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Water or glycerol temp monitoring?


GaryCheung
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What do you use in blood packs/containers that you are using to simulate product when monitoring blood fridges: water or a glycerol solution?

If glycerol, what concentration and why?

Has anyone had advice/rationale from MHRA or any other body on what to use?

Do you add preservative (e.g. azide) & have any manufacturers offered advice on liquids vis a vis corrosion of probes?

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Hi Gary,

The blood fridges I have currently have buffered core temperature probes. When I get a more user definable temperature monitoring system i'm not sure i would place my probes into any liquid. What does placing probes into the standard 200mls of liquid actually prove (regardless of this being water or glycerol)?

Components most likely to be affected by temperature fluctuations are your paediatric units (30ml volume), these are more likely to be at the "air" temperature of the equipment because of their small volume.

Why not just keep your monitoring probes at the air temp range ?

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MHRA want "buffered core temperature" but this seems to be being interpreted as "simulated product" from what recently inspected sites are saying. Whether this is MUST or SHOULD I don't know.

I don't know whether MHRA have picked up on paedi packs in this regard yet.

One site chose 100 ml water in an adult pack as a compromise, others are talking about adult and paedi pack simulated product into which probes are inserted.

Obviously, monitoring air temperature gives you earlier warning, but some systems allow alarm delay and door open events to be recorded anyway and the MHRA line seems to be

Alarm linits = 2-6C (water); 2-8C air

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As I have said before- you need to clarify for yourself ( and if necessary MHRA) why you are doing something the way you are. If you want to monitor without sticking the probes in liquid- state the reasons behind this: advantages/ disadvantages, based on evidence and comparisons of core vs air temps.

Regardless of whether MHRA have picked up on pedi packs, you should be thinking of patient safety - this is basically what it's all about. If a pediatric pack is stored incorrectly and harms the baby, this could be more difficult to detect in a neonate compared to an adult.

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Below is a Question to MHRA and their answer, may help

There appears to be some confusion about the appropriate method to use in

order to record refrigerator temperature. Whether core temp or air temp is

better and if core temp is monitored at all, what volume of fluid should be

used for the sensor to be placed into. What does the MHRA recommend and

why?

Response

For routine monitoring the MHRA recommends that core probes with a

representative volume (this will differ depending on whether the site handles

primarily paediatric or adult units) are used. The reason core is recommended

is that it gives a direct correlation to the actual condition within the

components, if core probes are used then there should be no delay on the

alarm and the alarms need to be set at 2 - 6ºC. Air probes can be used for

routine monitoring but in this case the site has to demonstrate how this

correlates to the component conditions especially where alarm delays are set

and where the alarm limits do not directly correlate to the BSQR art four

requirements e.g. 2 - 6ºC. Air probes can be problematic as they will show

temperature fluctuations very quickly e.g. door openings and may lead to

nuisance alarms. Air probes are however recommended for mapping

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As a vendor of automatic temperature monitoring systems we provide glycerine bottles with 33% water. That proportion has the lowest freezing point (under -45 F and C). Glycerin is only used to lower the solution's freezing point. Worth noting that pure glycerin is a gel solid way above freezing.

The solution is a worthwhile simulation and yes, it does seem to average (integrates) the temperature so you dont see the door opening for short moments nor the defrost cycles as prominently as you would with an air probe.

We provide the glycerin solution gladly and without hesitation. However for you to get the best of both worlds, our portal (Freshloc's that is) takes a standard air probe measurement and creates another seemingly live sensor that behaves just as if you had any amount of solution the probe was in. Then you get to see the "way it is" and as if it was in the glycerin. Alerts and all reporting can be based on either the real probe or the simulated probe. Anyone can graph any time, the actual data and the integrated data as well, whether they set up this added simulated probe or not.

In summary, the fast response probe simply alerts too quickly for some so the glycerin or simulation eliminates (or reduces) the number of alerts due to just a door opening for a minute or so.

Rik

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[QUOTE=jayjay;17357]

For routine monitoring the MHRA recommends that core probes with a representative volume (this will differ depending on whether the site handles primarily paediatric or adult units) are used. The reason core is recommended is that it gives a direct correlation to the actual condition within the components, if core probes are used then there should be no delay on the alarm and the alarms need to be set at 2 - 6ºC. Air probes can be used for outine monitoring but in this case the site has to demonstrate how this correlates to the component conditions especially where alarm delays are set and where the alarm limits do not directly correlate to the BSQR part four requirements e.g. 2 - 6ºC. Air probes can be problematic as they will show

temperature fluctuations very quickly e.g. door openings and may lead tonuisance alarms. Air probes are however recommended for mapping.)

Thanks for the info Joan. I presume if the blood fridges we use in the UK are BS4376 compliant then core temperature monitoring requirements should be met (using the chart record- of course I could be wrong in assuming this) ?

Then any additional monitoring using air temps could be used to give a faster alert to temp changes, and it would be easy to show correlation of air to core values.

Edited by RR1
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Does anyone have any information on the original question - water vs. glycerol solution?

