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Medicine Y3 TCD 1-12 > 6. Practical approach to Clotting Disorders > Flashcards

6. Practical approach to Clotting Disorders Flashcards

1
Q

3 main systems work together in the body to help blood remain liquid;

  1. which works to clot the blood
  2. which works to dissolve clots
  3. which works as natural inhibitors/anticoags
A
  1. intrinsic and extrinsic clotting cascade
  2. Plasminogen/plasmin system
  3. protein C, protein S, antithrombin III
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2
Q

How does the anticoag warfarin work

A

reduces the vitamin K dependant coat factors making it difficult to form a clot

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3
Q

How does heparin work

A

on antithrombin III by greatly increases its action (completely inhibiting clots)

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4
Q

rTPA (recombinant plasminogen activator), how does this work

A

it allows clots to be busted by increasing plasmin activity

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5
Q

Which substances work as natural anticoagulants in the blood

A

Protein C, protein S and antithrombin

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6
Q 
What are the common names of the following;
Factor I 
Factor II
Factor III
Factor IV
A

I is fibrin
II is prothrombin (gets converted into thrombin)
III tissue factor
IV is calcium

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7
Q

what factor does vWF bind to in order to stabilise it

A

factor VIII

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8
Q

Practically, what blood test results would you want to order in a patient who you suspect to have a clotting disorder

A 
FBC
PT 
APTT
Fibrinogen 
Platelet count 
50/50% mixture study
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9
Q

in a 50/50 mixture study you take a patients plasma and mix it with 50% of normal plasma
Q: if there is a deficiency, will adding the normal plasma correct the abnormal PT and APTT

A

yes

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10
Q

in a 50/50 mixture study you take a patients plasma and mix it with 50% of normal plasma
Q: if there is an inhibitor present in the patients plasma , will adding the normal plasma correct the abnormal PT and APTT

A

No

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11
Q

If nothing of significance is found on blood results when looking at clotting disorders, what tests would you want to order

A

Factor essay
vWF tests (VIII, vWF antigen, vWF activity
platelet aggregation and nucleotide release

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12
Q

what factor is released from damaged endothelial cells and what factor does it activate to initiate the extrinsic system

A

Tissue factor (TF) is released which activates factor VII

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13
Q

Pre-kallikrein (PK) and high molecular weight kininogen (HK) activate which factors that activate the intrinsic system

A

factors XI and XII

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14
Q

Which pathway causes the prothrombin (PT) time to be increased

A

the extrinsic pathway which converts TF to VIIIa and Xa

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15
Q

which pathway causes the activated partial-thromboplastin (APTT) time to be increased

A

the intrinsic system which coverts factors IX-XII to VIIIa and Xa

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16
Q

if PT and APTT time are both increased then what pathway is it

A

the common pathway which coverts Xa into thrombin

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17
Q

To measure the common pathway what test do you tend to just look at

A

the level of fibrinogen

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18
Q

What abnormalities (ie which factors) should be suspected if the patient has prolonged PT

A 
Warfarin 
II 
V 
VII 
X
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19
Q

what abnormalities (ie which factors) should be suspected if the patient has a prolonged APTT

A 
Heparin 
VIII 
IX
XI
XII (but will have no bleeding)
vWD (however in types 1 and 2 APTT is often normal)
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20
Q

if both APTT and PT are prolonged then what clinical conditions could this be

A

vitamin K deficiency (with low fibrinogen) due to liver disease or malabsorption

Disseminated intravascular coagulation (with low fibrinogen), will also see that D-dimers are raised, low platelets and red cell fragments

Heparin toxicity (will have normal fibrinogen)

Rarely you may have deficiencies in factor V or X but will have normal fibrinogen

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21
Q

what are the vitamin K dependant factors

A

II, VII, IX, X

protein C and S

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22
Q

What is in the diagnostic triad that a patient will present with if they might have clotting disorders

A

personal history of bleeding
family history of bleeding
supportive diagnostic tests

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23
Q

In the diagnostic triad: People with a personal history of bleeding, what symptoms may they present with

A
  • bruising; unexpected places, no injury, lumpy
  • epistaxis (nosebleed): duration and frequency
  • GI tract: start at the mouth and wok down
  • Menses: duration, flooding/clots, no of pads/tampons
  • Urine: haematuria
  • Surgical history
  • Dental history
  • Cuts and injury
24
Q

In the diagnostic triad: describe what would be seen in the family history of bleeding

A
  • if there are known bleeding disorders in the family
  • bleeding in family members especially after surgery or dentistry
  • if there is, get details of where tested, by whom and when
25
Q

In the diagnostic triad of bleeding disorders: what supportive diagnostic tests would you want to order

A

platelets (FBC)
tests of coagulation (PT, APTT, TT, fibrinogen, 50/50)
tests of clot stability (usually done by haematologists such as euglobin clot lysis, factor XIII assay and PAI-D [amish or Chinese])

26
Q

What is the difference between haemophilia A and haemophilia B

A

A is caused by deficiency in factor VIII

B is caused by deficiency in factor IX

27
Q

what kind of genetic disorder is haemophilia and what does this mean (in terms of demographics)

A

X linked recessive
means men only require one abnormal copy to have the disease
if only one copy is affected then they are a carrier
commonly only affects males

28
Q

What are the classical features of severe haemophilia

A

spontaneous bleeding into joints (haemoathrosis) and muscles
or any other abnormal bleeding

29
Q

Fill in the blanks for someone who has severe haemophilia in terms of ;

