Acquired bleeding disorders

Question 1

Clotting requires:

Answer 1

platelets; vessel wall; clotting factors

Question 2

Prothrombin time (PT)

Answer 2

Measures factors II,V, VII, X, fibrinogen - extrinsic pathway

• Only test that measures FVII
• Time in seconds from exposure to clot formation

Question 3

Causes of prolonged PT

Answer 3

Vitamin K deficiency

• Liver disease
• Massive blood transfusion due to dilution of clotting factors

Question 4

Isolated prolonged PT along with normal APTT =

Answer 4

Early liver disease
- (factor 7 drops the quickest as shortest half-life)
-

Question 5

Activated Partial Thromboplastin Time (APTT)

Answer 5

Measures other factors, not 7
- Kallikrein and HMWK and Factor XII are contact factors which can mess up APTT and make it look prolonged but deficiencies will not cause bleeding problems

Question 6

Causes of prolonged APTT

Answer 6

• Deficiency or inhibition of factors + fibrinogen

- Liver disease, Warfarin, Haemophilia

Question 7

Thrombin time

Answer 7

• Looking at function and amount of function

- Measures fibrinogen

Question 8

Causes of prolonged TT

Answer 8

Dysfibrinogenaemia – no fibrinogen, Hypofibrinogenaemia – low fibrinogen, Hepatocellular disease, DIC, Heparin

Question 9

Lupus anticoagulant (LAC)

Answer 9

• IgG/ IgM autoantibody – antiphospholipid antibody
• Interferes with APTT test in vitro and prolongs APTT
• Can do LAC screen
• In vivo more likely to have thrombosis than bleeding

Question 10

Heparin

Answer 10

• Wraps around antithrombin
• Inhibits Factor X
• UFH = inhibits Factor Xa and Thrombin and switch off coagulation cascade

Question 11

Unfractioned heparin monitoring (UFH)

Answer 11

• Badly monitored
• Half life - 45-90 mins
• Monitor with APTT
• Can be hard to anticoagulate some infants

Question 12

Low molecular weight heparin

Answer 12

• More reliable that UFH, renally excreted so may not reach therapeutic range
• Monitor anti-Xa levels

Question 13

HIT = heparin induced thrombocytopenia

Answer 13

Immune complex forms causing drop in platelet count

- Skin/allergic reactions and bleeding

Question 14

Treatment of bleeding

Answer 14

• Patients on UFH - Stop IV heparin, administer protamine sulphate - potential allergy
• Patients on LMWH - Stop LMWH, Protamine reverses 60% of the effects

Question 15

Warfarin

Answer 15

• prevents activation of vitamin K - Factors 2,7,9,10 are all vitamin K dependant
• Monitor treatment by INR

Question 16

Treatment of bleeding or excessive anticoagulation on warfarin

Answer 16

• Stop warfarin
• Give prothrombin complex concentration
• Vit K IV
• Measure INR 15 mins and 12 hours after PCC

Question 17

Fondaparinux

Answer 17

• Alternative to heparin – similar action
• Indirect anti-Xa activity
• Half-life of 17-20 hours
• No specific antidote
• Bleeding – stop treatment and general haemoastatic measures
• If critical bleeding – consider FVIIa

Question 18

Aspirin

Answer 18

• Anti-platelet agent
• Inactivates platelet cyclooxygenase
• Give 2-3 doses of platelets in critical bleeding

Question 19

Bleeding in vitamin K deficiency

Answer 19

• Deficiencies of factors II, VII, IX and X
• Treatment with IV/oral vitamin K
• Causes = obstructive jaundice, nutrition deficiency

Question 20

Bleeding in liver disease

Answer 20

• Aka cirrhotic coagulopathy
• Reduced plasma concentration of coag factors except FVIII
• Treated with platelet transfusions, FFP or prothrombin complex concentrate

Question 21

Bleeding in renal disease

Answer 21

Causes:

• Anaemia - RBC’s are needed for platelet function (release ADP)
• Uraemia - Disrupts platelet-platelet and platelet-vessel wall interactions

Question 22

Prevention of bleeding

Answer 22

• Correct anaemia - EPO and transfusions
  DDAVP - Desmopressin - stimulates release of vWF
• Tranexamic acid

Question 23

Haemostatic abnormalities in massive transfusion

Answer 23

• dilutional depletion of platelets and coagulation factors
• Acidosis
• Hypothermia
• Haemorrhages can cause DIC

Question 24

DIC = disseminated intravascular coagulation

Answer 24

• Characterised by systemic activation of pathways leading to and regulating coagulation, which can result in generation of fibrin clots that may cause organ failure with concomitant consumption of platelets and coagulation factors that may result in clinical bleeding

Question 25

DIC pathogenesis

Answer 25

``` oExcess thrombin generation Microvascular thrombosis – tissue ischaemia and organ damage oReduced natural anticoagulant activity oDecreased fibrinolysis Aetiology ```

Question 26

Causes of DIC

Answer 26

- Sepsis - Trauma - Acute intravascular haemolysis - Liver disease - Chronic causes = malignancy

Question 27

Diagnosis and management of DIC

Answer 27

- Diagnosed via presence of underlying disorder, Global coagulation tests - Low platelet count, elevated D-dimer, prolonged PT, low fibrinogen - Treat underlying cause - antibiotics, Vit K supplementation