Fluorescein Interferes With Hemoglobin Measurement During Intra-operative Point-of-Care Blood Gas Analysis: A Clinical Observation.

We highlight a clinically important but under-recognized interference in hemoglobin measurement caused by intravenous fluorescein during neurosurgical procedures. A 70-year-old woman undergoing brain tumor resection showed normal initial blood gas results, but repeated point-of-care co-oximetry failed to measure hemoglobin after fluorescein administration. An alternative method enabled successful measurement of hemoglobin and transfusion guidance. Similar measurement failures were recorded previously, with failure in 7 of 12 cases. The fact that analyzers using different absorbance wavelengths were less affected suggests that spectral overlap between fluorescein and co-oximetry wavelengths may underlie the interference. A volunteer study further demonstrated that measurement failure occurred shortly after fluorescein administration but resolved within approximately 1 h. Clinicians should be aware of this limitation and consider alternative or confirmatory methods, such as central laboratory testing, when accurate hemoglobin assessment is critical.