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haematology > haemophilia > Flashcards

haemophilia Flashcards

1
Q

product of coagulation cascade that allows secondary haemostasis

A

yields thrombin which converts fibrinogen to fibrin
- stabilises clot

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2
Q

fibrinolytic system

A

breaks down fibrinogen + fibrin
- activation of fibrinolytic system generates plasmin (in presence of thrombin) which is responsible for the lysis of fibrin clots

breakdown of fibrinogen + fibrin results in polypeptides results in polypeptides = fibrin degradation products = DDimer

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3
Q

how is fibrin converted to fibrin degradation products (DDimers)

A

by plasmin!

plasminogen –(tissue plasminogen activator)-> plasmin

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4
Q

disseminated intravascular coagulation (DIC)

A

excessive + inappropriate activation of haemostatic system (primary, secondary + fibrinolysis)

microvascular thrombus formation - end organ failure
clotting factor consumptom -> bruising purpura + generalised bleeding

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5
Q

pathophysio of DIC

A

process of coagulation + fibrinolysis are dysregulated -> result is widespreaf clotting with resultant bleeding

critical mediator of DIC = tissue factor (TF) - exposed to circulation after vascular damage

on activation, TF binds with coagulation factors that then triggers the extrinsic pathway (via factor VII) which subsequently triggers the intrinsic pathway (XIItoXItoIX)

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6
Q

causes of DIC

A

sepsis
trauma
obstetric emergencies - elevated LFTs, low platelets (HELLP)
malignancy - eats through tissue, slower process

hypovolaemic shock

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7
Q

investigation findings of DIC

A

low platelets
low fibrinogen
HIGH fibrinogen degradation products (DDimers)
high PT + APTT

schistocytes due to microangiopathic haemolytic anaemia

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8
Q

management of DIC

A

treat underlying cause
replacement therapy
- platelet transfusions
- plasma transfusions
- fibrongen replacement

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9
Q

prothrombin time, APTT, bleeding time + platelet count in warfarin administration

A

prothrombin time - prolonged
APTT - normal
bleeding time - normal
platelet count in - normal

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10
Q

prothrombin time, APTT, bleeding time + platelet count in aspirin administration

A

prothrombin time - normal
APTT - normal
bleeding time - PROLONGED
platelet count in - normal

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11
Q

prothrombin time, APTT, bleeding time + platelet count in heparin admin

A

prothrombin time - normal/maybe prolonged
APTT - prolonged
bleeding time - normal
platelet count - normal

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12
Q

prothrombin time, APTT, bleeding time + platelet count in DIC

A

prolonged - prothrombin time, APTT, bleeding time

LOW - platelet count

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13
Q

haemophilia

A

hereditary disorder in which abnormally prolonged bleeding recurs episodically
- no abnormaliry of primary haemostasis

x-linked recessive - 30% have NO fam history

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14
Q

types of haemophilia

A

haemophilia A (factor VIII def) - commonest

haemophilia B ( factor IX deficiency)

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15
Q

haemophilia features

A

recurrent haemarthroses (bleeds in joints)
- iron in these spots fuel neovascularisation - more blood vessels -> more prone to bleeds

recurrent soft tissue bleeds - bruising in toddlers
prolonged bleeding after denta extractions, surgery

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16
Q

investigation findings in haemophilia

A

prolonged APPT
normal bleeding time, thrombin time, prothrombin time

17
Q

arterial thrombosis

A

high pressure system
atherosclerosis
platelet rich thrombus

Mx = aspirin + other anti-platelet drugs
- modify atherosclerosis risk factors

18
Q

venous thrombosis

A

lower pressure system
virchows triad -> stasis, endothelial damage, hypercoagulability

platelets not activated
activates coagulation cascade - rich in fibrin clot

Mx = heparin/warfarin/new oral anticoags

19
Q

extrinsic pathway

A

Tissue Factor (TF, factor III) activates VII to VIIa

VIIa activates X to Xa

20
Q

common pathway

A

Xa + Va (prothrombinase complex) facilitates conversion of prothrombin (factor II) to thrombin

thrombin facilitates the conversion of fibrinogen (factor I) to fibrin (factor XIII, makes stable)

21
Q

intrinsic pathway

A

sub endothelial collagen (SEC) exposed in vessel injury converts XII to XIIa which converts XI -> XIa which converts IX -> IXa

–> VIIIa + vWF activates conversion of X -> Xa

22
Q

what inhibits the intrinsic pathway

A

heparin

23
Q

how is the intrinsic pathway measured

A

APPT

24
Q

what initially activates the intrinsic pathway

A

subendothelial collagen (SEC)

25
Q

what inhibits the extrinsic pathway

A

warfarin

26
Q

how is extrinisc pathway measured

A

prothrombin time

(extrinsic activated by tissue factor)

27
Q

immune/idiopathic thrombocytopenic purpura (ITP)

A

an immune mediated reduction in platelet count
- antibodies are directed against the glycoprotein IIb/IIIa or Ib-V-IV

kids = usually have an acute thrombocytopenia that may follow infection or vaccination

adults = more chronic condition

28
Q

ITP in kids

A

self limiting disease following viral infection/vaccination

bruising, petechial/purpuric rash
bleeding less common, typically present as epistaxis or gingival bleeding

no Mx - resolves in 80% within 6 months
- avoid activities involving trauma

29
Q

ITP in adults

A

chronic relapsing disease - 85% spontaneously remit in 3-6months
commoner in older females

maybe detected incidentally following routine bloods
symptomatic - petechia, purpura, bleeding (epistaxis)

Ix - isolated thrombocytopenia, diagnosis of exclusion

30
Q

management of ITP in adults

A

oral prednisolone
pooled normal human immunoglobin (IVIG) may also be used
- raises platelet count quicker than steroids, therefore may be used if active bleeding or an urgent invasive procedure required

31
Q

Evans syndrome

A

ITP assoc with autoimmune haemolytic anaemia (AIHA)

32
Q

thrombotic thrombocytopenic purpura (TTP)

A

abnormally cleaved von Willebrand factor (due to abnormal ADAMST13) leading to platelt aggregation, thrombus formation + systemic microangiopathu

rare, typically adult females

hereditary - congenital mutation of ADAMST13
autoimmune - AI inhibition of ADAMST13

33
Q

pathophysio of TTP

A

abnormally large + sticky multimers of von Willebrands factor cause platelets to clump in vessels

in TTP there is a deficiency of ADAMST13 which breaks down (cleaves) large multimers of vWF

(overlaps with haemolytic uraemic syndrome)

34
Q

features of thrombotic thrombocytopenic purpura(TTP)

A

fever
microangiopathic haemolytic anaemia (MAHA)
thrombocytopenic purpura
CNS involvement - headache, confusion, seizures
AKI/renal failure

35
Q

TTP investigations

A

urine dip - haematuria + proteinuria (non-nephrotic range)
FBC - normocytic anaemia, thrombocytopenia, raised neutrophils
U&E - raised urea + creatinine

clotting normal
blood film - reticulocytosis (2nd to haemolysis) + schistocytes

LFT, LDH, DDimers raised + haptoglobins low - consistent with haemolysis

DIAGNOSIS = low ADAMST13 activity

36
Q

management of TTP

A

plasma exchange started within 24hrs of presentation

caplacizumab(bivalent antibody)

haematology (21 decks)

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