Blood Clotting, Blood Types, and Rh Factor

Blood Clotting Medications

  • Medications are sometimes needed to prevent excessive blood clotting, which can lead to serious health issues.

Types of Drugs

  • Three main types:
    • Antiplatelet drugs: Prevent platelets from clumping together.
    • Anticoagulants: Interfere with steps in the clotting process.
      • Heparin: Acts quickly by inhibiting thrombin.
      • Warfarin (Coumadin): Reduces the liver’s use of vitamin K to make prothrombin, decreasing clot formation.
    • Fibrinolytic agents (clot busters) like TPA:
      • Dissolve clots that have already formed.
      • Used to treat heart attacks and strokes.
      • High risk of bleeding because it stops blood from clotting.

Blood Clots (Thrombi)

  • Dangerous if a piece breaks off, forming an embolus.
  • Embolus travels through the bloodstream and blocks vessels in vital organs, leading to:
    • Stroke
    • Heart attack
    • Pulmonary embolism
  • Deep Vein Thrombosis (DVT):
    • A clot in the leg veins.
    • Can travel to the lungs and cause sudden death.

Blood Thinners

  • Drugs do not actually thin the blood.
  • They make it less likely for the blood to clot.

Blood Types

Four Groupings

  • A, B, AB, O
Antigens
  • A: Has A antigen.
  • B: Has B antigen.
  • AB: Has A and B antigens.
  • O: Has no antigens.
Antibodies
  • Type A: A antigen, anti-B antibodies.
  • Type B: B antigen, anti-A antibodies.
  • Type AB: A and B antigens, no antibodies; universal recipient.
  • Type O: No antigens, both A and B antibodies; universal donor (specifically O negative).

O Negative

  • Used in emergencies when the patient's blood type is unknown.
  • Has no antigens, so it can be given to anyone.

Blood Transfusions

  • Blood is sent to the blood bank for cross-matching.
  • Two tubes of blood are drawn to double-check the blood type.
  • A section of donor blood is mixed with the patient’s blood to ensure compatibility.
  • Patients with multiple transfusions require constant double-checking due to potential antibody development.

Rh Factor

  • Rh antigen located on the membrane of red blood cells.
    • Rh positive: Has the Rh antigen.
    • Rh negative: Lacks the Rh antigen.

Pregnancy Implications

  • Rh negative mother carrying an Rh positive fetus can develop antibodies against Rh positive blood.
  • Can cause hemolytic disease of the newborn (erythroblastosis fetalis), especially in subsequent pregnancies.
RhoGAM
  • Given to Rh negative pregnant women to prevent antibody development.
  • Administered during pregnancy and after delivery.
  • If a woman has a miscarriage, she might receive RhoGAM if the father's Rh type is unknown.

Blood Type Compatibility

  • A: Can receive A and O blood; can donate to A and AB.
  • B: Can receive B and O blood; can donate to B and AB.
  • AB: Can receive A, B, AB, and O blood; can donate only to AB.
  • O: Can receive only O blood; can donate to O, A, B, and AB.
  • Compatibility rules mainly apply to red blood cells; platelets have slightly different rules (not covered).