Haematology

Question 1

What are the stages post-bleeding?`

Answer 1

Vasoconstriction —> primary haemostasis (platelet plug; von Willebrand factor) —> secondary haemostasis (clotting factors, fibrinogen) —> repair —> fibrinolysis

Question 2

What are the questions in the bleeding history?

Answer 2

• ?menorrhagia
• ?spontaneous bruising
• ?melaena
• ?haematuria
• childbirth complications: blood transfusion, repair req.
• tooth extraction: complications, blood transfusion

Question 3

What is the activated partial thromboplastin time (APTT) measuring?

Answer 3

• intrinsic factors: fXII, fXI, fIX, fVIII

- common factors: fI, fII, fV, fX

Question 4

What is the prothromin time measuring?

Answer 4

Platelet function

• extrinsic factors: fVII
• common factors: fI, fII, fV, fX

Question 5

What is the thrombin time measuring?

Answer 5

Conversion of fibrinogen to fibrin

Question 6

What is a mixing study?

Answer 6

Mix patient plasma with normal plasma

Normal APTT: factor deficiency (factor replaced by normal plasma)

Increased APTT: ?lupus anticoagulant (inhibitor present in patient plasma)

Question 7

Give some examples of causes of isolated raised APTT.

Answer 7

• fXII, fXI, fIX, fVIII deficiency
• heparin (try flushing line)
• lupus antibody against phospholipids interferes with APTT but not associated with bleeding
• antiphospholipid syndrome

Question 8

Give some examples of cause of isolated raised prothrombin time.

Answer 8

• fVII deficiency
• early liver disease
• vitamin K deficiency
• antiphospholipid syndrome

Question 9

Give some examples of causes of raised thrombin time.

Answer 9

• reduced fibrinogen
• drugs = dabigatran, heparin
• liver disease
• thrombolysis

Question 10

What are the indications for NOACs?

Answer 10

• prevention of VTEs in adults who have had total hip/knee replacements
• prevention of stroke/systemic embolism in non-vascular AF + 1+CVD risk factors
• treatment of VTEs

Question 11

Describe the pharmacokinetics of warfarin.

Answer 11

Effects intiation of clotting cascade (raised prothrombin time and raised APTT)

Reduces vit. K dependent factors: fVII, fIX, fII, fX

t1/2 = 42hrs

Metabolised in liver

Question 12

Describe the pharmacokinetics of rivaroxaban.

Answer 12

Inhibits fXa

t1/2 = 3-4hrs

66% renal clearance
Raised APTT and prothrombin time

Reverse with prothrombin complex concentrate

Question 13

Describe the pharmacokinetics of dabigatran.

Answer 13

Inhibits fIIa (thrombin)

t1/2 = 7-17hrs

88% renal clearance
Raised APTT, vaiable prothrombin time, raised thrombin time

Reverse with activated charcoal/dialysis

Question 14

Describe the pharmacokinetics of LMWH.

Answer 14

Inhibits fXa and fIIa (thrombin)

Can cause heparin-induced thrombocytopenia

t1/2 = 4hrs

Renal clearance (adjust dose according to renal function)

Monitor anti-fXa in kidney failure, low weight, elderly

Reverse with protamine sulfate