Hemostasis and Blood Disorders Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following best describes the role of plasminogen in tertiary hemostasis?

It directly stabilizes the fibrin clot.

It initiates the coagulation cascade.

It is activated to dissolve the fibrin clot. (correct)

It is a component of the platelet plug.

A patient presents with petechiae, purpura, and a prolonged bleeding time. Which category of disorders is MOST likely the cause?

Disorders of fibrinolysis.

Disorders of platelets. (correct)

Disorders of coagulation.

Disorders of blood vessels.

In a patient with von Willebrand disease, which aspect of hemostasis is primarily affected?

Platelet adhesion. (correct)

Platelet aggregation.

Fibrin stabilization.

Activation of the extrinsic clotting cascade.

Which of the following accurately describes the primary mechanism of acute Idiopathic Thrombocytopenic Purpura (ITP)?

Formation of antiplatelet antibodies in response to a past infection. (B) Signup and view all the answers

Which laboratory test is best used to evaluate the extrinsic coagulation pathway?

Prothrombin time (PT). (B) Signup and view all the answers

A patient with a suspected platelet disorder presents with prolonged bleeding after a minor cut. Which of the following platelet function tests would be the most appropriate first step in investigation?

Adhesion test. (C) Signup and view all the answers

Which of the following disorders is characterized by the presence of large platelets and failure of adhesion?

Bernard-Soulier disease. (D) Signup and view all the answers

What is the primary mechanism by which aspirin affects hemostasis?

It suppresses platelet aggregation. (B) Signup and view all the answers

What does HELLP syndrome stand for regarding pregnancy complications?

Hemolysis, Elevated Liver enzymes and Low Platelets (D) Signup and view all the answers

A patient is diagnosed with a bleeding disorder that affects both platelet function and Factor VIII levels, which condition is most likely?

Von Willebrand disease. (A) Signup and view all the answers

Which condition is characterized by delayed bleeding after trauma?

Coagulation disorder (A) Signup and view all the answers

Which of the following is a common manifestation of Factor VIII deficiency?

Spontaneous hematomas (A) Signup and view all the answers

What is the primary diagnostic test for Factor VIII deficiency?

Factor VIII assay (B) Signup and view all the answers

How does Factor IX deficiency differ from Factor VIII deficiency?

Factor IX deficiency is not indistinguishable from Factor VIII Deficiency therefore requiring specific testing to distinguish them. (A) Signup and view all the answers

What is the underlying cause of acute hemolytic transfusion reactions?

Preformed IgM antibodies against donor red blood cells (B) Signup and view all the answers

Which of the following is NOT a typical symptom of an acute hemolytic reaction?

Jaundice (B) Signup and view all the answers

What does a positive direct Coombs test indicate in the context of acute hemolytic reactions?

Complement has been fixed to donor red blood cells (A) Signup and view all the answers

If factor IX concentrate is unavailable, what is the recommended alternative treatment for Factor IX deficiency?

Cryoprecipitate (C) Signup and view all the answers

What is the primary cause of kernicterus?

Bilirubin induced neurological damage (B) Signup and view all the answers

Which laboratory finding is characteristic of an acute hemolytic reaction before red cell lysis is complete?

Positive direct Coombs test (D) Signup and view all the answers

Signup and view all the answers

Study Notes

Hemostasis and Hemostasis Testing

Normal hemostasis and hemostasis testing encompass platelet disorders, coagulation disorders, and fibrinolytic disorders.
Laboratory tests provide summaries of results in hemostasis disorders and include thrombosis syndromes.
Blood group antigens (ABO, Rh, and non-Rh) are used in transfusion therapy, and are relevant to hemolytic diseases of the newborn.

Types of Hemostasis

Primary hemostasis involves blood vessel constriction and platelet plug formation.
Secondary hemostasis includes activation of the clotting cascade and fibrin deposition/stabilization.
Tertiary hemostasis encompasses fibrin clot dissolution, which is dependent on plasminogen activation.

Classification of Blood Disorders

Disorders of blood vessels include scurvy, senile purpura, and Henoch-Schönlein syndrome.
Disorders of platelets encompass thrombocytopenia (ITP, TTP, HUS, DIC), aspirin therapy, and thrombasthenia.
Disorders of coagulation involve extrinsic, intrinsic, and combined coagulation pathways.

Tests of Hemostasis

Screening tests include bleeding time, prothrombin time (extrinsic), activated partial thromboplastin time (intrinsic), and thrombin time (common pathway, DIC).
Specific tests comprise factor assays for hemophilia, tests for thrombosis (TT, FDP, DDA), and platelet function studies (adhesion, aggregation, release, bone marrow).

Disseminated Intravascular Coagulation (DIC)

DIC is an acquired disorder stemming from excessive thrombin formation, disturbing normal hemostatic balance.
It's a dynamic process triggered by diverse conditions.
Activation of the clotting cascade generates excessive thrombin, inducing fibrin deposition in the microcirculation.
Microclot formation results in ischemic organ failure and/or hemorrhagic diathesis.

Causes of DIC

Obstetric causes include amniotic fluid embolism, abruptio placenta, placenta previa/accreta, postpartum bleeding, HELLP syndrome, preeclampsia/eclampsia, septic abortion/intrauterine infection, and acute fatty liver of pregnancy.
Non-obstetric causes include sepsis, trauma, organ damage, leukemia, vascular aneurysm, acute liver failure, toxic/immunological drugs, ABO incompatibility, and transplant rejection.

Triggers Leading to DIC

Endothelial cell injury, tissue injury, surgery, burns, malignant neoplasm, infections, and shock can trigger DIC.
These trigger increased clotting and platelet consumption, leading to the formation of microthrombi and endothelial injury.
This consequently leads to a hemorrhagic syndrome.

