Page 369 - Concise Pathology for Exam Preparation ( PDFDrive )

354 SECTION II Diseases of Organ Systems

Blood Storage

• Plasma potassium, ammonia and phosphate increase during storage while RBC
2,3-bisphosphoglycerate (BPG) and plasma pH decrease during storage.
• The basic purpose of efficient blood storage is to increase the shelf life of preserved
blood and to maintain high intra-erythrocyte BPG levels for the optimal oxygen ex-
change with tissue.
• CPDA (citrate–phosphate–dextrose–adenine) preserves cells for 35 days owing to the
action of citrate as an anticoagulant, phosphate and adenine as substrates for ATP syn-
thesis and dextrose as the source of anaerobic glycolysis in RBCs.

Crossmatch
The standard pretransfusion tests on the recipient consist of ABO group and Rh typing,
an antibody screen for atypical antibodies (indirect Coombs test), a direct Coombs test (to
identify IgG antibodies on RBCs) and a major crossmatch. The major crossmatch is ac-
complished in a test tube by mixing a sample of the recipient’s serum with a sample of
RBCs from the donor unit. The purpose of this crossmatch is to detect atypical (not natu-
rally occurring) antibodies present in the recipient’s serum that may be directed against
foreign antigens on the RBCs in the donor unit.

Q. Write briefly on blood component therapy.
Ans. Different types of blood components:
• Packed RBCs are useful in the treatment of anaemia, since they have less volume and
a higher haematocrit than whole blood. Each unit of packed RBCs should raise the Hb
by 1 g/dL and the haematocrit by 3%.
• Platelet transfusions are generally indicated when patients have a platelet count
, 50,000 cells/µL and have clinical evidence of bleeding or are candidates for a surgical
or invasive procedure. Each unit of platelets infused should raise the platelet count by
5000–10,000 cells/µL.
• Granulocyte transfusions are reserved for patients who have severe sepsis associated
with an absolute neutropenia , 500 cells/µL that has not responded appropriately to
antibiotics within 48 h.
• Fresh-frozen plasma (FFP) contains all the coagulation factors and is the component
of choice in bleeding associated with multiple factor deficiencies as seen in severe liver
disease, Warfarin overdose and disseminated intravascular coagulation.
• Cryoprecipitate contains Factor VIII, fibrinogen, Factor XIII and fibronectin and is the
component of choice in the treatment of mild von Willebrand disease and fibrinogen
deficiency.
• Factor VIII concentrates are primarily used in the treatment of haemophilia A.
• Albumin, plasma protein fraction (PPF), crystalloid solutions, (eg, normal saline,
Ringer lactate containing sodium, chloride, potassium, calcium and lactate) and colloid
substitutes, eg, dextran and hydroxyethyl starch are utilized as volume expanders.
• Immune serum globulin is useful in the treatment of hypogammaglobulinaemia.

Q. What are transfusion reactions?
Ans. Transfusion reactions include

Immediate Reactions

• Febrile reactions: The most common early reactions and are due to the cytokines (IL1,
IL6, IL8 and TNF) produced by leukocytes during storage. Characterized by fever, chills
and headache, febrile reactions can be reduced in frequency by depletion of leukocytes.
• Allergic reactions: Flushing, urticaria, fever, tachycardia, wheezing, dyspnoea and cya-
nosis are secondary to antibodies directed against plasma proteins in the donor unit
including IgA (Type I hypersensitivity reaction).

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