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    Hi all, can someone help me clear this up?

    From my knowledge ...
    ABGs - take when want to assess PAO2/oxygen, but the procedure is painful
    VBGs - can be used to take everything else (e.g. bicarb, pH, PCO2) apart from an accurate oxygenation level. It is just as quick to take/analyse (someone confirm this?)

    Lactate ...
    Can you measure lactate levels with both samples? Or is that a separate blood test?

    Glucose ...
    Same question as above (see: lactate). I'm getting a bit confused when thinking about taking glucose samples in someone who has shut-down. Oliguria maybe so no urine? I always assumed it was another coloured blood bottle, but remembered someone implying you can take it with a VBG, so again confused

    Thank you
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    (Original post by notespad)
    Hi all, can someone help me clear this up?

    From my knowledge ...
    ABGs - take when want to assess PAO2/oxygen, but the procedure is painful
    VBGs - can be used to take everything else (e.g. bicarb, pH, PCO2) apart from an accurate oxygenation level. It is just as quick to take/analyse (someone confirm this?)

    Lactate ...
    Can you measure lactate levels with both samples? Or is that a separate blood test?

    Glucose ...
    Same question as above (see: lactate). I'm getting a bit confused when thinking about taking glucose samples in someone who has shut-down. Oliguria maybe so no urine? I always assumed it was another coloured blood bottle, but remembered someone implying you can take it with a VBG, so again confused

    Thank you
    A VBG is arguably quicker to take, as you do it alongside other venous samples. If this is a first presentation in ED, you can do this when you put the cannula in. ABGs are not so painful if you use local anaesthetic. They both go in the same analyser so take the same amount of time to run.

    Some blood gas analysers can also test glucose and lactate, but not all, so it's worth checking at your trust. IIRC lactate samples degrade quickly so if you are sending it to the lab you need to send it on ice and call them to let them know it's coming so they can do it urgently.
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    As above.

    A venous lactate is indeed a huge faff so doing a blood gas is way easier, and there's very few circumstances where that would not be adequate.

    Not sure what exactly you're saying about glucose but basically there are 3 options:
    Finger prick (BM) - adequate in the vast majority of circumstances.
    Blood gas: Sometimes gives you a blood glucose, sometimes not. Possibly slightly more accurate than above - a V or ABG certainly removes problems from things like sweat dilution, but will be more inaccurate if you delay sample processing. But if you really want accuracy for some reason you go:
    Venous glucose from the lab. You do need a different coloured vacutainer (flouride - it stops residual metabolic processes from consuming the glucose).

    Capillary blood gases (CBGs) are also very useful in some instances e.g. babies, COPD patients needing frequent repeat blood gases.
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    (Original post by Helenia)
    A VBG is arguably quicker to take, as you do it alongside other venous samples. If this is a first presentation in ED, you can do this when you put the cannula in. ABGs are not so painful if you use local anaesthetic. They both go in the same analyser so take the same amount of time to run.

    Some blood gas analysers can also test glucose and lactate, but not all, so it's worth checking at your trust. IIRC lactate samples degrade quickly so if you are sending it to the lab you need to send it on ice and call them to let them know it's coming so they can do it urgently.
    Thank you for the reply - v. helpful!

    I suggested the use of local anaesthetic the last time I saw one done (I think I read your post about it before and it came to mind !), but I was given a look like "what are you talking about?" So I just ... stopped. Is this usually a thing only anaesthetists do because they know where the local anaesthetic is aha?

    Also, what is IIRC?

    (Original post by nexttime)
    As above.

    A venous lactate is indeed a huge faff so doing a blood gas is way easier, and there's very few circumstances where that would not be adequate.

    Not sure what exactly you're saying about glucose but basically there are 3 options:
    Finger prick (BM) - adequate in the vast majority of circumstances.
    Blood gas: Sometimes gives you a blood glucose, sometimes not. Possibly slightly more accurate than above - a V or ABG certainly removes problems from things like sweat dilution, but will be more inaccurate if you delay sample processing. But if you really want accuracy for some reason you go:
    Venous glucose from the lab. You do need a different coloured vacutainer (flouride - it stops residual metabolic processes from consuming the glucose).

