Coagulation Disorders Flashcards
Intrinsic Pathway
AMPLIFIES Contact activation Damaged surface XII → XIIa XI → XIa IX → IXa VIII → VIIIa
Extrinsic Pathway
Initial pathway
Tissue factor (III) + VII → X
PT 12-14sec
INR 0.9-1.2
Coagulation Cascade
- Vasoconstriction
- Platelet plug
- Blood clot
- Dissolution
Common Pathway
X → II → I
Prothrombin II → thrombin (IIa)
Fibrinogen I → fibrin Ia
CLOT
Single-Factor Deficiencies & Anesthesia
Treatment depends on deficiency severity
Several products available - factor concentrates, recombinant factors, FFP, gene therapy
Replacement therapy effect duration depends on each factor turnover time
Coagulation Disorders
Hereditary - Hemophilia A - Hemophilia B - Von Willebrand disease Acquired - Vitamin K deficiency - Liver disease - DIC - Autoantibodies
Hemophilia A
Factor VIII gene dependent on X chromosome
Inherited or gene mutation
Severe hemophilia - inversion or deletion
< 1% VIII activity
Mild 6-30%
Diagnosis - prolonged aPTT, specific factor, & gene testing
Hemophilia A & Anesthesia
Hematology consult
Factor VIII level at least >50% prior to surgery
Mild DDAVP 30-90min prior to surgery
Moderate to severe admin VIII concentrate
Half-life 12hrs
FFP & cryo
Consider TXA as adjunct
Hemophilia B
Factor IX deficiency
Christmas factor
X-linked
Less common
Severe bleeding IX <1%
Mild 5-40% often not detected until surgery or dental procedure
Diagnosis - prolonged aPTT, specific factor, & gene testing
Hemophilia B & Anesthesia
Similar to Hemophilia A Hematology consult Replacement therapy including recombinant factor IX, purified IX, prothrombin complex concentrate PCCs contain II, VII, IX, & X ↑risk thrombotic events Continue replacement therapy Factor IX half-life 18-24hrs Consider TXA as adjunct
Von Willebrand Disease
Most common congenital bleeding disorder in the world
Disorders caused by quantitative and/or qualitative defect
vWF mediates platelet adhesion & prolongs factor VIII half-life
Von Willebrand
Synthesis & Storage
Endothelial cells
Platelets
Von Willebrand
Hemostasis
Dual role affecting both platelet function & coagulation
- Platelet adhesion GIb
- Platelet aggregation GIIB/IIIa
- Factor VIII carrier molecule & factor IX co-factor
Von Willebrand Type 1
Most common 60-70%
Mild to moderate vWF level reduction
Mild bleeding symptoms - easy bruising & nosebleeds
Responsive to DDAVP
Von Willebrand Type 2
Qualitative defect vWF
9-30% patients
4 subtypes
Von Willebrand Type 3
< 1% patients
Nearly undetectable
Severe quantitative phenotype
Von Willebrand
Platelet-Pseudo Type
Defect in platelet GIb receptor
Von Willebrand Disease
Replacement Therapy Goals
Major - maintain factor VIII level >50% 1wk
Minor - maintain factor VIII level >50% 1-3 days & 20-30% additional 4-7 days
Dental extraction - single infusion to achieve factor VIII level >50%
DDAVP prior to procedure (type 1)
Spontaneous or post-traumatic bleeding - single infusion 20-40u/kg
FFP
Fresh frozen plasma
Prothrombin (II), V, VII, VIII, IX, X, XI, XIII, vWF
Cryoprecipitate
Fibrinogen, VIII, XIII, vWF
PCCs
Prothrombin (II), VII, IX, X
Factor Concentrates
VIII IX X XIII vWF
DIC
Disseminated Intravascular Coagulation
Thrombin generated in response to insulting factor (endotoxins or amniotic fluid embolism)
Intravascular clotting then disseminates
Blood clots throughout the body causing end-organ dysfunction
Coagulation factors are depleted & platelets become used up → dysfunction
Fibrinolysis activated & results in bleeding
DIC S/S
Widespread clot formation - Chest pain - SOB - Leg pain (DVT) - Difficulty speaking or moving - ST changes Patients present w/ clotting or bleeding or both Hemorrhages simultaneously w/ microcirculation thrombosis
DIC Causes
Sepsis - bacterial, viral, or fungal Surgery or trauma Cancer - more chronic, insidious onset, often leukemia Pregnancy complications - amniotic fluid bolus or HELLP syndrome Snake bites - venom Frostbite Burns Transfusion reaction
Acute DIC
Coagulation & fibrinolysis dysregulation
Widespread clotting w/ resultant bleeding
- Fibrin deposits as thrombosis in circulation
- Platelet depletion & clotting factors
Tissue factor present on multiple cell surfaces (endothelial, macrophages, monocytes) & tissues (lung, brain, placenta)
- Exposed & released
- Bind w/ factor VIIa & activates IX & X to form thrombin & fibrin in the common final pathway
Fibrinolysis
Creates fibrin degradation products - Inhibit platelet aggregation - Antithrombin activity - Impair fibrin polymerization All contribute to bleeding
DIC
Lab Values
Coagulation inhibitors consumed
↓inhibitor levels permit additional clotting
↑clotting factors → clotting
Thrombocytopenia d/t platelet consumption
Dysfunctional platelets d/t inflammatory processes
↓platelets & dysfunction ↓fibrinogen ↑PT/INR ↑PTT ↑d-dimer TEGs & ROTEMs
Thrombin
Potent pro-inflammatory protein & platelet aggregator
Excessive & unregulated → coagulation factors consumption ↑fibrinolysis
Platelets & clotting factors depletion
→ fibrin degradation products
Thrombotic complications
Throbomodulin
Binds to thrombin ↓pro-inflammatory response
Limited clinical trials
Direct thrombin inhibitors (no RCTs)
DIC Treatment
Identify Treat the underlying condition - Infection - antibiotics - Trauma - resuscitation Supportive therapy - platelets, cryoprecipitate, fibrinogen concentrate, FFP, Heparin (controversial), TXA, PCCs
Heparin
Controversial therapy
Variable outcomes as DIC treatment
Reserved in early or highly prothrombotic states
↑risk additional bleeding
Reduces end-organ dysfunction
Discontinue when overt bleeding occurs
Difficult to monitor b/c PTT already prolonged d/t coagulation factor consumption
TXA
Tranexamic acid (antifibrinolytic) CRASH-2 trial
