Anticoagulation, Coagulation mixing studies
Anticoagulation, Coagulation mixing studies
Dosing IV Heparin and PO Coumadin
Follow nomogram
Ensure no bleeding (nose, mouth, IV sites, urine, stool, vagina…etc….)
recheck PTT in 6 hours (for Heparin dose adjustment) or check PT/INR in AM (for Coumadin dose adjustment)
Heparin 1000 cc/hr or 750 cc/hr. Given as 25,000 units in 250 ml D5W. Next PTT in 6 hours after heparin started.
Loading: 60 U/kg bolus F/up with 14 U/kg/hr
Screening Test Abnormalities in Inherited and Acquired Coagulopathies
Mixing study:
Useful if ▲ PT or ▲ PTT.
Mix Pt's plasma 1:1 with normal plasma and retest. PT/PTT normalizes which means there is a factor deficiency. If PT/PTT remains elevated, it implies that there is a factor inhibitor. Factor VIII antibody is he most common cause. Check for lupus anticoagulant.
Coagulation factor levels are useful if mixing study suggest factor deficiency. In DIC all factors are consumed; therefor ▼ factor V and VIII.
Vitamin K deficiency → ▼ factors II, VII, IX, X (and protein C, S); therefore normal factor V and VIII.
Lupus anticoag test is assoc with increased risk of thrombosis and recurrent spont. AB. Lupus anticoag is a lab artifact, produces invitro prolonged aPTT. Does not cause bleeding d/o. Seen in 5 - 10% of Pts with SLE and taking Phenothiazines.
Checked as anticardiolipin Abs: IgA, IgG, IgM (<12 APL, <15 GPL, and <12 MPL)
Russel viper venom (RVV) is more sensitive assay for checking lupus anticoag.
Pts with antiphospholipid syndrome have mod. or high levels of cardiolipin abs and are +ve for IgG only or IgG and IgM.
Hemophilias
Hemophilia A (factor VIII) deficiency
X linked
Hemophilia B (factor IX) deficiency
Classification
mild - 5 to 25% normal factor activity
moderate - 1 to 5%
severe - <1%
Clinical manifestations: hematomas, hemarthroses, bruising, bleeding (mucosal, GI, GU)
Dx: ▲ PTT (normalizes with mixing study), normal PT & vWF; ▼ factor VIII or IX
Treatment: purified/recombinant factor VIII or IX concentrate, desmopressin (mild disease), aminocaproic acid; recombinant factors VIIa if factor inhib, cryo (only has factor VIII)
Coagulation factor inhibitors
Etiologies:
Hemophilia
Tx: replacement of factor VIII in hemophilia A; factor IX in hemophilia B)
Postpartum lymphoproliferative disorders and other malignancies
Autoimmune diseases, most commonly anti-factor VIII
Diagnosis: ▲ PTT (does not normalize with mixing study); Bethesda assay quantitates titer
Treatment: high titer → recombinant factor VIIa, porcine factor concentrates, activated PT complex; others → high-purity human factor, plasmapheresis, immune tolerance.
Vitamin K deficiency
Etiologies: malnutrition, ▼ absorption (ABx suppression of vitamin K-producing intestinal flora or malabsorption), liver disease (▼ stores), warfarin