00:01
Of course you can have a metabolic acidosis without an elevated plasma ion gap.
00:07
And some of the best examples of those happen in the kidney.
00:10
These are renal tubular acidosis of which there are three types that we need to discuss;
type I, type II and type IV.
00:19
To compare these, the best thing to do is to think about, where does the problem lie?
It just so happens that type I renal tubular acidosis is a problem with acid secretion.
00:31
While type II renal tubular acidosis is impaired bicarbonate reabsorption.
00:37
And type IV is also impaired acid secretion.
00:41
If you can keep these as straight as possible,
you'll hopefully be able to better diagnose what your renal tubular acidosis might be.
00:51
So, I and IV impaired acid secretion, type II bicarbonate reabsorption.
00:57
The disorders that are associated with these can be numerous, many of them involve some genetic disorder.
01:05
Rheumatoid arthritis is oftentimes associated with type I renal tubular acidosis.
01:11
Some drugs such as carbonic anhydrase inhibitors are associated with type II renal tubular acidosis.
01:19
And for type III renal tubular acidosis,
Addison's disease is a great example of trying to tie those together to a clinical condition.
01:28
All of them will respond with a renal tubular acidosis is a metabolic acidosis.
01:37
You notice we didn't mention type III right? You won't see it.
01:42
To summarize the acid-based disturbances, we can utilize this type of a chart.
01:50
Our respiratory acidosis always involves a decrease in pH,
a small increase in bicarb and a large increase in carbon dioxide.
02:06
Our respiratory alkalosis is an increase in pH,
a small decrease in bicarb and a large decrease in CO2.
02:18
Metabolic acidosis is a decrease in pH, a large change in bicarb with no change in CO2.
02:30
Our metabolic alkalosis is an increase in pH, a large increase in bicarb with really no change in PCO2.
02:40
The other thing to keep in mind with summarizing these acid-base disorders,
you have an initial disorder and then you might have a response to it.
02:52
If you think about the diagrams, it will always help you try to predict what the compensation is gonna be.
03:00
So, you have your four primary disorders that we just covered in the table,
you have a respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis.
03:12
How are you gonna try to fix these problems?
Well a partial fix usually involves the opposite system so if you have a respiratory acidosis,
you try to fix it with a metabolic alkalosis.
03:28
If you have a metabolic acidosis, you try to fix it with a respiratory alkalosis.
03:35
If you have a metabolic alkalosis, you try to fix it with a respiratory acidosis.
03:41
And finally, if you have a respiratory alkalosis, you try to fix it with a metabolic acidosis.
03:50
Partial compensation means you are moving your pH back towards normal,
but you may not have reached normal yet.
04:02
Once you reach normal, it's called perfectly compensated.
04:06
I would like to say that we usually become perfectly compensated, but life is not perfect.
04:13
Usually, you partially compensate and eventually are trying to move back to normal ranges
and often times, you never get there. But you're trying to do that process.
04:25
The last type of disorder that I'm just going to bring up as a problem
that happens is if the disorders are mixed.
04:34
Mixed or compound disturbances mean that you have more than one problem
and these are very serious conditions, a type when you could have a respiratory acidosis
and then metabolic acidosis at the same time.
04:50
Those are very hard to fix because both systems are moving pH
in the same way just like if you had a metabolic alkalosis with a respiratory alkalosis at the same time.
05:07
Again, very hard to fix because you have multiple compound problems. Okay.
05:16
Here we have another example of an arterial blood gas.
05:20
In this case, we're gonna have a pH of 7.25, a bicarbonate of 10 mEq/L
and a carbon dioxide partial pressure of 55 mmHg in the arterial blood.
05:35
So if we start off with the acid-based box, what is this gonna look like?
Red gnome for acidity. Also a red gnome because the bicarb value is below 22.
05:50
And finally, a third red gnome because the partial pressure of carbon dioxide is above 48.
05:58
Now, here we have a very special, special, special time in where we have three gnomes on the same side of the box.
06:08
Remember, we normally name things if you have two gnomes on the side of the box
such as a metabolic acidosis or a respiratory acidosis.
06:17
In this case, all three gnomes are there.
06:20
This is a mixed disorder, meaning that the acidosis is being caused
both from a metabolic reason and a respiratory reason.
06:31
Let's take another example. Here, we have an arterial blood gas of 7.5, a bicarb of 35 mEq/L
and a carbon dioxide partial pressure of 25 mmHg in the arterial blood.
06:48
Okay, let's fill in our acid-based box here.
06:51
We have a blue gnome here for an alkalotic condition.
06:56
We have a blue gnome because our bicarb level is above 28.
07:04
And finally, another blue gnome because our PaCO2 is below 32.
07:13
Again, special, special, special conditions here, you have three gnomes on the same side.
07:20
Therefore, this is another example of a mixed disorder,
meaning that you have two things that are both operating to move pH to a higher level,
so multiple reasons, both metabolic and respiratory that is causing this particular alkalosis.