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Flashcards in Clinical and Lab to diagnosis Deck (22)
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1
Q

List some guidelines for the basic approach to diagnosing a suspected disorder of hemostasis.

A

• Complete history and physical examination

– Family history important

• Screening laboratory work to assess global

hemostatic function

• Directed application of further studies only as

needed

• All clinicians should be able to interpret the

screening laboratory test results

• For more advanced testing, rely on those with

special expertise (hematologist, pathologist)

2
Q

Describe 7 physical findings that would point to a hemostatic disorder. Include what they look like and their etiology.

A

1) Petechiae: These are small red spots and are typically numerous in numbers. They are comprised of blood that has extravasated from intact small blood vessels due to
increased permeability. They are most commonly seen in patients with either thrombocytopenia or platelet function defects. (Remember that platelets are important in maintaining normal vascular integrity.)

2) Purpura: Generally defined, purpura are confluent petechiae. They are larger lesions, but the underlying pathophysiology is the same as for petechiae.
3) Ecchymosis: Also known as a bruise, this is a larger area of extravasated blood. The most common etiology is trauma to the blood vessels.

4) Hematoma: Essentially, a hematoma is a large bruise that has infiltrated subcutaneoustissue or muscle resulting in physical deformity or dysfunction at the site of bleeding.
Generally, the predisposing factors are more severe and include coagulation factor deficiencies, severe thrombocytopenia, and supratherapeutic levels of anticoagulant drugs.

5) Hemarthrosis: Hemorrhage into a joint. This is most typically seen in patients with severe coagulation factor deficiencies (i.e. hemophilia).
6) Hematuria: This is defined as blood in the urine. While lesions of the bladder and kidney (i.e. stones, neoplasms) may fairly commonly result in hematuria, it is also frequently seen in patients with severe coagulation disorders or supratherapeuticlevels of anticoagulant drugs.

7) Localized Bleeding and Bleeding after Minimal Trauma or Surgery: When observed, this may simply be a direct result of the trauma or intervention. For example,
epistaxis following sinus surgery may be entirely related to the procedure. However, if it is prolonged or excessive, it might reflect the presence of a mild bleeding disorder that was brought to clinical attention only after a challenge to the normal hemostatic balance. Bleeding from the gastrointestinal tract and excessive menstrual bleeding are other sites where this distinction becomes relevant. Clinical history of prior episodes of bleeding and a physical examination for a local anatomic lesion are
essential in the initial work-up of these patients.

3
Q

What are some things that should be included in a clinical history of a hemostatic disorder and how can the clinical history be helpful?

A

As suggested in the above section, careful history taking is absolutely essential in the work-up of

hemostatic disorders. A detailed description of bleeding after trauma and surgical procedures

should be obtained. This history should extend back to the neonatal period with questions

relating to any excessive umbilical stump bleeding or increased bleeding after circumcision, if

applicable. Any excessive bleeding with tooth extractions, tonsillectomy, abdominal surgeries,

or after minor trauma should be documented and explored. If a patient has had a tonsillectomy

or an abdominal surgery without bleeding complications, it is highly unlikely that a moderate to

severe inherited disorder is present.

4
Q

Contrast arterial and venous thromboses.

A
  • Venous Thrombosis – Lower limb typical – Obstruction of venous return – Swelling, pain, discoloration, ulceration – Pulmonary embolism
  • Arterial Thrombosis – Vascular disease – Obstruction of blood flow with ischemic cell death,

gangrene – Myocardial infarction; stroke

5
Q

Name 7 risk factors for thromboses.

A
  • Age >50
  • Obesity
  • Cigarette smoking
  • Estrogen / oral contraceptives
  • Venous stasis
  • Nephrotic syndrome
  • Pregnancy
  • Plus many more…
6
Q

List 6 situations in which it would be appropriate to investigate further after a thrombosis.

A
  • Recurrent thrombosis
  • Young age (< 50 years)
  • Atypical site
  • Family history of thrombosis
  • Both arterial and venous thromboses
  • Unexplained recurrent fetal loss
7
Q

What are 3 questions to ask when trying to identify a bleeding or thrombotic disorder?

A
  • 1) Is there a generalized hemostatic defect?
  • 2) Is it inherited or acquired?
  • 3) Is the defect vascular, platelet, coagulation, or a combined problem?
8
Q

What questions to ask to find out if a bleeding disorder is generalized? A thrombotic disorder?

A

– Bleeding:

  • Multiple sites?
  • Spontaneous?
  • Petechiae, hematomas, large ecchymoses, or hemarthrosis?

– Thrombosis:
• Multiple sites?
• Spontaneous?
• Combined arterial and venous?

9
Q

What are some features that favor a bleeding disorder being inherited? A thrombotic disorder?

A

• Features that favor inherited bleeding disorders:
– Presentation in infancy – Family history – History of bleeding with trauma / surgery – If mild, may not appear until adulthood…

• Thrombotic disorders: – Rarely present in infancy – Family history

10
Q

What bleeding disorders are autosomal dominant? Recessive? X-linked? What is there is a negative family history? Can it be hereditary?

