Blood Products

Blood Products

Blood loss

·        Giving blood isn‟t based on how much they‟ve lost, but on Hb measurement and pre-existing cardiac/respiratory disease. A normal person could survive an Hb of 50 if volume was adequate (below this CO falls dramatically). But a sick, old person can‟t use ­CO to compensate, so CO starts to drop below 100

Blood Component Therapy

·        Modern transfusion therapy is blood component therapy

·        Blood components are used to:

o   Correct intravascular volume (usually non-human products e.g. crystalloids)

o   Correct O2 transport deficiency

o   Correct bleeding disorders

·        Blood components available: 

o   Red cells: one unit is the red cells from one unit of donated blood (450 ml). Hb increases by 10 g/L per unit transfused. Red cell transfusions – transfuse at 1 unit per 2 – 4 hours (if cardiovascularly healthy then 2 hours, if older then 4 hours as you don‟t‟ want to go too fast otherwise volume overload) 

o  Platelet concentrates: Prophylactic platelet transfusions – 10 g/L pretty good maintenance level in leukaemia.

o  Fresh frozen plasma:  250 ml will provide approx 8% of an adult‟s circulating clotting factors

o  Cryoprecipitate: source of fibrinogen for DIC

o  VIII & IX concentrates

o  To separate these: centrifuge – take off plasma first, then platelets, then RBCs

·        Decision sequence:

o  What factor is deficient? 

o  Is the deficiency physiologically significant (hard to decide. Not the same as below the normal range, as normal range includes functional reserve)

o  What is the appropriate blood product

o  What is the correct dose to transfuse

o  Has the transfusion worked?

·        When blood is required:

o  Type O immediately, type specific in 10 – 20 minutes and full X match in an hour 

o  If massive transfusion (> 50% loss) use reconstituted red cells and colloid and consult haematologist re fresh frozen plasma (FFP), platelets and coagulation factors

o  Tests for coagulation during large transfusions should include:

§  Full blood count: baseline Hb and platelet counts before transfusion, and repeated throughout

§  APPT: intrinsic pathway

§  PT/INR: extrinsic pathway

§  Thrombin time: fibrinogen availability

§  Fibrin degradation products: for DIC

·        Risks:

o  Most common reaction to transfusion: febrile ½ an hour later: 

§  Due to leukocytes contaminating red cells. If necessary, insert leucocyte filter on line (@$50) ® leucocyte poor red cells 

§  Febrile reaction more common if multiple blood transfusions or multiple children (more antigenically primed)

o  ABO incompatibility (eg due to incorrect labelling):

§  Hypotensive, rash, tachycardia 

§  Symptoms of major intravascular haemolysis: nausea, vomiting, low back pain (renal reaction to free haemoglobin), feeling very unwell 

o  If allergic to plasma proteins ® washed red cells 

o  For immunocompromised: use irradiated red cells to stop leucocytes grafting into host & then attacking host

o  Infection risks (depend on prevalence in population):

§  Bacteria:

·        Yersinia Enterocolitica: is cryophilic (likes cold) and blood is a great culture medium. Comes from transient bacteraemia in infected donor.

·        Other bacteria: Brucella abortus, salmonella, M. Leprae

§  Viruses: HBV, HCV, HIV, HTLV-1, CMV, EBV

§  Parasites: Malaria, Toxoplasma gondii, Trypanosome cruzi

§  Specific risks:

·        HIV infection via transfusion: 1 in 1 – 2 million

·        CJD: no documented case worldwide (although has been done in animals)

·        HBV: 1 in 200,000

·        HBC: 1 in 80,000

o  Complications of massive blood transfusion: 

§  Over transfusion ® Fluid overload and pulmonary oedema

§  Coagulation defects: dilutional thrombocytopaenia, ¯factors V, VII & X, DIC

§  Hypothermia (blood products are stored at 4 C)

§  Hyperkalaemia: K moves out of red cells in storage

§  Acidaemia: stored blood becomes acidotic with age 

§  Hypocalcaemia & citrate toxicity ® cardiac depression and alkalosis

§  Hypomagnesaemia

§  Transfusion haemosiderosis (ie iron overload) if on chronic transfusions (eg thalassaemia)

·        Management of major reaction (either anaphylaxis/haemolysis or sepsis)

o   If worried during the transfusion, stop it

o   Call blood bank for advice

o   Send back blood + samples from the patient

o   Check for errors

·        Strategies to stop transmission of infection:

o   Donor screening – very effective

o   Blood screening:

§  But tests not 100% accurate & window periods

§  Move from serologic tests to PCR for viral antigens