Haematology Flashcards
what are the two broad causes of coagulopathies
medication
conditions
what are the two main congenital conditions causing coagulopathies
Haemophilia (A and B)
von Willebrand’s disease
name 5 congenital conditions that cause coagulopathies
Haemophilia A and B
Von Willebrands
Bernard Soulier syndrome
Wiscott Aldrich syndrome
Idiopathic thrombocypenic purpura
Ehlers Danlos syndrome
what is haemophilia a and b
A = factor VIII deficency
B = factor IX defiency
what is primary and secondary haemostasis
primary hemostasis makes a weak platelet plug at the injury site while secondary hemostasis makes it strong by generating a fibrin mesh on it
how does haemophilia cause coagulopathies
X linked rcessive mutation
deficient factor IX or VIII both affecting the extrinisc pathway of fibrin formation for secondary haemostasis
primary haemostasis can occur but secondary cannot
no strengthening of platelet clot = increased bleeding
what are some signs and symptoms of haemophilia
Nosebleeds with no cause
Easy bruising - large
Spontaneous gingival bleeding
GI bleeds - blood in urine or stool
Difficult clotting after cuts - very small
Bleeding into joints (haemarthrosis)
Cranial bleeds
what classifications of haemophilia are there and how do we classify(not A and B)
severe = clotting factor < 1% spotaenous bleed
moderate = 2 < clotting factor < 5% may bleed
mild = 6 < clotting factor < 40% bleed after trauma/surgery
carrier = factor level may vary
what percentage in the blood would class as ‘normal range’ for clotting factor VIII and IX
50-100%
what is the first, second and third line treatment for haemophilia
anti-fibrinolytics e.g. tranexamic acid
DDAVP - encourages release of factor VIII and VWBf
Direct factor replacements
why do we try other treatments for haemophilia before using direct factor replacement
they are expensive
over time body may build immunity to the factors
how does tranexamic acid work (2)
Anti-fibrinolytic agent that inhibits the breakdown of fibrin clots
Blocks the binding of plasminogen and plasmin to fibrin therefore preventing fibrinolysis
can a dentist prescribe tranexamic acid and why
no
not in dental BNF
what are the (post) instructions for use of tranexamic acid (5)
Use QDS, start 5-10 minutes post extraction
Rinse with 5mls of 5% solution and hold for 2 mins, then spit
Continue for 5 days
Can be used to soak in absorbent gauze, to provide additional pressure to extraction site
avoid drinking for 1 hour after
what is DDAVP and how does it work
desmopressin
synthetic vasopressin - hormone that reduces urine output
DDAVP stimulates the release of endogenous FVIII and VWF from stores in patients endothelium of blood vessels with mild Haemophilia A and VWD
how is desmopressin given
prescribed by haematologist
nasally, intravenously, or as an oral or sublingual tablet
what are the two functions of VWBf
Promotes platelet aggregation (primary haemostasis)
Carrier protein for factor VIII (secondary haemostasis)
what is type I VWBd (3)
commonest type 80%
autosomal dominant
quantative deficency
how do we treat the most common type of VWBd
80% of people have type I
autosomal dominant
trial of DDAVP desmopressin, if unresponsive then factor substitute
what is type II VWBd
autosomal dominant, 15% of people
qualitative deficiency of VWBf
how do we treat type II VWBd
factor VIII concentrate
what is type III VWBd
severe quantative deficency of VWBf
<1%
autosomal recessive
how dow e treat VWBd type III
factor concentrate
compare type I, II and III VWBd (4)
type I = dominant, 80%, quantitive deficiency, treat DDAVP then factor
type II = dominant, 15%, qualitative deficiency, treat concentrate
type III = recessive, severe, <1%, treat concentrate
which is the most severe type of VWBd
type 3, <1%
why might a coagulopathy be cause of dental anxiety
some pts may not be diagnosed until a large bleed after a dental XLA which would be traumatic and scary for the patient
associate with the dentist
what are barriers to dental care of coagulopathies
dental anxiety
tired of treatments
Transfusion infections e.g. hep from the past when no screening occur
Access to dental care
Previous refusal
Lack of knowledge and management
Bad previous experience (including hospital admissions)
Haemarthrosis and mobility
what types of treatment are risk of bleeding and what must we do prior to these treratments with a pt with a bleeding disorder
