Hematopoietic System: Case 3 Flashcards
Certain elements of the history are particularly useful in determining whether bleeding is caused by:
- an underlying hemostatic disorder
- by a local anatomic defect
One clue is a history of bleeding following common hemostatic stresses such as:
dental extraction, childbirth, or minor surgery
What merits special attention?
Bleeding that is sufficiently severe to require blood transfusion
What suggests a systemic disorder?
A family history of bleeding and bleeding from multiple sites that cannot be linked to trauma or surgery
Since bleeding can be mild, lack of a family history of bleeding does not exclude an inherited hemostatic disorder.
This is usually localized to superficial sites such as the skin and mucous membranes, comes on immediately after trauma or surgery, and is readily controlled by local measures.
Bleeding from a platelet disorder
Differences in the Clinical Manifestations of Disorders of Primary and Secondary Hemostasis
Primary
Platelet Defects
Onset of bleeding after trauma: Immediate
Sites of bleeding: Superficial— skin, mucous membranes, nose, GI and genitourinary tracts
Physical findings: Petechiae, ecchymoses
Family history: Autosomal dominant
Response to therapy: Immediate; local measures effective
Secondary
Plasma Protein Defects
Onset of bleeding after trauma: Delayed — hours or days
Sites of bleeding: Deep — joints, muscle, retroperitoneum
Physical findings: Hematomas, hemarthroses
Family history: Autosomal or X-linked recessive
Response to therapy: Requires sustained systemic therapy
In contrast, bleeding from plasma coagulation defects occurs when?
hours or days after injury and is unaffected by local therapy. Such bleeding most often occurs in deep subcutaneous tissues, muscles, joints, or body cavities.
● A thorough history may establish presence of a hemostatic disorder and guide initial laboratory testing.
The most common site to observe bleeding is in the:
skin and mucous membranes
Collections of blood in the skin are called ___________ and may be subdivided on the basis of the site of bleeding in the skin.
Purpura
Small pinpoint hemorrhages into the dermis due to the leakage of red cells through capillaries are called ________ and are characteristic of platelet disorders in particular, severe thrombocytopenia.
Petechiae
Larger subcutaneous collections of blood due to leakage of blood from small arterioles and venules are called:
ecchymoses (common bruises) or, if somewhat deeper and palpable, hematomas
They are also common in patients with platelet defects and result from minor trauma.
What may cause bleeding without any hemostatic defect?
Dilated capillaries, or telangiectasia
In addition, the loss of connective tissue support for capillaries and small veins that accompanies aging increases the fragility of superficial vessels, such as those on the dorsum of the hand, leading to:
extravasation of blood into subcutaneous tissue — senile purpura
What is sometimes a serious problem in women with severe thrombocytopenia or platelet dysfunction?
Menorrhagia
Some patients with primary hemostatic defects, especially von Willebrand’s disease, may have:
- recurrent gastrointestinal hemorrhage
- often associated with angiodysplasia
- a common vascular malformation in the gastrointestinal tract
Bleeding into body cavities, the retroperitoneum, or joints is a common manifestation of:
plasma coagulation defects
What may cause synovial thickening, chronic inflammation, and fluid collections and may erode articular cartilage and lead to chronic joint deformity and limited mobility?
Repeated joint bleeding
Joint deformities are particularly common in patients with deficiencies of factors what?
VIll and IX, the two sex-linked coagulation disorders referred to as the hemophilias.
For unclear reasons, _____________ are much less common in patients with other plasma coagulation defects.
hemarthroses
What can cause secondary necrosis of tissues or nerve compression?
Blood collections in various body cavities or soft tissues
Retroperitoneal hematomas can cause femoral nerve compression, and large collections of poorly coagulated blood in soft tissues occasionally mimic malignant growths:
the pseudotumor syndrome
Two of the most life-threatening sites of bleeding are in the ___________, where bleeding can compromise the airway, and in the central nervous system.
oropharynx
What is one of the leading causes of death in patients with severe coagulation disorders?
Intracerebral hemorrhage
Because of their need for plasma and factor concentrates derived from multiple donors, many patients with hemophilia were infected with:
HIV before effective testing of donors was in place
What can induce thrombocytopenia and exacerbate bleeding in hemophilia patients?
HIV infection
The most important screening tests of the primary hemostatic system are:
(1) a bleeding time (a sensitive measure of platelet function), and
(2) a platelet count
What is a sensitive measure of platelet function?
Bleeding time
What correlates well with the propensity to bleed?
platelet count
What is the normal platelet count?
150,000 to 450,000 /uL of blood
As long as the count is >100,000/uL, patients are usually:
Asymptomatic, and
Bleeding time remains normal
Platelet counts of 50,000 to 100,000/uL cause what?
Mild prolongation of the bleeding time;
bleeding occurs only from severe trauma or other stress.
Patients with platelet counts <50,000/uL have:
- easy bruising
- manifested by skin purpura after minor trauma
- bleeding after mucous membrane surgery.
