BACTERIA CONTROL IN DIALYSIS WATER SYSTEMS

BACTERIA CONTROL IN DIALYSIS WATER SYSTEMS
By Michael Verguldi, MBA

Maintaining adequate flow velocity in conjunction with regular chemical disinfection is widely considered the primary means of reducing biofilm in dialysis water treatment systems. In many cases, these actions are not sufficient for preventing the build-up of dangerous biofilm. In this article, we describe the limitations of flow velocity and challenges with chemical disinfection, offset by identifying different or additional measures that technicians can take to avoid toxic build-up of bacteria in their dialysis water distribution system.

Introduction

In 2008, the Center for Medical and State Operations/Survey & Certification Group (CMS) issued the ESRD Interpretive Guidance Update, Version 1.1, to outline coverage for end-stage renal disease facilities. The main objective of the CMS document is to promote effective, consistent treatments while advocating patient safety.

In the section on Water and Dialysis Quality, the CMS guidance document references that water distribution systems should be designed to operate with continuous flow rates to achieve bacterial control: “Water distribution system should be configured as a continuous loop designed to minimize bacterial proliferation and biofilm formation.” In order to achieve this mandate, the document states as per the Association for the Advancement of Medical Instrumentation (AAMI) via publication ANSI/AAMI RD52:2004, that “flow velocity of three ft/sec in the distal portion of an indirect feed system and a velocity of 1.5 ft/sec in the distal portion of a direct feed system,” as a strategy for bacterial control. It is here that surveyors and inspectors are prompted to verify that the minimum flow during times of operation is being achieved.

Still, while flow control is clearly important, recent research has raised questions about whether flow velocity is as effective as thought for preventing biofilm in a clinical filtration system. In its more recent publication, ANSI/AAMI/ISO 23500: 2011, AAMI delivers a different perspective: “In many dialysis facilities there is no flow through distribution systems when the dialysis facility is not in operation, such as at night and on Sundays… Further, it has been demonstrated that microbial growth and biofilm formation in hydraulic systems cannot be controlled by the fluid velocity (Soini, et al., 2002). Even in systems operating with a Reynolds number of 3,000, biofilm was found on the internal surface of the pipes." (Libman, 2006)

In other words, even those clinics that meet flow velocity metrics are at risk for unacceptable bacteria and endotoxin counts.

The other strategy of bacterial control that is publicized as necessary through CMS and AAMI is routine disinfection of the system. These are essential; however, many water distribution systems can only accommodate chemical disinfection protocols which can be hazardous, time consuming, and piping materials that are deemed acceptable, such as polyvinyl chloride (PVC), can also contribute to bacteria formation. In addition, poorly designed and installed distribution systems can contain pockets of residual disinfectant that could remain in the piping system even after disinfection. In fact, despite executing all of the recommended controls, a clinic may still find itself performing additional costly chemical disinfections and testing procedures in order to stay compliant.

http://www.renalbusiness.com/news/2013/10/bacteria-control-in-dialysis-water-systems.aspx