Blood Gases

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futuremedic

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Hey all....I am a medic student currently trying to master Blood Gas Interpretation...anyone have any secrets that will help me to figure them out??
 
Welcome,

What part of se NE you from?
 
Here's a calculator to experiment with ABGs and Anion Gaps. One can not fully appreciate ABGs unless you are aware of the Anion Gap relationship. The site has a few other interesting calculators also.

http://www.medcalc.com/acidbase.html

This calculator shows you the relationship as you change the variables.
http://www.health.adelaide.edu.au/paed-anaes/javaman/Respiratory/a-b/AcidBase.html


Altitude calculator - Also great site to learn about Altitude situations.
http://www.altitude.org/calculators/oxygencalculator/oxygencalculator.htm


Good slide programs:

Interpretation of Arterial Blood Gases (66 slides)

http://www.lakesidepress.com/ABGinterpretation.ppt


Blood Gases in Ventilated Patients

http://www.lakesidepress.com/NagpurTalk2.ppt

Interpretation of Arterial Blood Gases - Powerpoint Presentation by Dr. Deopujari, India

http://www.lakesidepress.com/ABGinterpDrDeopujari.ppt


More:
DIAGNOSING ACID-BASE DISORDERS FROM SERUM ELECTROLYTES: THE ANION GAP AND THE BICARBONATE GAP

http://www.lakesidepress.com/pulmonary/ABG/bicarbgap.98.htm

The Differences Between PaO2, SaO2 and Oxygen Content.
http://www.lakesidepress.com/pulmonary/ABG/PO2.htm

Diagnosing Mixed Acid-Base Disorders
http://www.lakesidepress.com/pulmonary/ABG/MixedAB.htm


It might be wise to start first with the links in the earlier posts.
 
VentMedic said:
Here's a calculator to experiment with ABGs and Anion Gaps. One can not fully appreciate ABGs unless you are aware of the Anion Gap relationship. The site has a few other interesting calculators also.

http://www.medcalc.com/acidbase.html

This calculator shows you the relationship as you change the variables.
http://www.health.adelaide.edu.au/paed-anaes/javaman/Respiratory/a-b/AcidBase.html


Altitude calculator - Also great site to learn about Altitude situations.
http://www.altitude.org/calculators/oxygencalculator/oxygencalculator.htm


Good slide programs:

Interpretation of Arterial Blood Gases (66 slides)

http://www.lakesidepress.com/ABGinterpretation.ppt


Blood Gases in Ventilated Patients

http://www.lakesidepress.com/NagpurTalk2.ppt

Interpretation of Arterial Blood Gases - Powerpoint Presentation by Dr. Deopujari, India

http://www.lakesidepress.com/ABGinterpDrDeopujari.ppt


More:
DIAGNOSING ACID-BASE DISORDERS FROM SERUM ELECTROLYTES: THE ANION GAP AND THE BICARBONATE GAP

http://www.lakesidepress.com/pulmonary/ABG/bicarbgap.98.htm

The Differences Between PaO2, SaO2 and Oxygen Content.
http://www.lakesidepress.com/pulmonary/ABG/PO2.htm

Diagnosing Mixed Acid-Base Disorders
http://www.lakesidepress.com/pulmonary/ABG/MixedAB.htm


It might be wise to start first with the links in the earlier posts.
Click to expand...


Thanks so much for all of these...hopefully I will be the master when I am done looking at them :)
 
Start with MMiz and Rid's links.

I like to give people a little more to the story than what is required just to demonstrate that the world of medicine has an unlimited supply of knowledge to be acquired. What may appear to be a single simple topic can usually be taken to greater depths. This is my way of showing that for a subject such as ABGs, that is barely skimmed in a decent overview during Paramedic school, can be much more complex. It is also not to be thought of as a single diagnostic test but used with other clinical assessments and lab values to form another piece of the body's puzzle of processes.
 
Awww.. the Anion Gap! My students will attest that I make them aware of the seriousness of such lab values, while performing clinicals in the ICU and CCU settings. Unfortunately, we in EMS do not have such in hand presume it must not be worthy for assessment and treatment modalities. Unfortunately, this just proves the point EMS is very ignorant in patient care.

As well, not just for ABG's but metabolism.. i.e. patient was ordered Demerol for analgesics. I required the Paramedic student to research the anion gap levels since the patient liver enzymes was off the chart as well as BUN, Creatinine, etc.. Again, understanding the break down and excretion of the med would not occur due to disease process. After research the student asked for a different analgesic and was given a new order.. lesson learned and as well a physician learned not all of those in ambulances are ambulance drivers.

R/r 911
 
Thank you all for your responses...I am going to jump in and master these!! I appreciate all of the comments and links I recieved. I want to be a great Medic when I am done so I will definitely delve in a little deeper than required.
 
We are just getting into this and it really opened my eyes to alot of things I was ignorant of. Are these ABG's normally just looked at on charts when you are transporting patients, so you will know what was/is going on with them?
 
I do one or more long distance transports a month. I read the chart that is included for the hospital. It is terrific because it gives me a much more complete picture of the patient. Obviously, on the 911 runs, which are 99% of my work, I can't do this. I will often get information on various values, etc. from the ED after the fact.
 
