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Clinical Pathology > Blood transfusion > Flashcards

Blood transfusion Flashcards

1
Q

What components are extracted from whole blood?

A
  • RBCs
  • Platelets
  • Plasma
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2
Q

What is the transfusion threshold (trigger)?

A

Lowest concentration of Hb that is not associated with symptoms of anaemia.

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3
Q

What are the mechanisms of adaptation to anaemia?

A
  • Increased cardiac output
  • Increased cardiac artery blood flow
  • Increased oxygen extraction
  • Increase of red blood cell 2,3 DPG (diphosphoglycerate)
  • Increase production of EPO
  • Increase erythropoiesis
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4
Q

What parameters does tissue oxygenation depend upon?

A
  • The concentration of Hb
  • The O2 saturation of Hb
  • The oxygen tension in the tissues
  • The affinity of Hb to O2
  • The O2 requirements of tissues
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5
Q

What might impair the adaptation mechanisms to anaemia?

A
  • Underlying conditions that affect the cardiac output, the arterial blood flow, O2 saturation of Hb
  • e.g. cardiovascular diseases, respiratory diseases
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6
Q

Why would you transfuse RBCs?

A

To restore oxygen carrying capacity

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7
Q

What are the triggers for RBC transfusion?

A
  • ≤70 g/L for patients with mild symptoms of anaemia

- ≤80 g/L for patients with cardiovascular disease

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8
Q

What are the alternatives to RBC transfusion?

A

Correction of treatable causes of anaemia

  • Iron deficiency
  • B12 and folate deficiency
  • Erythropoietin treatment for patients with renal disease

Correction of coagulopathy

  • Discontinuation of antiplatelet agents
  • Administration of anti-fibrinolytic agaents
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9
Q

According to BCSH guidlines, what percentage reduction in blood volume warrants a blood transfusion in acute anaemia due to haemorrhage?

A

30-40% (1.5-2.0l) - probably necessary

>40% (>2.0l) - necessary

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10
Q

What is the transfusion threshold for patients with chronic anaemia due to myeloid failure syndromes?

A

Hb 80-100g/dl

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11
Q

What are the aims of transfusion in patients with chronic anaemia due to myeloid failure syndromes?

A
  • Symptomatic relief of anaemia
  • Improvement of Quality of Life
  • Prevention of ischemic organ damage
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12
Q

What must be taken into account when transfusing patients with chronic anaemia due to myeloid failure syndromes?

A
  • co-morbidities that affect cardiac, respiratory function
  • iron overload
  • adaptation to anaemia
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13
Q

What is the aim of transfusing patients with chronic anaemia due to thalassaemia?

A

Suppression of endogenous erythropoiesis

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14
Q

What are the threshold and target ranges for patients with chronic anaemia due to thalassaemia?

A

Threshold 90-95, target 100-120g/L

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15
Q

What has to be taken into consideration when transfusing patients with chronic anaemia due to thalassaemia?

A

Iron overload (haemochromatosis)

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16
Q

What medication can be taken to ameliorate haemochromatosis?

A

Iron chelation

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17
Q

What is the adult therapeutic dose of platelets?

A

Platelets from 4 pooled donations

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18
Q

Why would you transfuse platelets?

A
  • Treatment of bleeding due to severe thrombocytopenia (low platelets) or platelet dysfunction
  • Prevention of bleeding
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19
Q

What are the clinical indications for platelet transfusion?

A

Massive haemorrhage
- Keep platelet count above 75 x 109/l

Bone marrow failure
- platelet count

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20
Q

What are the contraindications for platelet transfusion?

A
  • Heparin induced thrombocytopenia

- Thrombosis thrombotic thrombocytopenic purpura

21
Q

What is fresh frozen plasma?

A
  • Stored at –300C for up to 24 months
  • Thawed immediately before use (takes 20-30 min)
  • Usual dose 12-15 mL/kg (4-6 units for average adult)
22
Q

Why would you transfuse fresh frozen plasma?

A
  • coagulopathy with bleeding/surgery,
  • massive haemorrhage
  • thrombotic thrombocytopenic purpura
23
Q

When would you not transfuse fresh frozen plasma?

A
  • warfarin reversal.

- replacement of single factor deficiency

24
Q

Why are large volumes of fresh frozen plasma required for treatment?

A

Contains clotting factors in same concentration as donor blood.

25
Q

What is the optimal treatment available to treat life-threatening bleeding in patients on warfarin?

A

Prothrombin complex concentrate

26
Q

What is a ‘group and save’ test?

A
  • Determination of ABO and Rh(D) group

- Patient’s plasma “screened” for antibodies against other clinically significant blood group antigens.

