ABG Interpretation: Compensation and Mixed Disorders (Lesson 4)

A lecture discussing the phenomenon of physiologic compensation for derangements of acid-base balance, and how to use an understanding of compensation to identify the presence of mixed acid-base disorders.

[yannur]

After more than a decade!!! This channel is a miracle!! Thank you som much!! Just the shortcut is awesome by itself!

[omarsanduka]

By far the most informative, coherent video I've seen about ABG compensation. Thank you!

[StrongMed]

Although the PCO2 of 32 is lower than 40 (which would initially argue against a resp. acidosis), it is not nearly as low as predicted by the compensation equation. (Winter's formula predicts that the PCO2 in a metabolic acidosis will be approx. equal to (1.5 x HCO3) + 8, which in this case is 23.) In other words, if the resp. system was working normally, it would be doing some extreme hyperventilation in an attempt to counteract the extremely low pH from the metabolic acidosis.

[mc]

Thank you Erik your a true gentleman for allowing these learning resources to be shares around the world. The introductory music is fantastic too ☺

[drharveyshahnam]

one of the best lectures on acid-base I have come across on youtube

[sharonvaisberg]

REAL MVP. Literally crushed my cardio pulm unit in medical school because of you. The best

[ghaffasa]

Thank you very much for these lectures. Acid-base-physiology has always haunted me as one of my weaker points. Your videos however, have really helped to clarify the concepts!

[DocHemulin]

Hello Dr. Strong, I would like to note an exception to the statement you made regarding "compensation does not return the pH to normal".
"Chronic respiratory alkalosis when prolonged is an exception to this rule and
often returns the pH to a normal value. " (Harrison's 19th edition, ch. 66).

[StrongMed]

The converse of this is slightly incongruous, in that there can be "partial metabolic compensation" for a respiratory disorder if the respiratory process has not been going on for long enough for the kidneys to have completely adjusted their handling of H+ and HCO3- for the degree of respiratory-induced acid-base imbalance.

Hope this helps!

[laurentiu]

Difficult concept explained simply and clearly . Thank you .

[nu.wa.n]

For example 2, 12 is nowhere near 23. Is that a situation where the shortcut method is not useful?

[sunving]

Thank you Dr Strong, I listen to this second time.

[StrongMed]

In this case, the degree of hyperventilation is not extreme, but actually more modest. It's not uncommon for people to refer to this situation as "partial compensation", but I think that terminology is misleading since it under-emphasizes that there must be a primary respiratory disorder present in order for the respiratory compensation to not be complete. Sometimes, a resp. disorder that's labeled as "partial compensation" can actually be more acutely important than the metabolic process.

[darkdogisout]

Your answer will probably be: because it is more complicated then you think. Right?
My way of thinking about this problem is probably to superficial and needs adjusting.
Many thanks by the way for your effort to help the medical community.

[NaeemRiaz]

the shortcut method is really helpful.

[drnykterstein_]

at what time do we consider acute or chronic? Is over 24 hrs with the condition chronic? thanks

[basimali]

Hi Dr Eric. When evaluating compensation for metabolic disorders by looking at the last two digits of the pH and PaCO2 (shortcut method), how close do you think is 'close enough'? In the examples that you give in this video and when the problem has appropriate compensation, the last 2 digits of the pH and PaCO2 don't seem to differ by more than 2 numbers. But in later videos, even when they differ by up to 4 numbers (so eg: pH of 7.50 and PaCO2 of 54), this is still 'appropriate' compensation if calculated by the Winter's Formula.

[Linara]

01:32 I am not sure about the statement that "compensation does not return pH to normal".
How about partial and FULL compensation?

[bokbok-oosq]

Hello Dr Strong!
Thank you very much for helping us in medical studies! I really appreciate it!
The third exp of The fourth lesson of ABG interpretation is confusing me because i can not understand why The 2nd disorder is a metabolic alkalosis. I read all The answers that you gave to The other students but i still cant understand it. Is there any rules to follow to avoid my or our confusion?
Thank so much in advance and have a Nice weekend!

[ivanavujica]

Hi. How can we identify primary disorders if pH is normal? For example, pH is normal, pC02 is low, bicarbonate is low. Is it compensated respiratory alkalosis or compensated metabolic acidosis? Thank you!