To All Students Interested in Medicine

hey y13 here, great idea for a thread. i think the patient might be suffering from ketoacidosis bc of the acidic blood ph and ketones in their urine (which would also explain why ph is so low even when co2 and hco3 levels are low). i remember that ketoacidosis is mostly due to diabetes but blood glucose is probably too low and i read that alcohol use causes elevated breathing rate which would also account for increased o2/ decreased co2 so i think the patient is suffering from alcoholic ketoacidosis.

^^^ just for you @ecolier

Since you are all off ... thought if any of you are keen to read some medicine before you start your degrees I could put a random clinical case on here each day and we could discuss. Helps me learn stuff too (I am a medic FYI). Any keen beans?

I've looked up what an ABG is and it says that it's a blood test to measure the acidity/pH/oxygen and carbon dioxide levels in the blood from an artery.
It's a way to see how well the lungs are working. Looking at the normal pH levels, this person's blood pH is too low but closer to neutral pH.. I think more co2 in the blood causes pH to be more acidic.
However, what's slightly confusing is that the O2 levels are too high (high partial pressure of oxygen) and co2 levels are too low (low partial pressure of carbon dioxide). So there's too much oxygen in the blood and not enough carbon dioxide.
I also think that the low HCo3 levels also contribute to the abnormal blood pH level as I believe HCo3- ions act as a ph buffer to prevent changes in pH. If there's not enough of these ions then pH can fluctuate, I think.
I'm really not sure about any of these suggestions as I've just looked at the data and tried to apply any knowledge I have from A level bio.

Hi there, I am a reapplicant from Ireland. Thank you so much for having this thread. I was considering whether one of the values, the bicarbonate levels, in particular, could explain the other values. A reduction in bicarbonate explains why the ph is lower than normal and could explain the low concentration of carbon dioxide, as bicarbonate is exhaled from the lungs as CO2.
This is also accompanied by elevated ketones, therefore, I suspect a case of diabetic ketoacidosis (I just read about it) which is a complication of diabetes.

It sounds like a great suggestion and tbh as a yr13 I'm not too sure on what it is exactly either. I don't think it can be something intrinsically wrong with the Hb just because the patient is quite old so if something like that was wrong surely he would've displayed symptoms earlier?

Isn't ketones in urine a sign of diabetes??? Though with the blood glucose level that low je suis stumped!

Maybe it's just that the patient is just suffering from some sort of hypoglycemia?

Sksksk I'd really want to find the answer myself but I'm pretty sure I won't be able to without a whole load of help!

hey a year 12 here - fantastic idea for a thread! We've just covered haemoglobin dissociation curve at school (over an online lesson!) and was fortunate enough to see an ABG carried out on work experience. Looking at figures, CO2 concentration in blood is lower than expected + partial pressure of oxygen a bit higher. Dissociation into H+ and HCO3- is not happening at the rate it needs to - so CO2 is not associating with haemoglobin? Maybe something intrinsically wrong with hb?

hey y13 here, great idea for a thread. i think the patient might be suffering from ketoacidosis bc of the acidic blood ph and ketones in their urine (which would also explain why ph is so low even when co2 and hco3 levels are low). i remember that ketoacidosis is mostly due to diabetes but blood glucose is probably too low and i read that alcohol use causes elevated breathing rate which would also account for increased o2/ decreased co2 so i think the patient is suffering from alcoholic ketoacidosis.

@HumblyBumbly so aren't HCO3 and pCO2 levels similar? I'm guessing the HCO3 is the CO2 being dissolved in the plasma at which point it makes me ask the question on why both including both numbers?

