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It's just loading. Can you, can you see? Ok, I think we're live. Ok, good evening. Er, everyone. Thank you for joining um the first lecture of this Med Ed pathology lecture series. Uh My name is Dennis. I'm one of the colleagues, er, who's organized this series with my um colleague uh Ayo DEA, she's in the year above. Um And today's lecture is gonna be delivered by uh Piper Jackson. She's a final year medical student. Uh She won the Chemical Pathology Prize uh last year. So be rest assured that the content that's going to be delivered today is gonna be high yield um and very valuable. So I'll just hand over to Pippa now um to introduce the first lecture. Thank you. So, yeah, hi guys. Um As I said, I'm Pepper and I'm funny. Um So yeah, so today I'm doing half of Cath, if you have any questions throughout, like either put them in the chat or whatever, I can answer them throughout and then there'll be some time at the end as well for questions. Um and you can talk about Kath about general path about five as whatever you like or answer anything. So I don't feel like it's gotta be specifically che pa related. Yeah, so today in terms of Campath, this is what I'm gonna be covering. Um So it's not gonna be everything and it's not gonna be cos I think there's a Campath to talk um and it's not gonna be super, super in depth because there are gonna be like little bits that we're not going to cover, but this is the main stuff and it's all quite like the high yield stuff. Um So yeah, hopefully it will be useful for you guys. So first of we were talking about sodium fluid ba balance. First thing to get in your head is osmolality versus o osmolarity. It took me ages to get my head around this. Um It's kind of not that deep as to which is which cos they're essentially measuring the same thing. What's more important is to have an idea of the fact that there are two different things. Um But they should be vague, vaguely similar. Um Yeah, so you kind of your osmolality is more accurate because it is the actual measured um parameter and it's more accurate because if you imagine if you heat up a solution, so if you heat up a liter, it'll then go it become like larger, right? So it will become I know 1.1 L. And so it it changes, whereas a kilo is always a kilo regardless of the volume of it And so that's why osmolality is not accurate, but it's just harder to measure, which is why we often talk about osmolarity. OK. So thinking about osmolarity, this is the equation that my wants you to learn. And so this is the one that you need to make sure the E US and the osmolarity questions working out. The osmolarity questions are beautiful because they're basically free marks because if you look at the numbers, you can do the maths, it's just adding things up. Um But yeah, online you, you can sometimes see equations that are just two times sodium plus A plus glucose because I think sometimes the potassium is ignored because it's such a small number that it's just thought to be a bit irrelevant. Um But make sure you include the potassium in your exams because otherwise it will be wrong. Oh yeah. So we care about o minority so that we can calculate the gap, which is basically the difference between the Os Moity that you measure with the special machine and what you calculate based off of this equation. And basically, if it's high, it means that there's something in your blood that isn't, isn't like used in that formula. So it could be high sugars, high fats, high proteins, alcohols, they're the main ones. There are obviously weird and wacky other things, but these are the main ones and you're generally not asked what can cause a high osmolar gap. So I wouldn't be stress about learning too much about the causes of a raised osmolar gap. It's more about, can you do the maths, which I'm sure you all can. So, yeah, basically that's the first take home message just knowing how to calculate your osmolality. Um So we have ACP Q. So if you can rank from one to high, one to high, 1 to 5, what you would expect to have the highest and lowest osmolality, I think we don't, we only have a few CP QS and I'm sure Mire's already talked to you about the fact that they're not that deep. So don't stress it too much and we can talk through it in a minute if you guys want to put it into the chart. Maybe. So I don't know if you can shout out or not. Yeah. Does anyone know what the highest a morality or like what condition would have the highest of morality of the list? I'm just checking. Can you see the chart? I can, but I can't see that anyone's I II can see your response but I can't see anyone else. OK. So we have two responses. So we'll just go with that. So our highest osmolality will be your HHS um in the definition of HHS. Part of it is that your osmolality over 320 you will have profound dehydration. Your DKA is a very good second. Um They think about the main differences in the presentation between DK and HHS DK. They can be very dehydrated and they often are, but in HHS dehydration is the Hallmark sign. Um, yeah. Or you might expect them to be vomiting or, you know, abdo pain, that kind of thing as well. Um, but you were in, in HHS, they would be massively hyperglycemic, massively dehydrated. But a, like the ketones should be normal. The other ad is a very good second and then yeah, D I pneumonia si A DH. So with sa DH, you would expect your Osma to be, to be low. As that's again, that's kind of in the definition of the syndrome. Pneumonia can have S OAD H but it can just be normal and diabetes insipidus, you would expect it to be a bit, a bit dry. So you um osmolality would be a bit high but it wouldn't be anywhere near what you would see in HHS or DK. Does anybody have any questions about that? I think in the context of like time things, if you guys would have any questions, put them in the chat and I'll answer them as they come up or I'll answer them at the end. So moving on to our, it is to our sodium regulation. Basically, your, your sodium is controlled by two main parameters. So your blood volume and then your osmolality is controlled by your blood flow. You basically looking at your baroreceptors, um both in your atria and in your carotid sinus. And so if you have increased blood volume, there will be increased pressure in your atria and increased pressure in your across the sinuses. And so that will induce the production of A NP that's causing essentially reduce sodium concentration and reduce blood volume. Because if you remember, sodium regulation is basically about water regulation, that's what they really care about. Um Yeah, and then definitely looking at your osmolality, get a higher morality, I'm sure you guys will remember this from first year, you get increased and a release triggered in your hypothalamus, which then decreases your sodium concentration. And the lowest morality will increase your sodium by suppressing the A DH release. Now, it's important to note that there is a conflict in the role of ADH because it will increase your blood volume low but your osmolality um if you love, you expect your o will be high. But if your blood volume is low, a DH will both increase your, try to increase your blood volume, but also try to decrease your sodium. But in that kind of situation, the blood volume is more important. So kind of sometimes people can get caught out in that. But basically God volume is always more important.