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Clotting disorders > Clotting disorders > Flashcards

Clotting disorders Flashcards

1
Q

What tests should be done for coagulations disorders?

A

FBC (with platelet count)
PT (prothrombin time)
APTT (activated partial thromboplastin time)
Fibrinogen levels

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2
Q

How do you check whether there is a factor deficiency or a coagulation factor inhibitor present?

A

50/50 mixture study of patient:normal plasma

  • If it corrects = deficiency
  • If it does NOT correct = inhibitor

e.g. If APTT corrects when mixed with normal plasma it means that there is a coagulation factor deficiency

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3
Q

What factor deficiency causes Haemophilia A?

A

Factor VIII

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4
Q

What factor deficiency causes Haemophilia B?

A

Factor IX

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5
Q

What factors are measured in extrinsic pathway?

A

TF (tissue factor)
VIIa to Xa
PT (prothrombin time)

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6
Q

What is tissue factor’s function in the extrinsic pathway?

A

TF extruded from damaged endothelial cells of vessel walls activates factor VII to initiate extrinsic system

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7
Q

What factors are measured in the intrinsic pathway?

A

IX - XII to VIIIa to Xa

APTT

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8
Q

What factors are measured in the common pathway?

A

Xa -> thrombin
TT and PT, APTT
Often just measure fibrinogen

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9
Q

What differentials may be the cause of a prolonged PT?

A

Older patients - warfarin
2nd commonest cause - VII deficiency
Also affected by factors: II, V and X

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10
Q

What differentials may be the cause of a prolonged APTT?

A

Due to patient being on heparin
Also affected by factors: VIII, IX, XI and XII (but XII does NOT cause bleeding)
Von Willebrand’s Disease

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11
Q

If BOTH PT and APTT are prolonged what differentials should be considered?

A

Vitamin K deficiency + low fibrinogen -> Liver disease, malabsorption
DIC (disseminated intravascular coagulation) + low fibrinogen -> FDPs, D-dimers raised, low platelets, red-cell fragments
Heparin toxicity + normal fibrinogen
Rarely (deficiencies of factor V or X) + normal fibrinogen

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12
Q

What factors are dependent on vitamin K?

A

Factors II, VII, IX and X

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13
Q

What is the diagnostic triad for clotting disorders?

A
  • Personal history of bleeding
  • Family history of bleeding
  • Supportive laboratory tests
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14
Q

What is looked for in personal history of bleeding?

A
  • Bruising - in unexpected places, no injury
  • Epistaxis (nosebleed) - duration > 30 mins and frequency
  • GI tract: start at mouth and work down
  • Menses - duration, flooding/clots, no of pads/tampons
  • Urine - haematuria

Need to know
• Surgical history
• Dental history (may have been complicated due to bleeding)
• Cuts and injuries

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15
Q

What is looked for in family history of bleeding?

A
  • Known bleeding disorders
  • Bleeding in family members especially after surgery or dentistry
  • If there is - get details of where tested, by whom and when
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16
Q

What is looked for in diagnostic tests?

A

FBC - e.g. will show thrombocytopenia (low platelet level)
Microscopy
- Large platelets - Bernard Soulier Syndrome
- Small Platelets - Wiskott Aldrich Syndrome
- Neutrophil inclusions - May Hegglin Anomaly
- Platelet inclusions - Paris Trousseau/Jacobsen’s

PFA - screen of platelet function
Coagulation tests:
- PT (prothrombin time)
- APTT (activated partial thromboplastin time)
- TT (thrombin time)
- Fibrinogen 
- 50/50 mixture test
17
Q

What is vWF disease?

A
  • Endothelial cells are attached to the subendothelial collagen by von Willebrand factor (vWF) which these cells produce
  • vWF is also stored in the Weibel-Palade bodies of the endothelial cells and secreted constitutively into the blood. Platelets store vWF in their alpha granules
  • vWF carries FVIII in the blood
  • The commonest coagulopathy
  • Affects 0.5% of population
  • Mucocutaneous bleeding
  • 15% of menorrhagia
18
Q

What are the types of von Willebrand’s Disease?

A

Type 1 - REDUCED amount of normal vW protein
Type 2 - ABNORMAL vW protein (IIb overactive)
Type 3 - LITTLE/NO vW protein

19
Q

How is von Willebrand’s screened for?

A
  • Factor VIII - normal range: 50-150 iu/dl
  • von Willebrand’s Antigen - normal range: 50-150 iu/dl
  • von Willebrand activity - normal range: 50-150 iu/dl
20
Q

How is type 1 and type 2 vW disease differentiated?

A

By using ratio of vWF activity: vWF antigen

  • if ratio of vWF activity to vWF antigen is >0.6 = type 1
  • if ratio <0.6 = type 2
21
Q

How does type 1 vW disease present?

A
  • Mild disease
  • Bruising/mucosal bleeding
  • Menorrhagia
  • Operations - dental extractions
22
Q

How does type 2 vW disease present?

A 
• Clinically indistinguishable from type 1
• Type 2b:
	◦ OVERACTIVE protein
	◦ Can result in thrombocytopenia
	◦ Avoid DDAVP, use vWF concentrate
23
Q

How does type 3 vW disease present?

A
  • Severe illness
  • Serious mucosal bleeding
  • Operative treatment will cause severe bleeding
24
Q

How is type 1 and type 2 vW disease treated?

A

DDAVP - release vW protein from storage
- do NOT use in type 2b
Local measures - give iron (due to blood loss)
Use vWF concentrate if needed

25
Q

How is type 3 vW disease treated?

A

Local measures
vW concentrates
Consider prophylaxis
Genetic advice

26
Q

What is the normal range for factor VIII?

A

50iu/dL - 150iu/dL

Mild > 5iu/dL
Moderate 1-5 iu/dL
Severe < 1 iu/dL

27
Q

What are the basic principles of haemophilia treatment?

A

Treatment centre/multidisciplinary
Treat early (if in doubt treat)
Fast Track triage in A&E
Do NOT wait for clinical signs to develop
Take care of veins
Avoids drugs like aspirin - as it can cause platelet dysfunction
Early home therapy

28
Q

What is RICE?

A

R = rest
I = immobilise
C = cool
E =elevate

29
Q

What medications may be given for haemophilia A?

A 
Recombinant factor VIII
Desmopressin (DDAVP)
- releases stored factor VIII (good for mild haemophilia)
- raises VIII x2 or 3
Tranexamic acid: anti-fibrinolytic
30
Q

How to calculate the amount needed of recombinant factor VIII?

A

[Rise (in iu) x weight (kg)] / 2

Half-life 8 hours - 1 to 3 times daily

31
Q

What is treatment of haemophilia B?

A

Recombinant factor IX

Tranexamic acid

32
Q

How to calculate the amount needed of recombinant factor IX?

A

Rise (in iu) x weight (kg)

Half-life 18-24 hours, so 1x a day

33
Q

How is prophylactic done for haemophilia?

A

Primary - choosing to start between 3-18 months of age
Secondary - after 3 joint bleeds
Factor IX give 2x week
Factor VIII given alternate days but often 3x week
Very effective
Very expensive

Clotting disorders (2 decks)

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