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Minor Oral Surgery > SCD Acquired bleeding disorders > Flashcards

SCD Acquired bleeding disorders Flashcards

1
Q

What is prolonged bleeding?

A
  • continues beyond 12 hours
  • causes the patient to return to the dental surgery or to A&E department
  • results in large haematoma or ecchymosis (bruising) within the soft tissues
  • requires transfusion
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2
Q

List some extraoral features of a prolonged bleed

A
  • purpura
  • petechiae
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2
Q

What is purpura?

A

this is a discolouration that occurs in the skin and mucous membranes due to haemorrhage from small blood vessels

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3
Q

What are the main features of purpura ?

A
  • does not blanch
  • usually measures 0.3-1cm
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3
Q

What is petechiae?

A

these are small purpuric lesions which usually measure up to 2mm

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4
Q

Petechiae are usually associated with…

A
  • underlying acquired disorder of platelets

or

  • underlying acquired disorder of coagulation
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5
Q

Outline instances where petechiae are commonly seen

A

children or older people as a result of
* injury
* trauma
* ageing skin
* bacterial infection

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6
Q

What special test is particularly valuable for acquired bleeding disorders (e.g. patients on anticoagulant medication)?

A

prothrombin time (PT)

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7
Q

What are the main uses of prothrombin time (PT) tests?

A

determine clotting ability in patients on warfarin or patients with liver damage

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8
Q

What is the reference range of PT ?

A

12-15 seconds

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9
Q

What is the normal range for INR?

A

0.8-1.2

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10
Q

What clotting factors does the PT measure?

A

II, V, VII, X
(2, 5, 7, 10)
as well as fibrinogen

(factor 2 is prothrombin)

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11
Q

PT is used in conjuction with …

A

APTT
Activated partial thromboplastin clotting time

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12
Q

What drug therapies can result in the development of bleeding disorders?

A
  • antiplatelet drugs
  • anticoagulants
  • corticosteroids
  • chemotherapy
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13
Q

Antiplatelet drugs offer great benefit to patients with …

A

ischaemic heart disease

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14
Q

What is the main role of antiplatelet drug therapy?

A

to prevent thrombosis formation in atheroscletotic arteries which often lead to major complications such as ischaemic heart disease, stroke, intermittent claudation in limbs and heart failure

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15
Q

What represents the final common pathway of platelet aggregation?

A

binding of fibrinogen to gpIIb/IIIa

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15
Q

List the most commonly used antiplatelet drugs

A
  • aspirin
  • other NSAIDs
  • clopidogrel
  • dipyradamole
  • fibrinogen receptor inhibitors
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15
Q

What is the duration of action of aspirin? Why is this

A

8-10 days

Irreversibly binds to COX-1 in platelets
therefore it lasts the lifespan of aforementioned platelets; lifespan is usually 7-10 days

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16
Q

What is the MOA of aspirin?

A

irreversibly inhibits COX-1 in platelets
preventing production of TXA2

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17
Q

What is the role of TXA2 ?

A
  • potent vasoconstrictor
  • platelet aggregant
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18
Q

Following use of aspirin, platelet aggregation can occur by day 4 in 80% of cases. True or false
What is this indicative of ?

A

True

This shows that aspirin only has an effect on platelet function but not on platelet count

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19
Q

What is the usual oral prescription of aspirin?

A

75-300mg

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20
Q

Outline indications for use of aspirin

A
  • prevent thrombotic cardiovascular or cerebrovascular disease
  • following CABG / coronary bypass surgery
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21
Q

Briefly describe the effect of NSAIDs such as ibuprofen and diclofenac have on platelet aggregation and function

A

they have a reversible on platelet aggregation and function

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22
Q

Why are NSAIDs such as ibuprofen and diclofenac not used clinically for their antiplatelet action?

A

this is because their effects last as long as the half life of the drug

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23
Q

What is the MOA of clopidogrel?

A

inhibition of ADP signalling and thus reduces platelet activation

Metabolised by liver and binds to P2Y1 receptors (ADP platelet receptors) thus reducing platelet activation

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24
Q

What is th MOA of dipyradamole?

A

inhibition of phosphodiesterase and inactivation of cAMP

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25
Q

What is the clinical use of clopidogrel?

A
  • prevention of athero-thtombotic events in patients who suffer with MI, ischaemic stroke or in PAD

peripheral artery disease

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26
Q

State some instances when clopidogrel can be used in conjunction with aspirin

A
  • unstable angina
  • following insertion of coronary artery stent (unlicensed indication)
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27
Q

Upon cessation of clopidogrel, platelet function recovers fully after ____ days.