A
  • Autosomal dominant: – von Willebrand disease; antithrombin III deficiency; Protein C deficiency; Protein S deficiency
  • Autosomal recessive: – Deficiencies of Factors II, V, VII, X, and XI
  • X-linked inheritance: – Hemophilia A and B
  • Negative family history does not rule-out a

hereditary disorder (spontaneous mutations,

etc).

11
Q

What are some features associated with acquired bleeding disorders?

A
  • Adult onset
  • Underlying risk factor
  • No history of abnormal bleeding with past

surgeries / traumas

• No family history

12
Q

How do bleeding disorders manifest if there is a vascular/platelet defect? If there is a coag. defect?

A

• Vascular / Platelet Defect: – Petechiae and superficial bruises – Skin and mucous membrane hemorrhages – Spontaneous bleeding – Immediate, prolonged bleeding that is non-
recurrent

• Coagulation Defect: – Deep, spreading hematoma – Hemarthrosis; retroperitoneal bleed – Delayed, prolonged bleeding that is recurrent

13
Q

How do thrombotic disorders manifest if there is a vascular/platelet defect? If there is a coag. defect?

A

Vascular / Platelet Defect: – Atherosclerosis – Thrombocytosis (rare)

• Coagulation Defect: – Deficiency of antithrombin III, Protein C, Protein S – Deficient or abnormal tPA, plasminogen, or PAI

14
Q

What are 4 screening lab tests for primary hemostasis?

A

• Primary Hemostasis: – Bleeding time – no longer routinely performed! – PFA-100 – Peripheral blood smear – Platelet count

15
Q

How does PFA-100 work? What does it assess? What can’t it distinguish? What does aspirin do to it? GP IIb/IIIa inhibitors? What else can prolong it?

A

• Test platelet function under high shear conditions:
– Blood is aspirated through a capillary tube into a test cartridge that has a membrane coated either
with collagen and epinephrine or collagen and ADP and central aperture – Time to closure of the aperture is recorded in seconds (CT)

• Assessing interaction between vWF and platelets (GP
Ib/IX and GP IIb/IIIa) – Cannot distinguish between decreased vWF levels and platelet function disorders
• Aspirin  prolongs the epi CT, but not the ADP CT
• GP IIb/IIIa inhibitors  prolong both
• Patient factors can prolong the CT (thrombocytopenia, anemia, blood type O [less vWF], concentration of anticoagulant)

16
Q

How is a peripheral blood smear useful for primary hemostatic disorders?

A
  • Platelet morphology
  • Estimate of the platelet count (cross reference

to CBC data)

• Might provide another etiology for the

coagulopathy (i.e. acute leukemia)

17
Q

What screening lab tests exist for secondary hemostasis? What are some testing requirements?

A
• Secondary Hemostasis: 
– Prothrombin time (PT)
• International Normalized Ratio (INR) 
– Partial thromboplastin time (PTT) 
– Thrombin time

• Specimen handling very important

• Use 3.2% sodium citrate as the anticoagulant to
collect whole blood

  • Careful venipuncture
  • Completely filled tube that is mixed immediately

• Processed as soon as possible (centrifugation to form
platelet poor plasma) and testing run within 4 hours
of specimen collection

• Specimens can be frozen if testing will be delayed

18
Q

How does the Prothrombin time test work? What does it test? Deficiencies of what will lead to an abnormal test? what is the reference range?

A

Tissue factor and calcium are added to plasma. When tissue factor reacts with Factor VII, it is able to activate Factor X. Therefore, the extrinsic and the common pathway are tested.

  • Reference Range = 11-15 seconds
  • Abnormal in deficiencies of: – Factor VII – Factor X – Factor V– Factor II – Severe deficiencies of Factor I
19
Q

What is the INR?

A

• PT depends on a source of tissue factor – Difficult for companies to standardize the amount present in their

reagents

• INR is a way to correct the PT to have a number that is comparable across

laboratories – INR=[(PT patient) / (PT mean reference range)]n

  • n= International Sensitivity Index (ISI) – Provided from the reagent supplier and is specific for each reagent
  • INR reference range ~0.9-1.1
  • “Goal” INR for patients on warfarin therapy varies depending on

indication for treatment: – DVT, PE, atrial fibrillation, etc. – goal is 2-3 – Mechanical valves in mitral position, antiphospholipid antibody syndrome and a blood

clot while on warfarin therapy – goal is 2.5-3.5

20
Q

How does the Activated partial thromboplastin time test work? What does it test? Deficiencies of what will lead to an abnormal test? what is the reference range?

A
  • Solid phase activator activates the contact factors (HMWK, PK, Factor XII, and Factor XI)
  • Phospholipid added as a platelet substitute (activates Factors X, VIII, and II)
  • Calcium is added to  full clotting
  • Abnormal in deficiencies off all of the above plus Factors IX, V, and I
  • Not affected by Factor VII deficiency
21
Q

How is a thrombin time test performed? What does it assess? What will cause it to be prolonged?

A

The thrombin time is the easiest of all of these tests. Thrombin is added to platelet poor plasma, and the time to clot is measured. This is assessing the conversion of fibrinogen to fibrin. It will be prolonged in disorders of fibrinogen, heparin therapy, and in the presence of elevated fibrin-fibrinogen degradation products.

22
Q

See list in syllabus

A

of lab findings that signify certain disorders.