Patients with a platelet count <20,000/uL have:
- appreciable incidence of spontaneous bleeding,
- usually have petechiae, and
- may have intracranial or other spontaneous internal bleeding
What are the causes of thrombocytopenia?
Decreased marrow production of megakaryocytes
Marrow infiltration with tumor, fibrosis
Marrow failure __ aplastic, hypoplastic anemias, drug effects
Splenic sequestration of circulating platelets
Splenic enlargement d/t tumor infiltration
Splenic congestion d/t portal hypertension
Increased destruction of circulating platelets
Nonimmune destruction
> vacular prostheses, cardiac valves
> DIC
> sepsis
> vasculitis
Immune destruction
> autoantibodies to plt antigens
> drug-associated antibodies
> circulating immune complexes (SLE, viral agents, bacterial sepsis)
Patients with qualitative platelet abnormalities have a:
normal platelet count
prolonged bleeding time
What is ascertained by making a small, superficial skin incision and timing the duration of blood flow from the wounded area?
Bleeding time
What are the primary hemostatic (platelet) disorders?
Defects of platelet adhesion
von Willebrand’s disease
BSS (absence or dysfxn of GpIb/IX)
Defects of platelet aggregation
Glanzmann’s thrombasthenia (absence or dysfxn of GpIIb/IIIa)
Defects of platelet release
Decreased cyclooxygenase activity
> drug-induced — aspirin, nonsteroidal anti-inflammatory agents
> congenital
Granule storage pool defects
> congenital
> acquired
Uremia
Platelet coating (e.g., penicillin or paraproteins)
Defect of platelet coagulant activity
Scott’s syndrome
With careful standardization, what is a reliable and sensitive test of platelet function?
Bleeding time
A ______________________________ controls the length and depth of the incision (usually 1 mm deep by 9 mm long),
and a sphygmomanometer inflated to _______________ distends the capillary bed of the forearm uniformly.
A template or an automated scalpel controls the length and depth of the incision (usually 1 mm deep by 9 mm long),
and a sphygmomanometer inflated to 40 mmHg distends the capillary bed of the forearm uniformly.
The bleeding time test must be performed by an experienced technician, as small differences in technique have a big effect on outcome.
Any patient with a bleeding time _____________ has an increased risk of bleeding, but the risk does not become great until the bleeding time is _____________.
Any patient with a bleeding time >10 min has an increased risk of bleeding, but the risk does not become great until the bleeding time is >15 or 20 min.
the relationship between the platelet count and the bleeding time is
roughly linear
When a defect in ______________ is uncovered, specialized testing is needed to determine the cause of the platelet dysfunction.
Primary hemostasis (check again card 37)
Lab work-up of bleeding disorders facts:
● A precise diagnosis is important in determining the proper treatment.
● Occasional patients with a strong history of bleeding, particularly those with mild von Willebrand’s disease, may have a normal bleeding time when initially tested, owing to cyclical variations in the level of the vWF.
● Repeated testing may be necessary to establish an accurate diagnosis.
What is not an effective screening test for preoperative patients?
Bleeding time
Plasma coagulation function is readily assessed with the:
the PTT,
prothrombin time (PT),
thrombin time (TT), and
quantitative fibrinogen determination
Relationship between secondary hemostasis disorders and coagulation test abnormalities
Prolonged partial thromboplastin time (PTT)
No clinical bleeding — factors XII, HMWK, PK
Mild or rare bleeding — factor XI
Frequent, severe bleeding — factors VIII and IX
Prolonged prothrombin time (PT)
Factor VII deficiency
Vitamin K deficiency— late
Warfarin anticoagulant ingestion
Prolonged PTT and PT
Factor II, V, or X deficiency
Vitamin K deficiency — late
Warfarin anticoagulant ingestion
Prolonged thrombin time (TT)
Mild or rare bleeding — afibrinogenemia
Heparin-like inhibitors or heparin administration
Prolonged PT and/or PTT not corrected with normal plasma
Specific or nonspecific inhibitor syndromes
Clot solubility in 5M urea
Factor XIII deficiency
Inhibitors or defective cross-linking
Rapid clot lysis
a2 plasmin inhibitor
The PTT screens the:
Intrinsic limb of the coagulation system and tests for the adequacy of factors XII, HMWK, PK, XI, IX, and VIII.
The PT screens the:
Extrinsic or tissue factor-dependent pathway.
Both tests also evaluate the common coagulation pathway involving all the reactions that occur after the activation of what factor?
Factor X
Prolongation of the PT and PTT that does not resolve after the addition of normal plasma suggests a:
Coagulation inhibitor
A specific test for the conversion of fibrinogen to fibrin is needed when both the PTT and PT are prolonged — either a _______________ can be employed.
A specific test for the conversion of fibrinogen to fibrin is needed when both the PTT and PT are prolonged — either a TT or a clottable fibrinogen level can be employed.
