hemostasis

• Understanding the major systems of hemostasis—blood vessels, platelets, and plasma proteins is essential to interpreting laboratory test results and to prevent, predict, diagnose, and manage hemostatic disease.
• Hemostasis is a complex physiologic process that keeps circulating blood in a fluid state and then, when an injury occurs, produces a clot to stop the bleeding, confines the clot to the site of injury, and finally dissolves the clot as the wound heals.
• The absence of a single plasma procoagulant may destine the individual to lifelong anatomic hemorrhage, chronic inflammation, and transfusion dependence.
• Conversely, absence of a control protein allows coagulation to proceed unchecked and results in thrombosis, stroke, pulmonary embolism, deep vein thrombosis, and cardiovascular events.
• When hemostasis systems are out of balance, hemorrhage (uncontrolled bleeding) or thrombosis (pathologic clotting) can be life threatening.
• A pregnant woman developed a blood clot in her left leg (deep vein thrombosis, or DVT)
• Her mother reportedly had a history of thrombophlebitis
• The woman's brother was diagnosed with DVT after a flight from Los Angeles to Sydney, Australia
• Hemostasis is a complex physiologic process that keeps circulating blood in a fluid state and then, when an injury occurs, produces a clot to stop the bleeding, confines the clot to the site of injury, and finally dissolves the clot as the wound heals
• When hemostasis systems are out of balance, hemorrhage (uncontrolled bleeding) or thrombosis (pathologic clotting) can be life threatening.
• The absence of a single plasma procoagulant may destine the individual to lifelong anatomic hemorrhage, chronic inflammation, and transfusion dependence.
• Fibrinogen is the substrate for the enzymatic action of thrombin, the primary enzyme of the coagulation system.
• There are plasma glycoproteins that act as control proteins that serve the important function of regulating the coagulation process to avoid unnecessary blood clotting.
• In 1958 the International Committee for the Standardization of the Nomenclature of the Blood Clotting Factors officially named the plasma procoagulants using Roman numerals in the order of their initial description or discovery.
• When a procoagulant becomes activated, a lowercase a appears behind the numeral; for instance, activated factor VII is VIIa.
• Both zymogens and cofactors become activated in the coagulation process.
• The absence of a control protein allows coagulation to proceed unchecked and results in thrombosis, stroke, pulmonary embolism, deep vein thrombosis, and cardiovascular events.
• Vitamin K-dependent coagulation factors include Prothrombin (II), Protein C, Protein S, Protein VII, Protein IX, Protein X, Protein Z, and Protein XI.
• Other plasma procoagulants include Fibrinogen, Factor XIII, Phospholipids, Calcium, and Von Willebrand factor.
• The bound calcium enables these vitamin K-dependent coagulation factors to bind to negatively charged Procoagulants.
• Regulatory Proteins include Prothrombin (II), Protein C, Protein S, Protein VII, Protein IX, Protein X, Protein Z, and Protein XI.
• Procoagulant cofactors are tissue factor, factor V, factor VIII, and HMWK.
• Cofactors of the coagulation control proteins are thrombomodulin, protein S, and protein Z.
• Thrombomodulin is also a cofactor in control of fibrinolysis.
• Coagulation complexes form on tissue factor (TF)-bearing cells (TF:VIIa) and on platelet phospholipid membranes (IXa:VIIIa and Xa:Va).
• Understanding the major systems of hemostasis—blood vessels, platelets, and plasma proteins—is essential to interpreting laboratory test results and to prevent, predict, diagnose, and manage hemostatic disease.
• J., Aird, W

  C., Bennett, J

  S., et al

  (Eds.), Hemostasis and Thrombosis: Basic Principles and Clinical Practice

  (6th ed., pp

  341–348)

  Philadelphia: Lippincott Williams & Wilkins
• A brams, C

  S., & Brass, L

  F.
• Platelet signal transduction
• In Marder, V

  J., Aird, W

  C., Bennett, J

  S., et al

  (Eds.), Hemostasis and Thrombosis: Basic Principles and Clinical Practice

  (6th ed., pp

  449–461)
• B erndt, M

  C., & Andrews, R

  K.
• Major platelet glycoproteins
• GP Ib/IX/V
• In Marder, V

  J., Aird, W

  C., Bennett, J

  S., et al

  (Eds.), Hemostasis and Thrombosis: Basic Principles and Clinical Practice

  (6th ed., pp

  382–385)
• Y e, F., & Ginsberg, M

  H.
• Major platelet glycoproteins
• Integrin ! 2b " 3 (GP IIb/IIIa)
• Hemostasis involves the interaction of vasoconstriction, platelet adhesion and aggregation, and coagulation enzyme activation to stop bleeding.
• The coagulation system, similar to other humoral amplification mechanisms, is complex because it translates a diminutive physical or chemical stimulus into a profound life-saving event.
• The key cellular elements of hemostasis are the cells of the vascular intima, extravascular tissue factor (TF)-bearing cells, and platelets.