Signs and Symptoms of DIC

Bleeding, including GI bleeding, petechiae, ecchymosis, bleeding from IV lines, catheters, surgical sites, and serous cavities.
Renal failure and pulmonary involvement (dyspnea, hemoptysis, cough) as well as jaundice are potential symptoms.

Laboratory Findings in Acute DIC

Low platelet count, low fibrinogen, increased prothrombin time (INR), increased partial thromboplastin time (PTT), increased D-dimer, and a peripheral smear possibly showing schistocytes or helmet cells.

Thrombocytopenia Definition

Thrombocytopenia is a condition characterized by a decrease in platelet count in blood.
Normal platelet count ranges from 150,000-300,000/µL.
Anything below 100,000/µL is considered thrombocytopenia.

Causes of Thrombocytopenia

Increased destruction (immune mechanism, secondary to infection/drugs/SLE, non-immune mechanism, platelet consumption, microangiopathic hemolytic anemia).
Decreased production (bone marrow depression, hereditary conditions like Fanconi anemia/TAR syndrome, acquired conditions such as drugs/chemotherapy, infection/hepatitis/HIV, bone marrow infiltration/leukemia/neuroblastoma, storage disease).

Heparin-Induced Thrombocytopenia (HIT)

HIT is a clinicopathological syndrome triggered when heparin-dependent IgG antibodies bind to heparin/platelet factor 4 (PF4) complexes.
This activation causes platelets to become hypercoagulable, leading to thrombocytopenia and/or thrombosis shortly after heparin exposure.

Thrombotic Thrombocytopenic Purpura (TTP)

TTP is a rare blood disorder characterized by an increased number of blood clots throughout the body.
Pathology includes an unknown cause; often occurs with ADAMTS13 enzyme deficiency (leading to protein degradation resulting in a hypercoagulable state).

Types of TTP

Inherited TTP involves a faulty ADAMTS13 gene (lacking or dysfunctional enzyme).
Acquired TTP involves antibodies (proteins) that block the ADAMTS13 enzyme activity.

Thrombotic Microangiopathies

This group of disorders includes thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS).
Presentation in TTP often includes thrombocytopenia, microangiopathic hemolytic anemia (with associated schistocytes), increased lactate dehydrogenase (LDH), and acute kidney injury, with fever, headache, neurological symptoms, etc. possible.
HUS commonly presents in children, often triggered by Shiga toxin-producing E. coli bacterial infections.

Idiopathic Thrombocytopenic Purpura (ITP)

ITP is an autoimmune disorder, potentially post-infectious, causing chronic or acute thrombocytopenia in children/adults.
Associated with antiplatelet antibodies (IgG) that cause spleen removal of coated platelets and increased megakaryocytes in the bone marrow.

Inherited Platelet Dysfunction Disorders

Bernard-Soulier syndrome involves large platelets with adhesion failure.
Glanzmann's thrombasthenia involves normal-sized platelets with aggregation failure.

Platelet Disorders Overview

General platelet disorders show increased bleeding time, mucous membrane bleeding, and microhemorrhages (e.g., petechiae, epistaxis), often with a low platelet count, however count may be normal in qualitative disorders

Coagulation Disorders

Deficiencies of clotting factors (e.g., Factor VIII deficiency; Hemophilia A, Factor IX deficiency; Christmas disease, or Hemophilia B, other deficiencies) trigger delayed bleeding after trauma.
Bleeding manifests as deep bleeding (hematomas into joints—hemarthrosis), deep tissues—hematomas, and large skin bleeds—ecchymoses.

Factor VIII Deficiency (Hemophilia A)

X-linked disorder, primarily affecting males, leading to severe bleeding, including spontaneous hematomas.
Diagnosis involves an aPTT test (abnormal) and factor VIII assay.
Treatment includes factor VIII concentrates.

Factor IX Deficiency (Hemophilia B)

X-linked recessive disorder with similar bleeding symptoms to Factor VIII deficiency.
Requires factor VIII and IX activity level assessment for diagnosis.
Treatment includes factor IX concentrates, or cryoprecipitate.

Vitamin K Deficiency

Vitamin K deficiency compromises the synthesis of clotting factors (II, VII, IX, X, protein C or S).
This can cause an increase in prothrombin time (PT) and partial thromboplastin time (PTT).

Acute Hemolytic Transfusion Reactions (AHTR)

AHTR occurs when a patient receives incompatible blood, leading to antibody/complement attack on donor RBCs.
This results in hemolysis.
The antigen-antibody complex activates Hageman factor, leading to bradykinin production, thereby increasing capillary permeability and causing hypotension.

Blood Group Antigens

Blood groups (A, B, AB, O) are characterized by specific antigens on red blood cells and corresponding antibodies in the serum.

Rh Factor

Rh factor (Rhesus factor) is a protein on the surface of red blood cells.
Individuals are either Rh-positive (having the protein) or Rh-negative (lacking the protein).

Hemolytic Disease of the Newborn (HDN)

HDN is a condition where fetal/neonatal red blood cells are destroyed due to Maternal alloantibodies against red blood cell antigens (acquired from the father).
This leads to anemia, jaundice, potential liver dysfunction, and other complications in the newborn.

General Notes

Many of these disorders show overlapping symptoms, and lab tests are essential for accurate diagnoses. Individual disorders have particular characteristics as outlined in the slide summaries.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the key concepts of hemostasis and hemostasis testing, covering topics such as platelet disorders, coagulation disorders, and fibrinolytic disorders. Additionally, it delves into the classification of blood disorders and their implications in transfusion therapy and hemolytic diseases.