What is the difference between metabolic acidosis and respirat...

Question

What is the difference between metabolic acidosis and respiratory acidosis? What can cause these conditions?

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next question. What can cause respiratory and metabolic alkalosis respectively. A hypoventilation, severe vomiting, B, hyperventilation, severe vomiting, C, both A and B or D. None of the above. So let's think about what our question is asking us about. It's asking us what will cause the condition of alkalosis, which would mean that the blood ph is too high, so too basic and asking us about what would cause respiratory alkalosis. What would cause metabolic alkalosis? Well, respiratory may be slightly simpler or more straightforward to think about. We recall that the level of carbon dioxide is what determines the blood Ph, carbon dioxide dissolves in fluid and it becomes carbonic acid combined with water. So the higher the level of carbon dioxide, the lower the ph, the blood will be more acidic with more carbon dioxide. We're talking about a situation where the Ph is too high. So we would then be talking about a low level of carbon dioxide in the blood. So we have questions asking us about hypoventilation or hyperventilation. Hypoventilation would be a slow breathing rate and hyperventilation, a fast breathing rate. Well, as you are breathing, you are eliminating carbon dioxide. So the fast breathing hyperventilation would cause a very rapid elimination of CO2 leading to low levels in the blood. So we know that choice. A hypoventilation cannot be correct because a slow breathing rate will lead to high co two levels leading to low ph. So that cannot be correct. And therefore, that also eliminates both A and B. So we have our cause of respiratory alkalosis, which is hyperventilation. We just need to check if part two of this question would lead to metabolic alkalosis or if we need our choice D none of the above. So now let's think about metabolic acidosis. Well, then we're thinking about how the body controls ph balance and that is by balancing hydrogen ions and bicarbonate ions. So the H plus HCO three minus balance. So anything that would throw that balance off and in this case, it would be a depletion of hydrogen levels, iron levels or a an increase in bicarbonate levels that would cause alkalosis. So our question or our answer choice B talks about severe vomiting. Well, in severe vomiting, we would see a loss of hydrogen ions, we would also have a loss of chloride ions that would be due to that loss of stomach acid. Well, right away, we'll see we were losing hydrogen ions which would result in a raise in the blood ph. However, that loss of chloride ions will also affect blood ph. And this one's a little more complicated. Um You kind of have to think through all these different steps of what's going on in the kidneys. And we need to recall that in the kidneys, chloride ions are reabsorbed in exchange for bicarbonate ions being secreted. So, if we have fewer chloride ions, we have less bicarbonate secretion. If less bicarbonate ions are being secreted, then blood levels of bicarbonate are elevated and of course, that causes blood ph to increase. So that's another contribution. You're losing the acidic H plus ions and you're retaining more bicarbonate ions. Both of those things increase blood ph. So severe vomiting will lead to metabolic acidosis. So we can cross out none of the above and choose choice B as our answer. And just in the interest of being super thorough here. And again, another reason why metabolic conditions can be so complicated. You also have volume depletion. In the case of severe vomiting, you're losing fluids. That volume depletion activates the RAAS pathway. In an attempt to maintain blood pressure. That pathway leads to increased sodium ion re absorption in the kidneys which because of the exchanges happening there leads to increased H plus secretion, also increased potassium secretion. So again, we're losing more hydrogen ions. Again, making the blood more basic and increased potassium secretion, low potassium levels due to increased potassium secretion contribute to alkalosis by causing increased acid secretion. So it's this whole kind of positive feedback loop where they all contribute to each other causing that blood ph to rise. So for multiple reasons, severe vomiting causes metabolic alkalosis. So once again, respiratory and metabolic alkalosis respectively are caused by choice. B hyperventilation and severe vomiting. See you in the next video.

What is the difference between metabolic acidosis and respiratory acidosis? What can cause these conditions?

Key Concepts

Metabolic Acidosis

Respiratory Acidosis

Causes and Mechanisms

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