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Senior - Heme-Onc > Lecture 7 - Platelet Disorders > Flashcards

Lecture 7 - Platelet Disorders Flashcards

1
Q

Describe platelet hematopoiesis

A

Myeloid stem cells —> megakaryocyte

Megakaryocytes splinter into 2-3k fragments

Fragments get enclosed in plasma membrane

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2
Q

Describe a platelet

A

Disc-shaped with many vesicles

No nucleus

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3
Q

How do platelets stem bleeding?

A

They form a platelet plug

Their granules contain blood clot promoting chemicals

  • ADP
  • Thromboxane A2
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4
Q

Life span of platelets?

A

5-9 days

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5
Q

What controls platelet formation?

A

Thrombopoietin

Produced in the liver and stimulates megakaryocytes

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6
Q

You see a platelet abnormality on CBC, now what?

A

Ask yourself if its quantitive or qualitative

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7
Q

Fancy medical word for platelet clumping?

How do i r/o this with a platelet abnormality?

A

Pseudothrombocytopenia

R/o by repeating plt ct in non-EDTA containing tube
- sodium citrate tube

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8
Q

Youve narrowed it down to a quantative problem, what are some things that can cause this?

A

Reduced survival

Reduced production

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9
Q

What causes reduced survival of plt?

A
  • Immune thrombocytopenia
  • HIT
  • TTP
  • HUS
  • Hypersplenism
  • key
    HIT (heparin induced thrombocytopenia)
    TTP (thrombotic thrombocytopenic purpura
    HUS (hemolytic uremic syndrome
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10
Q

What will cause reduced production of plt?

A
  • Bone marrow disorder
  • infection
  • drugs
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11
Q

When are you more likely to notice qualitative plt disorders?

A

When clinically significant bleeding occurs

  • Von Willebrand’s disease
  • acquired disorders (uremia, drugs, ETOH)
  • congenital causes
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12
Q

What is immune thrombocytopenia?

A

Autoimmune condition - antibodies bind PLTs, results in accelerated PLT clearance

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13
Q

Primary vs secondary immune thrombocytopenia?

A

Primary: idiopathic thrombocytopic purpura (ITP)
- MC

Secondary: disease/drugs

  • autoimmune (SLE)
  • lymphoproliferative d/o (chronic lymphocytic leukemia)
  • connective tissue d/o
  • HIV/Hep C
  • drugs
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14
Q

Acute vs chronic immune thrombocytopenia?

A

Acute < 6mo

Chronic > 6 mo

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15
Q

Which populations are prone to acute vs chronic ITP?

A

Acute - kids
Chronic - adults
- secondary is also more likely to be chronic

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16
Q

Clinical features of ITP?

A
  • Mild mucosal bleeding
  • sever bleeding (old and sick pts)
  • splenomegaly (uncommon)
  • low plts (<50,000) if sever isolated form
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17
Q

Bleeding location follows the platelet count. As it descends what order does bleeding occur?

A

Skin

Mucous membrane

Viscera

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18
Q

If a ITP pt has no cutaneous petachie they have a low likelihood of?

A

Intracranial hemorrhage

I.e. they have a less sever form of ITP

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19
Q

How is ITP diagnosed?

A

Diagnosis of exclusion
- R/O Hep B, C, HIV

CBC - isolated thrombocytopenia

HX - must lack drug, etoh, food and herbal causes

Bone marrow bx

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20
Q

How long after starting a new drug will the pt get sever thrombocytopenia and mucotaneous bleeding if it is drug induced?

A

W/in 7-14 days

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21
Q

Who needs a bone marrow bx?

A

Older pts - r/o myelodysplastic syndrome

Unexplained cytopenias

Fail initial therapy

Prior to splenectomy

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22
Q

What is the goal of treatment with ITP?

A

To reduce risk of clinically important bleeding

- not to normalize plt count

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23
Q

Treatment for ITP?

A

Corticorsteroids =/- IVIG or anti-D
- mainstay of tx <30,000

PLT transfusion as needed

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24
Q

Tx for refractory cases of ITP?

A

Monoclonial antibodies
- rituximab

Splenectomy
- for failed tx or high dose steroids

Eltrombopag/romiplostim
- TPO-R agonist to stimulate plt production

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25
Q

Tx for asymptomatic pts or pts with plt count > 30,000-40,000?

A

There is only a 15% chance of sever thrombyctopenia requiring tx

  • serial PLT counts
  • watch for bleeding
  • counsel pts on s/s of bleeds
26
Q

What is HIT?

A

heparin induced thrombocytopenia

Lifethreatening complication of heparin (LMWH or unfractionated heparin)

  • 5-10 days post heparin
  • not dose related (even hep-locks)
  • seen in 5% of pts w heparin
27
Q

Pathophysiology of HIT?

A

Body forms IgG antibodies to heparin-platelet factor 4 (PF4) complexes

  • leads to prothrombotic state
  • macrophages eat the platelets —> thrombocytopenia
28
Q

Types of HIT?

A

Mild - type I
- can continue heparin

Severe - type II
- hypercoagulatable state lasts for months

29
Q

Describe type I HIT

A

Not immune mediated

  • no clinical consequence
  • modest thrombocytopenia (100,000)
  • begins 1-2 days after therapy
30
Q

What causes type I HIT?

A

We’re not sure but we think:

Direct effect of heparin on platelet activation (causing a non-immune platelet aggregation)

31
Q

Describe type II HIT

A
  • 5-10 days after tx
  • immune mediated ab against Heparin PF4
  • enhanced thrombin formation
  • paradoxical thrombosis
  • thrombocytopenia
  • risk of DVT/PE/thrombosis
  • hypercoagluatable state lasts weeks-months
32
Q

When to suspect HIT?