So now diabetic ketoacidosis:

this happens in people with type 1 diabetes typically. They do not have insulin so the body thinks glucose is very low, as if in starvation. So they do essentially the same as above (starvation mode). This is a very basic way of looking at it. Now you start building up ketones in your blood. And these bad boys make your blood more and more acidic (as in this case). Because your blood is acidic your body tries to respond by getting rid of carbon dioxide (because carbon dioxide increases H+ as we see here:

https://teachmephysiology.com/wp-content/uploads/2017/05/co2-transport-1024x505.jpg

and therefore lowers pH. These patients will be hyperventilating hence the low CO2 and low oxygen. We all know homeostasis is there to maintain physiological parameters within a narrow limit.

Now alcoholic ketoacidisos: this is slightly more complicated and actually involves more complex biochemistry. BUT ... essentially alcohol can be converted to ketones. Why is the glucose low? Often alcoholics will not eat regularly and may vomit food that they do eat, leading to episodes of starvation

ah so you don't always need potassium dichromate for ketones

However @Matthew Qurku is absolutely correct. This is alcoholic ketoacidosis. Well done I will explain both DKA and alcoholic ketoacidosis in more detail in my next post!

You've picked a very interesting case!

My question for you is, from the information given, why is this not euglycemic DKA.

now this is an interesting idea and I hadn't thought about it. A few reasons in my opinion as to why this is not as probable (although complicated for A-level students!). a) Euglycemic diabetic ketoacidosis is rare. b) nothing in the history suggests SGLT2 inhibitors which is one factor which might increase risk. Nor is diabetes even mentioned. c) the glucose in this case is actually low d) the cases of euglycaemic DKA I have heard of have very low bicarbonate (<10mmol/L).

Do you not think the distinction is as clear cut? I don't know that much about euglycaemic DKA so teach me!

It is complicated, but it is suggested by them above so if you're gonna say they were wrong better say why I'd just say 'you take a bit more history and she drinks 2.5 litres vodka per day' personally, no arguing with that

From what you have said though, I am not aware of a reason why it couldn't be. You also don't tell us how high ketones are - could easily be some mild starvation (especially with that glucose) plus any other metabolic cause of acidosis! Though we are getting into two-diagnosis territory here - very common irl , cruel in any question scenario!

Wrt the above: a) Alcoholic ketoacidosis is also rare b) Nothing in the history suggested alcohol! c) slightly low - I'm guessing it wouldn't be ruled out d) I've never actually seen one (you've seen multiple? wow), but I'm guessing that is not a rule

I have not actually seen any - I was saying cases I have heard of.

Either way I take your point the diagnosis is more complicated BUT !! I think the alcoholic ketoacidosis is more likely from what I said above but either way the exact diagnosis isn't that important in many ways. I kind of just wanted to show an ABG to them, because I think they are a cool use of their chemistry knowledge and applying it to physiological settings.

I agree with nexttime, there is really no reason why alcoholic ketoacidosis is more likely based on the details given.

I know you say nothing in the story suggests diabetes, but nothing in the story hints at alcohol use either - it most certainly would be mentioned in a med school or postgraduate exam so it seems a bit unfair not to give that detail in a question aimed at A Level students... Or you should accept the answer of euglycaemic DKA as correct as well, since several people did mention it

I agree with nexttime, there is really no reason why alcoholic ketoacidosis is more likely based on the details given.

I know you say nothing in the story suggests diabetes, but nothing in the story hints at alcohol use either - it most certainly would be mentioned in a med school or postgraduate exam so it seems a bit unfair not to give that detail in a question aimed at A Level students... Or you should accept the answer of euglycaemic DKA as correct as well, since several people did mention it

now this is an interesting idea and I hadn't thought about it. A few reasons in my opinion as to why this is not as probable (although complicated for A-level students!). a) Euglycemic diabetic ketoacidosis is rare. b) nothing in the history suggests SGLT2 inhibitors which is one factor which might increase risk. Nor is diabetes even mentioned. c) the glucose in this case is actually low d) the cases of euglycaemic DKA I have heard of have very low bicarbonate (<10mmol/L).

Do you not think the distinction is as clear cut? I don't know that much about euglycaemic DKA so teach me!