Sources of error ina- aD O 2 calculated from blood stored in plastic and glass syringes

Abstract

Wu, Eugene Y., Khalid W. Barazanji, and Robert L. Johnson, Jr. Sources of error in a-aDO2 calculated from blood stored in plastic and glass syringes. J. Appl. Physiol. 82(1): 196–202, 1997.—We studied the effects of time delay on blood gases, pH, and base excess in blood stored in glass and plastic syringes on ice and the effects of resulting errors on calculated alveolar-to-arterial [Formula: see text] difference (a-[Formula: see text]). Matched samples of dog whole blood were tonometered with gas mixtures of 5% CO2-12% O2-83% N2 ( mixture A), 10% CO2-5% O2-85% N2 ( mixture B), and 2.88% CO2-4% O2-93.12% N2 ( mixture C). Tonometered blood samples were transferred to 5-ml glass (5G), 5-ml plastic (5P), and 3-ml plastic (3P) syringes and stored on ice. Blood gases were measured every 1 h up to 6 h. In 5G,[Formula: see text] progressively decreased in blood tonometered with mixture A but rose in blood tonometered with mixtures B and C. O2 saturation progressively fell in all cases. In 5G, blood [Formula: see text]progressively rose regardless of which gas mixture was used, and pH as well as base excess progressively fell. The rise in[Formula: see text] was faster in plastic than in glass syringes, and O2 saturation always rose in plastic syringes. Differences between storage in plastic and glass syringes on [Formula: see text] change were greatest when initial blood [Formula: see text] was highest ( mixture A). At the highest[Formula: see text], O2 exchange was faster in 3P than in 5P. The rise of [Formula: see text] was just as fast in plastic as in glass syringes, but in both the rise in[Formula: see text] was faster at a higher initial[Formula: see text] ( mixture B) than at lower initial[Formula: see text] ( mixtures B and C). Rates of[Formula: see text] and[Formula: see text] change in matched samples were significantly faster in 3P than in 5P. Errors due to rises in[Formula: see text] and[Formula: see text] cause additive errors in calculateda-[Formula: see text], and when blood is stored in plastic syringes for >1 h significant errors result. Errors are greater in normoxic blood, in which estimateda-[Formula: see text]decreased by >10 Torr after 6 h on ice in plastic syringes, than in hypoxic blood.