Acid Base Balance

Acid base balance can be tricky...start with the basics

Ex. 1

pH 7.28

PCO2 66

HCO3 24

Normal values

pH 7.35-7.45

PCO2 35-45

HCO3 22-26

For simplicity, I am ignoring both PO2 and base excess/deficit.

Notice that in example 1, the pH is lower than normal. Anytime the pH is below normal, this means we have an acidosis. But, what kind? Look at the next bit of data. PCO2 is higher. What does this mean? The body is retaining CO2 which is considered an acid. Now look at the bicarb (HCO3).

It is normal. What you are looking at is an uncompensated respiratory acidosis. Why? The lungs eliminate CO2 via expiration. Through a complicated process, the kidneys can neutralize the acid, however this takes some time. I won't confuse you with details or the complex equations this entails. It is considered uncompensated because there is, at this time, nothing going on in the body to correct the acidosis

Ex. 2

pH 7.52

PCO2 38

HCO3 32

Ok, remembering normal values, this pH is above normal. Therefore it is alkalotic. The PCO2 is within normal limits. However, the HCO3 or bicarb is above normal. So, you are looking at an uncompensated metabolic alkalosis. Why? It is metabolic because the origin cannot be the lungs as the PCO2 is normal. It is uncompensated because the lungs are not "blowing off" CO2 that would be broken down from HCO3.

These are the most basic, simplified concepts. I know there are some acronyms out there that might help you. I learned the hard way though. You'll also need to study mixed conditions and partial compensation to gain full understanding. Keep practicing and you'll get it. Applying this to disease processes of your patients will also help it to "click".

Thank you sooooo much I have read and re-read this :)

Def helpful

I am preping for my nclex and this is my hardest thing!!!:banghead:I thought Pharm would be bad for me but I hope I dont get many questions on this!!!wish me luck

You can also remember the acronym ROME.

R=Respiratory O=Opposite (meaning that if your PAO2 and pH are of opposite values, you have a resp problem) M=Metabolic E=Equal (meaning that if your values are equal, both inc or both dec, then you have metabolic prob).

Then, to remember whether it is acidic or alkaline (base) look at the pH scale and know it goes 0-10 or 1-10 (I am half way asleep), and dependent on what side of the scale your value is on (with normal pH being 7.35-7.45 for adults and 7.36-7.44 for Pedi) tells you acid or base. A=acid B=base. They go in alphabetical order 7.45 is B for base. (It may make more sense if you draw it out!!)

I hope I did not confuse you more!!!

"You can also remember the acronym ROME. "

OMG I loveeeee this. I have to say these little tricks have saved my butt during exams lol.

Hi. I am having trouble with acid base balance also! It deffinately not coming easy for me. A lot of the replies posted really helped but i have another question that i did not see answered...

Can someone explain pH. I know acid, neutral, base lines but do not understand what blood pH is? And why decreasing carbonic acid would raise blood pH? I think im missing some points on this subject. Anything you know related to acid base balance please simplify for me........:)

thanks in advance nUrSeS:redbeathe:heartbeat:redbeathe:heartbeat....................................................................................................

rebecca...

I made a pretty lengthy post in THIS THREAD on how to read and interpret ABG's (it's post #19!)

Hopefully it helps!