Elevated methemoglobin levels in patients treated with high-dose hydroxocobalamin

Area of Science:

• Clinical Chemistry
• Critical Care Medicine
• Pharmacology

Background:

• Vasoplegic syndrome, often treated with hydroxocobalamin (OHCbl), presents challenges in monitoring.
• Accurate assessment of arterial blood gases and oximetry is crucial for managing these patients.

Purpose of the Study:

• To evaluate the impact of OHCbl infusion on arterial blood gas and oximetry parameters.
• To determine if OHCbl interferes with specific blood gas analyzer measurements.

Main Methods:

• Blood samples from 95 patients receiving OHCbl were analyzed pre- and post-infusion.
• Measurements included methemoglobin (MetHb), total hemoglobin (tHb), carboxyhemoglobin (COHb), SaO2, PaO2, and PaCO2.
• Interference was assessed by comparing pre- and post-infusion values.

Main Results:

• OHCbl infusion significantly increased blood MetHb and COHb levels.
• Median MetHb increased from 1.0 to 4.8 (P < .001); COHb increased from 1.3 to 1.7 (P < .001).
• No significant changes were observed in tHb, PaO2, PaCO2, or SaO2.

Conclusions:

• Hydroxocobalamin interferes with co-oximetry, leading to falsely elevated MetHb and COHb.
• Reliable measurement of MetHb and COHb using co-oximetry is compromised in the presence of OHCbl.
• Clinical decisions based on these specific measurements should consider potential OHCbl interference.