Ep 28 Acid Base


[audio:28_AcidBase.mp3] (43:20) This week Ron did his practical testing – ET, Combitube, IV, Patient Assessment Medical and we talk about that, including answering some listener questions about testing. Ron asks Kelly, “What are vitals?” and the answer is an interesting discussion. Ron’s medical scenarios was something he hadn’t studied since Basic. He could remember what it meant and how to treat it but not the name. And he got a little creative in the treatment.

Acid/Base lecture was the last lecture Ron had and the hosts talk about how Acid/Base works.

ROME = Respiratory Opposite Metabolic Equal

Memorize the normals:
pH 7.35 – 7.45
PaCO3 35-45 mmHg
HCO3 22 – 26 mEq/mL

Remember the 3 question algorithm:
1. Is the pH acidosis or alkalosis?
2. If PaCO3 is high it is respiratory acidosis, if it is low it is respiratory alkalosis, if normal it isn’t respiratory.
3. If it isn’t respiratory from step 2, its metabolic. If HCO3 is low, it is metabolic acidosis, if HCO3 is high it is metabolic alkalosis.

If the opposite one (PaCO3 vs HCO3) is in the other direction, then it is compensated.

Mean Arterial Pressure

MAP = Diastolic Pressure + ( 1/3 Pulse Pressure )

Listener Questions
Flo sent us 3 questions related to ep 26
– Why is an accurate BP so important? It smore of a trend thing I though, and generally “is the patient normo, hypo or hypertensive.”. Does it really matter if the patient has a BP of 130/90 or ?2140/8?

– When is a pre-hospital IV indicated? Some parameds here are just plain lazy, and never do one. I had a phase where I cannulated nearly everything that moved. I know there are pros and cons in both directions, but what would you say is best practice?

– last but not least – do you have any links to the studies about paramedics leaving patients at home, that would be interesting to read up, and to present to some colleagues who really like to indulge in such practices. Always good to back up your statements with hard facts… – Flo

Also found out last night(12/9) that I will be taking the practical portion of the nation registry exam next thursday (12/16) when I come to lab. I have been watching on youtube various vids of the stations. Is there any other advise you or Kelly can give me that could help me out next thursday?? – KJ Reed

Rogue Medic – purveyor of fine EMS research.
The Missing Protocol by Denise H Graham – out of print book.
House of God – book

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  • Excellent! Acid Base balance on on this week for me at uni 🙂

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  • Kj_reed

    Thanks guys for the good advise about taking my EMT-B national registry practical exam tommorow. I will let you know how I do. Looking forward to the email from Kelly about the other tips.

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  • Wee… acid base.

    There’s a few other things to consider also. Not only is there compensation, but this isn’t a one or the other thing. The mixed disorders are a fun little puzzle to work out because you can have a patient who has an anion gap metabolic acidosis, in addition to either a metabolic acidosis OR alkalosis, and that can be on top of a respiratory acidosis or alkalosis, and if you have a blood gas (which, admittedly, most paramedics don’t), you can work through it based just on the lab values, but the HPI can really tell just as much.

    Mean arterial pressure = 1/3 systolic + 2/3 diastolic OR 1/3 pulse pressure+ diastolic

    The way I calculate MAP is I just add systolic+diastolic+diastolic and divide by 3. To make it simple, just round to the nearest number divisible by 3. As an example,


    280 isn’t divisible by 3 (2+8+0=10. 10 isn’t divisible by 3), so go down to 279 (2+7+9=18. 18 is divisible by 3)

    279/3= 93. If you really want to, you rounded down by 1, so add 1/3 to get 93.333 if you want to be 100% accurate.

  • I’ll take a second to defend odd numbers for BPs even though I don’t use them just because that’s the convention for taking a blood pressure.

    Some clocks only have the hour marks, do you report time only in increments of 5 minutes? Does your car speedometer have a mark for every MPH, or do you estimate between the lines and say you’re going 62 instead of 60 MPH? As such, if the first Korotkoff’s sound is between two notches, is it really wrong to say, “well, it’s towards the middle, it’s 119 mmHg.”

    More importantly, though, does it really matter? Most cuffs have a margin of error of +/-3 mmHg. So a systolic of 120 can be anywhere between 117-123. More importantly, that means that anything less than a change of 6 mmHg can be attributed to error. After all, if a reading at 120 can actually be 117 (-3 mmHg)) (and this is assuming that you’re (generic “you”) taking a BP perfectly. I’ll be honest, I probably go faster than I should and I’ve tweaked the process a little bit besides that), a reading of 114 can ALSO be from the same reading of 117 (114+3).

    So, is an odd number BP wrong? I wouldn’t necessarily say “yes”, but I would agree that anyone not following the convention of using even numbers is more likely not doing so because they don’t know how to take a blood pressure until proven otherwise.

  • Kj_reed

    Just to let you know, I passed my national registry practical exam!!! Thanks again for the great advise. Merry Christmas guys!!

  • Cguiles

    Kelly mentions a “how-to” document on doing a medical patient history in this episode, and mentions he will send it to Ron for posting.  Could you please do that? Thanks!

  • Cguiles, Kelly mentions a patient assessment how-to lesson he wrote
    that is part of the things you get for signing up for our email list.
    Sign up in the right hand side bar and it will be sent to you along
    with some study tips I wrote.