    Capillary blood gases (CBGs) are also very useful in some instances e.g. babies, COPD patients needing frequent repeat blood gases.
    Thank you and thank you for clarifying the glucose thing!

    Are CBGs done as a heel prick (for babies?) And how is it routinely done for COPD patients? I don't think I've registered the existence of CBGs until now haha
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    (Original post by notespad)
    Thank you for the reply - v. helpful!

    I suggested the use of local anaesthetic the last time I saw one done (I think I read your post about it before and it came to mind !), but I was given a look like "what are you talking about?" So I just ... stopped. Is this usually a thing only anaesthetists do because they know where the local anaesthetic is aha?

    Also, what is IIRC?



    Thank you and thank you for clarifying the glucose thing!

    Are CBGs done as a heel prick (for babies?) And how is it routinely done for COPD patients? I don't think I've registered the existence of CBGs until now haha
    IIRC = If I remember correctly.

    As for the local, I was taught it at med school, can't remember if it was by the clinical skills teacher or a random doctor. It's certainly not an anaesthetist-only thing, I used it when I was an ED FY2, but it does seem to be regional - you're not the first person here to say that people seemed surprised at the suggestion. It's not hard to find out where the local is kept!
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    (Original post by Helenia)
    IIRC = If I remember correctly.

    As for the local, I was taught it at med school, can't remember if it was by the clinical skills teacher or a random doctor. It's certainly not an anaesthetist-only thing, I used it when I was an ED FY2, but it does seem to be regional - you're not the first person here to say that people seemed surprised at the suggestion. It's not hard to find out where the local is kept!
    lol I thought IIRC was a medical acronym

    Yes, it seems like such an obvious thing! I will try my best to do it when I get the opportunity - thank you once again! And my future patients thank you for the local anaesthesia reminder aha
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    (Original post by Helenia)
    A VBG is arguably quicker to take, as you do it alongside other venous samples. If this is a first presentation in ED, you can do this when you put the cannula in. ABGs are not so painful if you use local anaesthetic. They both go in the same analyser so take the same amount of time to run.

    Some blood gas analysers can also test glucose and lactate, but not all, so it's worth checking at your trust. IIRC lactate samples degrade quickly so if you are sending it to the lab you need to send it on ice and call them to let them know it's coming so they can do it urgently.
    PRSOM ... VBGs were never a thing until people started thinking about more point of care testing ...
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    (Original post by notespad)
    Are CBGs done as a heel prick (for babies?)
    Yes

    And how is it routinely done for COPD patients? I don't think I've registered the existence of CBGs until now haha
    Usually an ear lobe prick. Its much less painful and often much easier.

    Its only caught on in some centres so far.
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    (Original post by notespad)
    I was given a look like "what are you talking about?" So I just ... stopped. Is this usually a thing only anaesthetists do because they know where the local anaesthetic is aha?
    It's worth infiltrating some lignocaine under the skin when starting out doing ABGs. Any doctor can show you how to do it - as long as it's under the skin and not in a vein/artery then it's a very safe thing to do. It's helpful when you are unconfident/unpracticed as the patient will tolerate a lot more poking around with LA. Once you're confident in always hitting the artery with a single stab, most doctors don't trouble themselves with this extra step. Some patients will also say "just get on with it" when you ask them as they'd rather have one needle (the ABG) than two (LA then ABG).

    You'll see the occasional respiratory patient who insists on lignocaine because they've had so many ABGs in the past and remember the ones with LA being close to painless.
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      (Original post by Helenia)
      A VBG is arguably quicker to take, as you do it alongside other venous samples. If this is a first presentation in ED, you can do this when you put the cannula in. ABGs are not so painful if you use local anaesthetic. They both go in the same analyser so take the same amount of time to run.

