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M103 T2 > M103 T2 L7 > Flashcards

M103 T2 L7 Flashcards

1
Q

What are the thrombotic risk factors?

A 
Post-operative, especially orthopaedic
Hospitalisation
Cancer
Pregnancy
OCP
Long-haul flights
Obesity
i.v. drug abuse
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2
Q

How does DVT present?

A

Can be no symptoms at all – clinically silent
Unilateral calf swelling/ heat/ pain/ redness/ hardness
Potentially fatal if missed

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3
Q

What is the function of a doppler ultrasound?

A

shows the flow / lack of flow in a blood vessel

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4
Q

What is the initial treatment for DVT?

A

Therapeutic anti-coagulation using sub-cut LMW heparin (such as tinzaparin or enoxaparin)

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5
Q

How is the initial treatment of DVT administered / calculated?

A

Dosing is according to patient’s weight
No monitoring is required
patient needs to have adequate renal function

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6
Q

What is the patient treated with for DVt if they have renal impairment?

A

anti-coagulate with i.v. unfractionated heparin instead (maintain APTT 1.5-2.0)
only if the creatinine clearance of the kidney is less than 30ml/min

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7
Q

How is the patient treated after the initial treatment for DVT?

A

Load patient with oral warfarin for 3-5 days
warfarin levels monitored with INR tests
Stop LMW heparin once INR > 2.0 for 2 days
the first clot would be treated for six months - 1st DVT (femoral or iliac) - 6 months’ warfarin
the second DVT/PE: lifelong warfarin
Maintain INR between 2.0-3.0 (target 2.5)

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8
Q

What are the classical symptoms of DVT?

A

pleuritic pain - pain on inspiration
dyspnoea - difficulty breathing
haemoptysis - coughing up blood

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9
Q

What are the severe symptoms of DVT?

A

syncope

death

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10
Q

What are other conditions DVT patients might have?

A

O/E
tachycardic
tachypnoeic
hypotension

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11
Q

What are some statistics for DVT?

A

5% mortality with treatment
Cause of death in 10-30% of in-patient post mortems
Up to 60% have micro-emboli at post mortem

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12
Q

What is the treatment for DVT?

A

LMW heparin injections (better for cancer patients)
warfarin for 6 months
no oral contraceptive pill if associated with
IVC filter
DOAC / NOAC

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13
Q

Which age group would you consider doing a thrombophilia screen and why?

A

Sometimes done in younger patients with VTE to check for inherited risk factors

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14
Q

What are inherited risk factors for DVT?

A

deficiencies of anti-thrombin, Protein C and S
Prothrombin gene variant
Factor V Leiden

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15
Q

What is the function of warfarin?

A

Vitamin K antagonist - prevents post-translational modification / γ-carboxylation of factors II, VII, IX, X
in so doing it prolongs the extrinsic pathway (which is tested by measuring the prothrombin time)

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16
Q

What are the target INRs for warfarin patients?

A

Target INR for warfarin patients usually 2.5 for DVT/PE and AF
Target 3.5 for recurrent VTE or metal heart valves

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17
Q

How does warfarin work?

A

inhibits vitamin k reductase
it’s metabolized by p450
it prevents the formation of factors II, VII, IX, X

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18
Q

Why does it take warfarin a few days to work?

A

the different factors (II, VII, IX, X) have different half lives
so it takes 3-5 days to reach adequate levels of anti-coagulation for patients started on warfarin

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19
Q

Which four factors does warfarin affect?

A

II
VII
IX
X

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20
Q

How does warfarin affect the patient outside of the treatment?

A

warfarin also inhibits the formation of natural coagulants - protein C and protein S
bc these have very short half lives, when patients are started on warfarin they become pro-thrombotic before they become anti-coagulated bc their anti-coagulants are being depleted
Fall in protein C and S occurs within hours and can result in a temporary pro-coagulant state

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21
Q

How is warfarin prescribed?

A

Patient usually loaded with more warfarin then they need
then the level is brought down on day 3 to a maintanance level
warfarin is overlapped with LMW heparin until the INR is within the therapeutic range, above 2.0 for 2 consecutive days

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22
Q

What is the typical loading regime of warfarin?

A

10mg, 10mg, 5mg

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23
Q

What is a dangerous feature of warfarin?

A

patients have different levels of sensitivity to warfarin

24
Q

Can warfarin be prescribed without checking for other drugs?

A

no, need to be aware of interactions between warfarin and other drugs that are metabolized by the same enzyme in the liver as warfarin is - p450
those drugs that inhibit p450 will potentiate the action of warfarin
conversely those drugs that induce p450 will inhibit the action of warfarin

25
Q

What is the most important drug that interacts with warfarin and why?

A

alcohol
problem for alcoholics
will lead to high INR and high risk of bleeds

26
Q

What are the side-effects of warfarin?

