The microbial world and fluids in dialysis

Pseudo-outbreak of haemodiafiltration dialysis fluid contamination: results of a detailed epidemiologic investigation

Background

Compliance with dialysis fluid ultrapurity standards is a paramount for online modalities. More than 200 dialysis fluid samples have been analyzed monthly for years in our two dialysis units, with compliant microbiological results until mid-2020.

Aim

In mid-2020, an unusual occurrence (30%) of contaminated dialysis fluids in dialysis units led us to investigate to determine the source.

Methods

Microbiological methods for aquaphilic bacteria culturing and endotoxin detection in dialysis fluids were routinely performed on a monthly basis for all dialysis machines. As the contamination appeared randomly and almost simultaneously in our two units without any routine change or febrile syndrome, we searched for a common cause. Supplier's sampling kits as well as microbiological laboratory procedures were scrupulously investigated.

Findings

21 out of 30 sampling bags filled with sterile water brought back numerous fungi and bacteria. Laboratory's investigation, through the negative control tests performed routinely, exonerated the lab. All batches of bags analyzed later showed variable levels of contamination according to their transport/storage mode or date of manufacturing. Analyses performed by the supplier - methods complying with the medical device's standards but different from those recommended for dialysis fluids purity - remained negative.

Conclusion

Our investigation revealed that the contamination of our sampling kits came presumably from the manufacturer's supplying chain. Such false-positive results findings, created serious safety issues and disturbed clinical activities since positive machines were quarantined. Furthermore, it raised a serious concern about manufacturing, microbiological checking and shipping methods for the medical device industry that deserve further attention.

Clinical relevance of abstruse transport phenomena in haemodialysis

Haemodialysis (HD) utilizes the bidirectional properties of semipermeable membranes to remove uraemic toxins from blood while simultaneously replenishing electrolytes and buffers to correct metabolic acidosis. However, the nonspecific size-dependent transport across membranes also means that certain useful plasma constituents may be removed from the patient (together with uraemic toxins), or toxic compounds, e.g. endotoxin fragments, may accompany electrolytes and buffers of the dialysis fluids into blood and elicit severe biological reactions. We describe the mechanisms and implications of these undesirable transport processes that are inherent to all HD therapies and propose approaches to mitigate the effects of such transport. We focus particularly on two undesirable events that are considered to adversely affect HD therapy and possibly impact patient outcomes. Firstly, we describe how loss of albumin (and other essential substances) can occur while striving to eliminate larger uraemic toxins during HD and why hypoalbuminemia is a clinical condition to contend with. Secondly, we describe the origins and mode of transport of biologically active substances (from dialysis fluids with bacterial contamination) into the blood compartment and biological reactions they elicit. Endotoxin fragments activate various proinflammatory pathways to increase the underlying inflammation associated with chronic kidney disease. Both phenomena involve the physical as well as chemical properties of membranes that must be selected judiciously to balance the benefits with potential risks patients may encounter, in both the short and long term.

Hemodialysis-Associated Infections

Hemodialysis patients are at increased risk of infections, which are common adverse events among this patient population. We review factors contributing to infections among hemodialysis patients and epidemiology of common infections and outbreaks, including bloodstream infections, vascular access infections, and infections caused by bloodborne pathogens. Recommendations for prevention are discussed with emphasis on essential infection control practices for hemodialysis settings.

Multidisciplinary evaluation for severity of hazards applied to hemodialysis devices: an original risk analysis method

BACKGROUND AND OBJECTIVES

Risk analysis for medical devices is a crucial process to grant adequate levels of safety. Identification of device exposure-related hazards is one of the main objectives.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Hazard analysis for hemodialysis devices has been performed by a multidisciplinary team involving engineers and clinical experts. A potential harm list was identified from clinical and technical experience, postproduction information, and literature. Various hazardous situations (circumstances when the use of the dialysis device may lead to described harms) were described. Such hazardous situations were correlated to the extent of the deviation of a specific device parameter from expected ranges. The clinical severity that was relevant to any specific harm was categorized for each hazardous situation using a descriptive and numerical scale with five levels (from negligible [i.e., discomfort only] to catastrophic [i.e., potentially lethal]).

RESULTS

Harms in which the deviation of a parameter strictly coincides with the clinically measured effect on the patient are defined as "direct." Otherwise, when another clinical parameter must be involved to quantify severity, the related harm is considered "indirect." Two complete examples of multidisciplinary evaluation for severity of hazards (MESH) are given for a direct harm (air embolism) and for an indirect harm (hypothermia). For other harms, the maximum value of severity involved is provided.

CONCLUSIONS

MESH represents a possible example of risk management for dialysis equipment in which, although the manufacturer is directly responsible, a multidisciplinary task force may contribute to a better link between engineering and clinical perspectives.

Official recommendations for quality of fluids in dialysis -the need for standardisation

Recommendations/guidelines regarding the microbiological and chemical quality of fluids in dialysis are increasing in numbers, both nationally and internationally. As dialysis is a worldwide issue, with many elements being similar regardless of geographical area, it is logical to have the same quality requirements on fluids used in dialysis. At present, there are large differences between the different documents. This situation makes studies where several nations participate more difficult to interpret as the fluids used in dialysis are crucial for the dialysis session. A special situation applies for substitution fluid produced 'On-Line' for haemodiafiltration (HDF) and haemofiltration (HF), where some recommendations are questionable from a scientific standpoint. The International Organisation for Standardisation (ISO) is in the process of finishing a collection of standards including guideline for fluids in dialysis (water, concentrates, dialysis fluid, substitution fluid) and equipment used for water preparation. To have the same quality for reference worldwide will facilitate the interpretation of international studies as well as give dialysis patients treatments based on the same quality baseline.

Microbiology of water and fluids for hemodialysis

In hemodialysis, huge amounts of water are used for diluting the concentrates to produce dialysis fluid. The water is produced on site by reverse osmosis units. The chemical and microbiological quality of the water is essential for dialysis patients. Reverse osmosis units produce water of acceptable chemical quality that can be kept throughout the water system. The microbiological water quality, on the other hand, does not depend on the reverse osmosis unit but on the maintenance of the whole water system. All over the world, dialysis units take water samples and send them to laboratories for cultivation and endotoxin tests. Depending on the method of microbiological analysis, the water may be judged to be very good even if in reality it is much worse and outside of standard recommendations. When standardizing the methods with adequate cultivation of water samples, the accuracy of the tests will be better, and as a result, dialysis units can use their resources for keeping the water systems in good shape, i.e. disinfect preventively and frequently and use less effort in collecting samples. This will benefit patients, who will receive a high-quality dialysis fluid, thus eliminating the effects of microbiological impacts such as increased levels of inflammation markers (e.g. C-reactive protein). In the situation of performing hemodiafiltration by producing the substitution fluid "on-line", it is even more important to have a sensitive method of microbiological verification to follow-up the hygienic quality.