A

2

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27
Q

What can modified release preparations of clopidogrel be used for?

A

secondary prevention of
* ischaemic strokes
* transient ischaemic attacks

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27
Q

Clopidogrel has an effect on APTT. What is the consequence of this?

A

it has an effect on post-operative bleeding

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28
Q

According to UKMI guidelines, what clinical conditions require patients taking antiplatelet medication to be referred to secondary care/specialist service ?

A
  • dual antiplatelet therapy
  • liver impairment and/or alcoholism
  • renal failure
  • thrombocytopenia (reduction of platelet count) / other haemostasis disorder
  • patients receiving a course of cytotoxic medication
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29
Q

What are the most common coumarins (anticoagulants)?

A

warfarin
followed by heparin

30
Q

Warfarin is a true derivative of courmarin. True or false

A

True

31
Q

What is coumarin?

A

this is a chemical that is naturally found in plants

32
Q

What is the MOA of warfarin ?

A

inhibits biosynthesis of vitamin K dependent clotting factors II, VII, IX, X

33
Q

Whta is the effect of warfarin on PT and APTT?

A

prolongs PT and APTT

34
Q

When is the maximal effect of warfarin seen ?

A

at 36 hours

35
Q

How is the activity of warfarin expressed clinically?

A

INR (international normalised ratio) which is the PT ratio

36
Q

What should the INR of an individual not taking warfarin be?

A

1.0

37
Q

How is the effect of warfarin reversed?

A

administration of vitamin K

38
Q

Give examples of drugs that can interact with warfarin

A
  • antibiotics- metronidazole, tetracyclin
  • antifungals- miconazole, fluconazole, ketoconazole
  • analgesics- aspirin and NSAIDs
  • antidiabetics- chlropromamide
  • antiepileptics- phenytoin
  • homeopatic medications e.g. St John Wort
  • some foods such as grape fruit juice
39
Q

What effect can high protein bound drugs have on warfarin?

A
  • displace warfarin (from albumin)
  • causes an increase in serum/plasma warfarin thus increasing its effect
  • increase in INR
40
Q

Give examples of highly protein bound drugs that can impact the action of warfarin

A
  • simvastatin
  • NSAIDs
41
Q

Briefly describe the effect of metronidazole and antifungals on warfarin

A
  • they potentiate the effect of warfarin by decreasing its metabolism
  • [through competition for specific liver enzyme for metabolism]
42
Q

What is the effect of broad spectrum anitbiotics on warfarin?

A

decrease the gut bacterial flora
decrease synthesis of vitamin K?
increase INR; increase the effect of warfarin

43
Q

What is the effect of leafy foods on warfarin?

A

they contain vitamin K so they reduce the effect of warfarin

44
Q

What is the effect of grape fruit on warfarin?

A

increases the effect due to competition with liver CYP450 enzyme

45
Q

What is the effect of hyperthyroidism on warfarin?

A

increase the effect of warfarin
this may be due to a change in rate of metabolism of the clotting factors

46
Q

Why is discontinuing warfarin a few days prior to dental surgery no longer recommended?

A

this is because it increases the risk of thrombo-embolic events

47
Q

What INR is recommended for patients on anticoagulants to safely receive dental treatment?

A

4.0 or below

48
Q

What course of action should be taken for a patient with an INR of >4.0 requiring invasive dental treatment ?

A
  • consultation required with patients clinican responsible for anticoagulant regime
  • warfarin dose can then be adjusted if needed
49
Q

When should the INR be taken prior to undertaking dental procedure?

A
  • 24 hour before procedure
  • for patients with stable INR, it can be measured within 72 hours of the procedure
50
Q

Why is it prudent to time procedures to occur in the morning or earlier in the week for patients on anticoagulants?

A

this is because it allows time to deal with delayed bleeding episodes

51
Q

What is Heparin?

A

it is a natural sulphated glycosaminoglycan found in mast cells

52
Q

What is the MOA of heparin ?

A
  • it is a catalyst for plasma antithrombin III
  • antithrombin III regulates coagulation by inactivating coagulation proteases such as thrombin and factor Xa
  • also decreases platelet aggregation

they therefore prevent clot formation

53
Q

Outside of its use as an anticoagulant, state another biological effect of heparin

A

immunosuppresive effects

54
Q

How is heparin administered ?

A
  • intravenously
  • subcutaneously
55
Q

What is the half life of heparin?