A

teratogenic – therefore LMW heparin is used in pregnancy instead
there is a significant haemorrhage risk – intra-cranial bleeds up to 1% per year, increased risk in elderly and with higher INR target
Minor bleeding up to 20% per year
Skin necrosis
Alopecia

27
Q

How is warfarin reversed in a severe bleed?

A

Give vitamin K 2-10mg intravenously depending on INR level
will take 6-12 hours to work because of half life of factors being in excess of six hours
Patient can become refractory to re-loading with warfarin

28
Q

How is warfarin reversed in a life-threatening bleed?

A

vitamin K and Octaplex containing the factors
25-50 units per kg octaplex
Fresh frozen plasma (FFP) can also be used

29
Q

Why do we need to know how to reverse warfarin?

A

if patients come in with severe bleeds

30
Q

How is fresh frozen plasma dosed?

A

according to the patients’ weight and their INR

31
Q

How is heparin administered? Is it safe in pregnancy

A

always given by injection - parenterally

safe in pregnancy

32
Q

What is the function of heparin and how does it work?

A

it potentiates the action of anti-thrombin

by irreversibly inactivating factors IIa (thrombin) and Xa

33
Q

What are the two formulations of heparin and how are they administered?

A

Unfractionated heparin - IV or SC
LMW heparin - mostly s.c injections (can be IV but less common
sc = subcutaneous

34
Q

What conditions will unfractionated heparin be used in?

A

not often used due to inconvenience

only used in patients with renal failure

35
Q

Can unfractionated heparin be reversed?

A

it’s not very easy to reverse - can be partially reversed with protamine sulphate

36
Q

How is unfractionated heparin monitored to make sure levels are safe?

A

looking at the APTT with target range of 1.5-2.5 x normal

have to monitor the platelet count

37
Q

Why is the platelet count monitored in the use of unfractionated heparin?

A

level of platelets can fall due to development of thrombocytopenia
VTE is a rare complication resulting in heparin-induced thrombocytopenia or HIT

38
Q

What is the dosage of unfractionated heparin?

A

Given i.v. with 5000U bolus and ~1000U/hour infusion

39
Q

How (often) is LMW herparin administered to the patient and how is the dose calculated?

A

it is very convenient due to once daily subcutaenous injections
dosed according to patient’s weight

40
Q

What are the main three LMW heparin formations?

A

Tinzaparin (Innohep) 175U/kg
Enoxaparin (Clexane) 1.5mg/kg
Dalteparin (Fragmin)

41
Q

Does LMW heparin need to be monitored?

A

no, but usual renal function needs to be maintained - patient must have creatinine clearance of over 30ml/minute

42
Q

How are NOACs administerd? How are they monitored? How safe are they?

A

it is orally available
no monitoring
good safety profile

43
Q

What are the two classes of NOACs?

A

Dabigatran – direct thrombin (IIa) inhibitor

Rivaroxaban – direct factor Xa inhibitor

44
Q

How effective are NOACs? What is a disadv?

A

trials show that they are just effective as warfarin and LMW heparin
disadv - the anti-coagulant action is irreversible

45
Q

What is the dosing for dabigatran? How is it monitored and administered?

A

110mg bd or 150mg bd
confirm creatinine clearance > 30ml/min
administered orally

46
Q

What is dabigatran and rivaroxaban used for?

A

used for treatment of DVTs and PEs

stroke prevention in atrial fibrillation

47
Q

What is the dosing for rivaroxaban? How is it administered?

A

Dosing is 15mg bd for 3 weeks, then 20mg od

or 15mg od if CrCl is 15-50ml/min

48
Q

How does aspirin work as an antiplatelet drug?

A

inhibits cyclooxygenase
is a very effective anti-platelet agent
it disables platelet function and activation and aggregation

49
Q

What are the three main glycoprotein IIb/IIIa inhibitors?

A

Abciximab – monoclonal antibody
Eptifibatide – snake venom derivative
Tirofiban – blocks platelet aggregation

50
Q

How do fibrinolytic agents work?

A

lyse fresh thrombi (arterial) by converting plasminogen to plasmin

51
Q

What conditions are fibrinolytic agents used for?

A 
acute MI
recent thrombotic stroke
major PE 
iliofemoral thrombosis
strokes
52
Q

Give examples of fibrinolytic agents

A

Tissue Plasminogen Activator (tPA, Alteplase)

Streptokinase

53
Q

How are fibrinolytic agents administered? Describe the dosage

A

Administered systemically

Standardized dosage regimens aim to use within 6 hours

54
Q

What are signs of shock?

A

hypotension, acute dyspnoea, collapse, syncope

55
Q

What medication is used to treat a massive PE?

A

thrombolysis with tPA (Alteplase)
Tissue plasminogen activator (fibrinolytic)
iv unfractionated heparin
Monitor with APTR

M103 T2 (9 decks)

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