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Haemotology > Clotting disorders > Flashcards

Clotting disorders Flashcards

1
Q

How do we test for a factor deficiency or the presence of a coagulation factor inhibitor?

A

50/50 mixture study of patient/normal plasma

corrects - deficiency
no correction - inhibitor

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2
Q

How should you approach history-taking with regards to abnormal bleeding?

A
  • Emphasis on family history
  • Ask about siblings and parents, parents’ siblings
  • Particular emphasis on males - X linked disorders
  • Unusually severe injuries
  • Anaemia?
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3
Q

What tests should be ordered when investigating abnormal bleeding?

A
  • Full blood count

- Clotting tests

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4
Q

Which clotting factors affect one’s APTT?

A

APTT:

  • VIII
  • IX
  • XII
  • Von Willebrand factor
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5
Q

Which factor deficiencies are seen in Haemophilia?

A

Haemophilia A - Factor VIII

Haemophilia B - Factor IX

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6
Q

What is the treatment for Haemophilia?

A

LIFE THREATENING BLEED:

1st line:
- Factor concentrate (replacement)
+ supportive care and subspeciality consultations
- Antifibrinolytic agent

2nd line:
- Bypassing agent (recombinant factor VIIa or VIII inhibitor bypassing fraction)
+ supportive care and subspecialty consultations
- Antifibrinolytic agent
If patient has high titre factor inhibitor, 1st line starts with bypassing agent

NON-LIFE-THREATENING BLEED (into joint/muscle)

1st line:

  • Factor concentrate
  • Analgesics + physiotherapy evaluation
  • Orthopaedic + pain team evaluation

2nd line:

  • Bypassing agent
  • Analgesics + physiotherapy evsluation
  • Orthopaedic + pain team evaluation

If patient has high titre factor inhibitor, 1st line starts with bypassing agent

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7
Q

How are the intrinsic and extrinsic factors started?

A

Intrinsic:

  • Pre-Kallikrein (PK) and high molecular weight Kininongen (HK) activate factors XI and XII to activate the intrinsic system
  • Factors XI, XII and IV all activate factor Xa, which is the centre of the coagulation cascade

Extrinsic:

  • Tissue factor (TF) is extruded from damaged endothelial cells of vessel walls
  • This activates factor VII to initiate the extrinsic system
  • Xa forms thrombin, causing fibrinogen to create fibrin, creating a flot
  • The plasmin/plasminogen system is then activated to dissolve the clot
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8
Q

What is the extrinsic pathway?

A

Extrinsic:
- Tissue factor -> VIIa -> Xa
Measured by prothrombin time (PT)

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9
Q

What is the instrinsic pathway?

A

Intrinsic:
- IX-XII -> VIIIa -> Xa
Measured by APTT

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10
Q

What is the common pathway?

A

Common:
Xa -> Thrombin
- Msasured by thrombin time (TT) and PT and APTT
Often just measure Fibrinogen (I)

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11
Q

What may cause an isolated prolonged prothrombin time?

A
  • Warfarin**
  • Factor II
  • Factor V
  • Factor VII**
  • Factor X
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12
Q

What may cause an isolated prolonged APTT?

A
  • Heparin**
  • Factor VIII
  • Factor IX
  • Factor XI
  • Factor XII (but no bleeding)**
  • Von Willebrand’s disease
    (In types I and II the APTT is often normal)
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13
Q

What can cause both the PT and APTT to be prolonged?

A
  • Vitamin K deficiency
  • Disseminated intravascular coagulation (DIC)
  • Heparin toxicity
  • Severe factor V or Xa deficiency
    (Fibrinogen levels may be normal here!)
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14
Q

What is the diagnostic triad?

A

Personal history of bleeding:

  • Bruising, often lumpy or unexpected
  • Epistaxis: duration 30+ minutes and frequency
  • GI tract: start at mouth and work down
  • Menses: duration, flooding/clots, number of pads/tampons
  • Urine: haematuria

Family history of bleeding:

  • Known bleeding disorders
  • Bleeding in family members (surgery/dentistry)
  • Details of testing: where, by whom, when

Surgical history
Dental history
Cuts and injuries

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15
Q

What diagnostic tests are used in clotting disorders?

A

Platelet tests:

  • FBC
  • Microscopy
  • PFA (screen of platelet function)

Specialist tests

  • Aggregation and nucleotide release
  • Glycoproteins
  • Molecular genetics: MYH9
  • Bone marrow:- consumption vs production
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16
Q

How can we use microscopy to diagnose clotting disorders?

