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Year 3 > Case 6 - Clotting Disorders > Flashcards

Case 6 - Clotting Disorders Flashcards

1
Q

What is the difference between PT and PTT?

A

PT - measures the extrinsic coagulation pathway

PTT - measures the intrinsic coagulation pathway and common coagulation pathway

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2
Q

What are the normal values for PT and PTT?

A

PT: 10-12 seconds
PTT: 20-30 seconds

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3
Q

Which clotting factors are involved the extrinsic and intrinsic pathways?

A

Extrinsic - V, VII, X

Intrinsic - VIII, IX, X, XI, XIII (Also Von willebrand factor)

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4
Q

What do APTT mixing studies show?

A

If APTT is raised then mix patient plasma with normal plasma (50:50 ratio)
If APTT time fails to correct - suggests coagulation factor inhibitor present (e.g, acquired antibody)
If APTT time corrects itself - suggests coagulation factor deficiency

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5
Q

What are the two types of haemophilia and which clotting factors are they deficient in?

A

Haemophilia A - factor VIII deficiency

Haemophilia B - factor IX deficiency

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6
Q

What is Von Willebrand disease and when would you suspect it?

A

Clotting disorder characterised by platelet deficiency and factor VIII deficiny

Suspect when history of bleeding but both PT and pTT are normal

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7
Q

What are the 3 types of Von willebrand disease?

A

1) mild, quantitative deficiency, partial reduction in vWF (80% of patients)
2) mild-moderate, qualitative deficiency, abnormal form of vWF
3) severe, quantitative deficiency, total lack of vWF (autosomal recessive)

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8
Q

What is the diagnostic triad for bleeding disorders?

A

1) personal history - bruising, bleeding, nosebleeds
2) family history - any family history of clotting disorders
3) diagnostic tests - PT, PTT, FBC, factor assays, LFTs

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9
Q

What is disseminated intravascular coagulation?

A

A condition in which there is an over activity of clotting factors causing small blood clots to develop throughout the bloodstream

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10
Q

What is virchows triad?

A

The 3 primary abnormalities that lead to thrombus formation
Abnormalities of the vessel wall - endothelial injury
Abnormalities of blood flow - statis or turbulent blood flow
Abnormalities of the blood’s constituents - hypercoagulability of the blood

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11
Q

What is iodiopathic thrombocytopenia (ITP)?

A

Excessive bleeding disorder due to low levels of platelets

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12
Q

When would you initiate platelet transfusion in a bleeding patient?

A

Platelet count <30x10^9 for significant bleeding or haematemesis, melena, prolonged epistaxis
Platelet count <100x10^9 for patients with severe bleeding or bleeding at critical sites such as the CNS

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13
Q

What is factor V Leiden

A

Clotting disorder - where the body clots too much

Due to mutation in factor V making it less likely to be cleaved by protein C

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14
Q

What score on the two level DVT Wells score?

A

Active cancer
Paralysis or recent plaster immobilisation of lower extremities
Recently bedridden for >3days, or major surgery within 12 weeks requiring general or regional anaesthesia
Localised tenderness along distribution of deep venous system
Entire leg swollen
Calf swelling on symptomatic side
Pitting oedema on symptomatic side
Collateral superficial veins (non varicose)
Previous DVT

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15
Q

How would you respond to the scoring of the wells score?

A

> 2 points (DVT likely) - proximal leg ultrasound within 4 hours
< 2 points (DVT unlikely) - D dimer test, if D dimer test positive then arrange proximal leg ultrasound within 4 hours

If proximal leg ultrasound cannot be carried out within 4 hours then low molecular weight heparin should be administered whilst waiting (it then should be carried out within 24 hours)

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16
Q

How is DVT or PE treated?

A

LMWH or fondaparinux given immediately and continued for at least 5 days or until INR is 2.0 or above for at least 24 hours

Vitamin K antagonist (Warfarin) - given within 24 hours and continued for at least 3 months

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17
Q

What is the mechanism of action of dabigatran?

A

Direct thrombin inhibitor

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18
Q

Name a factor Xa inhibitor drug?

A

Rivaroxaban

Apixiban

19
Q

What is the mechanism of action of heparin?

A

Activates antithrombin III inhibitor

20
Q

What is the mechanism of action of warfarin?

