Anticoagulation Labs Flashcards
High citrate concentration in tube
Affects anti-factor Xa
Poor blood samples
Increase both anti-factor Xa and aPTT
Underfilled tubes
Increase aPTT
Prolonged time > 2 hours to sample analysis
Decrease both anti-factor Xa and aPTT
Inadequate centrifugation
Decrease both anti-factor Xa and aPTT
Antithrombin deficiency
Decrease both anti-factor Xa and aPTT
Increased acute phase reactants like factor 8 and fibrinogen
Decrease aPTT
Increased heparin binding proteins
Decrease both anti-factor Xa and aPTT
Obesity
Decreases both anti-factor Xa and aPTT
Decreased renal elimination
Increase both anti-factor Xa and aPTT
Decreased clotting factors (liver disease)
Increase aPTT
Consumptive coagulopathy (DIC)
Increase aPTT
Lupus anticoagulant
Increase aPTT
Decreased clotting factors (Not factor 8)
Increase aPTT
Elderly
Increase aPTT
Recent use of other anti-Xa meds
Increase anti-factor Xa
High triglycerides
Increase anti-factor Xa
High bilirubin
Decrease anti-factor Xa
COVID-19
Increase aPTT
Should you wait for anti-Xa and aPTT baseline labs to result before starting a heparin infusion?
No, infusion should be started immediately and lab results can later influence dosing
After a heparin infusion starts, when do you measure an anti-Xa level
4 - 6 hours after an infusion starts or infusion rate change without a bolus
If a heparin bolus is given that is < 2500 units, when do you measure an anti-Xa level
6 hours after
Since anti-Xa heparin assay is a chromogenic test, erroneous results can come from patients that have
Hemolysis, icterus, lipema (basically anything that affects how the blood looks)
Anti-Xa heparin assay vs. Factor X assay
Anti-Xa heparin assay detects heparin’s effect of the patient’s plasma based on inhibition of factor X in an assay reagent; Factor X assay measures a patient’s endogenous level of functional Factor X
What tests measure dabigatran?
Ecarin clotting assay, dilute thrombin time, or thrombin time
What test measures enoxaparin?
Anti-Xa LMWH assay
What is hematocrit?
Percent of red blood cells in the blood
What is hemoglobin?
Presence of oxygenated blood
What is d-dimer?
Product of fibrin degeneration
What is a d-dimer determining?
If a d-dimer is negative, patient likely does not have a VTE. If a d-dimer is positive, do more tests.
When to monitor platelets if heparin is started?
At baseline, 24 hours after, then every other day for 14 days
When to draw a CBC for LMWH?
Every 5 - 10 days for the first two weeks, then every 2 - 4 weeks
Critical prothrombin time value
> 100 seconds
Critical aPTT value
> 70 seconds
Critical chromogenic factor X level
11% or less
Therapeutic anti-Xa heparin assay values
0.3 - 0.7 units/mL