A

Microscopy:

  • Large platelets: Bernard Xoulier Syndrome
  • Small platelets: Wiskott Aldrich syndrome
  • Neutrophil inclusions: MAy Hegglin Anomaly
  • Platelet inclusions: Paris Trosseau/Jacobsen’s
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17
Q

What are tests of coagulation?

A
  • Prothrombin time (PT)
  • Activated Partial thromboplastin time (APTT)
  • Thrombin time (TT)
  • Fibrinogen (Clauss)
  • The 50/50 mixture test
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18
Q

How do we test clot stability?

A
  • Euglobin Clot lysis
    1. Make clot on orange stick
    2. Leave in fridge for 24hr
    3. Check if clot still there
  • Factor XIII assay

PAI-D: Amish/Chinese

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19
Q

What are the basic principles for haemophilia treatment?

A
  • Treatment centre/multidisciplinary
  • Treat early
  • Fast track triage in A&E
  • Do not wait for clinical signs to develop
  • Take care of veins
  • Avoid aspirin and similar drugs (causes platelet disorders)
  • Early home therapy
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20
Q

What should be the first step in haemophilia treatment?

A

RICE
Rest, ice compression, elevation

There is a tendency to think the only therapy requires id the coagulation factor

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21
Q

What is the formula for the amount of factor needed in Haemophilia A?

A

Factor VIII: recombinant, large molecule
Amount needed = (Rise x weight)/2

Half life = 8 hours: give 1-3x daily

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22
Q

What is the formula for the amount of factor needed in Haemophilia B?

A

Factor IX: recombinant, small molecule
Amount needed = Rise x weight

Half life 18-24 hours so give once daily

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23
Q

How is desmopressin used in clotting disorders?

A

Desmopressin (DDAVP):
Releases stored factor VIII so is useful for mild haemophiliacs
Raises VIII by 2-3x, test with a trial run as variable effects
SC, IV, or intranasal (IN)

24
Q

How is tranexamic acid used in the treatment of clotting disorders?

A

Used in both haemophilia A and B

An anti-fibrinolytic, given orally
Also used in von Willebrand’s during menses?

25
Q

How is home therapy used in haemophilia?

A

Home therapy

  • Parent/carer learns to inject when child is 2yrs
  • Patient learns at age 11
  • Very convenient
  • Very effective
  • Saves many hospital visits
26
Q

What is vol Willebrand’s disease?

A

von Willebrand’s

  • Commonest coagulopathy
  • 0.5% of population
  • Mucocutaneous bleeding
  • Accounts for 15% of menorrhagia
  • There are 2 types
  • Can be difficult to diagnose (especially type 1)
  1. Bleeding history
  2. Positive family history
  3. Laboratory tests
27
Q

What are the different types of von Willebrand’s disease?

A

Type 1
- Reduced amount of normal vW protein

Type 2
- Abnormal vW protein (IIb overactive)

Type3
- Little or no vW

28
Q

How do we test for von Willebrand’s disease?

A

von Willebrand’s screen:

  • Factor VIII (normal range 50-150iu/dl)
  • von Willebrand antigen (normal range 50-150iu/dl)
  • von Willebrand activity (normal range 50-150iu/dl)

Types 1 and 2 are differentiated by using the vWF activity:vWF antigen ratio

if the ratio is >0.6 = type 1
if the ratio is <0.6 = type 2

29
Q

How does type 1 von Willebrand’s disease present?

A

Type 1

  • Mild disease
  • Bruising/mucosal bleeding
  • Menorrhagia
  • Operations - dental extractions
30
Q

How does type 2 von Willebrand’s disease present?

A

Type 2

  • Mild disease
  • Bruising/mucosal bleeding
  • Menorrhagia
  • Operations - dental extractions

Watch for 2b:

  • Overactive protein
  • Can result in thrombocytopaenia
  • Avoid DDAVP (desmopressin)
  • Use vWF concentrate
31
Q

How does type 3 von Willebrand’s disease present?

A

Type 3:

  • Severe illness
  • Serious mucosal bleeding
  • Operative treatment will cause severe bleeding
32
Q

What are the treatments for the different types of von Willebrand’s disease?

A

Type 1: quantitative deficiency

  • DDAVP + tranexamic acid
  • Watch for diminishing returns in major surgery, vWFactor may be needed

Type 2: qualitative deficiency
under active OR over active (2b)
- vWFactor/DDAVP (avoid in 2b)

Type 3: absent vW factor
- vWFactor

33
Q

What is a venous thromboembolism?