I wouldn't have thought it mattered whether water or glycerol was used. Which ever one you select ( and the volume chosen )- you would need to show how your core and air temps were interrelated by performing a validation at high and low temperature points.

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In my opinion, if we are monitoring the temperature in a fridge, it really doesn't matter what liquid was used to immerse the probe in. After one hour, the thermometer reading will be the same no matter you use glyercol or water.

But I will have to take note of the possible temperature flacuations when you take the readings...

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In my experience we've utilized a 33% glycerol solution with an overal solution volume equivalent to the smallest volume stored in the refrigeratio/freezer. When dealing with solutions volumes that are exceedingly difficult (sample tubes come to mind), we'd utilize an air probe as the variations in air temperature were come close to correspondnig to that smaller solution volumes and would result in a more conservative response in the event of a temperature deviation.

As mentioned in the MHRA response above, the core temp monitoring does reduce alot of the pesky alarms that might result from door openings and air cycling events, and provides information that correlates to that of the stored materials themselves. Air temp does fluctuate more, resulting in more paperwork usually to document what happened, though you could put some alarm delays to compensate that, though one should be prepared to either document a justification for the delay periods or be prepared to have a consistent answer for the delay duration when asked by an investigator. The word consistent is the key in that previous sentence, nothing worse than three people giving three answers for the delay periods, hence why its never a bad thing to have it documented somehwre, such as the temperature mapping documentation or a validation somewhere. For core temps, no delay is usually the expectation, and I've seen a number of inspectors who prefer the alarm set points occur just before the min/max storage temp is reached to allow for a timely response in the event that products/materials must be moved to a new storage location.

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In my experience we've utilized a 33% glycerol solution with an overal solution volume equivalent to the smallest volume stored in the refrigeratio/freezer. When dealing with solutions volumes that are exceedingly difficult (sample tubes come to mind), we'd utilize an air probe as the variations in air temperature were come close to correspondnig to that smaller solution volumes and would result in a more conservative response in the event of a temperature deviation.

Hi David,

So in the situation where the blood fridge holds mainly adult size (250ml) units and a few (<8) paediatric (35ml) units and some vials of anti-D Ig, would you monitor on air temp or use a probe in glycerol because the main units being stored are the larger ones?

In this situation I would personally prefer to monitor on air temp, with my alarms set at 2'C to 6'C (rather than 2'C to 8'C)- but with a 10-15min time delay, but I would be happy for anyone to correct me on this.

many thanks!

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Hi Rashmi,

Personally, I'd take the conservative side and go with the air probe since that will give me information about temperature fluctuations that would adversely affect the smaller volume materials far sooner than it would affect the larger product volumes. By time something affected a probe within a 250mL solution, the smaller tubes might already be adversely affected an unsuitable for use, and would likely require a great deal more documented justification during a material review board to use them after a temperature event.

In short, from my personal take on things, it sounds like what you're doing is sufficient. About the only thing that might be a quibble point with an auditor is the time delay on the alarm. That said, so long as your continuous monitoring documentation shows minimal temperature extremes even within that time delay, I don't think there would be much room for argument against the current practice beyond personal preferences, which really shouldn't enter into a regulatory discussion fi there is no regulation/standard to fall back on.

Again, your mileage may vary,

David

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=/

I had always wondered about what would be best to monitor temperatures in a fridge. But after reading dferia's post, I realise that the air probes are probably the best over the rest.

Air probes will give you a warning of what's to come when the temperature deviates out of the normal range. By the time water/glycerol thermometers tells you something is wrong, the deviation of temperature in the blood units have already occurred.

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10% glycerol provides a conductivity similar to liquid (RBC/WB) products. The quantity of liquid should be less than or equal to the smallest container stored in the refrigerator. For frozen products ( less than -18C) you can move to 40% grlycerol or antifreeze again in the smallest quantities. If you don't want to use liquid at miminum. your probes should be in a container to prevent drafts (fans, all door openings) from activating your alarms. 10% glycerol also works for room temperature monitoring (platelets).

If you make up you quantities of solution in large amounts (1L or more) add a few drops of household bleach and it will delay mold. Only a small amount as not to corrode your temperature probes. Bring the solution(s) to whatever temperature you're going to monitor before you place the probes in to cut down on the alarming while the solutions come to temperature

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  • 2 weeks later...

Regarding a solution itself if you choose to use one - Not an advertisement - but a recommendation based on our experience.

Check out IceClear PGX by Orison. Our company went with them as a bio-based alternative to using petroleum based glycol solutions. It is a complex carbohydrate solution. http://www.orisonmarketing.com/deicers/PGX/pgx.html

TML M.S., MT(ASCP)

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  • 4 weeks later...
  • 1 month later...

Hi All,

Rashmi, has asked for our input Jay-Jay was spot-on in the response, we have access to a consultant who did actually train all the UK MHRA inspectors + Canada and Ireland, so she is highly respected and regarded, and asked the exact same question for a definitive answer, which is simply "Tap water"(200ml), however only 1 of our customers has asked for Glycerol and that was the NBS who asked for 10% to be added to the tap water.

I hope that helps and clarifys the issue.

Cheers.

Dave (ABBWalker).

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