How Does Furosemide Work? Understanding Loop Diuretics

hi this is tom from zero finals calm in this video I'm going to be explaining how loop diuretics like frozen mine work on the kidneys to help remove a lot of fluid from the body so let's jump straight in loop diuretics are powerful diuretics that are used to stimulate the kidneys to remove sodium and water from the body and they do this by acting on the loop of Henle in the nephron of the kidneys which is why they called loop diuretics and there's two examples fruisé amide and bumetanide and the indications for these medication are to reduce the amount of water in the body which is a very useful thing to be able to do in patients with congestive cardiac failure pond ridhima peripheral edema renal failure and hypertension so the main indications are edema and resistant hypertension so let's go through the mechanism of action firstly in order to understand how loop diuretics work we need to have a basic understanding of some of the functions of the kidney so to briefly go through those the kidney is made up of about 1 million tiny tubes called nephrons and these nephrons are responsible for filtering and balancing fluid and electrolytes between the blood and the urine now the nephron consists of five main landmarks that you need to be aware of the glomerulus the proximal convoluted tubule the loop of Henle the distal convoluted tubule and the collecting duct and the glomerulus and the convoluted tubules are up in the cortex of the kidney and the loop of Henle and the collecting duct passed down into the medulla of the kidney how it works is water and small molecules are filtered from the blood into what we call the filtrate in the glomerulus and then varying amounts of water and molecules are reabsorbed from the filtrate into the blood along the tubules loop of Henle and collecting ducts and what's left and the filtrate becomes the urine for the purpose of understanding loop diuretics we're most interested in the loop of Henle the loop of Henle is a key area where water is balanced between the blood and the urine a large amount of sodium and water are filtered from the filtrate into the blood in the loop of Henle it consists of a thin descending loop where the filtrate is flowing downwards and a thick ascending lis where the filtrate is flowing upwards there's also a small portion at the bottom of the ascending loop that's thin but don't worry about this part as it doesn't do very much the thick ascending loop contains columnar epithelial cells that tightly packed together making them impermeable to water and they contain loads of mitochondria to generate lots of energy the cells have a co-transporter molecule on the luminal side or the side of the filtrate that uses energy to actively transport sodium potassium and to chloride molecules out of the filtrate these ions then pass out the other side of the cell into the interstitial fluid of the medulla and create a high concentration of solutes in this area so as the filtrate enters the loop of Henle it's isotonic which means it has equal concentration between the solutes in the blood and the filtrate as it flows down the descending loop of Henle it enters the medulla where remember that interstitial fluid has a high concentration of sodium and other solids that have been pumped out of the ascending loop the descending loop has squamous cells lining its wall and these are very permeable to water so water flows by osmosis from the area of low concentration of solids in the filtrate to the area of high concentration of solids and the interstitial fluid of the medulla this results in the filtrate becoming more concentrated as it loses water on the way down the descending loop and then becoming less concentrated as it loses sodium and potassium and chloride as they're pumped out in the ascending loop the overall effect of the loop of Henle is that sodium potassium and chloride in water are removed from the urine and reabsorbed into the blood this complex system of secreting solutes from the thick ascending loop to draw water out of the thin descending loop is called the counter-current multiplier the loop of Henle is responsible for reabsorbing about 20% of the filtered sodium and 15% of the filtered water out of the filtrate and back into the blood and loop diuretics like freeze amide and bumetanide work by blocking the function of the membrane co-transporter protein in the cells of the thick ascending loop so what they do is they prevent sodium from being pumped out of the filtrate into the interstitial fluid of the medulla of the kidney and as a result there's a lower concentration of sodium and other solutes in the interstitial fluid and so water is not drawn out of the descending loop and remains in the filtrate so the overall effect is that more sodium potassium and water remain in the filtrate and get released into the urine and they're really powerful Doretta 'kz that can prevent the reabsorption of 20% of the filtered sodium and 15% of the filtered water which results in a significant increase in the output of water in the urine so a little bit of practical advice they start working within an hour if you give them orally and they actually start working within five minutes with IV freeze amide so they're really effective in acute pulmonary edema and acute heart failure and the effects lasts about six hours it's worth giving them earlier in the day because if you give them later at night they're going to be passing urine a lot and it will affect their sleep and it can increase the risk of things like Falls if you give them to an elderly person that's then getting up in the night to go and pass urine there's a few notable adverse effects they obviously drop the potassium level in the blood and cause hypokalemia because it's being excreted in the urine they can cause hypotension or low blood pressure because of the reduced circulating volume they can cause an acute kidney injury they can cause you're near attention where the outflow is a bit restricted just because it's producing so much more urine that can't be passed quick enough so you end up with large amount of urine retention it can actually worsen diabetic control and cause hyperglycemia can exacerbate gout and they have been known to cause ototoxicity or damage to the inner ear and finally a few cautions and contraindications use with caution in hepatic encephalopathy patients with hypokalemia patients with hyponatremia dehydrated patients or hypovolemic patients and in patients who are on lithium treatment it can increase the lithium level in the blood so it's worth being aware of that if you start to use loop diuretics in these patients so thanks for watching I hope you found this video helpful if you did don't forget there's plenty of other resources on the zero to finals website including loads and loads of notes on various different topics that you might cover in medical school with specially made illustrations there's also a whole test section where you can find loads of questions to test your knowledge and see where you're up to in preparation for your exams there's also a blog where I share a lot of my ideas about a career in medicine and tips on how to have success as a doctor and if you want to help me out on YouTube you can always leave me a thumbs up give me a comment or even subscribe to the channel so that you can find out when the next videos are coming out so I'll see you again soon

Channel: Zero To Finals

Views: 140,574

Rating: 4.952723 out of 5

Keywords: medical, education, medicine, doctor, furosemide, kidney, heart failure, renal, cardiology, diuretics, bumetanide

Id: 5k5btYZTKhQ

Length: 8min 39sec (519 seconds)

Published: Wed Jan 16 2019