A second-year PG resident tells you to perform an ABG of a patient. All of the following are true about performing an ABG except:
(A) Before performing the ABG, syringe should be loaded with 0.3 cc of heparin (B) Normal pH, HCO. and PCO, levels may not indicate absence of an acid-base imbalance (C) A different site should be tried i f modified Allen's test is negative (D) Radial aery is the preferred site
(A) Ans: A. Before performing the ABG, syringe should be loaded with 0.3 cc of heparin(Ref: Harrison 18/e p364; http:// emedicine.medscape.comlaiclell 902703-overview).Care should be taken when measuring blood gases to obtain the aerial blood sample without using excessive heparin.Heparin should be expelled from the syringe after loading as it may lead to false pCO2 readings.Precautions:Most syringes come pre-packaged & contain a small amount of heparin, to prevent coagulation.Other syringes may need to be heparinized, by drawing up a small amount of liquid heparin & squiing it out again to remove air bubbles.Once the sample is obtained, care is taken to eliminate visible gas bubbles, as these bubbles can dissolve into the sample & cause inaccurate results.