CHAPTER 1 Cardiovascular System^79
- Coagulation studies [prothrombin time (PT), INR (Internationalized Nor-
malized Ratio),partial thromboplastin time (PTT), platelet count]. These are
bleeding time tests to indicate the patient’s clotting ability. Most interfere at
some point in the clotting cascade. INR is used to monitor stable patients
taking warfarin. PT is used to help screen patients taking warfarin. Since PT
is made in the liver, this test is also useful to monitor liver functions.
Abnormalities in the PTT indicate defects in the patient’s coagulation status
and with blood factors. Used to monitor heparin therapy.
HOW DOES THE TEST WORK?
Three to five milliliters is sampled. The abnormal results are:
- RBC count—usual indication is to look for anemia.
- WBC count—when elevated, it shows infection.
- Erythrocyte sedimentation rate (ESR)—shows inflammation when elevated.
- Bleeding (prothrombin time, INR, partial thromboplastin time, platelet count)
—measure clotting of blood. - Hemoblogin (Hgb) and hematocrit (Hct) show the level of iron- and oxygen-
carrying capability of the blood.
WHAT TO DO?
- Check for bleeding at venipuncture site.
Arterial Blood Gas (ABG)
WHY IS IT BEING TESTED?
This determines the patient’s ventilation, tissue oxygenation and acid-base status.
HOW DOES THE TEST WORK?
Three to five milliliters of blood is obtained from an artery. Usually the radial,
brachial or femoral arteries are used. The abnormal results are:
- Increased pH shows metabolic alkalosis or respiratory alkalosis.
- Decreased pH shows metabolic acidosis or respiratory acidosis.