemia, pulmonary edema.
   • Cause: Donor anti-leukocyte antibodies interacting with recipient leukocytes.
   • Management: Supportive care, oxygen supplementation, and potentially mechanical ventilation.

Blood Transfusion Safety

To ensure safe transfusions and prevent complications, several safety measures should be followed:

1. Proper Identification: Verify patient identity and match it with the blood product before transfusion.

2. Crossmatching: Perform ABO and Rh compatibility testing between recipient and donor blood.

3. Infectious Disease Screening: Screen donated blood for infectious diseases such as HIV, hepatitis B and C, syphilis, and others.

4. Transfusion Reactions: Monitor patients during transfusion for signs of adverse reactions.

5. Documentation: Accurately document the transfusion process, including patient details, blood product information, and any adverse events.

Conclusion

Transfusion Medicine plays a crucial role in patient care, requiring knowledge of blood components, indications for transfusion, potential adverse reactions, and safety measures. Understanding these concepts will be valuable for the USMLE and in clinical practice, ensuring safe and effective blood transfusions.