A

Inhibitors clotting factors II, VII, IX and X

21
Q

When would you extend the dose of warfarin for more than 3 months for treating DVT

A

If it is an unprovoked DVT (e.g, not due to surgery), extend to 6 months of warfarin

Only if there is no additional risk of bleeding

22
Q

How would you treat a patient with a DVT who had an active cancer?

A

Low molecular weight heparin (LMWH) for 6 months

23
Q

What further investigation would you do in a patient aged over 40 years with a first unprovoked DVT?

A

Abdominal-pelvic CT scan - to look for any cancer/malignancy that might have caused DVT

24
Q

What is post-thrombotic syndrome and how would you treat it?

A

Complication following DVT where venous outflow obstruction result in chronic venous hypertension. Symptoms include: painful, heavy calves, pruritus, swelling, varicose veins, venous ulceration

Treat with compression stockings

25
Q

What are the differentials for a unilateral, swollen, painful leg?

A

DVT
Cellulitis
Ruptured bakers cyst (fluid filled cyst behind knee)
Muscle haematoma

26
Q

On examination what signs would indicate a DVT?

A

Warm, swollen leg
Tenderness in the calf - worse with dorsiflexion of the ankle (Homan’s sign)
Calf circumference greater than 3cm compared with unaffected leg

27
Q

What are the typical symptoms of a pulmonary embolism (PE)?

A

Sudden onset of plueritic chest pain
Shortness of breath
Haemoptysis

28
Q

What are the physical signs of a PE?

A

Increased respiratory rate
Tachyarrthymias (most common sinus tachycardia but can also be AF)
Signs of DVT

29
Q

Which group of patients do the wells score not apply to?

A

Pregnant women

30
Q

What is a massive pulmonary embolism and how does it differ from a normal pulmonary embolism?

A

Large clot which lodges in the right side of the heart, or in BOTH pulmonary arteries (saddle embolus)

Presents with syncope as well as other symptoms of PE
Presence of arterial hypotension (systolic <100mmHg) or cardiogenic shock/cardiac arrest

31
Q

If the PT and APTT are both prolonged then what could this be due to?

A

Vitamin K deficiency - liver disease, malabsorption
Disseminated intravascular coagulation
Factor V or Factor X deficiency?

32
Q

Why does disseminated intravascular coagulation (DIC) cause too much clotting AND too much bleeding?

A

Too much coagulation in one area uses up platelets and clotting factors

Too little clotting factors in other areas causes excess bleeding

33
Q

When is a CTPA contra-indicated in investigation of a PE?

What is used instead?

A

In patients with renal impairment
Patients who are allergic to contrast media

V/Q scan

34
Q

What are the common ECG changes shown on a patient with a PE?

A

Sinus tachycardia (or AF)
Right bundle branch block
S1Q3T3 sign

35
Q

What investigations should be done in a patient with suspected PE?

A

Wells score (PE likely if greater than 4)
Chest X-Ray (to exclude other pathology)
CTPA (or V/Q if renal impairment)

36
Q

What would the arterial blood gas show on a patient with a PE?

A

Respiratory alkalosis - due to hyperventilation

37
Q

In what situation would you use thrombolysis for a PE?

A

Where there is a massive PE with circulatory failure (e.g, hypotension)

38
Q

What salt level should be monitored when patients are taking LMWH for longer than 7 days and why?

A

Potassium

Patients with diabetes, chronic renal impairment and on medication than can increase potassium levels are more susceptible to hyperkalamia

39
Q

Name the common LMWH given in practice?

A

Enoxaparin

42
Q

What is the difference between a thrombus and an embolus?

A

Thrombus is a blood clot within the body
An embolus is any material which is transported in the blood stream and lodges in a blood vessel at a different site (it can be an gas bubble or a solid clot)

43
Q

When are anti-embolus stockings contra indicated?

A

In patients with pre existing peripheral arterial disease

44
Q

How are the different types of Von willebrands disease treated?

A

Type I - desmopressin + tranexamic acid
Type II - Von willibrand factor
Type III - Von willibrand factor

45
Q

How does desmopressin work?

A

Stimulates the release of Von willebrand factor from cells

Year 3 (24 decks)

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