AULA AO VIVO 5 - HEMATOLOGIA CLÍNICA

Name: AULA AO VIVO 5 - HEMATOLOGIA CLÍNICA
Uploaded: 2026-02-21T21:47:00.000Z
Duration: 3 h 54 s

Welcome to the Fifth Class of Clinical Hematology

Announcements and Updates

The live session will be rescheduled for Monday at 19:00, accessible via the same link as the previous class.

Activity Study Three is now available; students should review it alongside the fifth chapter of the textbook.

The Santander campaign "Top Spain" is ongoing; interested students should check the Santander website for details.

There are issues with video access for some students, which will be addressed soon. Additionally, registrations for GEPS (Interdisciplinary Study and Research Group in Health) have been extended.

Introduction to Today's Topic

The instructor introduces Ana, who will lead today's discussion on plaquetogram analysis within hemograms. She mentions personal challenges faced during the week but emphasizes readiness to proceed with the lesson.

Importance of Platelet Analysis

Today's focus is on understanding platelets and their role in coagulation through a detailed examination of hemograms. A visual representation of blood components is provided to illustrate platelet appearance in circulation.

Knowledge about platelets is crucial as they play a significant role in diagnosing various pathologies through hemogram screening, although they do not provide definitive diagnoses alone. Instead, they guide further testing by physicians.

Clinical Relevance of Platelet Counts

Identifying abnormalities in platelet count or morphology can alert healthcare providers to critical conditions such as severe thrombocytopenia associated with dengue hemorrhagic fever, potentially saving lives through timely intervention.

Accurate platelet analysis contributes significantly to surgical safety assessments; it helps determine whether patients are fit for surgery based on their coagulation status and may prevent unnecessary procedures if risks are identified early on.

Understanding Hemostasis and Its Mechanisms

Introduction to Clinical Decision-Making

The concept of clinical decision-making is crucial for physicians to take appropriate and timely actions in response to diagnostic results, such as thrombocytopenia or coagulopathy.

Basic Concept of Hemostasis

Hemostasis is defined as a physiological mechanism that maintains blood in a liquid state while allowing it to form clots (thrombi) when necessary. This balance prevents excessive bleeding (hemorrhage) or inappropriate clot formation (thrombosis).

Components of Hemostasis

Key components involved in hemostasis include:

Platelets: Essential for initial clot formation.

Coagulation Factors: Such as factors 3, 4, 8, 9, and 10.

Inhibitors of Coagulation: Prevent random thrombus formation.

Fibrinolytic System: Breaks down unnecessary thrombi.

Blood Vessels: Transport all cellular elements involved in hemostasis.

Types of Hemostasis

Primary Hemostasis

Occurs at the microcirculation level (capillaries) involving:

Blood vessels

Platelets

Endothelial cells that release factors activating platelets.

Disorders related to primary hemostasis are often referred to as purpuras. The main goal is to stop bleeding through platelet plug formation.

Secondary Hemostasis

Takes place in larger blood vessels (arteries and veins), aiming to prevent rebleeding by forming a fibrin mesh over the platelet plug, solidifying the clot into a stable structure. It occurs after primary hemostasis has initiated the process. The distinction between thrombus and coagulum is highlighted here; thrombus forms within vessels while coagulum typically forms outside them.

Formation of Platelets

Platelet production begins with stem cells in the bone marrow differentiating into multipotent progenitor cells, which further specialize into megakaryocyte progenitors before becoming megakaryocytes—large cells that extend their cytoplasm and fragment it into platelets. This process illustrates how platelets are formed from larger precursor cells rather than being produced individually.

Understanding Platelet Structure and Function

Morphology of Platelets

Platelets lack a nucleus but contain organelles such as mitochondria and actin filaments, which provide structural support.

They possess dense granules filled with calcium, serotonin, and ADP, crucial for various phases of hemostasis.

Calcium plays a significant role in activating platelets by being released during shape changes that activate the actin-myosin complex.

Activation Process of Platelets

The phospholipid layer enhances platelet adhesion when they need to aggregate.

