Coagulation Studies Flashcards
Which clotting pathways are evaluated by PTT or aPTT?
Intrinsic and common
Which drug therapy is monitored by PTT or aPTT?
Unfractionated heparin
Which clotting pathways are monitored by PT?
Extrinsic and common
What drug therapy is monitored with PT?
Warfarin
What is INR?
It’s a more accurate reflection of PT.
Its the ratio of the patient’s PT to a control PT, and it’s independent of the individual lab used
What is a normal INR/
1
What is the target INR for prophylaxis?
1.5-2.0
What is the target INR for DVT/PE?
2-3
What is the target INR for afib?
2-3
What is the target INR for mechanical mitral valve?
2.5-3.5
What is the target INR for a mechanical aortic valve?
2-3
What is an inhibitor screen (mixing test)?
Coagulation factor deficiency vs inhibitor problem
What is thrombin time (TT)?
Measures the final step of coagulation, the conversion of fibrinogen to fibrin.
What can low fibrinogen levels cause?
Impaired clot formation and increased bleeding risk
What is on the hypercoagulable panel?
Antithrombin
Factor V-Leiden
Protein C
Protein S
Prothrombin gene mutation
Lupus anticoagulant (Antiphospholipid antibodies)
MTHFR gene
(I know this card sucks and idk if its important or not, but i thought I’d make it just in case)
What are the 3 congenital coagulation disorders?
Hemophilia A (Factor VIII deficient)
Hemophilia B (Factor IX deficient)
Von Willebrand disease
What kind of drugs can cause acquired platelet dysfunction?
Chemo
Antibiotics
What is the management of platelet dysfucntion?
Treat the underlying cause
Platelet transfusion
What efffect will splenomegaly have on platelet levels?
Decrease
That big old spleen eats them all up
What effect will cirrhosis have on the spleen and therefore the platelets?
It causes vascular congestion, causing splenomegaly, and then low platelet levels
What 4 things can cause increased destruction of platelets?
Immune thrombocytopenia (ITP)
Disseminated intravascular coagulation (DIC)
Heparin-induced thrombocytopenia (HIT)
Thrombotic microangiopathies (TTP and HUS)
What are the two types of thrombotic microangiopathy (TMA)
TTP
HUS
What is thrombotic microangiopathy?
Low platelets due to the incorporation of platelets in the micro vasculature and microangiopathic hemolytic anemia.
(Microangiopathic hemolytic anemia is anemia caused by the shearing of RBCs as they pass through the little thrombi in the micro vasculature)
Is Thrombotic Thrombocytopenic purpura (TTP) a medical emergency?
Yes
What are the 2 ways you can wind up with TTP?
Acquired: developing antibodies against ADAMTS-13
Inherited: ADAMTS-13 mutations
Who is more likely to get TTP?
Black females
What might cause you to develop antibodies against ADAMTS-13?
Pregnancy
What happens with TTP?
Microthrombi are formed throughout the entire body. Purpura/petechiae appear on skin. Results in this CLASSIC PENTAD**
- microangiopathic hemolytic anemia
- thrombocytopenia
- acute kidney injury (uncommon)
- neurological defects**
- fever
What happens with hemolytic uremic syndrome?
Someone, usually a CHILD, eats SHIGA toxin from E. Coli O157:H7** and then they have BLOODY DIARRHEA. After that, they get microangiopathic hemolytic anemia, thrombocytopenia, and ACUTE KIDNEY INJURY.
Do yourself a favor https://youtu.be/U3VbjS7WqOE
Don’t 5 this card until you watched that
What will you see on the blood smear of someone with microangiopathic hemolytic anemia (TTP or HUS)?
Schistocytes aka HELMET CELLS**
(Remember the RBCs get sheared by all the little thrombi forming in the tiny vasculature, and the schistocytes/helmet cells are the carnage left behind)
Will a Coombs test be positive or negative in someone with microangiopathic hemolytic anemia (TTP or HUS)?
Negative
Coombs test tests for antibodies that destroy RBCs. The RBCs are being destroyed by thrombi, not attack by antibodies
Will PT and aPTT be normal or elevated with thrombotic microangiopathy (TTP or HUS)?
Normal
What do you do to treat thrombotic microangiopathy?
Plasma exchange
Supportive care (give antibiotics and fluids for the kid with e.coli HUS)
Which one is TTP and which one is HUS:
Neurological deficits
Acute kidney injury
TTP: neurological deficits
HUS: acute kidney injury
(Yes, kidney injury is part of the classic Pentad for TTP, but its not as bad as it is in HUS)
What kinds of things can impair the production of platelets?
