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Laboratory Tests for Anticoagulant Therapy

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Clotting or Coagulation Time
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>amount of time drawn blood takes to clot >normal time 3-7 minutes. Will be prolonged > 10 minutes if thrombocytopenia (<100,000 mm3)
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Prothrombin Time (PT)
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>also referred to as Protime >Activated Prothrombin Time – more precise >*Used to monitor warfarin (Coumadin) therapy* measures the time blood takes to clot – common pathway >sensitive to alterations in vitamin K-dependent factors (Prothrombin) >An increased PT refers to a longer time for clotting to occur, with clotting ability being less than normal >Normal: 10-14 seconds >Therapeutic warfarin is used to keep the PT at 1.5 – 2.5 times the normal level
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INR
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>International Normalized Ratio (INR) >>Because test results of PT can vary widely among labs and to insure that test results among different labs are comparable, results are now reported in terms of an INR. >>An INR of *2 to 3 is appropriate for most patients on warfarin- although for some patients the target is 3 to 4.5.* —Examples: -Prevention of embolism in patients with atrial fibrillation 2-3 -Prevention of recurrent DVT 2.5-4.0 -Prevention of arterial thrombosis, prevention of clots with mechanical heart valves – 3.0-4.5
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PTT or APTT
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>Activated Partial Thromboplastin Time (APTT) – more precise -used to assess initial pathways (intrinsic/extrinsic) of clot formation -*Used to monitor heparin therapy* -Therapeutic heparin is used to keep the APTT at 1.5 to 2.5 times the normal level -Normal: 24-40 seconds
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PTT
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Heparin
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PT
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Coumadin
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Sliding Scale
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Daily PTT —If Heparin by 200 Or —or > 80, then < Heparin by 200
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OLL’s Chart
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1. Heparin units IV bolus given at o’clock. 2. Begin Heparin 25, 000 u/500 cc at 20 cc/hr 3. PTT in 6 hours and q am – use the following to adjust Heparin If PTT Give bolus Change Rate Repeat (sec) dose to PTT < 39 5,000U +30 cc/hr 6 hr 40-49 3,000 U +20 cc/hr 6 hr May give you how long to stop the infusion
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Weight Based
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>Client is weighed on a daily basis and dose is adjusted according to weight >Thought to be more accurate
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What do you think?
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Patient is on Heparin Drip Lab results return: PTT patient time 41 u/sec control time 12 sec INR 3.5 Space bar for answer: PTT too high and INR too high – decrease dose and recheck
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What do you think?
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Patient is on Heparin Drip Lab results return: PTT patient time 26 u/sec control time 12 sec INR 2.0 Space bar for Answer: All ok – leave dose same
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What do you think?
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Patient is on Heparin Drip Lab results return: PTT patient time 13 u/sec control time 12 sec INR 1.5 Space bar for answer: PTT and INR too low, need to raise dose
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Drugs Used to Treat Thromboembolic Therapy
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>Drugs fall into three categories: 1) Antiplatelet drugs and Aspirin 2) Anticoagulants —Heparin —LMWH —Coumadin 3) Thrombolytic drugs
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Bleeding
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>The risk for bleeding is present in all 3 categories >If the drug works high in the clotting cascade, the side effect of bleeding is less >*The chance of bleeding increases when the action of the drug occurs lower in the clotting cascade*
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Antiplatelets
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>Increase platelet cyclic AMP levels >Decreases platelet aggregation >Alters platelet surface membrane —>WORK HIGH IN THE CLOTTING CASCADE —>Bleeding will be in the form of excess bruising, may have to hold pressure longer, or light pink urine
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Anticoagulants
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Low Molecular Weight Heparin (LMWH) Prevents conversion of factor X to thrombin WORK LOWER IN CLOTTING CASCADE Bleeding will be in the same form as Antiplatelets
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Anticoagulants
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Heparin and Coumadin work by inactivating thrombin and other clotting factors by helping antithrombin III inactivate thrombin WORK LOWER IN THE CLOTTING CASCADE Bleeding will be more frank, oozing sites when injections of any kind have occurred, blood in bowel (dark and tarry) and urine, as well as a nose or gum bleeding
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Thrombolytics
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>drugs bind to plasminogen (a proenzyme in the blood) to form a complex (I.e. t-PA: tissue plasminogen activator) >This complex then acts on other molecules of plasminogen to cause their conversion into plasmin, an enzyme that digests the fibrin meshwork of clots. >WORK THE LOWEST IN THE CLOTTING CASCADE
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Thrombolytics
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Bleeding can be excessive, squirting out of an artery in cath lab, oozing everywhere, may have to hold for 15 minutes or more to stop bleeding
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Anticoagulant Precautions for all 3 classes
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>Avoid ASA, NSAIDs and all drugs that decrease platelet function >Avoid sharp objects >Wear shoes >Avoid injections or notify healthcare personnel that they are on the drug >Medic Alert bracelet >let dentist and MD know are on anticoagulant therapy
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Anticoagulant Precautions for all 3 classes
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>Warning: extreme caution in pts with bleeding disorders >Hold pressure longer if cut themselves >Shave with electric razor >Avoid bruising, handle cautiously >Good Oral hygiene – soft toothbrush >Good Hydration to prevent thrombus formation
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Assessment for Anticoagulant Meds
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>Assess Bleeding: petechiae, hematuria, hemoptysis melena, abd pain, frank bleeding, altered LOC, decreased b/p, increased HR, bruises, pelvic pain >Routinely assess skin, mucous membranes, and gums for bruising, bleeding, or petechiae. >Frequently check I.V. sites for bleeding >Assess for changes is menstrual flow >If suspect intra-abdominal bleeding, measure abdominal girth once a day >Monitor neurologic functioning, including LOC to detect early signs of intracranial bleeding >Stay alert for signs of hemorrhage, such as increased heart and respiratory rates, hypotension >Obtain stools for OCB if suspect GI bleed