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BLOOD COAGULATION STUDIESPT—Prothrombin Time; Pro Time; Protime
aPTT/PTT—Activated Partial Thromboplastin Time
INR—International Normalized Ratio
WHAT DO THESE LAB TESTS MEASURE?
PT and INRProthrombin Time and
International Normalized
Ratio
The PT test measures how long it takes for a clot to form in the sample of blood
The reagents that are used to perform these tests vary from lab to lab. This causes normal values to fluctuate
INR with PT tests was set by the World Health Organization (WHO) to standardize the results across the world.
WHAT DO THESE LAB TESTS MEASURE?
aPTT or PTTActivated Partial
Thromboplastin Time
The PTT test measures the functionality of the intrinsic and common pathways of the coagulation cascade.
WHY ARE THESE LABS ORDERED?
PT and INRProthrombin Time and
International Normalized
Ratio
Detect how well the
patient’s blood thinning
medication is working to
prevent blood clots
To confirm a patient’s blood clotting status prior to surgery
aPTT or PTTActivated Partial Thromboplastin
Time
To monitor standard heparin anticoagulant therapy
To investigate an episode of unexplained bleeding or thrombotic episode.
WHAT IS THE NURSING RESPONSIBILITY?
PRETEST PREPARATION OVERVIEW
Perform hand hygiene Identify patient Assemble all equipment and supplies Put on clean gloves Explain procedure to patient
Explain that mild and brief discomfort may be felt
o Verify (if required) that fasting has taken place
WHAT IS THE NURSING RESPONSIBILITY?
PRETEST PREPARATION (SPECIFIC)
aPTT/PTT * If the patient is
receiving heparin by intermittent injection plan to draw the specimen 30-60 minutes before the next dose.
* With a continuous heparin infusion, specimen can be drawn at anytime
PT and INR Explain to patient
there is no need to fast before the procedure.
*If the patient receiving warfarin, the specimen must be taken before given the daily dose.
WHAT IS THE NURSING RESPONSIBILITY?
SUPPLIES NEEDED
Gloves Alcohol Blue-Top (Sodium Citrate) Tubes Tourniquet Needle Gauze Bandage/Tape Labels for Tube
WHAT HAPPENS INTRATEST?GENERAL OVERVIEW
Position patient to access the anticubital fossa Ask patient to make a fist to distend veins Select vein for venipuncture Apply a tourniquet above the puncture site Cleanse site with alcohol, and allow to dry Perform venipuncture at a 15-degree angle to the skin Ease the Vacutainer tube forward in the holder as soon
as the needle is in the holder When tube is filled, remove. Another tube may be
inserted into holder Release the tourniquet when the blood flow begins Properly dispose of contaminated materials List on lab slip any drug that the patient is taking that
may affect the test results.
WHAT HAPPENS INTRATEST?HTTP://WWW.YOUTUBE.COM/WATCH?V=_8ZSQXFQVQM
The nurse collects a venous blood specimen from the patient’s arm, filling the vacuum tube. The Blue-Top vacuum tube must be filled
completely to ensure a proper blood-to-anticoagulant (sodium citrate) ratio.
The sample should be immediately mixed by gently inverting the tube back and forth to ensure adequate mixing of the anticoagulant
with the blood. Properly dispose of contaminated
materials List on lab slip any drug
the patient is taking that mayaffect test results
WHAT HAPPENS POSTTEST?
Pressure or a pressure dressing is applied to venipuncture site.
The site must be monitored for bleeding. *Bleeding time will be
increased if patient is receiving anticoagulants or has coagulopathies
The nurse must also check for blood in the urine and all other excretions and assess the patient for bruises, petechiae, and bleeding gums.
Apply pressure to the venipuncture site and assess site for bleeding.
If severe bleeding occurs, the anticoagulant effect of warfarin can be reversed by the slow parenteral administration of Vitamin K.
If coagulation must be returned to normal more quickly, plasma can be given.
aPTT/PTT PT and INR
WHAT ARE THE EXPECTED VALUES? MANY HOSPITALS ARE NOW REPORTING PT TIMES IN BOTH ABSOLUTE AND
*INR NUMBERS
Normal Values aPTT: 30-40 seconds PTT: 60-70 seconds
Patients receiving Heparin, expect results 1.5-2.5 seconds greater than normal
Critical Values aPTT: < 50 seconds,
therapeutic anticoagulation may not have been met and more heparin is needed
aPTT: > 100 seconds, shows too much heparin has been given; risk for serious spontaneous bleeding exists.
Normal Values PT: 11.0-12.5 seconds *INR: 0.8-1.1
Patients receiving Coumadin, expect results 1.5-2.5 greater than normal
Critical Values: PT: > 20 seconds INR: > 5.5 * report for
patients on anti-coagulant drugs
aPTT/PTT PT and INR
INTERFERING FACTORS
Prolonging Factors Antihistamines Ascorbic acid Chlorpromazine Heparin Salicylates
Prolonging Factors Alcohol intake Diarrhea
Shortening Factors A diet high in leafy
green vegetables
aPTT/PTT PT and INR
WHAT MAY CAUSE AN INCREASE OR DECREASE IN RESULTS?
Increase Congenital clotting factor
deficiencies, cirrhosis of liver, vitamin K deficiency Disseminated intravascular
coagulation (DIC Heparin administration Coumarin administration
Decrease Early stages of DIC,
Extensive cancer.
Increase Liver disease Hereditary factor deficiency Vitamin K deficiency Bile duct obstruction Coumarin ingestion, Disseminated intravascular
coagulation (DIC) Massive blood transfusion Salicylate intoxication.
DecreaseN/A
aPTT/PTT PT and INR
REFERENCES
AASN. (18 June 2010). PT and INR. Lab tests online. Retrieved September 29, 2010, from http://www.labtestsonline.org/understandin
g/analytes/pt/test.html AASN. (18 June 2010). PTT. Lab tests online.
Retrieved September 29, 2010, from
http://www.labtestsonline.org/understanding/analytes/appt/test.html
Pagana, K. D., & Pagana, T. J. (2010). Mosby’s manual of diagnostic and laboratory
testing. St. Louis, Missouri: Elsevier Inc.