coagulation and blood banking
Terms
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- Assessing bleeding with history
- negative experience (against congenital bleeding) more important than positive
- Significance of petechiae in assessment of bleeding
- suggest a platelet problem
- Significance of ecchymoses in assessing bleeding
- large bruises - suggest a disorder of clotting factors
- Significance of bleeding into joints in assessment of bleeding
- suggests a disorder of clotting factors or (less commonly) von Willebrand’s disease
- Significance of purpura in assessment of bleeding
- small bruises – non-specific
- Significance of palpable purpura in assessment of bleeding
- vasculitis (not a hematologic problem)
- the pathway from __ to __ is measured by the PTT, partial thromboplastin time
- XII to fibrin
- the pathway from __ to __ is measured by the PT, the prothrombin time
- VII to fibrin
- what percent below normal of clotting factors will give abnormal PT or PTT
-
below 30% of normal
This is clinically useful since levels above 30% don’t give clinical bleeding. - The PTT measures which pathway (intrinsic, extrinsic)?
- intrinsic
- The PT measures which pathway (intrinsic, extrinsic)?
- extrinsic
- The PTT is abnormal in deficiencies of which clotting factors?
-
XII
XI
IX
VIII
X
II (prothrombin)
V
fibrinogen - When PTT is markedly abnormal, i.e >100 s, consider what artifactual cause
- line may have been flushed with heparin
- The PT will be abnormal in deficiencies of which clotting factors?
-
VII
X
V
II (prothrombin)
fibrinogen. - Which clotting factors are tested by both PT and PTT?
-
X
V
II (prothrombin)
fibrinogen. - Which clotting factors are tested exclusively by PT (and not PTT)?
-
XII
XI
IX
VIII - Which clotting factors are tested exclusively by PTT (and not PT)?
- VII
-
In a high power field of a blood smear, each platelet represents how many per cu mm?
How many per field is normal? -
20,000/ cu mm
7-22 is normal -
Which tests measure quantitative platelet problems?
Which are for qualitative? -
Platelet count
PFA100 and Bleeding time - Name the tests which are used to evaluate a bleeding disorder
- PT, PTT, platelet count, +/- PFA 100/bleeding time
- Which clotting factor is deficient in hemophilia A?
- factor VIII
- Which clotting factor is deficient in hemophilia B
- factor IX (christmas disease)
- clinical picture of factor XIII deficiency
-
associated with forming a clot and then having delayed bleeding.
XIII converts loose fibrin to tight fibrin. - how to calculate clotting factor replacement amount
-
plasma volume (40ml/kg)
desired level
and half life - Sources of factor VIII
-
Cryoprecipitate
Mono VIII--extracted with monoclonal antibody
Human recombinant VIII--$$ - Name the 6 acquired disorders of clotting factors
-
1 Liver disease
2 Vitamin K deficiency
3 Coumadin ingestion
4 Dilution
5 DIC
6 Circulating anticoagulant - When to suspect that liver disease may be cause of bleeding problem
- suspect this if clinical liver disease, or if albumin is low
- Which clotting factors are vitamin K dependent
- II, VII, IX, and X
- how does coumadin work?
- anticoagulant, which blocks synthesis of Vitamin K
- Lab diagnosis of DIC
-
more specific:
Elevated FSP’s (fibrin split products)
Not specific:
PT>15, Platelets <150,000, Fibrinogen<150 mg/dl - Screening test for circulating anticoagulants
-
1) Perform a 1:1 mix of normal plasma and the test plasma
2) In a deficiency, the mix will have a level of 50% (1+0)/2=1/2 and the PT or PTT will be normal since 50% levels give normal tests.
3) In an inhibitor, (1+0)/2 gives a level near zero because the inhibitor will neutralize the normal factor.
Note: The samples must be incubated at 37 degrees for 1-2 hours since the reaction of inhibitor and clotting factor is NOT instantaneous (antigen/antibody). - which bleeding test is most affected by heparin in the line?
- PTT >PT
- Definitive way to tell if thrombocytopenia is due to decreased production or increased destruction
- bone marrow exam
- significance of peripheral blood smear when evaluating if thrombocytopenia is due to dec production or inc destruction
-
if peripheral destruction: increased platelet production, therefore large platelets (young)
large platelets evidence against marrow failure - diagnosis suggested by isolated thrombocytopenia (other cells normal)
-
peripheral destruction of platelets via anti-platelet antibody
immune thrombocytopenia - Differential diagnosis of thrombocytopenia, 3 big classes of thrombocytopenia
-
1 decreased production
2 sequestration
3 increased destruction - Conditions which cause thrombocytopenia via decreased production of platelets
-
1 aplastic anemia
2 leukemia
3 myelodysplasia
****Other counts, in addition to platelets, will be abnormal
Diagnosis will be made by marrow exam - Conditions which cause thrombocytopenia via sequestration of platelets (expected lab values?)
