Mannitol (Nursing)

00:00 Okay there's our friend, the nephron, again. You got the glomerulus all the way through where urine leaves the body. We put that up there again because now we want to talk about mannitol and this one is uniquely different than any of the other diuretics that we talked about. You won't give this one as often as you give furosemide or hydrochlorothiazide but it's got some pretty unique properties because most of it is not reabsorbed like the other drugs. So that's why mannitol is a little bit different. It stays in the nephron and it creates this osmotic force and has decreased passive reabsorption of water so the urine is increased. Okay, so what's different about this one? Is that it remains in the nephron and it creates this osmotic force and that's what ends up having the increased urine output. Now mannitol has to be given IV. It's considered an osmotic diuretic because of what it does to the osmotic force and we give it IV. Remember, most of the filtered drug remains in the nephron which is very unusual. So it increases the osmotic pressure in the lumen of the proximal tubule and the Loop of Henle that's why we have the increase in water diuresis. So, mannitol has some really unusual uses. We use it for elevated intracranial pressure. Now intracranial pressure is made up of 3 things; your brain, your cerebrospinal fluid, and blood. All that is encased in your skull. Right? And when one of those gets to be out of alignment, gets to be too much, you have intracranial pressure that starts to go up. The really danger of elevated intracranial pressure is that could cause brain death. Right? It can cause the pressure to be so great that your brain kind of squishes through the holes in your skull.

01:45 Mannitol is an old drug but it's still one we use to try to bring that elevated intracranial pressure down because if we can get fluid volume off, we're going to lower pressure and hopefully bring down that elevated intracranial pressure. We can also use it in low output acute renal failure. Hey, that's pretty cool. So if I'm in acute renal failure and I'm not putting out very much urine, mannitol is another drug we may try. It's also good for your eyes. So think about it.

02:12 Intracranial pressure, your eyes and low output acute renal failure. Now mannitol also has some risks because it causes so much fluid to move from inside the cells into the intravascular space, it will have a significant increase in circulatory volume. Okay, that sounds like a bunch of nursing terms. Let's break it down. My fluid can either be inside my cell or outside my cell. So when mannitol causes fluid to move from inside my cell into the intravascular space, I'm going to have a pretty big increase in circulatory volume. See that's why mannitol helps us in your brain too because we're moving fluid out of those brain cells and the other areas. So that's why mannitol causes this increase in volume. Now, that's a problem with somebody who has CHF. They're already volume overloaded or someone who has pulmonary edema. They've got this edema in their lung cells. So mannitol is used cautiously. We want to make sure they don't have a head injury and CHF going on at the same time. We'd really have to balance out the risks and benefits of that medication.