Hematology

Introduction

  • Quotes by Maxwell Maltz: "You Make Mistakes, Mistakes Don't Make You"

Hematology Overview

  • Definition: Study of blood and its disorders.

Blood Composition

  • Whole Blood: 8% of total body weight.

    • Components: 92% other fluids and tissues.

  • Plasma: 55% of total blood volume.

    • Composition:

      • Water: 91%

      • Proteins: 7%

        • Albumins: 57%

        • Globulins: 38%

        • Fibrinogen: 4%

        • Prothrombin: 1%

      • Other Solutes: 2% (ions, nutrients, waste products, gases, regulatory substances).

  • Formed Elements: 45% of blood volume.

    • Leukocytes: <1% (types include Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils)

    • Erythrocytes: >99% of formed elements.

Erythropoiesis (RBC Production)

  • Stimuli for RBC production:

  1. Hemoglobin synthesis.

  2. Blood flow.

  3. Hemorrhage.

  4. Increased O2 consumption by tissues.

  • Erythropoietin (EPO): Hormonal control of erythropoiesis regulated by O2 levels.

Hemoglobin Structure

  • Heme Molecule:

    • Composed of polypeptide chains.

    • Contains Iron (Fe2+) at its core.

  • Globin:** Composed of alpha and beta chains.

Hematopoiesis and Hemolysis

  • Process:

    • Old/damaged RBCs are removed by spleen and liver.

    • Hemoglobin is broken down into components:

      • Amino acids recycled.

      • Iron recycled to bone marrow or stored.

      • Bilirubin processed in the liver for excretion.

Hemostasis

  • Stages of Hemostasis:

    • Primary and Secondary hemostasis.

  • Mechanisms involve:

    • Platelet activation and aggregation.

    • Clotting factors create a fibrin clot.

    • Fibrinolysis breaks down the fibrin mesh.

Anemia Definitions and Concepts

  • Anemia: Functional inability of blood to supply adequate oxygen to tissues.

    • Causes include:

      • Reduction in erythrocyte number.

      • Impaired production.

      • Blood loss.

      • Increased destruction.

  • WHO Diagnosis Criteria:

    • Hb < 13 g/dL in men.

    • Hb < 12 g/dL in women.

Anemia Classification

  • By Morphology:

    • Microcytic (size): Iron deficiency.

    • Normocytic: Anemia of chronic disease.

    • Macrocytic: Vitamin B12 or folate deficiency.

Symptoms of Anemia

  • Generalized symptoms result from oxygen deficits:

    • Fatigue, tachycardia, shortness of breath, pallor, dizziness, and neurological symptoms (difficulty concentrating, insomnia).

Specific Types of Anemia

  • Macrocytic Normochromic Anemia:

    • Characterized by large stem cells due to DNA synthesis defects.

    • Commonly arises from vitamin B12 or folate deficiencies.

  • Microcytic Hypochromic Anemia:

    • Characterized by small RBCs with reduced hemoglobin content; most commonly due to iron deficiency, chronic disease, or thalassemia.

  • Normocytic Anemia:

    • Caused by hemolysis or blood loss; particularly associated with chronic kidney disease.

Platelet Dysfunction and Coagulopathy

  • Definitions:

    • Hemorrhage: Escape of blood from a vessel; can range from benign to fatal.

    • Thrombosis: Clot formation leading to complications.

  • Pathogenesis of Disorders:

    • Platelet dysfunction results in prolonged bleeding and various manifestations (petechiae, purpura).

  • Dysfunction Examples:

    • von Willebrand Disease, Hemophilia, Vitamin K deficiency and its effects on coagulation factors.

  • Disseminated Intravascular Coagulation (DIC):

    • Complex coagulopathy characterized by simultaneous clotting and bleeding; often triggered by infection, trauma, etc.

Anemia Workup Case Study

  • 56-year-old male with anemia (Hb 9.6g/dL).

    • Key features to identify: Age, sex, duration of symptoms.

    • Investigations include CBC with parameters like H&H, RDW, MCV, MCHC, ferritin, iron levels, etc.