For those operating the Nipro Surdial X machines, as we have for 4 years now, we have experienced significant issues in regards to the UF Pump performance and specifically, leakage of fluid past the UF Pump when it has stopped running.
We have reported this problem to both Nipro & the MHRA to investigate as there is the realistic possibility for excessive fluid to be removed from the patient during treatment when either no UF Goal is set or during a UF Profile where the UF Pump has stopped. I won't go into the specifics of our incident as the investigation is ongoing.
Nipro recommend the UF Pump Leakage & Accuracy checks are completed as part of the 24 month routine PPM, however I would urge all operators to check their machines at the earliest possible opportunity to reassure themselves that the pump is not passing fluid when stopped.
The UF leakage check allows for a tolerance of 1ml leakage per minute and the check should run for 5 minutes, therefore anything greater than 5ml leakage is a failure, with the UF pump requiring replacement. The 'stop' position of the UF Pump is random, therefore we usually perform 3 x UF Leakage checks to reassure ourselves that we have pump integrity.
If a UF goal has been programmed and the machine runs the UF pump continuously during treatment, then we have not experienced any issues in fluid inaccuracy. This problem appears to only cause an issue when the UF Pump is not running and allows fluid to pass.
Anybody wishing to discuss this issue are welcome to contact me directly on: DW@Renalservices.com
Thanks for highlighting this. Was it picked up by clinical staff during operation or under test in the workshop? I'm surprised that leakage at this point isn't picked up by the circuit integrity test. What's the maximum leakage you have detected?
Initially, following a weight discrepancy post treatment, the nursing staff removed the machine from clinical use and requested we investigate.
When we ran a dummy treatment with a set UF Goal, the fluid removed after 1 hour & 2 hours was spot on. It was when we ran a UF Leakage & Accuracy check, we discovered the UF pump was passing fluid when of course it shouldn't.
The limit is 5ml leakage after 5 minutes, (1ml per minute), however we have seen a 56% failure rate so far on our fleet. The failed machines have leakage volumes after 5 minutes of between 6ml - 33ml, which is 1.2ml per minute to 6.6ml per minute.
At the maximum leakage rate observed, 6.6ml per minute, this could lead to a >1500ml volume removed on a 4 hour treatment when no fluid should be removed.
The problem here is that the leakage occurs when the UF Pump has stopped and the position of the pump shaft determines if there is no leak or a small leak or a greater leak. As there is no actual definite 'stop' position of the UF Pump, the final random resting position of the pump when the UF is either manually switched off by the operator or by the machine during a UF Profile determines if a leak will or won't occur.
I need to double check, what the closed circuit test during self test is actually looking for in regards to leakage limits to cause a failure error, however, our experience is that we have not seen many closed circuit test failures, but UF Pump leakage rates are significant.
We are also aware that the UF Pump is used to create a negative pressure during the Cut Filter tests and if a UF Pump leaking would impact upon this test success given the very high number of filter failures on the Nipro machines. It could just be a problem with filter production as has previously been expressed by Nipro or if the two are connected??
I've asked the question but the investigation is ongoing.....
Thanks for the detail Danny,
I know Nipro changed the heat disinfection program recently to stop the UF pump running during the citric acid intake phase as the pump was seeing a high concentration before the circuit had a chance to dilute. I'm surprised the pump does not seal off at any point on its rotation, but maybe there is a bit of wear caused by the acid?
We see CUT filter failures also and our machines are only six months old so not sure this is linked.