Intravenously administered indocyanine green may cause falsely high near-infrared cerebral oximetry readings.

BACKGROUND

Near-infrared spectroscopy assesses cerebral tissue oxygen saturation (Scto2) based on the absorption spectra of oxygenated and deoxygenated hemoglobin. It has been reported that IV-administered dyes including methylene blue, indigo carmine, and indocyanine green (ICG) may cause falsely low-pulse oximetry readings (Spo2). Although methylene blue and indigo carmine may also decrease Scto2, the effect of ICG has not been documented.

METHODS

Simultaneous changes in the heart rate, arterial blood pressure, Scto2, and Spo2 were measured after IV administration of ICG (12.5 mg diluted in 5.0 mL 0.9% NaCl) in 15 patients undergoing carotid endarterectomy under sevoflurane-remifentanil anesthesia.

RESULTS

After the dye administration, no change in heart rate or arterial blood pressure was observed in any patient. Scto2 increased by 13.3±4.0 percentage points, reaching the peak at 42.0±28.4 seconds after the administration, whereas Spo2 decreased by 1.9±1.2 percentage points, reaching the peak at 64.0±42.5 seconds (P<0.0001 both).

CONCLUSIONS

ICG falsely increases the spectroscopy-determined cerebral oxygen saturation for up to 12 minutes but dampens pulse oximetry readings.