[Pulse oximetry and methemoglobinemia].

BACKGROUND

Cyanosis associated to low oxygen saturation may reveal hemoglobin pathology.

CASE REPORT: A 3 year-old child had a nephroblastoma with pleural effusion. He suddenly developed persistent cyanosis despite pleural effusion drainage; transcutaneous and measured oxygen saturations were low and PaO2 on arterial blood gases was high. Methemoglobinemia was diagnosed, due to prilocaine-lignocaine cream used for local anesthesia, associated to partial G6PD deficiency. The methemoglobinemia disappeared after methylene blue treatment.

CONCLUSION

Cyanosis with low oxygen saturation and high or normal PaO2 should lead to the search of a hemoglobin pathology, especially methemoglobinemia, by appropriate methods.