Epidemic hypotension in a dialysis center caused by sodium azide

The water used for dialysate (dialysis fluid) in hemodialysis centers is produced by water treatment systems (WTS), which require careful and frequent monitoring. On November 3, 1988, nine patients receiving hemodialysis treatments at a single dialysis center suddenly developed hypotension within 30 minutes of onset of dialysis. Eight patients exhibited symptoms and two experienced syncopal episodes; there were no deaths. The incidence of dialysis-associated hypotension occurring within 30 minutes after dialysis onset for these patients was significantly higher during outbreak treatments than during preoutbreak (September 1 through November 2, 1988) treatments, (9 of 9 vs. 0 of 238, P less than 0.00001, Fisher's t-test). Sodium azide, a potent hypotensive agent, was identified as the probable contaminant within the WTS of the dialysis center at the time of the outbreak because: 1) it was mixed with glycerine as the preservative solution of each of the four ultrafilters that were put on-line in the WTS without rinsing, 12 hours before the outbreak; and 2) high levels of total organic carbons were detected from dialysis water collected at point-of-use sites at the time of the outbreak, suggesting contamination of the WTS with the sodium azide-glycerine preservative solution. To prevent similar occurrences, we recommend that ultrafilters (and other components of the WTS) be rinsed free of potentially toxic chemicals prior to use. Dialysis center personnel need to be aware of the potential affects that each modification of disinfection of the WTS may have upon the product water used to prepare dialysate for patient treatments.