EVALUATION OF QUANTITATIVE ACID-BASE-BALANCE AND DETERMINATION OF UNIDENTIFIED ANIONS IN SWINE

Arterial blood samples were collected from 19 anesthetized pigs before and after hemorrhage was induced. Blood gas tensions and concentratio ns of sodium, potassium, chloride, lactate, and total protein were mea sured. Results indicated that hydrogen ion (H+) concentration calculat ed from a specific formula was a biased and imprecise estimate of meas ured H+ concentration. The bias was 5.45 nEq/L, with limits of agreeme nt from -7.92 to 18.83 nEq/L. Because albumin is the fraction of plasm a protein most important in acid-base balance, the agreement between p redicted and measured He concentration was reevaluated, using an album in charge estimate and a reference swine albumin-to-globulin ratio. Th is improved the ability of the formula to predict H+ concentration; th e bias decreased to 1.33 nEq/L with limits of agreement from -12.16 to 9.49 nEq/L. The formula and a simplified approach for clinical applic ation were biased and unacceptably imprecise esti mators of lactate (L (-)) concentration. The formula approach underestimated L(-) concentra tion by 2.8 (-12.4, 6.7) mEq/L, whereas the simplified method overesti mated L(-) concentration by 5.0 (-3.8, 13.9) mEq/L.