A

1-2 hours

56
Q

The dose of heparin is adjusted in accordance with …

A

APTT

57
Q

The effects on clotting are lost within ____ of stopping heparin

A

6 hours

58
Q

Give examples of low molecular weight heparin

A
  • certoparin
  • dalteparin
  • enoxaprin
  • riviparin
  • tinzaparin
59
Q

LMWH interacts mostly with …

A

factor Xa
(activated factor 10)

60
Q

What is the half-life of LMWH ?

A

2-4 hours
(longer than heparin)

61
Q

What are the indications of use of LMWH?

A
  • long term out-patient prophylaxis for pregnancy
  • patients intolerant to warfarin
  • prophylaxis for patients with lupus anticoagulant factor
62
Q

What is the main caveat with using LMWH?

A

they do not affect standard blood results so their use poses a difficulty with assessing bleeding tendency prior to invasive dental treatment

63
Q

Why are patients receiving heparin able to be scheduled to receive simple dental extractions the day after its administration?

A

this ie because it hase a shorter half life than warfarin

64
Q

Give examples of local haemostatic measures

A
  • local anaesthetic
  • minimise trauma
  • haemostatic agents e.g. surgicel, gelatine sponge
  • suture
  • POI
  • tranexamic mouthwash- not in DPF
65
Q

What is a possible indication for ginger and what is its effect on INR?

A

Nausea

increase INR (increased bleeding risk- blood is clotting too slowly)

65
Q

What is a possible indication for St Johns Wort and what is its effect on INR?

A

Depression

decreases INR (lower risk of bleeding)

66
Q

What is the effect of ginger, ginseng and gingko on INR?

A

increased INR- increased risk of bleeding

67
Q

What is the effect of ginger, gingseng and ginko on platelets?

A

inhibit platelet adhesion and aggregation

(increased risk of bleeding)

68
Q

What is a possible indication for the use of ginseng?

A

increase energy levels

69
Q

What is the possible indication for use of garlic as herbal medication?

A

decrease cholesterol

70
Q

What is the possible indication for use of gingko as herbal medication ?

A

increase cerebral flow therefore improving memory and decreasing dementia

71
Q

What are the indications for use of heparin ?

A
  • atrial fibrillation
  • prophylaxis and treatement of peripheral arterial emboli
  • prevention of clotting
  • prevention of clotting during heart surgery
  • acute thrombo-embolic episdoes
  • prevention of DVT and pulmonary emboli following surgery
  • IV renal hameodialysis to prevent thrombosis in pumps
  • prophylactic prevention of thrombosis after MI
72
Q

How do coroticosteroids gain their anti-inflammatory effect?

A
  • suppression of phospholipase A2
  • therefore the inhibit the main products of inflammation
73
Q

Why would a patient on corticosteroids experience prolonged bleeding?

A
  • decreases plalete function as a result of inhibition of TXA2
  • effects of corticosteroids on vessel wall; interferance with initial haemostatic interactions between vessel wall, platelets and clotting factors
  • immunosuppresion leading to increased risk of infection and therefore fibrinolysis [!!]
74
Q

What does chemotherapy refer to?

A

generally refers to targetting neoplastic cells

75
Q

Chemotherapy also damages cells that divide rapidly under normal circumstances. True or false

A

True

76
Q

How might chemotherapy cause prolonged bleeding?

A

target rapidly dividing cells in bone marrow
This results in myelo-suppresion and a reduction in platelet count

77
Q

Give an example of a cancer that is sensitive to chemotherapy. State why

A

Hodgkins lymphoma

this is because a large proportion of the targeted cells are undergoing cell division at any time

78
Q

Aside from cancer, give other conditions where chemotherapy is appropriate?

A
  • autoimmune disorders such as rheumatoid arthritis or multiple sclerosis
79
Q

When should dental procedures be scheduled for patients on chemotherapy? Explain your reasoning

A
  • One cycle of chemotherapy lasts for approx 6 weeks with a 6-week rest in between cycles
  • life span of platelets is 7-10 days
  • lifespan of leucocytes is 4 weeks
  • dental procedures should be scheduled around week 4 to allow optimal healing and haemostasis before next cycle
80
Q

Give indications for corticosteroid use

A
  • addisons disease- adrenal insufficiency
  • suppression of allergic reactions e.g. asthma, dermatitis
  • suppression of inflammatory conditions e.g. arthritis, IBD, crohns dsease, UC, termoral arteritis
  • suppression of SLE, sarcoidosis
  • post transplant immunosuppresant
  • grafts versus host disease to prevent transplant rejection
  • chemotherapy

Minor Oral Surgery (36 decks)

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