Pharmacology
Routes of heparin and warfarin
Heparin: SC/IV
Warfarin: PO
Is Helen's Day 1 and 2 INR of 1.0 therapeutic?
No
Which value is monitored for titration of a heparin infusion?
PTT/aPTT
Why is warfarin therapy started while heparin therapy is still in place?
To provide anticoagulation while warfarin slowly takes effect
Antidote for Warfarin overdose
Vitamin K
Warfarin's mechanism of action
Vitamin K inhibitor - decreases production of clotting factors in the liver which depend on Vitamin K for synthesis
On Day 4, Helen is taking heparin and warfarin. Which medication will she be discharged with?
Warfarin
True/False: bolus doses are always administered at the beginning of a continuous heparin infusion
False
What is the therapeutic range of INR?
2-3
antidote for heparin overdose
protamine sulfate
How heparin works on the clotting cascade
Blocks prothrombin from converting into thrombin and fibrinogen from converting into fibrin
What tool should be used to help maintain/titrate Helen's heparin infusion to a therapeutic level?
what is a nomogram and how is it used to heparin infusions?
mathematical model which demonstrates the relationship between variables to determine outcomes based on those variables, used to guide initiation and titration of heparin infusions
Why is warfarin continued as an outpatient instead of heparin?
Heparin must be injected and poses the risk of HIT
What is a manifestation of heparin/warfarin overdose?
Increased bleeding
Lab value to monitor for effectiveness of heparin and dalteparin
PTT (therapeutic range: 1.5-2.5 times higher than control value)
What in Helen's past medical history is a contraindication for dalteparin therapy?
CRF - renal impairment
what are indications for lower doses of heparin infusion?
recent thrombotic stroke, surgery, bleeding, or conditions which increase bleeding
at least 24 hours
Name 3 manifestations of increased bleeding in anticoagulant therapy
petechiae, bruising, melena, hematuria, bleeding gums, nosebleeds
Why should a patient with HIT not receive dalteparin?
HIT antibodies will cross-react with dalteparin as it is low molecular weight heparin
Why is Helen's unsteadiness and dizziness a concern with anticoagulant therapy?
If Helen is at a risk for falls due to the aforementioned symptoms, then she could injure herself while mobilizing, which could trigger an elevated level of bleeding and bruising due to anticoagulant therapy
what are indications for higher doses of heparin infusion?
obesity or great urgency for anticoagulation
What are some contraindications to bridging heparin to dalteparin?
HIT, impaired renal function
Describe how HIT manifests
The body forms heparin-platelet antibodies, which decrease platelet count and lead to increased thrombosis