(P-BT-14) Hemopure and Blood Gas Results: A Question of Bias

Background/Case Studies: Hemopure, or Hemoglobin glutamer-250 (HBOC-201), is a hemoglobin-based oxygen carrying solution. HBOC-201 is a delipidated and glutaraldehyde-crosslinked bovine hemoglobin tetramer with a 19-hour circulatory half-life. HBOC-201 is used in critically ill patients with anemia to improve oxygen carrying capacity when matched donor red blood cells are unavailable or declined. These patients are frequently monitored with blood gas analysis to assess acid-base, ventilation, and oxygenation status. Given the importance of these measurements for clinical decision making, it is critical to understand what blood gas analytes may be affected by HBOC-201 administration.

Study

Design/Methods: A retrospective chart review from 2014 to 2022 was completed for patients treated with Hemopure. A total of 47 patients were identified and split into two cohorts based on type of blood gas: arterial (ABG) or venous (VBG). If either pre- or post-infusion results were missing, patients were excluded from this study. Additionally, if the last dose of hemopure and the post-infusion testing occurred greater than 24 hours later, that event was excluded.

Results/Findings: Methemoglobin (MetHb) values increased from pre- to post- HBOC-201 administration with ABG measurements increasing +2.93% and VBG measurements increasing +2.02% (Figure 1). Total hemoglobin (tHb) on ABG measurements increased on average by +0.23 g/dL and on VBG measurements by +0.32 g/dL. Electrolytes, including, sodium, potassium, ionized calcium, and chloride showed bias between pre- and post- blood gas results following the administration of HBOC-201. Additionally, other analytes including, pH, pCO2, pO2, HCO3, lactate, base excess, COHb, FiO2, and glucose did not show biases between pre- and post-infusion blood gas results following the administration of HBOC-201.

Conclusions: As predicted, MetHb showed an overall increase from pre- and post-HBOC-201 based on laboratory data. According to the investigator brochure for HBOC-201, each unit of hemopure contains approximately < 5% of MetHb per unit. Given the 19 hours circulatory half-life of HBOC-201 and the study’s exclusion criteria of patients with post labs after 24 hours from HBOC-201 administration, an MetHb increase was expected. Both ABG and VBG measurements showed a mean increase of tHb less than 0.5 g/dL, less than what other studies have shown. The remaining analytes measured in the ABG and VBG showed no consistent trend, leading to the conclusion that no analytical interference from Hemopure is affecting blood gas analysis.

Importance of research: Blood gas measurements are routinely performed on critically ill patients and their results guide further medical management. Clinicians should be aware of any potential biases, including HBOC-201, that could affect patient results. In this retrospective chart review, HBOC-201 showed no consistent bias in blood gas results. The only change observed was in MetHb, which is expected after HBOC-201. This demonstrates that the resulting analyte values can be reliably used for patient management.