      Some blood gas analysers can also test glucose and lactate, but not all, so it's worth checking at your trust. IIRC lactate samples degrade quickly so if you are sending it to the lab you need to send it on ice and call them to let them know it's coming so they can do it urgently.
      lactate doesnt need to be on ice but does need to be processed within 20-30 minutes.
      Some labs have an analyser though so need to pull their reagents out of fridge and set up the machines...
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        (Original post by MonteCristo)
        It's worth infiltrating some lignocaine under the skin when starting out doing ABGs. Any doctor can show you how to do it - as long as it's under the skin and not in a vein/artery then it's a very safe thing to do. It's helpful when you are unconfident/unpracticed as the patient will tolerate a lot more poking around with LA. Once you're confident in always hitting the artery with a single stab, most doctors don't trouble themselves with this extra step. Some patients will also say "just get on with it" when you ask them as they'd rather have one needle (the ABG) than two (LA then ABG).

        You'll see the occasional respiratory patient who insists on lignocaine because they've had so many ABGs in the past and remember the ones with LA being close to painless.
        I can't help but roll my eyes at these sort of comments. Do you always apply the same logic to suturing by the way?

        My use of local anaesthetics for all ABGs except in a dire emergency is not because of lack of confidence or experience but BECAUSE of confidence and experience. I know that I can hit the artery in 95% of patients first time. But I also know it is extremely challenging to work out which 5% of patients I will struggle with and which I won't. I also know my odds of first time success and the odds of the patient having a good experience go up if I spend 1 minute getting an insulin syringe, drawing up 0.5ml lignocaine 1%, infiltrating it over the radial artery, then setting up the abg syringe, wipe area, position wrist over a vomit bowl (my wrist cocking method of choice) and doing the do.
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          (Original post by nexttime)
          Yes



          Usually an ear lobe prick. Its much less painful and often much easier.

          Its only caught on in some centres so far.
          CBGs can be heel prick for little babies or taken from the cannula for infants.

          The ear lobe prick is very rarely done outside of spc resp nurse practice but is very widespread in use in COPD clinics and Sleep clinics.
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          (Original post by Jamie)
          I can't help but roll my eyes at these sort of comments. Do you always apply the same logic to suturing by the way?
          I have applied the same logic on the few occasions when I've needed to place a single suture, yes. I personally haven't found patients to be very troubled by ABGs, although those I see usually only require a single stab, i.e. not serial ABGs. I would probably feel differently if expecting the same patient to undergo the procedure on multiple occasions.

          I often give patients the choice and most just tell me to get on with it. I've not thought about using an insulin syringe before (always just a blue needle) and will happily give that a try.
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          Just to switch tangent a little bit....if doing lumbar punctures get into the habit of sending formal lab blood glucose and not just a BM. And if you are sending CSF for ?meningitis always send another fluoride sample for CSF lactate, quite a useful differentiation between viral and bacterial especially if done before antibiotics are given.
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            (Original post by MonteCristo)
            I have applied the same logic on the few occasions when I've needed to place a single suture, yes. I personally haven't found patients to be very troubled by ABGs, although those I see usually only require a single stab, i.e. not serial ABGs. I would probably feel differently if expecting the same patient to undergo the procedure on multiple occasions.

            I often give patients the choice and most just tell me to get on with it. I've not thought about using an insulin syringe before (always just a blue needle) and will happily give that a try.
            See therein lies the problem. You are anaesthetising incorrectly. An insulin needle (they come already on the syringe of course) is 29G versus 22G for the blue needle. It is so tiny most patients don't even notice it, just a small sting from the 0.5ml lignocaine.
            I advice you try it for a week or so. See how your patietns feel about it, see if it adds much time for you etc and then you'll have a decent comparison.

            The one issue wardies have versus ED folk however is kit. Learn where it is on your ward, and do it on your ward. Either carry it with you or give up re rest of hospital because my experience of most (not all) ward nurses in late evening and at night is they don't know where stuff is kept and dont want to know.
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            Slight tangent but... My brother is an A&E reg and once claimed that there is no useful information to be gained from an ABG that you can't get from a VBG, and that the culture of requiring ABGs has very little basis in fact/need. He particularly highlighted COPD patients in A&E as an example where ABGs are cruel, unnecessary, and do nothing to inform practice. He refuses to do them. Any perspectives on this?