Activated platelets change shape from disc-like to more irregular forms with pseudopodia, facilitating interaction with other platelets.

Normal platelets are oval-shaped (1.5 to 3 nanometers), have an average lifespan of 7 to 10 days, and are produced at a rate of 100 billion daily.

Role of von Willebrand Factor

Von Willebrand factor is a large glycoprotein essential for platelet aggregation; it acts as adhesive glue between platelets and blood vessel walls.

It also transports factor VIII, vital for coagulation cascades, synthesized by endothelial cells in blood vessels.

Pathophysiology Related to von Willebrand Factor

Deficiency in von Willebrand factor leads to von Willebrand disease, the most common hereditary coagulopathy affecting 1% to 2% of the population.

Cascading Events in Platelet Activation

Vascular injury exposes subendothelial collagen leading to initial platelet adhesion.

Adhered platelets release ADP which promotes further aggregation by making additional platelets sticky through morphological changes.

Aggregation occurs via fibrinogen linking plates together; thromboxane and serotonin are released causing vasoconstriction to reduce blood flow during clot formation.

Understanding Platelet Count and Measurement Methods

Key Parameters in Platelet Analysis

The most important parameter in a platelet count is the total platelet count, which is crucial for medical assessments.

Other significant metrics include Mean Platelet Volume (MPV), typically ranging from 7 to 11 femtoliters, and the plateletcrit, indicating the percentage of platelets in total blood volume.

Platelet Distribution Width (PDW) measures platelet size variation, known as anisocytosis.

Methods for Counting Platelets

The most common method for counting platelets today is through automated hematology analyzers that utilize bioimpedance technology.

These analyzers measure cell sizes and characteristics by passing cells through a channel where an electric pulse detects their properties.

Interference can occur due to platelet aggregates or small cellular fragments affecting accurate counts.

Manual Counting Techniques

A manual counting method involves using a Neubauer chamber, particularly useful for confirming low platelet counts.

Samples are diluted with a solution containing 1% ammonium oxalate to lyse red blood cells, allowing clearer visibility of platelets under the microscope.

Advanced Counting Methodologies

Another technique discussed is the "Fônio" method, where one counts platelets within fields containing approximately 1000 erythrocytes across multiple fields to ensure accuracy.

Class Discussion Dynamics

During class discussions, there were interruptions regarding scheduling conflicts and technical difficulties faced by the instructor while teaching.

Students expressed concern over the instructor's ability to continue effectively due to these issues but showed support for her efforts.

Counting Platelets in Hemograms

Methods for Counting Platelets

The process involves counting platelets across 10 fields, each containing approximately 100 erythrocytes, and calculating the total by multiplying the count of platelets by the total number of erythrocytes from the hemogram, then dividing by 1000.

An alternative method suggests averaging counts from these 10 fields and multiplying by a factor of 13,000 to estimate platelet numbers.

Ideal Field for Hemogram Reading

A visual field with around 100 erythrocytes is ideal for reading hemograms as it allows differentiation between leukocytes and morphology of erythrocytes while counting platelets.

The ideal field should have erythrocytes neither overlapping nor too spaced out; dividing the field into quadrants can help ensure accurate counting.

Evaluating Platelet Morphology

In addition to counting, evaluating platelet morphology is crucial for confirming low platelet counts and identifying aggregates or abnormal sizes (macro or micro).

Observations include checking for hypogranular platelets which should appear granular rather than smooth, and assessing satellite formation where platelets cluster around other cells.

Techniques for Analysis

Morphological analysis is performed at a magnification of 100x using Romanowsky stains to observe granulation, size relative to erythrocytes, aggregation presence, and adherence to leukocytes.

The "prainha" region at the end of the slide is preferred for viewing clearer platelet images due to fewer overlapping cells.

Common Platelet Abnormalities

Various rare platelet abnormalities are discussed including megakaryocyte maturation stages and size variations compared to normal erythrocytes.