A

Most VTE occur in the deep veins of the leg

  • Normally contraction of the calf muscles squeezed blood up the deep veins of the leg
  • Internal valves prevent backflow

In varicose veins etc:

  • This mechanism does not work, there is backwash of blood
  • Veins bulge and blood pools in the deep veins
34
Q

What is the epidemiology of VTE?

A
  • 25,000 deaths per year
  • More than annual death toll from RTA, HIV and breast cancer
  • Major avoidable cause of death in modern medicine
  • 66% DVT, 33% PE
  • Causes 10% of hospital deaths, most are sudden and unexpected`
35
Q

What is Virchow’s triad?

A

Triad of risk factors learning to VTE

  • All hospitalised patient need to be considered at risk
  • Immobile (in bed)
  • Often hypercoagulable (acute phase reactant proteins include fibrinogen, factor VIII and vWF
  • Endothelial injury (previous leg or pelvic operation, post operative plaster cast)
  1. Stasis of blood flow
  2. Endothelial inury
  3. Hypercoagulability
36
Q

Who is at risk of VTE?

A
  • Any surgical patient
  • Anaesthesia leads to immobility, stasis and reduced blood flow in the legs
  • Post-operative period with bed rest - increased risk with increased duration
  • Acute reactants post-surgery
  • Open surgery greater risk that laparoscopic

!!Medical patients make up the majority of hospital VTE deaths!!

All adult patients (18+) undergo a formal assessment of VTE risk

37
Q

How do we prevent VTE?

A
  • Risk assess each patient (Wells score)
  • Early ambulation for all
  1. Mechanical:
    - Anti-embolism stockings
    - Intermittent pneumatic compression sleeves
    - Cheap
    - Do not affect cogaulation system
    - Poor compliance with optimum fitting
    - May exacerbate pre-existing arterial insufficiency
    - Less effective than pharmacological management
  2. Pharmacological:
    - Low dose low molecular weight heparin (sc)
    - Low dose unfractionated heparin (iv)
    - Direct anti-Xa and antithrombin drugs (po)
    - Effective
    - Know that dose has been given
    - Cost!!
    - Risk of bleeding
    - Allergies and heparin induced thrombocytopaenia and thrombosis (HITT)

Do not use warfarin - intensity of anticoagulation is less predictable and erratic bleeding risk higher than hepatin or DOAC

38
Q

How do we manage acute VTE?

A
  • If suspected according to clinical signs and wells scores then treat immediately
  • Do not investigate first unless this can be done within 1 hour for PE or 4 hours for DVT
  • Use heparin (LMWH) but sometimes post op use unfractionated (UFH) as it can be immediately reversed if further surgery required
  • At the same time as starting heparin, start oral warfarin
  • Takes 48-72 hours to reach its therapeutic range at which time the heparin can be discontinued
39
Q

What are thrombi and emboli?

A

Thrombus:
- A clot within the body

Embolus:

  • Some material which is transported in the blood stream and lodges in a blood vessel at a different site
  • Can be gaseous, e.g. an air bubble, or solid, e.g. part of a thrombus
  • When it impedes or blocks blood flow in the artery it causes an embolism, the consequences of which are infarction of the tissue supplied by the artery
  • The bigger the embolus the bigger the artery it blocks and the bigger the area of infarction
40
Q

What is a pulmonary embolism?

A
  • When a thrombus travels up venous circulation
  • Enters right atrium, then right ventricle
  • Then into the pulmonary arteryies
  • Lodges and blocks the artery

A ‘massive’ pulmonary embolism is when the flow of blood to the right side of the heart is blocked
- Results in a cardiac arrest

41
Q

How does a DVT present?

A
  • Unilateral swollen leg
  • Warm
  • Calf tenderness, worth with dorsiflexion (Homan’s sign)
  • Calf circumference more than 3mm wider than the other leg
  • Measure 10cm from tibial tuberosity
42
Q

What are some common differential diagnoses for a DVT?

A
  • Cellulitis
  • Ruptured baker’s cyst
  • Muscle haematoma
43
Q

What are the risk factors for a DVT?

A
  • 60+
  • Overweight
  • Smoking
  • Previous DVT
  • Take the combined pill or HRT
  • Cancer
  • Heart failure
  • Varicose veins
  • Hospital stay
  • Bedbound
  • Long journeys (3+hrs)
  • Pregnancy
  • Dehydration
44
Q

What are the signs and symptoms of a PE?

