Sodium Analysis

[paul spark]

Hello.

May I ask what policies are in place for Sodium Analysis.

Here at Sheffield, we take two samples at commissioning and each PPM.
 1 A bicarbonate only sample
 2 A total sample with both acid and bicarb

We analyse sodium content with a IL 943 Flame Photometer.

The Flame photometer is no longer supported.

As there is no sodium calibration on the HD machine (Dialog+/Evo),
we are toying with the idea of relying on the conductivity calibration during commisioning/PPM and sending random samples off to the Labs for Sodium Analysis.

I dont recall ever recalibrating a machine because there was an incorrect reading from the Flame Photometer.

We have been offered an ionometer as a replacement - it doesn't seem very cost effective tho!

[Chris Bates]

Hi Paul,
When we were getting a lot of high bicarb results from our labs I looked into trying a freezing point depression Osmometer. This seems to be a very accurate, quick and reproducible way of testing. The total osmolarity of the dialysis fluid is known as it is written on the acid can (291 mosm/l on ours). I don't know if anyone uses this technique but it always seemed like a very good method. They are around £3-4k and reference/cal solutions are not expensive. I couldn't get one to try but they analysed some of our samples and we got what I hoped.
Wolflabs and Camlab were the main suppliers of basic units as I recall. I considered splitting the costs with our QC dept but since then they have purchased an all singing new analyser.
I have heard of people having difficulties with ionometers but I believe Ian Morgan was happy with his Roche 9180 (?) electrolyte analyser.
Chris

[Ian Wilde]

Hi Paul,

We've never tested a sodium or bicarbonate in the 18 years I've been in renal.  My bosses never did it so in turn I have never done it (be this right or wrong).  I know that when we have a new machine commissioned there are no samples taken by the company either.
As with any sample, it's only accurate at the moment it is taken anyway!?  Can, worms, everywhere!

[paul spark]

thanks Chris.

I had an Instrumentation Labs Ilyte in for a trial.
It gave the results we wanted but the servicing costs seemed ridiculous!!.

Ian, I was considering doing away with sodium analysis - but, after looking at the post about bicarb conductivity and the table supplied by nikkiso, I think I would prefer to have some sort of sodium analysis available to me!!

Would be interesting to know how many other places rely solely on their conductivity meters!

[Ian Wilde]

If you're using a volumetric system and it is set up correctly and the calibration of your pumps checked then can it be wrong?
I know with the make of machine we use, if we got a bad result from the lab we would just check the volumes of the pumps was correct - and that would be pretty much all we could do anyway.