Normal-sized platelets should be about one-tenth the size of an erythrocyte; deviations such as microplatelets may indicate functional issues.

Reporting Findings in Hemograms

When confident in diagnoses regarding abnormalities like macroplatelet presence or bubble formations within platelets, these observations can be included in lab reports.

Analytical Errors in Blood Sampling

Common analytical errors arise during venous puncture attempts that may lead to activation of coagulation cascades due to vessel damage. This issue frequently occurs with elderly patients or restless children.

Understanding Hemogram Collection and Analysis

Importance of Proper Sample Handling

The aggregation of platelets and consumption in vitro does not reflect the patient's condition; issues arise during sample handling rather than in the patient.

Immediate homogenization of blood samples is crucial after collection to ensure contact with anticoagulants, avoiding cell lysis and microclot formation.

Timing for Hemogram Analysis

Analyzing hemograms within 2 hours is ideal; delays beyond 4 hours can lead to cellular damage, affecting leukocytes and erythrocytes.

Even if initial collection was proper, using deteriorated or insufficient anticoagulant can worsen results over time.

Sample Volume and Coagulation Issues

Adhering to the recommended blood volume for each tube is essential to maintain appropriate anticoagulant concentration.

Observations of sample density changes over time may indicate slow clot formation, which could lead to erroneous results.

Identifying Clots in Samples

Small platelet aggregates can be identified under a microscope; larger clots appear as massive platelet masses among red blood cells.

Practical tips include transferring samples between tubes carefully to detect any small clots that might not be visible otherwise.

Training for Blood Collection Techniques

Analysts must train staff on proper techniques to minimize hemogram recollections due to coagulation issues, which account for about 80% of such cases.

Key practices include limiting tourniquet application time, ensuring single punctures without trauma, and maintaining free blood flow during collection.

Order of Tube Collection Matters

The hemogram should never be the first tube collected due to potential contamination from tissue factors that activate platelet aggregation.

Proper homogeneization involves gentle inversions immediately after collection—at least 8–10 times—to prevent clotting before analysis.

Understanding Skin Lesions and Blood Sample Analysis

Types of Skin Lesions

The speaker distinguishes between different types of skin lesions, specifically petechiae and ecchymoses. Petechiae do not disappear when pressure is applied to the skin, unlike raised lesions such as rashes.

Ecchymoses are described as larger spots resembling bruises, indicating a need for careful examination of bleeding symptoms like nosebleeds or gum bleeding. This information is crucial for diagnosis.

Importance of Accurate Sample Handling

When dealing with multiple blood tubes, it’s essential to know which ones require homogenization before centrifugation; citrate tubes should be homogenized while others may not need it due to their gel separator.

Understanding the difference between serum and plasma is vital: serum lacks coagulation factors present in plasma (found in citrate tubes), impacting test results significantly.

Analyzing Previous Test Results

The speaker emphasizes the importance of reviewing previous test results when faced with abnormal findings, such as low platelet counts, to avoid unnecessary retesting if it's a known condition for that patient. This practice can prevent misdiagnosis and ensure accurate patient care.

If no prior results exist, a new sample should be collected for confirmation; if consistent results appear again, they should be documented appropriately with observations noted on the report.

Pseudothrombocytopenia Awareness

A critical point discussed is pseudothrombocytopenia, where platelet counts appear falsely low due to an in vitro reaction with EDTA anticoagulant; this can lead to misinterpretation unless further testing is conducted using alternative methods like citrate collection alongside EDTA samples.

Patients exhibiting no signs of thrombocytopenia or atypical lymphocytes should have both EDTA and citrate tests compared to confirm true platelet levels accurately. This distinction helps in diagnosing conditions like dengue fever correctly by ruling out false positives from lab errors.

Platelet Aggregation Issues

The phenomenon of platelet satellitism occurs when patients produce antibodies against their own platelets due to immune dysfunction; this can complicate test interpretations and requires careful analysis during laboratory assessments. Understanding these nuances ensures better diagnostic accuracy in hematology practices.

