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Clotting Disorders > Investigations > Flashcards

Investigations Flashcards

1
Q

What is the practical approach to a bleeding patient?

A
  • FBC with platelet count
  • Prothrombin time (PT)
  • Activated Partial Thromboplastin Time (APTT)
  • Fibrinogen
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2
Q

What does mixture of patient and normal plasma show?

A

50/50 mix will show:

  • Corrects = deficiency
  • No correction = inhibitor
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3
Q

What clotting factors affect APTT?

A

VIII, IX, XI, XII and vW factor

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4
Q

What is the diagnostic triad of clotting disorders?

A
  1. Personal history of bleeding
  2. FH of bleeding
  3. Supportive laboratory tests
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5
Q

What will FBC and clotting tests show you?

A
  • Hb, haematocrit and WBC
  • Platelets (normal 150-400 x10^9/L)
  • Prothrombin time (PT) - normal 10-12 sec (tests VII, measures extrinsic pathway)
  • Activated Partial Thromboplastin Time (APTT) (normal 20-30 secs) - measures intrinsic pathway
  • APTT 50:50
  • Fibrinogen
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6
Q

What conditions could the patient have if the APTT returns to normal after the 50:50 test?

A
  • Factor VIII deficiency (haemophilia A)

- Factor IX deficiency (haemophilia B)

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7
Q

What factors are measured in the extrinsic pathway?

A
  • Tissue factor (TF) to VIIa to Xa

- PT

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8
Q

What factors are measured in the intrinsic pathway?

A
  • IX-XII to VIIIa to Xa
  • APTT
  • PK + HK > XI x XII
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9
Q

What are the causes of prolonged PT?

A
  • Warfarin (most common)
  • II
  • VII (2nd most common)
  • X
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10
Q

what are the causes of APTT prolonged?

A
  • Heparin
  • VIII
  • IX
  • XI
  • XII (but no bleeding)
  • vW disease
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11
Q

What are the causes of prolonged PT and APTT?

A
  • Vitamin K deficiency and low fibrinogen - liver disease, malabsorption
  • DIC (disseminated intravascular coagulation) + low fibrinogen&raquo_space; FDPs, d-dimers raised, low platelets, red cell fragments
  • Heparin toxicity (normal fibrinogen)
  • Rarely (normal fibrinogen) - deficiencies of factor V or X
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12
Q

What are the vitamin K dependent factors?

A

II, VII, IX, X, protein C, protein S

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13
Q

What are the platelet tests?

A
  • FBC
  • Miscroscopy
  • PFA - screen of platelet function
  • Specialist tests - aggregation + nucleotide release, glycoproteins, molecular genetics (MYH9), bone marrow
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14
Q

What are the tests for clot stability?

A
  • Euglobin clot lysis
  • Factor XIII assay
  • PAI-D
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15
Q

What tests are used for VW screen?

A
  • Factor VIII (normal 50-150iu/dl)
  • VW antigen (normal 50-150iu/dl)
  • VW activity (normal 50-150 iu/dl)
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16
Q

How is type 1 and 2 VW disease differentiated?

A

Ratio of VWF activity : VWF antigen

If ratio is >0.6 = type 1 and if <0.6 = type 2

17
Q

What are the typical ECG findings of PE?

A
  • Sinus tachycardia

- May see AF or evidence of right heart strain (right axis deviation or RBBB) with classical S1 Q3 T3 pattern

18
Q

What would an ABG show for PE?

A

Hypoxia of T1 respiratory failure

19
Q

What tests are done for PE and DVT?

A
  • If Wells score is low then do d-dimer (detects fibrin breakdown products), if result is normal or negative DVT and PE can be excluded
  • If Wells score low and d-dimer positive then further imaging.
  • If Wells score is high probability then recommend going for highly specific imaging tests
20
Q

What are differentials for a positive d-dimer test?

A
  • Infection
  • Pregnancy (Wells score doesn’t apply)
  • Malignancy
  • Post-op
21
Q

What imaging tests are done for DVT and PE?

A
  • DT - US doppler scan

- PE - CT pulmonary angiogram (CTPA)

22
Q

What are the highly specific imaging tests for DVT and PE?

A

U+E, ABG, LFT, CXR (exclude other causes such as pneumothorax), clotting screen (baseline clotting), FBC, CTPA, ECG

23
Q

What would a CXR for a PE show?

A
  • Reduced vascular markings/oligemia
  • Dilated pulmonary artery
  • Pleural effusion
  • Exclude pneumothorax
24
Q

Who should a V/Q test be done on?

A

Pregnant women as CTPA is not good

25
Q

What does an ABG show in DVT/PE patients?

A
  • Normal in 20%
  • Decreased pO2, decreased pCO2, increased pH due to hyperventilation and poor gas exchange > respiratory alkalosis
  • Leads to type 1 respiratory failure as there is a ventilation/perfusion mismatch - parts of lungs getting air but no blood flow for gas exchange
  • This means not enough oxygen in blood > respiratory alkalosis as their RR is high so CO2 diffuses more freely across alveolar membranes than O2.
26
Q

What are the results for tests for VW?

A
  • Increased APTT
  • Increased bleeding time
  • Decreased factor VIIIc (clotting activity)
27
Q

What are risk factor surgeries for PE and DVT?

A
  • Hip or knee replacement (both)
  • Abdominal or pelvic surgery (PE)
  • Pelvic and orthopaedic (DVT)

Clotting Disorders (4 decks)

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