Dear All,

I am looking for some advice on how to test HDF reinfusion fluid. I only have experience of Gambro ‘Ultra’ machines & Nikkiso DBB-05’s. Both of these filter the dialysis fluid internally before passing the ultrapure fluid through a disposable single use endotoxing filter. We routinely test the output of the machines (without the single use filter) to ensure it complies with the current RA guidelines; TVC <0.1cfu/ml and endotoxin <0.03 IU, we send the lab. 500ml of the fluid so they can filter and culture for 7 days on TGEA; we occasionally have a TVC of 4 or 6 in 500ml (TVC 0.012 cfu/ml) but mostly it is zero. We have the Fresenius 5008 here at King’s to trial and I am not sure how to sample as this machine does not use a single use filter, only the internal one; therefore the RA guidelines for this fluid say it must be sterile (<1 cfu/1000 litres). Is a 500ml sample enough, and clearly even 1 cfu in 500ml would be unacceptable. Having read the 5008 operator manual it states that the unfiltered dialysate must have a TVC of <1000 cfu/ml and the ‘High-purity dialysate’ must have a TVC of <1 cfu/ml. If you follow this through this recommendation it would mean it is acceptable to have a cfu of 9/10ml in the reinfusion fluid. When you multiply this up to a substitution volume of 20 litres it would mean you have infused into the patient enough bacteria to produce 18,000 colony forming units! Any advice gratefully received.

Ian

Hello Fraser,

Thanks for replying to this posting. Since then I have done some literature searches and come up with more details as well as speaking to a few other users. There appears to be no consensus about how much fluid should be collected when testing the substitution fluid with, some units collecting 10ml, and others collecting 100ml; whilst Fresenius in the UK only use 1ml when testing this fluid in their laboratory.

The EDTNA/ERCA Guidelines; Quality assurance for dialysis-quality water and dialysis fluid site a French document, Circulaire DGS/DG/AFSSAPS No 311 which has now been replaced with the following standard: http://www.sante.gouv.fr/adm/dagpb/bo/2007/07-03/a0030058.htm

This recommends collecting 100ml of ultrapure dialysis fluid and ensuring the TVC is <10cfu (<0.1cfu/ml). For the substitution fluid it recommends collecting a minimum of 500ml and ensuring there are 0cfu. This standard also recommends making these measurements once every three months.

This makes sense as a smaller volume cannot guarantee to show very low bacterial levels. Whilst this does not meet the stringent requirement needed to demonstrate sterility as defined by the European Pharmacopoeia (this requires 10% of a container be filtered and cultured for 14 days) it is achievable. This has reassured me that they processes we currently use are adequate for testing on-line HDF machines without a single-use filter.

Best regards

Ian

Hi

Lizzie's full article is available in our Document Index under Artery Newsletter Issue 41.

Gordon

Maurice has just asked if this document could be posted http://jasn.asnjournals.org/cgi/content/full/13/suppl_1/S78

In reply:

Hello Maurice,

Thanks for this; though I have already seen it and I have to say it did not help much when trying to validate a practical program of monitoring. Obviously this paper is biased to showing how safe the Gambro system is: my concern was how to test a system without a single use filter. Here they validated the sterility of the final infusion fluid by collecting 2 x 15 litres which is not practical for us. I think the information that needs to be got across is that you must collect as large a volume as is practical, and I don’t think 10 or 100ml is acceptable. I am currently waiting for information from Fresenius to see how they validated their process, but I bet they too used larger volumes than we could hope to send to our labs on a routine basis.

Best regards

Ian