Artifactual reduction in oxygen saturation readings affected by indocyanine green in ophthalmic angiography

To investigate time-dependent changes in oxygen saturation (SpO₂) readings during fluorescein angiography (FA) or simultaneous fluorescein and indocyanine green angiography (F/I).

A prospective observational study.

One hundred twenty-five consecutive patients underwent FA or F/I. After application of the exclusion criteria, 67 patients (28 underwent FA, 39 underwent F/I) were included in the study. During angiography, SpO₂ was measured by using a pulse oximeter and recording each second. The arm-to-retina circulation time (ARCT) was measured on the angiography video images. Latency time was defined as the time from intravenous injection of the dye to observation of a 3% decrease in the SpO₂ reading, and variation SpO₂, as the difference between baseline SpO₂ and the lowest SpO₂ value.

The mean variation SpO₂ was - 1.0 ± 0.6 during FA, and - 6.1 ± 1.5 during F/I. Variation SpO₂ was within 2% during FA and > 3% during F/I. No corresponding changes were observed in the other vital signs or subjective symptoms. The mean latency time was 33.3 ± 6.4 s. Latency time was positively correlated with the ARCT in the F/I group (r_s = 0.766, P < .001).

Reductions in SpO₂ readings were identified during F/I, but not during FA. Our results suggest that clinicians should be mindful that reductions in SpO₂ readings during F/I may be artifactually caused by indocyanine green.