A Comparison of Four Bedside Methods of Hemoglobin Assessment During Cardiac Surgery

Abstract

The purpose of this study was to compare the accuracy of conductivity, adjusted conductivity, photometric, and centrifugation methods of measuring or estimating hemoglobin (Hb) with Coulter measured HB as the reference. These bedside methods were studied in 25 cardiac surgery patients during euvolemia and hemodilution and after salvaged autologous red blood cell transfusion. In vivo patient blood samples were obtained before induction, at the start of cardiopulmonary bypass (CPB), after CPB, and after blood transfusion. In 10 patients, blood was sampled in vitro from units of processed blood. Hb values were determined using conductivity by Stat-Crit, adjusted conductivity by Nova Stat Profile 9, bedside photometry by HemoCue, and centrifugation methods. The calculated bias values of Coulter test method Hb (mean +/- SD) for in vivo patient blood samples (n = 90) were: Stat-Crit = 0.6 +/- 0.8 g/dL; Nova Stat Profile 9 = -0.7 +/- 0.4 g/dL; HemoCue = -0.1 +/- 0.2 g/dL; and centrifuge = 0.1 +/- 0.5 g/dL (P < 0.0001). Hb bias values (g/dL) for in vitro samples (n = 10) obtained from processed blood were Stat-Crit = 5.1 +/- 0.6; Nova Stat Profile 9 = 3.0 +2- 0.6; HemoCue = 0.4 +/- 0.4; and centrifuge = 0.6 +/- 0.3 (P < 0.0001). Hb assessment by different test methods may be significantly affected during hemodilution and after blood transfusion. In vitro conditions exaggerated the inaccuracy of conductivity and adjusted conductivity Hb estimates. The rank order of closest approximation to the Coulter measurement for all in vivo blood samples was provided by bedside photometry, followed by centrifugation, adjusted conductivity, and uncorrected conductivity methods.

Methods and analyzers for hemoglobin measurement in clinical laboratories and field settings

“…Spielmann et al found two different clinical blood gas analyzers (CBGA-1 and CBGA-2) to have a higher mean Hb concentration (5.8–8.0 g/L) and one analyzer (CBGA-3) to have a lower mean Hb concentration (0.5 g/L) compared with the reference. 138 When applying the mean concentration difference threshold of ±7% for the studies comparing the other portable photometric invasive POC analyzers or clinical laboratory blood gas analyzers with the reference, 11 studies including 17 comparisons 18,31,43,102,106,110,113,120,121,138 met the allowable degree of variation with one study exceeding the ±7% bias 42 (Fig. 4).…”

Accuracy of Estimated Blood Loss in Predicting Need for Transfusion after Delivery

“…After a vaginal delivery, a spun Hct value was determined for each patient using the average of three spun samples from a finger prick at 12 hours postpartum, a method shown to correlate well with laboratory Hct values. 14 For patients who underwent cesarean delivery, a complete blood count was performed at 12 hours postoperative. Calculated EBL (cEBL) was determined using a validated method in which maternal blood volume {0.75 × [(maternal height in inches × 50) + (maternal weight in pounds × 25)]} is multiplied by percent of blood volume lost [(predelivery Hct − postdelivery Hct)/predelivery Hct].…”

Utilization management in the blood transfusion service

“…The choice of methods has implications for the end-user, who must understand the limitations of each device. For instance, the use of different point-of-care devices for measuring hemoglobin was shown to have varying results [33]. Apart from the specific platform (i.e.…”