Blood transfusion

Question 1

How is blood prepared for transfusion

Answer 1

Whole blood is filtered before processing to remove white cells – this is called leucodepletion. After leucodepletion blood is centrifuged and separated into 3 components: RBC, platelet and plasma

Question 2

Plasma is processed to make:

Answer 2

• Fresh frozen plasma – within 8 hours of separation
• Cryoprecipitate

Fractionated to form:

• Factor concentrates (FVIII, FIX, prothrombin complex)
• Albumin
• Immunoglobulins

Question 3

RBCs

Answer 3

• normal: male = 130-180 g/L, female = 115-165 g/L
• Usual transfusion time = 1.5-3 hrs
• Volume of 1 unit = 280ml +/- 60
• Haematocrit = 60 %
• 1 unit expected to raise Hb by 10g/L

Question 4

Indications/ contra - RBC transfusion

Answer 4

• Indications – significant bleeding; acute anaemia; chronic anaemia
• Contra-indications - avoided in patients with chronic anaemia due to iron or vitamin deficiencies

Question 5

Platelets

Answer 5

• normal = 150 - 450 x 109/L
• 250-350 ml. Usual transfusion time = 30 mins
• risk of contamination by bacteria from donor’s arm

Question 6

How are platelets collected

Answer 6

• Pooled platelets – 1 unit from unit of blood; 4-6 donors’ blood are pooled together in a single pack
• Apheresis platelets - blood cycled through apheresis machine, platelets are removed. The amount of platelets collected with this procedure = 4-6 units of random donor. Single donor reduces risk of disease transmission - 4-6 donations = single apheresis donation

Question 7

Indications/ contra - Platelet transfusion

Answer 7

• Indications - used to prevent and treat bleeding in patients with thrombocytopaenia or platelet dysfunction
• Contra-indications:
  o Immune thrombocytopenic purpura
  o Thrombocytic thrombocytopenic purpura
  o Heparin-induced thrombocytopenia and thrombosis

Question 8

Fresh Frozen Plasma (FFP)

Answer 8

• Stored at -30oC for up to 36 months.
• Contains all clotting factors at physiological levels
• Therapeutic dose = 12-15 Ml/kg
• Thawed 20-30 mins before use

Question 9

Indications/ contra - FFP transfusion

Answer 9

• Indications - significant bleeding in patients with abnormal clotting results and to correct abnormal clotting results prior to invasive procedures
• Contra-indications - single factor deficiencies, to reverse warfarin

Question 10

Prothrombin complex concentrate (aka Factor IX Complex)

Answer 10

• Contains high concentration of vitamin K dependent factors (II (prothrombin), IX, VII and X)
• Indications - reversal of warfarin

Question 11

Cryoprecipitate

Answer 11

• Stored at -30oC for up to 3 years. One dose has 6-10 units.
• Extracted from FFP - contains fibrinogen (F I), von Willebrand, F VIII, F XIII
• Indications - source of fibrinogen in acquired coagulopathies

Question 12

Risks of transfusions

Answer 12

Acute reactions:

• Anaphylactic reaction
• TRALI = transfusion-related acute lung injury
• TACO = transfusion associated circulatory overload
• FNHTR = febrile non-haemolytic transfusion reaction
• Anaphylaxis

Question 13

FNHTR (Febrile Non-Haemolytic Transfusion Reactions)

Answer 13

• most common reaction to transfusion
• temperature increase of >1oC from baseline
• Resolves after discontinuation of transfusion
• due to cytokines or other biologically active molecules that accumulate during storage of blood components

Question 14

TACO - transfusion-associated circulatory overload

Answer 14

• Acute left ventricular failure with pulmonary oedema
• Onset up to 24h after transfusion
• Most common cause of transfusion related deaths
• Signs and symptoms: sudden dyspnoea, orthopnoea

Question 15

Transfusion of bacterial contaminated components

Answer 15

• Onset within first 15 mins
• Fatal 35% of the time
• Confirm by blood cultures from patient and blood bag
• Signs and symptoms: rigors, high fever, severe chills
• Contamination may come from donor’s skin, environment or unrecognised bacteraemia

Question 16

Acute haemolytic reaction due to incompatible transfusion – ABO mismatch

Answer 16

• most often ABO incompatibility
• Free Hb is released from transfused cells and goes into circulation and causes oxidative damage
• severe may occur within first 15 mins
• Fatal 20-30% of the time
• Back pain is indicator
• Fever, chills, DIC, sense of impending death

Question 17

Pre-transfusion testing on patients

Answer 17

• can prevent ABO mismatch with “group and screen”
• Determination of ABO and Rh(D) group
• Donor red cells of the correct ABO and Rh group and antigen negative for the antibodies detected in screen are selected from blood bank
• Mixed with sample of patient’s plasma to see if there is agglutination (reaction)

Question 18

Delayed haemolytic reaction

Answer 18

• Formation of new immune IgG antibodies against RBC antigens other than ABO
• Onset 3-14 days following transfusion of RBCs
• fatigue, jaundice, +/- fever
• Lab findings: anaemia, increased LDH, increased indirect bilirubin

Question 19

Direct Anti-globulin Test (DAT) to detect antibodies bound on RBCs

Answer 19

• Coomb’s Test
• Red cells coated with IgG antibody
• Anti-human globulin reagent added
• Visible agglutination

Question 20

Allergic reactions - anaphylaxis

Answer 20

• onset soon after transfusion; happens 1: 20-40000
• Signs and symptoms: laryngeal oedema, bronchospasm, hypotension, swelling
• Patients with IgA deficiency and anti-IgA antibodies at higher risk

Question 21

TRALI = transfusion-related acute lung injury

Answer 21

• Due to antibodies against leucocytes causing leaky pulmonary capillaries
• Criteria for diagnosis: hypoxaemia, new bilateral CXR infiltrates, no evidence of volume overload
• Sudden onset of acute lung injury occurs within 6 hours of transfusion
• complicates transfusion of plasma rich components