L31 Blood products and pretransufusion testing Flashcards
List 3 indications for the transfusion of whole blood/ red cells.
- Hb <7, transfuse according to the rate of ongoing blood loss
- Hb 7-10: consider Sx, comorbidities, and rate of blood loss
- Higher Hb: target in those who may tolerate anemia poorly, e.g. patients > 65y, patients with CV/respi disease
How many g/dL Hb increase would u expect with 1 standard unit of whole blood/red cell transfusion in 70kg adult?
- 2 g/dL Hb increase
* 4ml/kg = 1g/dL Hb in children
How many g/dL Hb increase would u expect with 1 small unit of whole blood/red cell transfusion in 70kg adult?
0.85 g/dL Hb increase
1 unit of apheresis platelets is equivalent to 1 unit of a standard adult dose.
Dosage of adult and children transfusion?
Adult: 4 random donor units
Children: 5 units/M^2 for (by total body surface area)
Indications of platelet transfusion? (5)
- Platelet <10 x 10^9/L in stable patients
(except ITP, SLE, TTP, HUS) - Platelet <20 in patients with fever or sepsis
- Platelet <50 with diffuse microvascular/ mucosal bleeding, major bleeding or before invasive procedures
- Platelet <50 in stable premature neonates
- Platelet <100 with retinal/ CNS bleeding/surgery, or with active bleeding in postcardiopulmonary bypass
What is the typical dosage for plasma/fresh frozen plasma (FFP) in adults and children?
- 2-4 units for adults
2. 12-15 ml/lg for paediatric patients
What are the indications for plasma transfusion? (5)
- TTP (thrombotic thrombocytopenic purpura)
- DIC
- Clotting factors deficiency
- Immediate reversal of warfarin OD (active bleeding/impending surgery)
- PT/APTT >1.5x control values with active bleeding or before the invasive procedure in
a) single/ multiple clotting factor deficiency other than hemophilia A/B
b) DIC
c) hepatic failure
Rather than reversal of warfarin OD by plasma transfusion, what are methods can be done which is of lesser risk of volume overload and is more preferred in the elderly?
Prothrombin complex concentrate (factor 9 complex)
The dosage of __________depends on target factor levels, usually ______ units per dose for adults.
Cryoprecipitate;
10 units/dose
How is cryoprecipitate prepared?
Prepared by thawing FFP (for 45mins - 1hour) and collecting the precipitate, which is then frozen.
Indications for cryoprecipitate transfusion? (3)
- von Willebrand disease (if desmopressin or factor concentrate is in appropriate
- Documented fibrinogen deficiency (<1g/dL) or dysfunction
- Documented factor 13 deficiency
Cryoprecipitate contains?
- vWF
- fibrinogen
- factor 8,13
- small volume prevents volume verload
Fresh whole blood is a special blood product which is indicated when?
- Exchange transfusion
2. Massive blood loss in neonates
What special blood product is given when there is neutropenia (<0.5) unresponsive to Abx (including antifungal) >48 hours?
Irradiated leucocytes
Which of the following are indications for leukodepleted (filtered) red cells?
A. All thalassemia patients on regular transfusion regimens
B. Hematological diseases
C. Documented severe febrile non-hemolytic transfusion reaction (> 2 episodes)
D. Paediatric oncology patients
E. Patients with HIV and are CMV-antibody +ve.
All except E!
should be CMV antibody -ve (for reducing CMV transmission transmission of patients who has never been exposed to CMV before)
Irradiated cellular blood components are for the prevention of ________________________ in the below circumstances:
- Fetuses requiring intrauterine transfusion
- Patients with severe congenital cerlular immunodeficiency
- HSCT patients
- Patients receiving transfusion from close relatvies.
transfusion-related graft versus host disease
____________ (proteins, glycoproteins or glycolipids_ are present on the surface of RBC.
Antigens
Give an example of each of the below causes of the difference in blood group antigens
A. Presence or absence of the whole molecule
B. Single amino acid difference
C. Single monosaccharide difference
A: RhD
B: Duffy Fya & Fyb
C: ABO
Blood group antibodies are developed due to the lack of a particular blood group antigen.
