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TECHNOLOGY, COMPUTING, AND SIMULATION

Does Methemoglobin from Oxidized Hemoglobin-Based Oxygen Carrier (Hemoglobin Glutamer-200) Interfere with Lactate Measurement (YSI 2700 SELECT^TM Biochemistry Analyzer)?

Stephen L. Osgood, MD^*, Jonathan S. Jahr, MD^*, Poonam Desai^*, Jessica Tsukamoto^*, and Bernd Driessen, DVM, PhD^*

*Department of Anesthesiology, David Geffen School of Medicine at University of California Los Angeles; Charles R. Drew University of Medicine and Science, Martin Luther King Jr./Drew Medical Center, Los Angeles, California; and Department of Clinical Studies, University of Pennsylvania School of Veterinary Medicine, Philadelphia

Address correspondence and reprint requests to Jonathan S. Jahr, MD, Department of Anesthesiology, David Geffen School of Medicine at UCLA, PO Box 951778, Los Angeles, CA 90095-1778. Address e-mail to jsjahr{at}mednet.ucla.edu.

In this study, we validated the accuracy of lactate measurements (YSI 2700 SELECT^TM 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^TM 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.