Obtaining Blood Gas in the Field

On the critical care inter-facility calls we get where the patient is on the vent when we arrive, we typically get a gas before removing them from the hospital vent, then obtain a gas 5-10 minutes after switching to the transport vent. We also will do repeat gases as necessary to evaluate the how effective our vent setting are and what impact we are having on the respiratory side of the patient's chemistry.

It amazes me how many hospitals will sit on a terrible blood gas without intervention, only to have us arrive and hand us the terrible lab values as if nothing is wrong.

The only reason I throw this info out there is to inform you guys, don't assume that the gas is ok just because it is documented and the staff acts as if it is not a problem.

Anyway, we use the i Stat with an EG-7 cartridge to run CBG, ABG, and VBG values. As far as I know, this is the only tool used for these tests in the field. There may be others, but I think this is the standard.
 
WTEngel said:
It amazes me how many hospitals will sit on a terrible blood gas without intervention, only to have us arrive and hand us the terrible lab values as if nothing is wrong.
Click to expand...

There are reasons why the ABGs don't look "normal" at the hospital.

The protocol that they are using may allow for a PaO2 of 55 mgHg. The PaCO2 may also be allowed to climb and the pH may be acceptable to 7.20. They may also realize the limitations of their technology (ventilator) as should you especially with a transport ventilator and the damage it can do by obtaining the settings to "make normal" a blood gas. Thus, that could be part of the reason for the transfer with allowance for "abnormal" ABGs to get to a facility that offers advanced technology for safer correction.

Buffering may not be advisable depending on whether it is gap or nongap associated. NaHCO3 may also not be advised depending on Sodium level and glucose instability may leave our Tham as an option. Unless you are running other cartridges on your iSTAT or take careful notes of recent hospital labs and do not have a long transport time, you probably shouldn't be screwing around too much with things you can not adequately monitor.

Also, getting an ABG when you know you are switching to your machine is reduntant and causes the patient considerable pain if there is no A-line and it is very costly. Match the MVs and know the flow capability of your ventilator.

The iSTAT is not the only POC machine but so far others have not done the necessary studies for out of hospital situations. Consider yourself lucky to have it if you are not hospital based because few labs like to monitor Paramedics for compliance and ambulance services don't like to fork out the serious money for their own lab license as well as the responsibilty that goes with it.
 
There is a difference between an abnormal blood gas that is allowable, and one that is fixable with intervention, and no intervention is taken. In my previous post, I was referring to the latter, not the former.

As far as repeat blood gases, if we anticipate getting multiple blood gases we will do VBG or CBG, not stick the patient multiple times for ABGs. I find comparing gases pre and post vent change is valuable, particularly if we intend to change the vent settings from what the referral has set.

We are hospital based, and our transport times range from 20 minutes, all the way to 12 hours or longer. We transport locally, regionally, nationally and internationally.

Being a critical care team, we typically try to get the patient on the right track and stabilized before we leave the hospital. That being said, we have the training and experience to make those decisions. I wouldn't advise anyone with limited vent knowledge or experience to decide that they don't like the patient's gas and change the prescribed settings...
 
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WTEngel said:
There is a difference between an abnormal blood gas that is allowable, and one that is fixable with intervention, and no intervention is taken. In my previous post, I was referring to the latter, not the former.
++++++++++++++++++++++++++++++++++
Being a critical care team, we typically try to get the patient on the right track and stabilized before we leave the hospital. That being said, we have the training and experience to make those decisions. I wouldn't advise anyone with limited vent knowledge or experience to decide that they don't like the patient's gas and change the prescribed settings...
Click to expand...

Ventilator knowledge is just one part of it. The hemodynamics and lab values play a big part which is why ABG values are ran "abnormal" until other situations can be stabilized and not because the other hospital is lazy or stupid. One can not hit an ARDs protocol with a PEEP of 25 cmH20 unless you have the pressors and fluids to support the BP MAP. Since few transport vents give Pplat, you may not know when you are at a danger point of pressure. If the hospital's technology is not the latest and greatest, they may be cautious to attempt to hit the serious settings. And, few if any transport ventilators should be trusted to "correct" and do an ARDS protocols safely. As well, if you are running it in combo with a sepsis protocol, you will have to support the SvO2.

I hope you at least have an RN as a partner who has ICU experience.
 
We have an RN, RT, and sometimes a physician. We do the best with what we have...(tongue firmly in cheek)

Adjusting vent settings isn't to be taken lightly, and is always a gradual process. Just like you said, the technology of the vent doesn't always support the outcomes you are trying to achieve, also taking into account what factors the human body can tolerate. All in all, if it isn't broken (or in some cases, SERIOUSLY broken) you don't have to fix it.

All things being equal, this conversation is somewhat moot as 95% of the readers in this thread, while they may be aware of the topics we are discussing, probably won't be doing anything along the lines of what we are talking about. It is great to have conversations like this though...I always enjoy listening to other practitioners, and I definitely appreciate your viewpoint as an RT with EMS knowledge...
 
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