Jim,
We did investigate the effect of glucose on sodium measurement with direct and indirect electrodes and found an effect with the
direct ISE showing a slight false positive result with (very) high glucoses. Out index case had a serum glucose of 160 mmol/L.
From in vitro studies the slope for the line of best fit for the difference between direct and indirect sodium results for the in
vitro study is 0.021 mmol/L sodium per mmol/L glucose with 90% CI being 0.019–0.0319.
The effect did seem more marked in patients but measurement uncertainty makes exact interpretation somewhat difficult. Given the extremes of glucose involved the cases with potentially significant differences my thoughts are that the exact measurement of the sodium is not the major issue with the management of these patients and "better" results become available as the treatment proceeds and the glucose is reduced.
Reference: Glucose interference in direct ion-sensitive electrode sodium measurements Asila Al-Musheifri and Graham R D Jones. Ann Clin Biochem 2008; 45: 530–532
Regards,
Graham
Graham Jones
Staff Specialist in Chemical Pathology
St Vincent's Hospital, Sydney
Ph: (02) 8382-9160
Fax: (02) 8382-2489
>>> James J Miller <[log in to unmask]> 10/10/2010 10:56 pm >>>
My understanding is that the low sodium in DKA is "false" only in that
it may not have to be replaced. It is due to glucose drawing water out
of cells and tissues, diluting the Na (etc.). The measured Na using
either direct or indirect ISEs is accurate and I've heard of no bias
between indirect and direct during DKA. Please correct me if I'm wrong
about this. -Jim
>>> "COLLINS MICHAEL (RM1) Norfolk and Norwich University Hospital"
<[log in to unmask]> 10/8/2010 5:11 AM >>>
How was the sodium measured? Direct electrodes can give falsely low
sodium results in diabetic ketoacidosis. Indirect ISEs are OK.
Mike Collins
BMS3
Biochemistry Automation
Norfolk& Norwich University Hospital
England
[log in to unmask]
http://www.nnuh.nhs.uk/
From:Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of Mohammad
Al-Jubouri
Sent: 08 October 2010 09:16
To: [log in to unmask]
Subject: Re: Osmolal gap in DKA
Another DKA case from yesterday for comaprison; 20 year old known T1DM
admitted with DKA, the biochemistry including osmolal gap as follows:
Sodium - 126
Potassium 4.6
Urea + 8.1
Creatinine + 186
eGFR 42
R. Glucose + 46.0
S.Osmolal + 336
Bicarb - 5.0
pH 6.956
Chloride - 86
Anion gap + 39.6
Osmolal gap = 30 mosmol/L
It appears that the osmoal gap could be another marker for the severity
of DKA as both patients were admitted to ICU.
What do you think?
Mohammad
From:Mohammad Al-Jubouri <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, 1 October, 2010 15:29:25
Subject: Osmolal gap in DKA
Looking beyond DKA, a case to share
A 35-year-old male was found in his house with reduced GCS lying on the
floor. He lives alone and was not seen by a member of his immediate
family for at least 3 days and is not a known diabetic patient. His
admission blood sample clearly indicates DKA & rhabdomyolysis as
follows:
Sodium - 128
Potassium 4.8
Urea + 26.3
Creatinine + 398
CK + 23844
R. Glucose + 59.0
Bicarb - <5.0
Chloride 98
pH 6.876
Anion gap + 34.8
Lactate 3.0
Measured S.Osmolal ity + 379
Calculated S. Osmolality + 342
Osmolal gap = 37 mosm/L
Because of the high osmolal gap, even for a DKA, and the obscure
history, a sample was analysed for ethanol, methanol & ethylene glycol,
all were not detected, however his serum acetone was 271 mg/L and
B-hydroxybutyrate 1358 mg/L. So the big osmolal gap could be accounted
for by the ketones in this case. I was not aware that DKA could produce
such a big osmoal gap due to ketones only, but I suspect that in a late
presenting DKA like this case, it reflects the severity of ketoacidosis
as it proceeded without treatment for > 48h at least.
Your thoughts/experience are welcome.
Best regards
Mohammad
Dr. M A Al-Jubouri, MB ChB, MSc, FRCP Edin, FRCPath
Consultant Chemical Pathologist
------ACB discussion List Information-------- This is an open
discussion list for the academic and clinical community working in
clinical biochemistry. Please note, archived messages are public and can
be viewed via the internet. Views expressed are those of the individual
and they are responsible for all message content. ACB Web Site
http://www.acb.org.uk ( http://www.acb.org.uk/ ) Green Laboratories
Work http://www.laboratorymedicine.nhs.uk (
http://www.laboratorymedicine.nhs.uk/ ) List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List
Instructions (How to leave etc.) http://www.jiscmail.ac.uk/
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed.
If you have received this email in error please notify the originator
of the message. This footer also confirms that this
email message has been scanned for the presence of computer viruses but
this should not be relied upon as a guarantee that the contents are
virus free.
Any views expressed in this message are those of the individual sender,
except where the sender specifies and with authority,
states them to be the views of the Norfolk and Norwich University
Hospitals NHS Foundation Trust. The information contained in this e-mail
may be subject to public disclosure
under the Freedom of Information Act 2000. Unless the information is
legally exempt from disclosure, the confidentiality of this e-mail and
your reply cannot be guaranteed
------ACB discussion List Information-------- This is an open
discussion list for the academic and clinical community working in
clinical biochemistry. Please note, archived messages are public and can
be viewed via the internet. Views expressed are those of the individual
and they are responsible for all message content. ACB Web Site
http://www.acb.org.uk Green Laboratories Work
http://www.laboratorymedicine.nhs.uk List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List
Instructions (How to leave etc.) http://www.jiscmail.ac.uk/ ------ACB
discussion List Information-------- This is an open discussion list for
the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the
internet. Views expressed are those of the individual and they are
responsible for all message content. ACB Web Site http://www.acb.org.uk
Green Laboratories Work http://www.laboratorymedicine.nhs.uk List
Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List
Instructions (How to leave etc.) http://www.jiscmail.ac.uk/
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
**********************************************************************
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.
This footnote also confirms that this email message has been virus
scanned and although no viruses were detected by the system, St Vincents &
Mater Health Sydney accepts no liability for any consequential damage
resulting from email containing any computer viruses.
**********************************************************************
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
|