Intravenously administered indocyanine green (ICG) may cause misreadings of cerebral oximetry and pulse oximetry in patients undergoing carotid endarterectomy under general anesthesia. The present study determined the effects of two different doses (12.5 mg vs. 25 mg) of ICG on regional cerebral tissue oxygen saturation (SctO₂) and percutaneous peripheral oxygen saturation (SpO₂).

Twenty-six patients receiving ICG for videoangiography were divided into two groups according to the dosage (12.5 mg and 25 mg, n = 13 in each group). Heart rate, arterial blood pressure, SctO₂, and SpO₂ were measured before and after an intravenous bolus administration of ICG.

Following the dye administration, no changes in heart rate or arterial blood pressure were noted in either group. SctO₂ was increased in both groups; however, the magnitude of the increase was greater (21.6 ± 5.8% vs. 12.6 ± 4.1%, P < 0.0001) and more prolonged (28.4 ± 9.6 min vs. 13.8 ± 5.2 min, P < 0.0001) in the 25 mg group than in the 12.5 mg group. In contrast, SpO₂ was decreased in both groups; the magnitude of the decrease was greater in the 25 mg group than in the 12.5 mg group (4.0 ± 0.8% vs. 1.6 ± 1.0%, P < 0.0001). There were no differences in the time to reach the peak SctO₂ or to reach the nadir SpO₂ between the two groups.

In patients given ICG for videoangiography, a 25 mg bolus results in a greater and more prolonged increase in SctO₂ and a greater reduction in SpO₂ than a 12.5 mg bolus, with no differences in the time to reach the peak SctO₂ or to reach the nadir SpO₂.