BPE
Local anaesthetic - particularly IANB
Supragingival restorations with use of matrix bands
Scaling or periodontal disease management
Extractions
Biopsies
Any of these - liase with haematoligist
how do we safely manage an examination of a pt with bleeding disorder (4)
no BPE
safe, careful soft tissue examination
place intra-oral films carefully with x-rays or use OPT
thourough pt MH with point of contact established
how do we take a bleeding MH (7)
history of bleeding
how it is controlled - medications
what happens if they get a cut
wether affects primary or secondary coagulation
have they had injections before
haematologist point of contact
if they live far away and if they live alone
what parts of a dental procedure can cause bleeding with haemophiliacs
LA: Dental blocks and lingual infiltrations can cause haematomas that cause airway issues
Matrix bands, cotton wool rolls (can dry, sticky, tear out = bleed) and aspirators
BPE, 6 point chart, USS
which dental injections are likely to cause bleeding and what is the implication of this with haemophiliacs
Dental blocks and lingual infiltrations can cause haematomas that cause airway issues
what types of isolation are dangerous for haemophiliacs (2)
matrix bands
cotton wool (stick, tear off = bleed)
how can we prevent a bleed in surgery with a bleeding disorder pt
refer, very safe low risk examination
have point of contact established and thorough MH
follow local and government guidelines
how do we manage a bleeding emergency
call for help
stay calm
Patients generally know how to manage their condition
Local measures – apply pressure
Contact haemophilia centre or point of contact on MH and seek advice over phone
what are some acquired bleeding disorders
Chronic kidney disease
Liver disease (alcohol dependence/misuse, HIV, hepatitis)
Chemotherapy
Heart failure
Haematological malignancy
Myeloproliferative disorder
what blood tests should be taken prior to a dental procedure for haemophiliacs
Full blood count (which includes platelet levels) - find from haemotologist
Normal platelet levels 140-350 x 109/litre
Thrombocytopenia can aggravate surgical or traumatic bleeding
<20 spontaneous bleeding
>80 haemostatic and safe for surgical procedures
Clotting screen - for XLA but liaise with haemotologist
what is a safe, normal and dangerous level of platelets in the blood
Normal platelet levels 140-350 x 109/litre
<20 spontaneous bleeding
>80 haemostatic and safe for surgical procedures
what needs to be included in medication medical history of a bleeding disorder pt (3)
What medicines are you taking?
Prescribed and non prescribed (over the counter)
Herbal and complimentary medicines (e.g. St Johns Wort, garlic, Gingko biloba)
How long will you be taking them for? (e.g. LMWH can be a few weeks after large surgery) - Short term or long term
what needs to be included in medication medical history of a bleeding disorder pt (3)
What medicines are you taking?
Prescribed and non prescribed (over the counter)
Herbal and complimentary medicines (e.g. St Johns Wort, garlic, Gingko biloba)
How long will you be taking them for? (e.g. LMWH can be a few weeks after large surgery) - Short term or long term
which drugs affect the bleeding of a patient and how (9)
NOACS
antiplatelets
anticoagulants
LMWH
cytotoxic drugs associated with bone marrow suppression
NSAID (impair platelet function)
SSRI anti-depressants e.g Citalopram - platelet aggregation
Immunosuppressants - reduce number of available platelets
Drugs affecting nervous system
how do cytotoxic drugs affect bleeding
leflunamide, hydrochloroquine, infliximab, gold
associate with bone marrow suppression = less platelets
how do NSAIDs affect bleeding (4)
NSAIS are COXI and COXII inhibitors
prevent formation of thromboxane from arachidonic acid
thromboxane needed for vasoconstriction and platelet aggregation
affects primary coagulation
which anti-depressant causes changes in bleeding and how
Citalopram - platelet aggregation
give examples of immunosupressants and how they affect bleeding
methotrexate, azathioprine, mycophenolate
reduce number of available platelets
give two exmaples of nervous system drugs that affect bleeding
gabapentin may impair platelet function
carbamazepine may cause thrombocytopenia
which drug can cause thrombocytopenia
carbamazepine may cause thrombocytopenia
pt is on Dalteparin (Fragmin)
Enoxaparin (Clexane)
Tinzaparin (Innohep)
