[Brutal decrease in pulse oxymetry in paediatric anaesthesia: a story of artefact]

Pulse oxymetry is frequently used in anaesthesia, notably in paediatric anaesthesia. This device can however present artefacts. We report the case of a sudden decrease in pulse oxymetry during surgical exploration of wound of the face in a child. This was preceded by the injection of patent blue, used for vascular cartography, and interfering with pulse oxymetry. After excluding real oxygen desaturation, this error of measurement has to be confirmed by arterial gazometry. In our case, pulse oxymetry normalized few hours later, without complication.