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Old 12-13-2011
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Question How come we use Mannitol in shock!

pg 474 of FA 2011 version says that mannitol can be used in shock, how can this be? won't this kill the patient.
also what kind of urine is produced with mannitol use viz iso or hypertonic, what is the influence of mannitol use on plasma osmolarity.
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Old 12-14-2011
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I guess it is used in shock to prevent kidneys from being infarcted. In shock, flow to kidney is decreased and cuz of hypotension the Renal vessels vasoconstrict and further decreasing RBF and leading to infarction of kidney> CRF. but i am not too sure bout that, has someone got a better explanation??

It will cause the plasma osmolarity to increase! as u are the excess fluid is out of the system.
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Old 12-14-2011
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I forgot to add that when u have osmotic diarrhea, u lose hypotonic fluid, that explains the rise in plasma osmolarity
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Old 12-14-2011
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Default mannitol

It is used in shock cuz remmeber that in shock, you arent getting enough flow to the kindneys and one can develop prerenal azotemia and then acute renal failure so mannitol will keep the kidneys working by its osomotic diuretic properties.
Remember, when you push normal saline, only 1/3 of it stays in vessels, the rest goes to cells, extracellular-non-vessel areas, etc. By putting Mannitol or something similar in the vessels, you pull water back in (or keep it from leaving). By keeping enough volume availible, you can prevent the deeper parts of the kidney from beign damaged via vasoconstriction and lack of flow. Some diuresis is good, as massive kidney failure is a bad outcome.
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Old 12-14-2011
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@native doc

I'm an IMG and a praticing physician. While Mannitol can theoretically be used for the correction of hypovolemic shock (to a certain degree), its use is limited by pratical realities....seizures, death!

Think of 3 compartments (vascular, interstitial and intracellular) separated by 2 membranes (capillary membrane, cell membrane). Now imagine a patient with an IV infusion of mannitol, an osmotically active compound that rapidly equilibrates in both vascular and interstitial compartments bt lacks the ability to pass through the cell membrane into the intracellular compartment (the largest fluid compartment).

The end result is simple, rapid movement of water frm the ICF into the ECF (interstitium and vascular compartments) hence increasing ciculating blood volume. That's the theory!

In practice, an infusion of mannitol used this way would rapidly dehydrate cells include neurons in the CNS with acute increase in intracellular osmolarity that could trigger seizures...hence limiting its use in clinical pratice in the mgmt of shock.
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Old 04-20-2012
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Mannitol increases the tonicity of the ECF causing water to move out from the ICF especially from out of the brain. Otherwise dangerous cerebral edema would occur in the setting of trauma or shock.
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