what are they taking and why
types of LMW herparin
anticoagulant
thin blood to prevent blood clots
how do patients administer LMWH
Usually administered subcutaneously by injection
what are some advantages of heparin
short onset of action
short half life
when would herparin be prescribed
Short term prescription for Prevention of VTE in pregnancy
after valve replacement
VTE and cancer
spinal injury
what is a VTE
venous thromboembolism
how do antiplatelet drugs work and give 4 examples
Impair primary haemostasis by interfering with platelet aggregation, reversibly or irreversibly
Clopidogrel (Plavix)
Aspirin
Dipyradimole (Persantin)
Ticagrelor (Brilique)
compare aspirin and clopidogrel
both antiplatelet drugs
aspirin is irreversible inhibiton of COX enzymes, clopidogrel is reversible
clopidogrel is a stronger antiplatelet
what is the bleeding time of dual therapy antiplatelets e.g. aspirin + clopidogrel
45-60mins
do antiplatelets/anticoagulants affect primary or secondary haemostasis
antiplatelets = primary
anticoagulants = secondary
what is warfarin and how does it work (4)
Vitamin K antagonist - anticoagulant
prevents formation of vitamin K dependant coagulation factors 2,7,9,10
affecting intrinsic and extrinsic pathways of the coagulation pathway
DVT, AF, Strokes, Valve replacements
what are the disadvantages of warfarin (3)
Multiple drug and dietary interactions - BNF
Variation in patient response to the drug
Needs careful monitoring with regular blood tests for INR (International Normalised ratio) is the time taken for a clot to form in a blood sample relative to a standard of 1
why do we ask how much pt has INR checked (3)
indication of how stbale their management of haemostasis is
Stable INR history, can be assessed up to 72 hours before the dental procedure - if checked every few months = stable
Unstable INR must be assessed within 24 hours of the dental procedure - if checked every week = unstable
how do we use INR with our management of pt
Dental procedures unlikely to cause bleeding continue without adjusting dose. Apply principles of safe treatment, use local measures routinely
Dental procedures likely to cause bleeding (low or high risk) with stable INR check INR at least 72 hours beforehand. Apply principles of safe treatment, use local measures routinely
Dental procedures likely to cause bleeding (low or high risk) with unstable INR check INR 24 hours beforehand. Apply principles of safe treatment, use local measures routinely
what are the principles of safe treatment of a pt with INR checks
Principles of safe treatment. Limit to single extraction, sub-gingival scaling 3 teeth then assess before continuing, staged treatment over separate visits, local measures pack and suture
how do we manage a pt with INR > 4
Refer back to medical practitioner for advice before proceeding
Do not stop medication yourself- Patient takes this for a clear medical reason and is likely to be at risk of a blood clot.
If providing urgent care, remember warfarin interacts with many antibiotics and antifungals (erythromycin, fluconazole, metronidazole) which can increase the bleeding risk to the patient, refer to the BNF!
what are some drugs that we cannot prescribe with warfarin (3)
‘azole’ antifungals = miconazole, itraconazole, fluconazole (nystatin is okay)
metronidazole
amoxicillin
macrolides (erythromycin ,azithromycin, clarithromycin)
basiclaly things that end in azole, mycin and amoxicillin
what are the four major DOACs
Dabigatran (Pradaxa)
Rivaroxaban (Xarelto)
Apixaban (Eliquis)
edoxaban
how do the four major DOACs work (2)
Dabigatran is a direct thrombin (factor II) inhibitor acting at the final step of the coagulation process preventing fibrinogen to fibrin
Rivaroxaban and Apixaban and Edoxaban inhibit a different clotting Factor - Xa (Xa in name)
give some advantages and disadvantages of DOACs
As effective as warfarin
Fast onset
Fixed doses
No blood tests
Less drug interactions
Lower risk of major bleeds
Increased risk of GI bleeding
BUT no antidote but with warfarin, vitamin K is an antidote
how are the 4 major DOACs administered
Dabigatran and Edoxaban once daily, AM or PM
Rivaroxaban and Apixaban twice daily AM and PM
what 2 senarios can we not omit DOAC medication for surgery
If the patient has started the medication or had a PE/DVT within 3 months they must be discussed with their haemotologist prior to omitting the DOAC