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            (Original post by Ghotay)
            Slight tangent but... My brother is an A&E reg and once claimed that there is no useful information to be gained from an ABG that you can't get from a VBG, and that the culture of requiring ABGs has very little basis in fact/need. He particularly highlighted COPD patients in A&E as an example where ABGs are cruel, unnecessary, and do nothing to inform practice. He refuses to do them. Any perspectives on this?
            So, he's definitely wrong - it is useful in some instances. But i suspect the instances he's thinking of i would agree with.

            I await being told how wrong I am by someone more knowledgeable but this is my perspective as someone who started as a paeds FY1 then moved to adults.

            Resp complaints are super common in paeds. Paediatricians are probably more experienced in respiratory complaints than A&E docs. Wheezey patients at risk of tiring is a big worry. Did i see a single patient ever have an ABG? No. Nor any other blood gas for a resp complaint. They went by clinical signs and obs. If someone looked like they weren't improving and were tiring... they were assumed to be critically unwell and put in HDU/ITU. So it was a bit of a surprise when i was moved to adults and told to do an ABG on an alert young adult with athma who had only just arrived to "see if they were tiring". And the thing is... i think the clinical assessment would end up overruling the ABG results anyway. I never really saw an example where it helped.

            My med school was actually very against doing ABGs in asthmatics, citing studies showing that young asthmatics often avoid coming to A&E until late because they were afraid of having an ABG (perhaps the LA debate comes back into play here...).

            I also always find it amusing when a colleague has a patient on oxygen. They then do an ABG and come in looking all proud saying 'thank god I did that ABG - their pO2 was 8! They must be really sick!".
            ...erm, the oxygen dissociation curve is such that your sats will not drop below 95ish if your pO2 is above 9ish. If your patient is on oxygen, and its well titrated with a good sats trace, obviously their pO2 is going to be low! If it was normal then they've got some weird haemoglobin thing going on which I'd be a lot more worried about!.

            However... pO2 is a useful prognostic marker in a range of diseases. This includes, for instance, sepsis (where pO2 was an identified as a key marker in the Sepsis-3 guideline) and pancreatitis (Glasgow pancreatitis prognostic score). I think its still pretty necessary in people who might need/are on BiPAP - they're just sufficiently sick to need closer monitoring, although I guess you could still argue its over-used and other monitoring with less frequent ABGs would be adequate.

            The outreach nurses in my old hospital were an absolute nightmare - every patient they saw with a resp complaint they wanted an ABG for, and couldn't do it themselves so would essentially drag the on call FY1 behind them who had to do all their procedures. Such ABGs were rarely truly needed.
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            (Original post by notespad)
            Are CBGs done as a heel prick (for babies?
            You can do them as a heel prick, but you can also use a big toe or a thumb, depending on how old the child is (as a rule, after the patient is about six months of age, it's best not to use heels for bloods).
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            (Original post by nexttime)
            The outreach nurses in my old hospital were an absolute nightmare - every patient they saw with a resp complaint they wanted an ABG for, and couldn't do it themselves so would essentially drag the on call FY1 behind them who had to do all their procedures. Such ABGs were rarely truly needed.
            Every single patient. Once on a patient who had a fall with epistaxis - ABG ??!
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            (Original post by Ghotay)
            Slight tangent but... My brother is an A&E reg and once claimed that there is no useful information to be gained from an ABG that you can't get from a VBG, and that the culture of requiring ABGs has very little basis in fact/need. He particularly highlighted COPD patients in A&E as an example where ABGs are cruel, unnecessary, and do nothing to inform practice. He refuses to do them. Any perspectives on this?


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            From an ICU perspective they are useful for initiating/managing ventilation, but those patients will all have an art line so no worries about multiple stabs. In the ED/acute medical setting I completely agree that too many are done, (particularly asthmatics, COPD and DKA where the PaO2 is even less relevant!) but I don't think I could say they're NEVER needed.
           
           
           
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