-
Sequestration – hypersplenism (usually mild thrombocytopenia – 50,000-100,000)
Expect hematocrit near 30 in women, near 35 in men
WBC often in 2500 to 3500 range - Conditions which cause thrombocytopenia via increased destruction of platelets
-
1) ITP –immunogenic thrombocytopenic purpura can be idiopathic drug related (HEPARIN, quinidine) of due to SLE or lupus
2) Post –transfusion purpura
3) Disseminated Intravascular Coagulation – (PT,PTT also abnormal)
4) TTP – thrombotic thrombocytopenic purpura - why are platelet disorders considered as von Willebrand's deficiency vs everything else?
-
intrinsic disorders treated with platelet transfusion
only one type of extrinsic disorder, von willebrand's - von willebrand's disease inheritance
- autosomal dominant
- von willebrand's vs hemophilia biochemistry
-
hemophilia--100% level of VIII. VIII activity is reduced.
VWD--decreased number of molecules - ristocetin cofactor
- test of platelet function, clumps normal platelets, but not in vWD
- Lab diagnosis of von Willebrand's disease
-
Bleeding time – prolonged
VIII activity decreased, VIII antigen (vW antigen) proportionately decreased
Ristocetin cofactor – low
Ristocetin aggregation decreased - Koate-HP
- a “semi-pure†pooled lyophilized concentrate has vW activity, and is used at Vanderbilt to treat vWD.
- Humate-P
- a lyophilized anti-hemophiliac product which has von Willebrand factor activity. Not used in hemophilia where it has been replaced by monoclonal or recombinant products, it is used in von Willebrand’s disease.
- DDAVP
-
arginine vasopressin – causes the release of vW factor from endothelial cells.
Though prolonged use can cause refractoriness, it can be used in mild vW patients to get them through an acute event without ANY risk of viral transmission. - how does heparin work?
- blocks the activity of thrombin on firbrinogen
- heparin affects which bleeding tests?
- both the PT and PTT, but mostly PTT
- synthesis of what clotting factors impaired by coumadin?
-
II,VII,IX,and X
--vitamin K dependent - which test used to monitor coumadin?
-
INR of PT is used to monitor coumadin anticoagulation
--affects PT and PTT - why does coumadin necrosis occur?
- before the levels of factors II, VII, IX, and X fall, the levels of protein C and protein S fall, and a result, patients are temporarily hypercoagulable.
-
ITP
TTP
DIC
Basic mechanism -
Antibody mediated immune destruction of platelets
Endothelial damage leads to fibrin thrombi getting deposited in small vessels. Red cells become fragmented, platelets stick to thrombi
Intravascular activation of thrombin leads to consumption of clotting factors and platelets putting patient at risk of bleeding -
ITP
TTP
DIC
Laboratory features -
Isolated thrombocytopenia, i.e. low platelets but normal WBC and hematocrit though the hematocrit may be a little low from hemorrhage
Microangiopathic hemolytic anemia with thrombocytopenia
Decreased platelets
Prolonged PT
Prolonged PTT
Specific Test:
Increased fibrin degradation products or D-dimer -
ITP
TTP
DIC
Clinical association -
Patient appears well
May occur after viral illness
Seriously ill patient
May occur after viral illness
A complication of serious illness such as shock, sepsis, or severe complication of pregnancy -
ITP
TTP
DIC
Red cells -
Normal, or anemia due to hemorrhage
Microangiopathic anemia with schistocytes
DIC will cause anemia if hemorrhage occurs.
Microangiopathic changes are none to minimal -
ITP
TTP
DIC
WBC -
Normal unless corticosteroid therapy raises the WBC
Elevated as a reflection of serious illness
Elevated as a reflection of serious illness -
ITP
TTP
DIC
Platelets -
Low
Low
Low - CLASSIFICATION OF VON WILLEBRAND’S: TYPE 1
- PARTIAL QUANTITATIVE DEFICIENCY OF VWF
- CLASSIFICATION OF VON WILLEBRAND’S: TYPE 2
- QUALITATIVE DEFICIENCY OF VWF
- CLASSIFICATION OF VON WILLEBRAND’S: TYPE 2A
- Qualitative variants with decreased platelet dependent function associated with the absence of high molecular multimers
- CLASSIFICATION OF VON WILLEBRAND’S: TYPE 2B
- Qualittaive variants with increased affinity for GP Ib
- CLASSIFICATION OF VON WILLEBRAND’S: TYPE 2M
- Qualittaive variants with decreased platelet dependent function NOT associated with absence of high affinity multimers
- CLASSIFICATION OF VON WILLEBRAND’S: TYPE 2N
- Qualitative variants with decreased affinity for Factor VIII
- CLASSIFICATION OF VON WILLEBRAND’S: TYPE 3
- Near complete quantitative deficiency of VWF
- Platelet Aggregometry
-
test in which platelet rich plasma is placed in a cuvette, the test reagent (ADP, epinephrine, collagen, ristocetin) is added, and transmission of light as a function of time is determined
$$$$ - PFA-100
-
platelet rich plasma is pulled through a membrane that has been impregnated with ADP or epinephrine
The time for the aperature to close is determined -
INTERPRETING THE PFA-100 TEST FOR PLATELET FUNCTION:
C/ADP & C/EPI BOTH NORMAL -
Normal result.