Understanding Platelet Satelliteism and Its Clinical Implications

Importance of Reporting Platelet Satelliteism

The phenomenon of platelet satelliteism occurs in neutrophils and is rare, with an incidence of approximately 1 in every 12,000 samples. It should be documented in lab reports.

Specifying the presence of platelet satelliteism in leukocytes or lymphocytes helps physicians monitor patients effectively, especially if there are changes in platelet counts.

This condition may indicate underlying issues such as tumors depending on the cells to which platelets adhere, making it crucial for accurate diagnosis.

Two articles referenced discuss pseudothrombocytopenia due to EDTA and the relationship between platelet satelliteism and B-cell neoplasms, emphasizing its diagnostic significance.

While some authors argue that platelet satelliteism has limited clinical value, it remains essential to report any findings from a complete blood count (CBC).

Reference Values for Platelets

Normal platelet counts range from approximately 140,000 to 450,000 per microliter; variations exist based on analyzer type and patient demographics.

Premature infants may exhibit mild thrombocytopenia (100,000 - 300,000), which is considered normal due to immature hepatic function.

Pregnancy can lead to slight reductions in platelet counts due to increased plasma volume diluting blood components.

Factors Affecting Platelet Counts

Intense physical exercise can cause transient increases in platelet counts as adrenaline prompts the spleen to release stored platelets into circulation.

The body reacts to intense exercise by preparing for potential injuries through increased blood flow and recirculation of platelets.

Clinical Interpretation of Platelet Levels

A reference range above 150,000 generally poses no surgical risk; however:

Counts between 100,000 - 50,000 require monitoring and possible hydration or corticosteroid treatment.

Counts between 50,000 - 20,000 present risks during invasive procedures necessitating potential transfusions.

Below 20,000 indicates spontaneous bleeding risk; below 10,000 constitutes a hematological emergency.

Emergency Protocol for Low Platelet Counts

For patients with counts between 20,000 - 50,000 or lower thresholds:

Immediate notification of medical staff is critical as these levels often require intervention like blood transfusions.

Continuous monitoring is essential regardless of whether surgery is planned.

Overview of Hemostatic Disorders

The discussion transitions into purpuras—conditions affecting primary hemostasis caused by either low platelet numbers or functional abnormalities.

Understanding Vascular Disorders and Their Classifications

Overview of Mucocutaneous Bleeding

Vascular disorders are characterized by mucocutaneous bleeding, which includes symptoms like gum bleeding, nosebleeds, and skin ruptures.

Types of Vascular Disorders

These disorders can be classified as:

Primary or Idiopathic: No identifiable cause.

Secondary: Associated with other conditions such as autoimmune diseases (e.g., lupus), viral infections (e.g., cytomegalovirus, HIV, hepatitis), medication use (e.g., heparin), or neoplasms.

Clinical Manifestations

Common clinical manifestations include:

Petechiae: Small red spots that do not blanch when pressed.

Ecchymoses: Larger purple bruises over 1 cm in size.

Nasal and gingival bleeding.

Immune Thrombocytopenic Purpura (ITP)

One type of purpura is immune thrombocytopenic purpura (ITP):

An autoimmune condition where IgG antibodies bind to platelet membrane glycoproteins leading to accelerated destruction by macrophages in the spleen and liver.

Pathophysiology

The spleen's macrophages mistakenly target altered platelets for destruction due to antibody binding. This results in increased megakaryocytes in the bone marrow as a compensatory mechanism for low platelet counts.

Forms of ITP

ITP can present as:

Acute: More common in children post-viral infection; often self-limiting within six months without specific treatment.

Chronic: More gradual onset in adults; may take years to resolve.

Laboratory Findings

Key laboratory findings include:

Thrombocytopenia with platelet counts below 100,000.

Normal erythrogram and leukogram since these cells are unaffected.

Presence of macroplatelets on blood smears and prolonged bleeding time while TTPA remains normal.

Treatment Options

Initial treatment typically involves corticosteroids like prednisone. If ineffective, intravenous immunoglobulin may be used. In refractory cases, splenectomy is performed to remove the organ responsible for excessive platelet destruction.

