Prolonged interference of patent blue on pulse oximetry readings.

Background: We evaluated the effect of intra-arterial injection of Patent Blue (PB) on pulse oximetry. Methods: Ten consecutive female patients who underwent intra-arterial insertion of catheter for chemotherapy were enrolled in this study. All patients received general anesthesia and ECG, pulse oximetry, and direct arterial blood pressure were monitored throughout the perioperative period. Baseline arterial blood saturation (SpO2), haemoglobin concentration (Hgb), estimated arterial saturation (SaO2), arterial oxygen partial pressure (PaO2) were obtained through arterial blood gas analysis, and true arterial saturation (ScoO2) through CO-Oximetry analysis. The subsequent values obtained at various points of time following the intra-arterial administration of PB were compared with the baseline data. Results: The 5pia2 readings taken after intra-arterial injection of PB were significantly lower than the baseline reading. The extent of the reduction of SpO2 readings two hours after the administration of PB was relevant to the total accumulative dosage of PB (r(subscript s)=-0.846, P ＜0.05). Howevet; the reduction of SpO2 bore no significant relation with Hgb concentration or with the ratio of PB dosage to Hgb concentration. Conclusions: Intra-arterial administration of PB interferes with pulse oximetry readings and the effect lasts for a variable duration. The extent of desaturation may be related to the total accumulative dosage ofintra-arterial PB injected.