A

Any of the following w/in 5-10 days of heparin

  • unexplained thrombocytopenia
  • venous/arterial thrombosis from thrombocytopenia
  • PLT count drops 50% or more
  • necrotic skin lesions at inj site
33
Q

How is HIT usually diagnosed?

A

Clinically

The lab can confirm but it is slow

  • ELISA test
  • Serotonin release assay
  • heparin-induced platelet aggregation
34
Q

What is the 4Ts score for HIT?

A

Objective measure to determine if thrombocytopenia is HIT or something else

  1. Thormbocytopenia
  2. Timing of platelet count fall
  3. Thrombosis/sequelae
  4. Thrombocytopenia (Other causes)
35
Q

Tx for HIT?

A

STOP HEPARIN

Switch to

  • agratroban
  • bivalirudin
  • fondaparinux

After 3 months or when plt count reaches 150,000 pt can have warfarin

36
Q

HIT pts also cannot have?

A

Warfarin - may worsen hypercoagulability

Until their platelet count is >/= 150,000

37
Q

Prognosis?

A

Usually can use heparin again 100 days later (IgG ab dont last)
- < 100 days recurrence is high

But since other meds are available its best to just give them the other drugs

38
Q

What is TMA?

A

Thrombotic microangiopathy

Acute complex syndrome w

  1. VASCULAR ENDOTHELIAL INJURY leading to WIDESPREAD THROMBI FORMATION in the microvasculature
  2. TTP AND HUS
39
Q

Primary feature of vascular endothelai injury, TTP, and HUS that are required to be present for a diagnosis of TMA to be made?

A

MAHA - microangiopathic hemolytic anemia
- shearing of RBC (schitocytes)

Thrombocytopenia

40
Q

Therapy for TMA?

A

Plasma exchange - removal of pt plasma and replacement with donar plasma

41
Q

Most cases of TTP (thrombotic thrombocytopenic purpura) involve?

A

Acquired inhibitor of von Willebrand factor-cleaving protease
- ADAMTS 13

42
Q

What is ADAMTS 13?

A

ADAMTS 13 attaches to endothelial cells and cleaves large vWF multimers

43
Q

What happens with ADAMTS 13 when you get TTP?

A

Idiopathic:
Autoantibodies form against ADAMTS 13 leading to large accumulation of large vWF multimers that cause plt aggregation and thrombosis

  • can also be 2/2 drugs, chemo, cancer
44
Q

TTP presentation: FAT RN

A

F: fever
A: microangiopathic hemolytic ANEMIA
T: thrombocytopenia

R: renal disease (AKI)
N: neurologic complications (altered/confused)

45
Q

What is HUS?

A

Hemolytic uremic syndrome

Simultaneous occurence of

  • Microangiopathic hemolytic anemia
  • Thrombocytopenia
  • Acute kidney injury
46
Q

Common cause of kidney injury in kids?

A

Hemolytic uremic syndrome

Kids always exhibit the classic triad

47
Q

HUS s/s?

A

Petechial rash
HTN
Renal failure

Preceded by Gastroenteritis

48
Q

If your HUS is not preceded by 0157:H7 or STEC it is considered?

A

Atypical

Usually medication, autoimmune, or some other type of infection

49
Q

Therapy for HUS?

A

Supportive

50
Q

FAT RN is the classic pentatd for TTP and HUS the presence of ___ and ___ should increases your suspicions

A

MAHA (microangiopathic hemolytic anemia)
and
thrombyctopenia

51
Q

What findings common with TTP?

A

Neurologic

- Scattered thrombi formation in brain and subsequent impaired blood flow and O2 delivery

52
Q

What findings are more common in HUS?

A

Renal findings

- microvascular thrombus formation and hemoglobinuria from intravascular hemolysis causing renal failure

53
Q

Labs for TTP and HUS?

A
  • thrombocytopenia
  • fragmented cells on PBS
  • hemolytic labs
    — H LDH
    — L haptoglobin
    — H indirect bilirubin
  • NEG DAT (coombs)
  • POS stool cx (HUS)
54
Q

TTP tx?

A

Plasma exchange - removes antibodies to ADAMTS 13
- performed daily x 2 days

2nd line/refractory - immunosuppresion

  • corticosteroids
  • rituximab
  • cyclosporine
55
Q

quantitive platelet disorder causing reduced survival?

A

Hypersplenism - splenomegaly —> increased plt sequestration

56
Q

quantitive platelet disorders causing decreased production?

A

Bone marrow disorder
Infection
Drugs

57
Q

qualitative platelet disorder inherited?

A

vWF - coagulation problem

Platelet count is otherwise normal

58
Q

Qualitative platelet disorder that is acquired?

A

Uremia

- renal failure from circulating toxins

59
Q

Qualitative platelet disorder that are myeloproliferative?

A

Myleoproliferative disorders
- paradoxical bleeding risk - essential thrombocythemia and polycythemia vera

Normal numbers of platelets but they have abnormal function

60
Q

Drugs that cause platelet disorders?

A

Aspirin - reduced aggregation

GP IIB/IIIA inhibitors

  • abciximab
  • eptifibantide
  • tirofiban

Adenosine diphosphate inhibitors

  • clopidogrel
  • ticlodipine
61
Q

You mama so FAT

A

When Dracula sucked her blood her got diabetes

Senior - Heme-Onc (6 decks)

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