Hey. Its me again. I will be talking about blood gas, the station where I was attached to. I have learnt to use the Roche cobas b 221 analyzer to test for blood gases. Actually, there are three modules in this analyzer ( ISE, Co-oximetry and BG module), but I am going to touch on the BG module only. This BG module helps to determine the pH, pO2 and pCO2.
Blood gas (BG) tests are important in evaluating the respiratory as well as the metabolic conditions of the patient. These tests help to detect whether the lungs are effective in delivering the o2 and eliminate co2 from the body. In addition, the tests help to detect abnormal blood pH that influences the metabolic conditions.
These analyzers employs the assay of potentiometry and amperometry. pH and pCO2 are measured by potentiometry whereas pO2 is measured by amperometry. These assays measure the potential generated by the electrodes so as to determine the concentration of the analytes of interest.
Specimens for BG tests are arterial blood in heparinized syringes. These syringes are transported along with ice so as to prevent clotting of blood.
To perform BG test:
1. The syringe containing blood is taken out from the plastic biohazard packet.
2. Rub the syringe with both hands so to homogenize the blood sample.
3. A clot catcher is then attached to the syringe.
4. Dispense one or two drops of blood to make sure that there is no clot in the blood.
5. The syringe is then injected into the analyzer and blood sample is aspirated.
6. Results are then obtained.
To look at how the BG analyzer looks like, you can go to this website: http://rochediagnostics.ca/lab/pct/gas/
Siti Shahimah Samat
0702717J
Subscribe to:
Post Comments (Atom)
Hi
ReplyDeleteMay I know what are heparinized syringe? Is there any reason why this kind of syringe is used?
Liyana
0703827F
Hi.
ReplyDeleteHeparinized syringe contain heparin in it. As blood gas anlaysis require unclotted blood, heparin ( which is an anticoagulant), helps to prevent the clotting of blood in the syringe.
siti shahimah
0702717J
:)
hi siti,
ReplyDeletewhat does it mean by homogenize? How does rubbing the syringe with both hands
homogenize the blood sample? Thanks!
zi shuang
hi siti!
ReplyDeleteis it necessary to do calibration and quality control everyday for this analyzer?
thanks!
stella
hey siti:]
ReplyDeleteis it necessary to use the clot catcher for every blood samples?
thanks!
Natasha.
Siti, what are potentiometry and amperometry? Thanks.
ReplyDeleteIndah
0705361D
hey hey Siti =D doing fine yeah? hahaaha
ReplyDeletejust wanna ask if there is any chance that the heparin will affect the results ^^ btw, is the heparinized syringe commercially made or manually coated by u?
Vo Thu Hong Anh [Jess]
0705364H
If using a heparinized syringe could prevent the blood from clotting, due to the presence of heparin, an anti-coagulant. Why do you still need to transport the sample on ice to prevent clotting? If ice is still needed to prevent clotting, does it mean that heparin is not efficient in preventing blood clotting?
ReplyDeleteOr is the ice required for some other purposes? For example, slow down the metabolism rate of blood cells so as to not affect the concentration of each gases as you are doing a blood gas testing afterall. Any metabolism of blood cells will cause oxygen to drop and carbon dioxide to increase.
Alvin
Reply to zi shuang:
ReplyDeleteHOmogenize means to ontain a uniform mixture. As blood has many components such as red blood cells. So, by rubbing the syringe with both hands will give out heat and this heat helps to disintegrate any clumped red clood cells or other blood components. In addition, we also invert the syringe so as to mix the blood in the syringe well.
Reply to stella:
Yes, it is necessary as it helps to validate the measurements. Calibrtaion is done automatically by the analyzer every 1 hour (1 point calibrtaion) and every 12 hours ( 2 point calibration). Quality controls are done at certain intervals:
1. 9 am ( level 2)
2. 5 pm ( level 3)
3. 1 am ( level 1)
Reply to Natasha:
Well, it is good to use the clot catcher for every blood samples and possible clotted samples so as to prevent any damage to the analyzer.
Reply to Indah:
Potentiometry and amperometry are methods to measure the concentration of the analyte in question , based on the electrical potential
generated by the electrodes.
Reply to Alvin:
Yes, heparin ( anti-coagulant) helps to prevent the clotting of blood. And yes, the ice helps to slow down the rate of cell metabolism. Sorry for the confusion.
Reply to Jess:
No, heparin will not affect the results. The heparinized syringe is commercially made. :)
Hey =)
ReplyDeleteHope you are well =)
Could you explain further the concepts of potentiometry and amperometry ?
Also, what exactly is a clot catcher ?
Sorry i ask such qsns cuz I don't really understand e concepts and never seen clinical chem side before. Thanks =)
Ng Tze Yang Justin
0703747F
okay, thanks for the answers, Siti =D
ReplyDeleteVo Thu Hong Anh [Jess]
0705364H
I have to correct the purpose of rubbing the syringe between palms before analysis. There are two purposes. 1. To homogenise the whole blood sample because blood cells will settle down with time during transportation. 2. To warm the sample (not to disintegrate any clot in sample; mentioned in Siti's reply to Zi Shuang). The purpose to warm the blood is because the sample is sent in ice and the blood gases analysis is to carried out at 37oC. Temperature can affect the oxygen binding to red blood cells and will affect the O2 saturation and pO2 results.
ReplyDeletehello siti,
ReplyDeletewhy must the test uses heparinized syringes, why it don't uses heparinized test tube?
thanks!
yaNLing xD
This comment has been removed by the author.
ReplyDeleteReply to Justin:
ReplyDeletePotentiometry is the measurement of potential difference between two electrodes when there is no current flow. Amperometry involves the measurement of current flow from an electrode at any given potential.
Both methods employ two electrodes. The first electrode is the indicator electrode, which involves in responding to the activity of the analyte in question. The second electrode is the reference electrode. For potentiometry, the indicator and reference electrodes are immersed in a test solution and the electrical potential is measured in volts.Amperometry involves the measurement of current flows between the indicator electrode and a reference electrode in the test solution and the measurement is related to the concentration of the analyte. Units for amperometry is amperes.
A clot catcher is basically to trap clots from entering the analyzer.
Reply to yanling:
well, the analyzer itself was designed to make ues of syringe as the tip of the syringe is able to be injected nicely to the analyzer. we can still use the tube, but that would be a troublesome as we need to use capillary tube and insert it to the analyzer, and let the analyzer aspirate the sample by itself.
Reply to Justin:
ReplyDeleteoh, i forgot to attach the website. You can refer to it.
1. http://books.google.com.sg/books?id=cAoG7M9Ol38C&pg=PA1516&lpg=PA1516&dq=Potentiometry+is+the+measurement+of+potential+difference+between+two+electrodes+when+there+is+no+current+flow.&source=bl&ots=1fR-nzHL9_&sig=rzwtZrA6p6ejACz-BH65NwV676M&hl=en&ei=N6PESoe1MJLy6gO33bDMDQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAgQ6AEwAA#v=onepage&q=&f=false
2. http://books.google.com.sg/books?id=ba_b6tQkhv4C&pg=PA221&dq=Amperometry#v=onepage&q=Amperometry&f=false