LU1 8 8 RBC PATHOLOGIES RBC LOSS HEMOLYTIC EXTRINSIC

Hemolytic Blood Loss: Overview

  • Definition: Hemolytic blood loss is characterized by the destruction of red blood cells (RBCs) that can lead to anemia.

  • Types: It can be categorized into acquired (extrinsic) and genetic disorders.

  • Causes: Destruction of RBCs in circulation can occur due to various factors.

Causes of Red Blood Cell Destruction

Immune Responses

  • Autoimmune Disorders: Certain autoimmune conditions can lead to the immune system attacking RBCs.

  • Transfusion Reactions: A mismatch between donor and recipient blood types can result in the immune system destroying transfused RBCs due to recognized antigens.

    • Key Rule: Avoid transfusing blood with antigens that the recipient’s antibodies will recognize; this can lead to agglutination and hemolysis.

Erythroblastosis Fetalis

  • Occurs when a mother’s immune system attacks fetal RBCs in cases of blood type mismatch (e.g., mother O type and baby A/B type, or Rh negative mother and Rh positive baby).

  • Mechanism: Maternal IgG antibodies can cross the placenta and target fetal RBCs.

  • After birth, these maternal antibodies may remain in the baby’s bloodstream leading to hemolytic disease of the newborn (HDN).

Hemolytic Venoms and Toxins

  • Certain snake venoms contain hemolytic and neurotoxic properties.

  • Venom proteins can destroy neurons or RBCs, resulting in severe symptoms, including blood loss.

Drug-Induced Hemolysis

  • Some medications can have hemolytic effects, contributing to red blood cell destruction.

Clinical Indicators of Hemolytic Anemia

  • Red blood cells produced normally, but they are destroyed in circulation.

  • For diagnostic indices: We expect:

    • Normal morphology of RBCs.

    • Normal indices: Mean corpuscular volume (MCV), Mean corpuscular hemoglobin (MCH), and Mean corpuscular hemoglobin concentration (MCHC).

  • Despite normal indices, anemia symptoms arise due to decreased hemoglobin concentration and fewer RBCs.

Consequences of Mismatched Transfusions

  • Agglutination of mismatched blood can lead to blood clots, resulting in hypoxia and potential tissue death.

  • Major complications include acute kidney failure due to the release of hemoglobin damaging the filtration membranes in nephrons.

Inheritance and Blood Types

  • No evolutionary predisposition indicating babies favor taking on the mother’s blood type over the father’s.

  • Blood type inheritance explained through Punnett squares based on parent genotypes (homozygous vs. heterozygous) regarding antigens.

Prophylactic Treatment with Rhogam

  • Administered to Rh-negative mothers to prevent immune responses during pregnancy.

  • Important to administer even if testing prior to delivery generally shows insufficient antigen presence from the fetus at birth.

  • Aims to prevent erythroblastosis fetalis and HDN.

Rattlesnake Venom and Treatment

  • Southern Pacific rattlesnake venom contains a combination of hemolytic and neurotoxic proteins.

  • Antivenom treatment (CroFab) can be used across viper species, but may be less effective against unique venom proteins of Southern Pacific rattlesnakes.

  • Continuous blood transfusions may be required for severe cases, emphasizing the critical nature of such bites and the treatment involved.