What are the hazards associated with hemoglobin‑based oxygen carriers (HBOCs) when they are resuspended in excipients containing Ringer's D,L‑lactate and antioxidants to prevent methemoglobin formation during storage?

Hazards of HBOCs resuspended in Ringer’s D,L‑lactate with antioxidants

Bold recommendation: Avoid HBOCs formulated or co-infused with Ringer’s D,L‑lactate; prefer L‑lactate or saline excipients and minimize pro-oxidant exposures to reduce vasoconstriction, arrhythmias, organ injury, and mortality risk 1.

• Primary patient-centered risks (morbidity, mortality, quality of life):
  • Vasoconstriction with hypertension → reduced organ perfusion, ischemia, myocardial strain 2, 3.
  • Cardiac arrhythmias and hemodynamic instability reported with D,L‑lactate solutions 4.
  • Oxidative injury (ROS burst) and endothelial dysfunction → multiorgan toxicity, sterile inflammation 4, 5, 3.
  • Methemoglobinemia (functional anemia, tissue hypoxia) if oxidative balance is exceeded despite antioxidants 6, 2.
  • Increased adverse events (including severe events and deaths) when HBOCs in D,L‑lactate excipients are combined with Ringer’s D,L‑lactate resuscitation and older stored RBCs 1, 7.

Mechanisms linking excipient choice to harm

• D‑lactate component hazards:
  • Stimulates granulocyte ROS generation; L‑lactate inhibits glycolysis—together can amplify oxidative stress around cell‑free Hb 4.
  • Reported association with cardiac arrhythmias after infusion of Ringer’s D,L‑lactate 4.
• Synergy with HBOC:
  • Cell‑free Hb scavenges NO and generates ROS; D,L‑lactate–driven ROS further oxidizes NO, intensifying vasoconstriction and hypertension 4, 5, 3.
  • ROS/NF‑κB activation and apoptosis pathways → endothelial injury and organ dysfunction 4.
  • Oxidation to methemoglobin (Fe3+) reduces oxygen delivery; antioxidants in excipient may be insufficient under high ROS load 6, 2.
• Clinical signal:
  • Clusters of severe adverse events when D,L‑lactate used both as excipient and resuscitative fluid, especially alongside liquid‑preserved RBCs stored >2 weeks 1, 7.

Practical algorithm to minimize harm

1. Excipients/resuscitation fluid
   • Do NOT use Ringer’s D,L‑lactate in HBOC excipient or as concomitant resuscitation fluid 1.
   • If HBOC must be used, select:
     • Ringer’s L‑lactate or 0.9% NaCl as excipient/resuscitative fluid; avoid D‑lactate isomer exposure 1.
     • Consider alternative buffers under study (e.g., beta‑hydroxybutyrate) only within trials; not recommended for routine care 4.
2. Oxidative/NO balance
   • Limit concurrent pro‑oxidants (e.g., older stored RBCs); if RBCs are required, use freshest available or frozen–deglycerolized RBCs to reduce adverse events 7.
   • Monitor for methemoglobinemia and treat promptly per guideline to prevent functional hypoxia and organ injury 6.
3. Monitoring and mitigation
   • Continuous BP and rhythm surveillance for vasoconstriction/arrhythmias; be prepared to manage hypertensive crises and ischemia 2, 3.
   • Watch for signs of tissue hypoxia (cyanosis, low pulse ox gap, lactic acidosis) indicating MetHb rise; confirm with co-oximetry and intervene per guideline 6.

Key pitfalls to avoid

• Assuming antioxidants in the excipient neutralize risk: they do not reliably prevent ROS‑mediated NO depletion or methemoglobin formation under D,L‑lactate–augmented stress 4, 2.
• Co-infusing Ringer’s D,L‑lactate during HBOC therapy: amplifies toxicity and adverse outcomes 1.
• Transfusing older liquid‑stored RBCs with HBOCs: associated with higher morbidity/mortality; prefer fresher or frozen–deglycerolized units when needed 7.

Notes on evidence:

• Highest‑quality directive for methemoglobinemia pathophysiology and clinical harm is the 2021 hematology guideline, underscoring the morbidity/mortality impact of MetHb‑mediated tissue hypoxia 6.
• Human clinical safety signals linking D,L‑lactate excipients/resuscitation with severe adverse events come from peer‑reviewed analyses (Transfusion and Apheresis Science, 2008) and mechanistic studies detailing ROS/NO pathways 1, 4. These align with broader HBOC reviews on vasoconstriction and organ toxicity affecting outcomes 2, 3.