A
  • Chest pain, sometimes upper back
  • Difficulty breathing
  • Sharp pain (pleuritic)
  • Sudden onset
  • Shortness of breath
  • Coughing up blood
45
Q

What signs of PE are seen on examination?

A
  • Increased respiratory rate
  • Tachyarrhythmias (usually sinus tachy but can be AF)
  • Signs of DVT
46
Q

What would be seen on an ECG that could suggest a PE?

A
  • Sinus tachycardia
  • Possibly atrial fibrillation
  • Evidence of right heart strain (right axis deviation/RBBB)
  • S1Q3T3 pattern
    (numbers indicate leads)
  • T wave inversion on lead 3
47
Q

What would be seen on an ABG that could indicate a PE?

A
  • Hypoxia

- Type 1 respiratory failure (low oxygen, normal or low CO2)

48
Q

How should we use the Wells score and D-Dimer test?

A
  • If Wells score is ‘low clinical probability’, do a D-Dimer
  • If D-Dimer is then negative/normal range, we can exclude a VTE because it is highly sensitive (but not specific)
  • If Wells score is ‘low clinical probability’ and D-Dimer is positive (raised), then do further imaging
  • Imaging is usually US doppler of the leg for DVT
  • Or CT pulmonary angiogram (CTPA) for a pulmonary embolism
    Both of these tests are highly specific
  • If Wells score is ‘high clinical probability’ then go straight for imaging tests

NOTE: these recommendations are not used for pregnant women, hospitals will have local guidelines for pregnancy

49
Q

What is the PERC rule?

A 
Rules out PE if no criteria are present and pre-test probability is less than 16%
 If any of the following are positive, the PERc rule cannot be used to rule out a PE
- Age 50+
- HR 100+
- O2 sats on air are less than 95% 
- Unilateral leg swelling
- Haemoptysis
- Recent surgery or trauma
- Prior PE or DVT
- Hormone use (combined pill, HRT)

All of the above add 1 point each

50
Q

What is the threshold of the Wells score?

A

More than 4 points = PE likely

Fewer than 4 points = PE unlikely

51
Q

What should be the initial investigations for patients who present with signs of PE?

A
  • ABCDE
  • General medical history
  • Physical examination
  • Chest x-ray to exclude other causes
  • Assess PERC/Wells score
52
Q

What treatment is given to patients with a DVT or PE?

A
  • FBC, U&Es, PT and APTT
  • Start anticoagulation before results available
  • Review and act on results in 24 hours

No renal impairment/active cancer/antiphospholipid syndrome:

  • Apixaban or Rivaroaxavan
  • Alternative: LMWH 5 days followed by dabigatran or edoxaban
  • Offer LMWH and a VKA for at least 5 days or INR is 2.0 on 2 consecutive readings

Renal impairment:

  • CrCl 15-50 ml.min, offer apixaban, rivaroaxaban, or LMWH for 5 days followed by edoxaban or dibagatran
  • CrCl less than 15ml/min, offer LMWH, UFH
  • Offer LMWH and a VKA for at least 5 days or INR is 2.0 on 2 consecutive readings

Active cancer:

  • Consider a DOAC
  • If not suitable consider LMWH
  • Offer LMWH and a VKA for at least 5 days or INR is 2.0 on 2 consecutive readings

Offer anticoagulation for 3-6 months, taking into account tumour site, drug interactions, and bleeding risk

Antiphospholipid syndrome:
- Offer LMWH and a VKA for at least 5 days or INR is 2.0 on 2 consecutive readings

53
Q

What is a massive pulmonary embolism?

A
  • Large clot which lodges in the right side of the heart OR in both pulmonary arteries (saddle embolus) OR one of the pulmonary arteries

Present with:

  • Syncope
  • Shortness of breath
  • Haemoptysis
  • Sudden sharp chest pain
  • Arterial hypotension (systolic less than 100)
  • Cardiogenic shock/cardiac arrest

Medical emergency, requires urgent thrombolysis

54
Q

When are anti-embolus stockings contra-indicated?

A

Intermittent claudication - stockings exacerbate preexisting peripheral arterial disease

55
Q

What should we monitor when a patient is on LMWH for a week or more?

A

Potassium levels should be monitored when patients take LMWH for longer than 7 days
- Those patients that have diabetes, chronic renal impairment and on medication that can increase potassium levels are more susceptible to hyperkalamia
(eg ACE inhibitors)

Haemotology (2 decks)

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