Flashcards in Blood transfusion Deck (48):
What components are extracted from whole blood?
What is the transfusion threshold (trigger)?
Lowest concentration of Hb that is not associated with symptoms of anaemia.
What are the mechanisms of adaptation to anaemia?
- 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
What parameters does tissue oxygenation depend upon?
- 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
What might impair the adaptation mechanisms to anaemia?
- Underlying conditions that affect the cardiac output, the arterial blood flow, O2 saturation of Hb
- e.g. cardiovascular diseases, respiratory diseases
Why would you transfuse RBCs?
To restore oxygen carrying capacity
What are the triggers for RBC transfusion?
- ≤70 g/L for patients with mild symptoms of anaemia
- ≤80 g/L for patients with cardiovascular disease
What are the alternatives to RBC transfusion?
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
According to BCSH guidlines, what percentage reduction in blood volume warrants a blood transfusion in acute anaemia due to haemorrhage?
30-40% (1.5-2.0l) - probably necessary
>40% (>2.0l) - necessary
What is the transfusion threshold for patients with chronic anaemia due to myeloid failure syndromes?
What are the aims of transfusion in patients with chronic anaemia due to myeloid failure syndromes?
- Symptomatic relief of anaemia
- Improvement of Quality of Life
- Prevention of ischemic organ damage
What must be taken into account when transfusing patients with chronic anaemia due to myeloid failure syndromes?
- co-morbidities that affect cardiac, respiratory function
- iron overload
- adaptation to anaemia
What is the aim of transfusing patients with chronic anaemia due to thalassaemia?
Suppression of endogenous erythropoiesis
What are the threshold and target ranges for patients with chronic anaemia due to thalassaemia?
Threshold 90-95, target 100-120g/L
What has to be taken into consideration when transfusing patients with chronic anaemia due to thalassaemia?
Iron overload (haemochromatosis)
What medication can be taken to ameliorate haemochromatosis?
What is the adult therapeutic dose of platelets?
Platelets from 4 pooled donations
Why would you transfuse platelets?
- Treatment of bleeding due to severe thrombocytopenia (low platelets) or platelet dysfunction
- Prevention of bleeding
What are the clinical indications for platelet transfusion?
- Keep platelet count above 75 x 109/l
Bone marrow failure
- platelet count
What are the contraindications for platelet transfusion?
- Heparin induced thrombocytopenia
- Thrombosis thrombotic thrombocytopenic purpura
What is fresh frozen plasma?
- 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)
Why would you transfuse fresh frozen plasma?
- coagulopathy with bleeding/surgery,
- massive haemorrhage
- thrombotic thrombocytopenic purpura
When would you not transfuse fresh frozen plasma?
- warfarin reversal.
- replacement of single factor deficiency
Why are large volumes of fresh frozen plasma required for treatment?
Contains clotting factors in same concentration as donor blood.
What is the optimal treatment available to treat life-threatening bleeding in patients on warfarin?
Prothrombin complex concentrate
What is a 'group and save' test?
- Determination of ABO and Rh(D) group
- Patient’s plasma “screened” for antibodies against other clinically significant blood group antigens.
What is 'crossmatching'?
- 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
What are the acute transfusion reactions?
- Acute haemolytic transfusion reaction (ABO incompatibility)
- Allergic /anaphylactic reaction
- TRALI (Transfusion-related acute lung injury)
- Bacterial contamination
- TACO (transfusion associated circulatory overload)
- Febrile non-haemolytic transfusion reaction
What are the delayed transfusion reactions?
- Transfusion-associated graft-versus-host disease (TA-GvHD)
- Post transfusion purpura
- Transfusion Transmitted Infection (TTI) –viral/prion
When do delayed transfusion reactions occur?
>24 hours of transfusion
What are the infective risks of blood transfusion?
Hepatitis B - 1.5 in 1 million
HIV - 1 in 6 million
Hepatitis C - 1 in 30 million
What occurs in the case of an acute haemolytic reaction-ABO incompatibility?
- 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
How common are acute haemolytic reactions due to ABO incompatibility?
1 in 25,000
What are the signs and symptoms of acute haemolysis due to ABO incompatibility?
- 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”
What is a delayed haemolytic reaction?
- Due to immune IgG antibodies against RBC antigens other than ABO
- The antibodies are formed after the transfusion
- Onset 3-14 days following transfusion
What are the clinical features of a delayed haemolytic reaction?
- and/or fever
What are the laboratory findings in in a delayed haemolytic reaction?
- Drop in Hb
- Increased LDH
- Increased indirect bilirubin
What does the Coomb's test detect?
IgG Ab on red cells - e.g. anti-Rh in a Rh +ve patient
What is transfusion-related acute lung injury (TRALI)?
- 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)
What is the criteria for diagnosis of TRALI?
- 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)
What is the treatment for TRALI?
- Mild - O2 therapy
- Severe - mechanical ventilation and ICU
What laboratory investigations are required in the case of TRALI?
- Donor is tested for HLA and granulocyte antibodies.
- The recipient is tested for expression of neutrophil antigens:
How is a diagnosis of TRALI confirmed?
Donor has antibodies against antigens that are expressed on recipient’s granulocytes.
What is the presentation of transfusion-associated circulatory overload (TACO)?
- sudden dyspnea
- Raised BP
- elevated jugular venous pulse
What are the risk factors for TACO?
- elderly patients
- small children
- patients with compromised left ventricular function
- increased volume of transfusion
- increased rate of transfusion
What is the aetiology of febrile non-haemolytic transfusion reactions?
Due to cytokines or other biologically active molecules that accumulate during storage of blood components
What are the signs/symptoms of febrile non-haemolytic transfusion reactions?