27
Q

What is ‘crossmatching’?

A
  • Donor red cells of the correct ABO and Rh group are selected from blood bank
  • “Crossmatching” : Patients plasma is mixed with aliquots of donor red cells to see if a reaction (agglutination or haemolysis) occurs
  • Final test before transfusion to check for patient Ab that could react with the transfusion
28
Q

What are the acute transfusion reactions?

A

Immunological

  • Acute haemolytic transfusion reaction (ABO incompatibility)
  • Allergic /anaphylactic reaction
  • TRALI (Transfusion-related acute lung injury)

Non immunological

  • Bacterial contamination
  • TACO (transfusion associated circulatory overload)
  • Febrile non-haemolytic transfusion reaction
29
Q

What are the delayed transfusion reactions?

A

Immunological

  • Transfusion-associated graft-versus-host disease (TA-GvHD)
  • Post transfusion purpura

Non immunological
- Transfusion Transmitted Infection (TTI) –viral/prion

30
Q

When do delayed transfusion reactions occur?

A

> 24 hours of transfusion

31
Q

What are the infective risks of blood transfusion?

A

Hepatitis B - 1.5 in 1 million
HIV - 1 in 6 million
Hepatitis C - 1 in 30 million

32
Q

What occurs in the case of an acute haemolytic reaction-ABO incompatibility?

A
  • Release of free Hb
  • Deposition of Hb in the distal renal tubule results in acute renal failure.
  • Stimulation of coagulation results in microvascular thrombosis
  • Stimulation of cytokine storm
  • Scavenges NO resulting in generalized vasoconstriction
33
Q

How common are acute haemolytic reactions due to ABO incompatibility?

A

1 in 25,000

34
Q

What are the signs and symptoms of acute haemolysis due to ABO incompatibility?

A
  • Fever and chills
  • Back pain
  • Infusion pain
  • Hypotension /shock
  • Hemoglobinuria (may be the first sign in anesthetized patients)
  • Increased bleeding (DIC)
  • Chest pain
  • Sense of “impending death”
35
Q

What is a delayed haemolytic reaction?

A
  • Due to immune IgG antibodies against RBC antigens other than ABO
  • The antibodies are formed after the transfusion
  • Onset 3-14 days following transfusion
36
Q

What are the clinical features of a delayed haemolytic reaction?

A
  • fatigue,
  • jaundice,
  • and/or fever
37
Q

What are the laboratory findings in in a delayed haemolytic reaction?

A
  • Drop in Hb
  • Increased LDH
  • Increased indirect bilirubin
38
Q

What does the Coomb’s test detect?

A

IgG Ab on red cells - e.g. anti-Rh in a Rh +ve patient

39
Q

What is transfusion-related acute lung injury (TRALI)?

A
  • Serious complication of transfusion
  • Estimated rate of fatalities is 5 – 10%
  • Donor has antibodies to recipient’s leucocytes
  • Almost always complicates transfusion of plasma rich components (platelets, FFP)
40
Q

What is the criteria for diagnosis of TRALI?

A
  • Sudden onset of “Acute Lung Injury” occurring within 6 hours of a transfusion
  • Acute Lung Injury (Hypoxemia, New bilateral chest X-ray infiltrates, No evidence of volume overload)
41
Q

What is the treatment for TRALI?

A
  • Supportive
  • Mild - O2 therapy
  • Severe - mechanical ventilation and ICU
42
Q

What laboratory investigations are required in the case of TRALI?

A
  • Donor is tested for HLA and granulocyte antibodies.

- The recipient is tested for expression of neutrophil antigens:

43
Q

How is a diagnosis of TRALI confirmed?

A

Donor has antibodies against antigens that are expressed on recipient’s granulocytes.

44
Q

What is the presentation of transfusion-associated circulatory overload (TACO)?

A

Signs

  • sudden dyspnea
  • orthopnoea
  • tachycardia
  • hypertension
  • hypoxemia

Signs

  • Raised BP
  • elevated jugular venous pulse
45
Q

What are the risk factors for TACO?

A
  • elderly patients
  • small children
  • patients with compromised left ventricular function
  • increased volume of transfusion
  • increased rate of transfusion
46
Q

What is the aetiology of febrile non-haemolytic transfusion reactions?

A

Due to cytokines or other biologically active molecules that accumulate during storage of blood components

47
Q

What are the signs/symptoms of febrile non-haemolytic transfusion reactions?

A
  • Fever
  • Shakes/rigors
  • Tachycardia
48
Q

What is the timeframe for acute transfusion reactions?

A

Clinical Pathology (65 decks)

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