Does methemoglobin from oxidized hemoglobin-based oxygen carrier (hemoglobin Glutamer-200) interfere with lactate measurement (YSI 2700 SELECT Biochemistry Analyzer)?

In this study, we validated the accuracy of lactate measurements (YSI 2700 SELECT glucose/lactate analyzer) in the presence of methemoglobin from an oxidized bag of hemoglobin-based oxygen carrier (Met-HBOC), hemoglobin glutamer-200 (Oxyglobin; Biopure Corp). Different combinations of concentrated L-lactate solution, pooled canine plasma, and Plasmalyte A were added to 4 sample groups (1%, 10%, 20%, and 40% Met-HBOC [1.3 g/dL]) to yield linear increases in lactate concentration in consecutive samples. The mean difference between measured and calculated lactate was -5.1 mg/dL (1% Met-HBOC), -5.8 mg/dL (10% Met-HBOC), -4.6 mg (20% Met-HBOC), and -8.5 mg/dL (40% Met-HBOC). The root mean square error was 6.5 mg/dL, 7.4 mg/dL, 6.8 mg/dL, and 10.3 mg/dL, respectively. The Bland-Altman correlation (r) was r = -0.94 (P = 0.01), r = -0.91 (P < 0.001), r = -0.90 (P < 0.001), and r = -0.94 (P < 0.001), respectively, where r = 0 for perfect agreement between measured and calculated values. Results indicate that true lactate levels in the presence of Met-HBOC are underestimated when measured by an YSI 2700 analyzer independent of the amount of Met-HBOC present. When interpreting lactate concentrations from a patient with a HBOC present in plasma, underestimation of true lactate levels may occur unrelated to methemoglobin concentrations.