Local anesthetics had not been administered to any of the patients.All patients were clinically asymptomatic and showed no signs of suffering from selleck inhibitor hypoxia, such as newly occurring cardiac or cerebral symptoms, or hemolysis. Therefore, further laboratory tests, such as the determination of haptoglobin, were not carried out.A sequence of all methemoglobin values obtained during a seven-day period in one patient is displayed in Figure Figure1.1. Disinfection of the water supply on the fifth day was associated with a marked increase in the methemoglobin concentration.Figure 1Methemoglobin fraction during a seven-day period in a patient undergoing five sessions of extended hemodiafiltration during that time (marked as horizontal bar). On the fifth day, (i.e., during the third session of dialysis), disinfection of the hospital .

..Starting in February 2009, a carbon filter was routinely interposed in the water supply of the portable reverse osmosis system. Since that time, we have not observed either hydrogen peroxide in the permeate and dialysate or increases in the methemoglobin fraction. The maximum methemoglobin fraction was 1.0%, 1.4%, and 1.2% in three patients undergoing extended hemodialysis/hemodiafiltration on days with water disinfection, and the hemoglobin concentration was 11.0 g/dl, 9.3 g/dl, and 9.9 g/dl, respectively. Hydrogen peroxide was not detectable in the permeate and dialysate, whereas its concentration was 10 mg/l at the peripheral water outlet.

DiscussionThe retrospective evaluation of arterial blood gas analyses demonstrated a constant association between hospital water disinfection, using a hydrogen peroxide/silver ion preparation, and the occurrence of methemoglobinemia during extended hemodialysis/hemodiafiltration in critically ill patients. Adverse effects of water disinfection with hydrogen peroxide have only been described in a few case reports until now. Davidovits and colleagues observed an association between methemoglobinemia up to 11% and hemolysis in children undergoing dialysis after the water storage tank had been disinfected with hydrogen peroxide and not sufficiently washed out [1]. Gordon and colleagues reported on children who developed hemolysis due to contamination of the dialysis fluid with hydrogen peroxide [2].A systematic association between methemoglobinemia during dialysis and the water disinfection protocol of a hospital has not been described before.

We observed methemoglobinemia in the context of a regularly performed water disinfection technique using a hydrogen peroxide/silver Anacetrapib ion preparation. We could not find evidence for secondary methemoglobinemia due to other causes. Only a few patients were treated with drugs known to have oxidizing properties [3,4], and most of those treatments were performed on disinfection-free days. On these days, all patients, with the exception of one, had a methemoglobin fraction of 2% or lower.