[Outbreak of hemolytic reactions associated with chlorine and chloramine residuals in hemodialysis water].

OBJECTIVE To investigate the process of water contamination and to assess the subsequent outbreak in the hemodialysis center. METHODS In September 2000, sixteen patients undergoing chronic hemodialysis at a dialysis center in Minas Gerais, Brazil, experienced hemolytic reactions compatible with toxic symptoms due to chlorine and chloramine water contamination. Chlorine and chloramine concentrations in samples obtained from various sites of the dialysis center's water treatment and distribution system were measured. Case-patients were identified by reviewing medical records and nursing notes for all dialysis sessions carried out during the study period. Interviews with technicians, nursing and medical staff members were conducted. RESULTS Reaction rate was significantly higher (p<0.028) during the outbreak period (September 25 to 27, 2000) than the pre-outbreak period (September 18 to 20, 2000). All patients with toxic symptoms had been under dialysis with water treated by reverse osmosis equipment and had used dialysers manually reprocessed. Chlorine and chloramine residuals concentrations found in the dialysis water as well as in the dialysers were at levels higher than regulations, </=0.5 mg/L for chlorine and </= 0.1 mg/L for chloramine. Individuals exposed to high chlorine and chloramine concentrations presented a relative risk of 2.58 (1.0-6.28) of having hemolytic reactions. CONCLUSION There is a need to observe surveillance procedures to secure that the maximum allowable concentrations of regulated substances in the water used in the hemodialysis process are not exceeded.