Thrombotic Thrombocytopenic Purpura (TTP)

Another critical type is thrombotic thrombocytopenic purpura (TTP):

Characterized by a high mortality rate if untreated (~90%).

Treatment Approach

Urgent treatment involves plasma exchange therapy to filter out harmful antibodies from the blood.

Pathophysiology of TTP

TTP arises from a deficiency in the enzyme AdamTS13 which cleaves von Willebrand factor. Without this enzyme, large multimers accumulate leading to widespread platelet aggregation and microthrombi formation.

Classic Pentad Symptoms

The classic pentad associated with TTP includes:

Thrombocytopenia,

Hemolytic anemia,

Microangiopathic changes causing hemolysis,

Clinical Implications

Patients may experience jaundice due to hemolysis and significant pain from microvascular obstruction caused by fibrin accumulation resembling barbed wire within capillaries.

Understanding Hemolysis and Thrombocytopenia

Mechanisms of Hemolysis

Hemolysis occurs in capillaries where fibrin webs trap red blood cells, leading to inflammation and pain in extremities. Symptoms include yellowing of the skin, fever, and renal failure due to increased hemolysis.

Clinical Findings

Only 40% of patients exhibit all symptoms; laboratory findings typically show signs of hemolysis such as elevated LDH levels and more than 1% schistocytes (abnormally shaped red blood cells).

Types of Heparin-Induced Thrombocytopenia (HIT)

There are two types:

Type I (non-immunological): Occurs within 24-72 hours post-heparin administration with mild thrombocytopenia (>100,000 platelets), self-limiting within four days.

Type II (immunological): Antibodies form against the heparin-PF4 complex, occurring 5-14 days after heparin use, potentially leading to severe thrombocytopenia (<100,000 platelets) and a high risk of thrombosis.

Pathophysiology of HIT

In Type II HIT, antibodies bind to the heparin-PF4 complex activating more platelets which leads to a cascade effect resulting in further platelet aggregation and thrombus formation. Immediate cessation of heparin is critical upon diagnosis.

Trombocitose Overview

Trombocitose refers to an elevated platelet count (>450,000). It can be reactive or secondary but rarely pathological. Common causes include physiological responses during childhood or conditions like iron deficiency anemia in adults.

Causes and Implications of Reactive Thrombocytosis

In children, immature liver function may lead to temporary elevations in platelet counts. In adults with iron deficiency anemia, excess erythropoietin stimulates megakaryocyte proliferation leading to increased platelet production.

This structured summary provides a comprehensive overview while linking back to specific timestamps for deeper exploration into each topic discussed.

Understanding Thrombopoiesis and Its Clinical Implications

Mechanisms of Platelet Production

Trombopoietin (TPO) activation leads to increased platelet production by megakaryocytes, which mistakenly bind to erythropoietin, thinking it is TPO.

In response to blood loss, the body compensates by producing more TPO and platelets; this also occurs after severe infections due to interleukin-6 stimulating platelet production.

Post-splenectomy patients can experience platelet counts exceeding 1 million due to the absence of splenic clearance of platelets.

Primary Thrombocytosis

Primary thrombocytosis, such as essential thrombocythemia, is a myeloproliferative neoplasm characterized by abnormal megakaryocyte proliferation in the bone marrow.

Atypical megakaryocytes have less cytoplasm than normal ones; despite their name, they are still large but exhibit atypical features that affect platelet production control.

Genetic Factors and Clinical Monitoring

The lack of cytoplasmic abundance in atypical megakaryocytes leads to uncontrolled cell production and hypercellularity in the bone marrow.

Mutations in the JAK2 gene occur in 50% to 60% of essential thrombocythemia cases, contributing to disease pathology.

Critical Values for Platelet Counts

Critical thresholds for platelet counts include immediate notification for counts around 10,000 or below due to risks of spontaneous internal bleeding.

