Methemoglobinemia is currently an extremely rare complication in home hemodialysis patients. However, contamination of the water circuit with an oxidizing agent is still possible. The tolerance of methylene blue is limited in anuric patients as the drug is also not eliminated by hemodialysis. We present a recent case complicated by a significant hemolysis.

A 54-year-old anuric woman with end-stage renal disease treated by home hemodialysis was admitted to the ER for altered mental status, cyanosis, dyspnoea and nausea. Symptoms started a few hours before, at the end of a home hemodialysis session. There was no history of new drugs prescription. Vital signs were: BP 113/84mmHg, HR 120bpm, RR 40/min, SaO2 94%. The diagnosis of methemoglobinemia (MetHb) was rapidly obtained, with an initial value of 20.9%. Severe hemolysis was simultaneously present, with Hb 4,7g/dl. Methylene blue was administered at the dose of 1mg/kg, with a second dose of 1mg/kg after 1 hour. Intubation was required for progressive worsening of neurological and respiratory status. The patient became hypotensive and norepinephrine infusion was started. Hemodialysis was also initiated. Due to persisting signs of hemolysis, partial exchange transfusion was considered. Extreme cyanosis persisted for several days, even when MetHb had dropped below 10%. Neurological and cardiocirculatory condition gradually improved and extubation was possible after two days. Hemoglobin electrophoresis was normal, with also no deficit in pyruvate kinase or G6PD; sulfhemoglobin was not found. Despite extensive toxicological investigations in serum but also in the fluids collected from different parts of the dialysis circuit, the offending agent could not be determined.

Acquired methemoglobinemia is now a rare complication in hemodialysis patients. With home dialysis, the risk exists that the circuit filled with tap water could be contaminated by an oxidizing agent, likely nitrate or chloramine. The tolerance of methylene blue in anuric patient is usually poor at a dose greater than 1mg/kg, with a possible worsening of neurological symptoms and hypotension.