Symptoms depend on the concentration of methemoglobin. When methemoglobin comprises approximately 10 to 30 percent of the total hemoglobin, only cyanosis occurs. In cases where anemia is also present, oxygen delivery is further compromised and toxicity may be more severe at lower concentrations of methemoglobinemia. Accurate diagnosis and rapid therapy will prevent serious damage. Diagnosis of methemoglobinemia should be strongly suspected when oxygen administration fails to affect cyanosis.
Treatment depends on clinical severity.
Efforts should be made to identify an oxidant stress and, once exposed, remove the causative substance. Within several hours, red blood cells with normal metabolism will reduce the methemoglobin. If symptoms are present l hour later, a second dose can be administered. Failure of methylene blue to improve methemoglobinemia may be the result of a G6PD deficiency. Once these symptoms are recognized, the baby should be taken to the doctor immediately.