Bone marrow failure
Chemo/radiation
Bone marrow infiltration (neoplasmic/infections)
Nutritional deficiencies- B12, folate, iron
Too much alcohol 🍺
What is the other name for Warfarin (Coumadin)?
Vitamin K antagonist (VKA)
What are the 4 Factor Xa Inhibitors?
Fondaripinux (Arixtra)
Rivaroxaban (Xarelto)
Apixaban (Eliquis)
Edoxaban (Savaysa, Lixiana)
Which drug is an oral direct thrombin inhibitor?
Dabigatran (Pradaxa)
What are the 4 drugs that are DOACs (Direct Oral Anticoagulants)
Dabigatran (Pradaxa)
Apixaban (Eliquis)
Rivaroxaban (Xarelto)
Edoxaban (Savaysa, Lixiana)
(They spell DARE. And the 3 that are Xa inhibitors have “Xa” in their name. Then dabigatran is the direct thrombin inhibitor)
Everybody knows that warfarin takes a few days to kick in. What should we use to get our patients anticoagulated in the meantime?
Heparin or LMWH
What is the preferred anticoagulant for patients with kidney disease
Warfarin aka VKA
vitamin K antagonist
What is the preferred anticoagulant for pregnant women?
LMWH
None of the others are OK.
Which anticoagulants are contraindicated in patients with kidney diseae?
Direct oral anticoagulants
LMWH
Which baseline labs are necessary when you start a pt on unfractionated heparin?
aPTT
PT/INR
CBC
What labs need to be monitored when your pt is on unfractionated heparin?
aPTT
OR
Factor Xa
What are the baseline labs required if you start a pateitn on LMWH?
PT/INR
aPTT
CBC
Creatinine* (risk of kidney injury)
What labs do you need to monitor while your patient is on LMWH?
Usually none
What are the preferred anticoagulants for patients with DVT or PE as long as they don’t have cancer?
DOACs»_space; Warfarin > LMWH
If your patient has cancer, what is the preferred anticoagulant?
LMWH
What is the MOA of Warfarin?
It inhibits the conversion of vitamin K to its active form, and therefore depletes all clotting factors that depend on vitamin K. It also inhibits protein C.
~inhibits propagation, does not remove thrombi!~
Will warfarin dissolve a thrombus?
No
What are some indications for using warfarin?
VTE (PE or DVT)
Inherited thrombophilia
AFib
Prosthetic heart valve
Stroke
When starting a patient on warfarin, should we give a “loading dose”?
No, won’t help. Only increases risks of bleeds
Ok i know i have to start heparin at the same time i start warfarin. Should i start them together at the same time?
Warfarin should be initiated on day 1 or 2 of heparin.
The heparin and warfarin should then overlap for at least 5 days and until the INR is therapeutic for 24 hours or 2 consecutive days
(?)
What is the initial dose of warfarin we should give?
5mg/day and then tweak it until you get to the target INR
How often do we need to monitor the patients INR when they are on Warfarin?
Daily for first 6 days, then weekly.
Once stabilized, every 2-4 weeks
It seems like every drug interacts with warfarin! Which ones were in red boxes on the UpToDate chart that was lazily pasted into this half ass lecture?
Tylenol
Aspirin
Cephalosporins
Diclofenac
Macrolides
Bactrim
Oral contraceptives
Well shit your patient took way too much of his warfarin and his INR is now way too high. What should you do?
If his INR is 4.5-10 and he’s not bleeding out, don’t do anything.
If his INR is over 10 and he’s still not bleeding, you need to give him PO vitamin K
If he’s having a major bleed, you need to give PCC and IV Vitamin K (5-10mg)**
Your patient took too much warfarin and he’s having a major bleed. What do you do?
this is probably a test question*
IV Vitamin K 5-10mg
PCC (prothrombin complex concentrate)
Stop the warfarin too lol
What is the reversal agent for heparin?
either type
Protamine
Andexanet$$$
PER977$$$
What is the reversal agent for Warfarin?
4Factor PCC (prothrombin complex concentrate)
Vitamin K
What is the reversal agent for dabigatran (Pradaxa)?
Idarucizumab (Praxbind)
Supportive care for bleeding
What is the reversal agent for the direct thrombin inhibitors that are not Pradaxa?
Supportive care for bleeding (good luck!)
What is the reversal agent for Direct Xa Inhibitors?
Xarelto, Eliquis, Lixiana, Savaysa
Supportive care for bleeding 😃
Andexanet$$$
PER977$$$$