Attention is required for counts above 50,000; confirmation through retesting is necessary before notifying medical personnel about significant findings.

Documentation and Communication Protocol

It’s crucial not only to notify physicians about critical values but also maintain thorough documentation of communications regarding patient results.

Keeping a detailed log helps protect healthcare professionals from liability if issues arise concerning patient care notifications.

Clarification on Blood Components

Blood consists of various components including erythrocytes (red blood cells), plasma, proteins, etc.; "erythrocyte" specifically refers to red blood cells while "blood" encompasses all components.

Discussion on Blood Collection and Related Topics

Questions about ACD Tube

The speaker acknowledges a question from Helena regarding the ACD tube, admitting limited knowledge on the subject. They promise to research it further and provide supplementary reading later.

Collection Procedures in Different Settings

Darlene inquires whether blood collection is performed by biomedical professionals or doctors. The speaker explains that it varies by location; they have worked in settings where they collected samples themselves and others with dedicated collection teams.

In pediatric ICUs, doctors sometimes perform collections, but generally, it's not their area of expertise. This can lead to basic errors requiring repeat collections.

Coagulated Blood Analysis

Vanessa asks about transferring coagulated blood to another tube and potential anticoagulant excess. The speaker clarifies that using a dry glass tube avoids this issue while emphasizing the importance of proper handling during analysis.

They explain that using an EDTA tube could introduce excess anticoagulant but may not significantly affect results if handled correctly.

Causes of Thrombocytopenia

Cíntia questions what causes thrombocytopenia. The speaker lists several conditions including leukemia, chemotherapy effects, dengue fever, and viral infections like HIV as potential causes alongside purpura.

Understanding Antibody Excess

Maryene's question about excess antibodies leads to clarification that it's not truly an excess but rather misdirected antibodies affecting platelets in autoimmune diseases.

Fibromyalgia and Bleeding Disorders

Flávia raises a question about fibromyalgia causing small vessel bleeding. The speaker notes the inflammatory nature of fibromyalgia might influence platelet function but commits to researching further for clarity.

Von Willebrand Factor Clarification

Darlene asks if Von Willebrand factor is a protein; the speaker confirms it is indeed a large protein essential for blood clotting processes.

Study Tips for Complex Terminology

Sand shares her struggle with memorizing complex names related to medical terms. The speaker humorously suggests keeping notes as a study aid while stressing continuous learning in healthcare fields.

Treatment Approaches for Thrombocytopenia

Helena queries treatment options for thrombocytopenia. The response indicates treatments depend on underlying causes—autoimmune cases may require corticosteroids or splenectomy, while severe cases might need platelet transfusions as symptomatic relief rather than addressing root issues.

This structured summary captures key discussions from the transcript while providing timestamps for easy reference back to specific points made during the conversation.

Understanding Essential Thrombocythemia

Mechanisms of Essential Thrombocythemia

The speaker discusses the intrinsic mechanisms of essential thrombocythemia, noting that it leads to a cascade effect despite not having an adequate initiation due to hypercellular responses.

There is a mention of megakaryocytes and how their hyperproduction results from a mutation in a specific gene, leading to increased platelet production without affecting coagulation factors.

The discussion highlights that while there is an activation of the thrombus formation cascade, the presence of mechanisms that inhibit thrombus formation prevents excessive clotting.

It is emphasized that high platelet counts can lead to greater aggregation during tissue injury, which may increase thrombus formation speed but does not necessarily result in constant thrombosis.

The speaker clarifies that the primary issue in essential thrombocythemia is the hyperproduction caused by genetic mutations rather than problems with the coagulation cascade itself.

Conclusion and Reflections

As the session wraps up, participants express relief at completing the class and share light-hearted moments about their experiences during it.

A participant encourages feedback on the lesson through an evaluation link provided for better future sessions.

The conversation shifts towards personal anecdotes about challenges faced during teaching, including health issues impacting performance but ultimately maintaining a positive outlook on learning experiences.

Plans for future classes are discussed, indicating ongoing engagement and preparation for upcoming topics.