Chapter 17 part 4

Insufficient blood supply to areas like the heart can lead to:
- Heart attack due to lack of oxygenation.
- Stroke if insufficient blood reaches the brain.
Heparin's role in clotting:
- Enhances the activity of antithrombin III, inhibiting thrombin formation.
- Inhibits the intrinsic pathway of the coagulation cascade.
- Secreted by basophils and mast cells on the endothelial cell surface.

Endothelium: Inner lining of blood vessels.
Damage leads to clot formation as the body attempts to repair the endothelial lining.
Factors preventing undesirable clotting:
- Platelets do not adhere to smooth, intact endothelium.
- Endothelial cells secrete antithrombotic substances like nitric oxide and prostacyclin.

Thromboembolic disorders: Result from undesirable clot formation leading to thrombosis.
Thrombus: A solid mass of blood components that develops within a blood vessel and obstructs circulation leading to tissue ischemia and potentially infarction (tissue death).
- Example: Myocardial infarction (heart tissue death).

Abnormalities that impede normal blood clotting:
- Hemophilia: Caused by deficiency of clotting factors, notably:
  - Factor VIII (Hemophilia A): Most common, accounts for 77% of cases.
  - Factor IX (Hemophilia B).
  - Factor XI (Hemophilia C, less severe).
These disorders can lead to profuse bleeding from minor injuries.
Thrombocytopenia: Decrease in platelet count resulting in spontaneous bleeding and purplish patches (petechiae) on the skin, treated through platelet transfusions.

Affects the clotting and bleeding pathways leading to widespread clotting and bleeding.
Symptoms include excessive bruising, confusion, and dyspnea.
Causes include:
- Infections (sepsis), cancer, liver disease, etc.

Thrombus: A stationary clot that obstructs blood flow in a vessel.
Embolus: A traveling thrombus that can lodge in smaller vessels, leading to complications like pulmonary embolism.

Atherosclerosis: Accumulation of cholesterol leading to narrowed arteries and increased risk of clots.
Immobility: Prolonged inactivity can slow blood circulation exacerbating clot risk.
- Post-surgery patients often prescribed anticoagulants to mitigate this risk.

Aspirin: Inhibits thromboxane A2 to prevent platelet aggregation.
Heparin: Administered IV in clinical settings to prevent venous thrombosis, particularly post-op.
Warfarin: Interferes with vitamin K and clotting factors, used in stroke risk reduction.

Loss of 15-30% of blood can lead to signs of pallor and weakness.
Loss of over 30% can cause severe shock and can be fatal without blood replacement.
Replacement therapies include normal saline or Ringer's lactate, supporting circulation but not replenishing oxygen-carrying capacity.

Blood transfusions must be compatible to avoid fatal reactions due to agglutination of RBCs.
Types:
- ABO groups: Blood type is determined by antigen presence.
  - Type A: A antigen.
  - Type B: B antigen.
  - Type AB: Both A and B antigens (universal recipient).
  - Type O: Neither (universal donor).
Rh factor: Determines positivity or negativity of blood groups (85% are Rh positive).

Can occur if an Rh-negative mother carries an Rh-positive fetus, leading to complications in subsequent pregnancies due to maternal Rh antibodies attacking fetal blood cells.

Crossmatching: Testing whether donor and recipient blood can mix without agglutination.
Blood typing involves mixing blood with anti-A and anti-B serums to determine antigen presence, crucial for safe transfusion practices.

Understanding clotting disorders is critical for managing patient care, especially in surgeries and underlying health conditions that predispose to clotting or bleeding disorders.