Evaluation of Preanalytical Error Sources in Arterial Blood Gas Analysis

Cho, Hee Soon; Kim, Kyung Dong

Abstract

BACKGROUND: Although arterial blood gas analysis is very important for the critically ill patients, it can be easily influenced by many errors. With good control of analytical errors, preanlytical sources of error can be eliminated or minimized. So laboratory standardization for the test is necessary.
METHODS
The samples from 33 patients in the plastic syringes were stored at room temperature and in ice box up to 120 minutes and analyzed for pH, PaCO2 and PaO2. The effects of air bubbles in the samples were studied by adding 10%, 20% and 40% of air of total sample volume. To evaluate the dilutional effect of heparin solution as an anticoagulant, each sample was diluted as 6, 10, 20 and 40 volume percentage of sodium heparin solution.
RESULTS
Delayed measurement resulted in progressive increase in PaCO2 and decrease in pH. This changes were amplified with the incease of temperature. PaO2 was decreased at room temperature but increased on ice box. The major effect of air bubbles in blood sample was significantly increased in PaO2. Excess sodium heparin solution led to significant decrease in PaCO2 and HCO3.
CONCLUSIONS
The ideal condition for blood gas analysis was within 15 minutes in ice box. However, with plastic syringe in room temperature clinically allowable result can be obtained within 30 minutes. For accurate measurement of blood gas, it is neceaasary to expel all air bubbles immediately and to mix the heparin less than 10% of total blood volume.