A COMPARISON OF 4 BEDSIDE METHODS OF HEMOGLOBIN ASSESSMENT DURING CARDIAC-SURGERY

The purpose of this study was to compare the accuracy of conductivity, adjusted conductivity, photometric, and centrifugation methods of mea suring or estimating hemoglobin (Hb) with Coulter measured HE as the r eference. These bedside methods were studied in 25 cardiac surgery pat ients during euvolemia and hemodilution and after salvaged autologous red blood cell transfusion. In vivo patient blood samples were obtaine d before induction, at the start of cardiopulmonary bypass (CPB), afte r CPB, and after blood transfusion. In 10 patients, blood was sampled in vitro from units of processed blood. Hb values were determined usin g conductivity by Stat-Crit(R), adjusted conductivity by Nova Stat Pro file 9, bedside photometry by HemoCue(R), and centrifugation methods. The calculated bias values of Coulter test method Hb (mean +/- so) for in vivo patient blood samples (n = 90) were: Stat-Crit(R) = 0.6 +/- 0 .8 g/dL; Nova Stat Profile 9 = -0.7 +/- 0.4 g/dL; HemoCue(R) = -0.1 +/ - 0.2 g/dL; and centrifuge = 0.1 +/- 0.5 g/dL (P < 0.0001). Hb bias va lues (g/dL) for in vitro samples (n = 10) obtained from processed bloo d were Stat-Crit(R) = 5.1 +/- 0.6; Nova Stat Profile 9 = 3.0 +/- 0.6; HemoCue(R) = 0.4 +/- 0.4; and centrifuge = 0.6 +/- 0.3 (P < 0.0001). H b assessment by different test methods may be significantly affected d uring hemodilution and after blood transfusion. In vitro conditions ex aggerated the inaccuracy of conductivity and adjusted conductivity Hb estimates. The rank order of closest approximation to the Coulter meas urement for all in vivo blood samples was provided by bedside photomet ry, followed by centrifugation, adjusted conductivity, and uncorrected conductivity methods.