Renal Tubular Acidosis: Types & Acid-Base Summary

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.