In which 2 ways are antibodies developed?
- Naturally occuring antibodies
e. g. Anti A and B - Immune (e.g. anti-D)
- in response to exposure to antigens by transfusion/ trans-placental passage e.g. in RhD- mother
How is whole blood transfusion done regarding the ABO compatibility of different blood products?
A. Only same blood group (e.g. O to O)
B. Red cells/ leukocytes only (contain ABO antigen) only
A: only the same blood group transfused (because contains both ABO antigen and antibodies)
B: Blood group O is a universal donor (because it has no antigens), otherwise A to A, B to B
How is whole blood transfusion done regarding the ABO compatibility of different blood products?
- FFP
- Platelet/cryoprecipitate
- as plasma contains ABO antibodies only, while AB blood group does not contain any, AB is a universal donor
- Contains very little plasma with no ABO antibodies, thus no restriction
______________ is the largest blood group system of 30 blood gropus, with 50 antigens encoded by RhD and RhCE genes.
Rhesus blood group system
Percentage of RhD+ and RhD-?
RhD+ 97.7%, RhD- 0.3%
What is Haemolytic disease of the newborn (HDN)? (3)
- Occurs in RhD- mother with RhD+ fetus
- any feto-maternal hemorrhage, e.g. during labor/prenatal bleed, sensitizes mother to produce anti-D IgM (cannot cross placenta)
- in subsequent pregnancies, a repeat encounter with the RhD antigen stimulates the rapid production of antiD IgG > cross the placenta and enter the fetal circulation and destroy the fetal RhD+ RBC
What are the clinical presentations for HDN (Haemolytic disease of the newborn)? (5)
- Anemia
- Cardiac hypertrophy
- Hepatosplenomegaly
- Hydrops fetalis
- Kernicterus (=accumulation of conjugated bilirubin in brain > irreversible brain damage)
What is hydrops fetalis?
- Abnormal accumulation of fluid >2 fetal compartments e.g. ascites, pleural effusion, skin edema
- ?pathophysiology, but related to hypoalbuminemia (liver shifts to erythropoiesis), increase capillary permeability (secondary to tissue hypoxia)
What is the treatment for HDN (Haemolytic disease of the newborn) (2)
- Phototherapy
2. Exchange transfusion (slowly removing patient’s blood and replace it with fresh donor blood/plasma)
What 2 main tests are done in pre-transfusion compatibility testing (what is type and screen) ?
- ABO and Rh typing
2. Antibody screening
If the antibody screen is positive, what to do next? (2)
- Antibody identification
> if Ab is clinically significant, locate antigen -ve, ABO-compatible RBCs
> perform a 2. serological cross-match: done with the reaction between donor red cells and patient serum
If the antibody screen is negative, what to do next? (2)
- proceed with computer crossmatch: without contact between donor red cells and patient’s serum >
- Issue RBC
How is ABO and RhD typing done? (3)
- Forward grouping: patient’s blood with anti-A, anti-B, and anti-AB serum»_space;> find out what antigen is on the patient’s RBC!!
- Reverse grouping:
patient’s serum with the blood of known blood type (thus known Ag)»_space; find out what natural occurring Ab!! - Blood type confirmed by the agreement of the 2 tests
Antibody screening is the detection of __________________ in patient’s plasma against reagent screening cells by ________ test?
Alloantibodies; indirect antiglobulin (IAT)/Coombs test (ICT)
What is the indirect antiglobulin test?
demonstration of immunoglobulin in patient’s plasma only
(Ab is in the plasma rather than on RBC, thus indirect) + reagent red cells to mix with it + anti-humanglobulin to link them up for agglutination
if have the Ab > agglutinate
c.f. direct antiglobulin test: demonstration of immunoglobulin/complement protein bound to patient’s RBCs (Ab at RBC)