  1. Clotting factor levels in the blood
  2. degree of bleeding
  3. Frequency of bleeding
  4. Site of bleeding
A
  1. less than 1 iu/dl (normal range is 50-150)
  2. spontaneous
  3. 1-2 X per week
  4. Often joint
30
Q

Fill in the blanks for someone who has moderate haemophilia in terms of ;

  1. Clotting factor levels in the blood
  2. degree of bleeding
  3. Frequency of bleeding
  4. Site of bleeding
A
  1. 1iu/dl- 5iu/dl (normal range is 50-150)
  2. slight injury
  3. 1 X per month
  4. less often joint
31
Q

Fill in the blanks for someone who has mild haemophilia in terms of ;

  1. Clotting factor levels in the blood
  2. degree of bleeding
  3. Frequency of bleeding
  4. Site of bleeding
A
  1. more than 5 iu/dl (normal range is 50-150)
  2. trauma
  3. rare
  4. rare
32
Q

What are some of the basic principles for the treatment of haemophilia

A

treat in tertiary care
treat early if in doubt and fast track triage in A&E
don’t wait for clinical signs to develop
take care of veins, treatment
Early home therapy (RICE)

33
Q

In haemophilia A what factor is given and what amount and what frequency

A 
factor VIII (large molecule) 
Amount needed= Rise required x weight in kg / 2
1 dose 3 times a day (half life of 8 hours)
[ example if have internal knee bleed then raise the levels by 50% whereas if have haemorrhage more like 100% raise]
34
Q

in haemophilia B what factor is given and what amount and what frequency

A 
Factor IX (small molecule)
amount needed = rise x weight (based on clinical situation 
Once daily (half life is 18-24 hours)
35
Q

in which condition would you prescribe desmopressin (DDAVP) and why

A

Haemophillia A only
releases stored factor VIII and so useful for mild haemophiliacs
raises VIII by 2-3 times
make sure to test this when patient is well to see is suitable

36
Q

in which condition would you prescribe tranexamic acid and why

A

haemophilia A and B
it is an anti-fibrinolytic (oral)
slows down the palsminogen/plasmin system which allows blood clots to stay there longer

37
Q

what is the difference between primary and second prophylaxis treatment

A

primary is where you start to give the missing factors from the age of 18 months - 2 year
secondary is where you start treatment after the patient has had 3 joint bleeds

38
Q

for prophylaxis treatment of haemophilia A and B what frequency should the missing factors be given

A 
A= factor VIII alternate days but still often 3 times a week 
B = factor IX can be given 2 times a week
39
Q

What is the most common coagulopathy

A

Von Willebrand disease

40
Q

in terms of vWD

  1. what kind of bleeding occurs
  2. what percentage of women have menorrhagia (heavy menstrual bleeding)
  3. How many types of the disease are there
  4. what kind of inheritance
A
  1. mucocutaneous bleeding
  2. 15%
  3. 3 types
  4. autosomal dominant disease
41
Q

What is the difference in classification of the vWF disease types

A

type 1 - reduction in the amount of normal vWF protein
type 2- there is an abnormal vwF protein ( in type 2B it is overactive)
type 3- there is little or no vWF protein

42
Q

what would be the treatment for type 1 vWF disease

A

DDAVP (desmopressin) and tranexamic acid

watching for diminishing returns in major surgery as they may need vWF

43
Q

what would the treatment for type 2 vWF disease be

A

vWF

not DDAVP in type 2b

44
Q

what would the treatment for type 3 vWF disease be

A

vWF concentrate

consider prophylaxis and genetic advice

45
Q

what makes up a vWF screen

A

factor VIII
vW antigen
vW activity

46
Q

how to do differentiate type 1 and type 2 vWF disease

A

by using the ratio of vWF activity: vWF antigen
ratio greater than 0.6 its type 1
ratio less than 0.6 its type 2

47
Q

why would you use desmopressin (DDAVP)

A

stimulates the release of vWF

48
Q

What clinical signs would you see in types 1 and 2 of vWF disease

A

mild brusing
bruising/mucosal bleeding
menorrhagia
operations - dental extractions

49
Q

what is the rare 2B vWF disease

A

you have an over reactive vWF protein which can result in thrombocytopenia (low levels of platelets)

50
Q

in patients with type 2B vWF disease, why would you use vWF concentrate rather than desmopressin (DDAVP)

A

desmopressin will release vEF from stores (just in the same way in haemophiliacs it releases stored factor VIII) and of course this will be detrimental

51
Q

What other component in the blood is it important to check in patients who bleed

A

their iron levels as they will probably have iron deficiency

52
Q

What is the role of vitamin K

A

regulates blood coagulations by making coagulation factors mature

53
Q

Producing which clotting factors requires an enzyme that uses vitamin K

A

II, VII, IX and X

54
Q

what kind of vitamin is vitamin K and where is it synthesised

A

fat soluble and synthesised by bacteria in the gut

55
Q

in platelet plug formation what is the role of vWF

A

helps bind platelets to the exposed collagen

thromboxane A2 helps with vasospasm and platelet aggregation

56
Q

what converts fibrinogen into fibrin in the clotting cascade

A

thrombin and calcium

57
Q

how does the blood vessels slow down coagulation (anticoagulation)

A

protein C and S binds to thrombomodulin which inactivates factors V and vIII
antithrombin also binds directly to thrombin so blood clot can’t form

Medicine Y3 TCD 1-12 (30 decks)

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