Essentially rules out von Willebrand’s and platelet function defects -
INTERPRETING THE PFA-100 TEST FOR PLATELET FUNCTION:
C/ADP & C/EPI BOTH ABNORMAL -
Suggests severe von Willebrand’s or a severe platelet function defect
Can also be seen when the hematocrit is very low
Can be seen with drugs that affect platelet function including aspirin
Can be seen with severe thrombocytopenia -
INTERPRETING THE PFA-100 TEST FOR PLATELET FUNCTION:
C/EPI ABNORMAL BUT C/ADP NORMAL -
Mild von Willebrand’s or mild platelet function defect
Mild thrombocytopenia
Drug effect such as aspirin
Anemia
Could follow up with platelet function studies and tests for vonWillebrand’s disease - INTERPRETING THE PFA-100 TEST FOR PLATELET FUNCTION:
- Because the C/EPI is the more sensitive test, this result is very very uncommon
- what type immunoglobulin against mistyped blood
- IgM
- haptoglobin
-
Plasma glycoprotein that binds to oxyhemoglobin that is free in plasma and the complex is then removed in the liver.
www.nutritionperspectives.com/Other/siteGlossary.cfm
Haptoglobins are proteins in the blood that bind free iron, preventing bacteria from using the iron to grow.
en.wikipedia.org/wiki/Haptoglobin - Approach to febrile transfusion reaction:
-
1. STOP the transfusion
2. Work up for a possible mismatch
3. Give antipyretics
4. Continue the transfusion (Blood is a precious resource, do not waste it.) - 4 possible Causes of a positive direct Coombs test
-
Autoantibody in immune hemolytic anemia
Alloantibody, if patient was transfused, might have an antibody on the cells due to mismatch (major or minor).
In infant, can reflect maternal antibody to paternally inherited antigen on neonate’s RBC’s.
Non-specific adherence of immunoglobulin to RBC - components of a direct coombs test
-
Patient’s RBCs and antiglobulin
A positive test means globulin, presumably immunoglobulin and/or complement on the cells. - Antibody screen (Indirect Coombs test)
-
Patient’s serum plus two red cells that are Type O and that are chosen so that all clinically significant antigens are included between the two. Add anti-IgG.
If the cells aggulutinate (when the direct Coombs is negative) that means that an alloantibody is present. To identify the antibody, a panel of cells must be tested. This test is important in determining pre-transfusion antibody - Type and Screen
-
Determine ABO and Rh type of the patient
Do an antibody screen.
Run the patient’s serum against two screening Type O red cells to see if any antibodies exist.
If screen cells are positive, run a panel of cells to identify. - Approaches to ordering blood: 2
-
1. Type and screen: ABO type, Rh type, antibody screen with identification of antibody.
2. Type and cross: Type and screen. Also cross match for number of units ordered. The crossmatch involves incubating the patient’s serum with specific units and adding antiglobulin sera looking for agglutination. - Bllod Options in critical situations (The Emergency Room), 4
-
1. Type and crossmatch STAT (30-45 minutes)
2. Type and screen, immediate release. If screen is negative, skip the crossmatch.
3. ABO compatible without a screen (takes 10 minutes)
4. Type O blood. Available for immediate release. Risk is missing alloantibodies. Only packed cells should be used to avoid transfusing anti-A and anti-B. Would generally give O negative to females of childbearing age and O positive to others. May be lifesaving in case of exsanguinating hemorrhage. - Fresh frozen plasma components
- Contains all clotting factors.
- Cryoprecipitate components
-
Contains VIII, von Willebrand’s factor (VWF), fibrinogen, and XIII.
Also useful for unknown reasons in the platelet dysfunction of uremia.
***may contain anti-A or anti-B - Prothrombin complex concentrate components
-
Contains II, VII, IX, and X
**contraindicated in liver disease - PLATELET TRANSFUSIONS--usefullness
-
raise count 10k
useful to control bleeding in thrombocytopenic patients when the low platelets are due to decreased production
***if due to increased destruction (ITP) won't help much
disorders of platelet function (except vWB)
prophylaxis against counts <10k -
FRESH FROZEN PLASMA
usefullness -
FFP should be used ONLY to increase the level of clotting factors in the face of a demonstrated deficiency
given to bleeders on coumadin
helps patients w/ TTP -
Recipient Blood type O
compatible RBC's? - O
-
Recipient Blood type O
compatible Plasma? - AB, A, B, O
-
Recipient Blood Type A
Compatible RBC's? - A, O
-
Recipient Blood type B
Compatible RBC's? - B, O
-
Recipient Blood Type A
Compatible Plasma? - A, AB
-
Recipient Blood type B
Compatible Plasma? - B, AB
-
Recipient Blood type AB
Compatible RBC's? - AB, A, B, O
-
Recipient Blood type AB
Compatible Plasma? - AB