I don't understand why mannitol would cause pulmonary edema. It seems counterintuitive to me.
It's because the increase in hydrostatic pressure overcomes the increase in osmotic pressure in the lung. This is most apparent in a case of CHF, where cardiac output is diminished. Everywhere else, water is leaving the interstitium to enter the vasculature; in the lungs this increased blood volume pushes water out into the lungs and causes edema.
I don't understand why mannitol would cause pulmonary edema. It seems counterintuitive to me.
In CHF, the increased hydrostatic pressure proximal to the left atrium causes transudation in the lungs. Although mannitol can act as a diuretic, it initially increases plasma volume due to its effects on elevating plasma oncotic pressure. Increased plasma volume --> increased left atrial preload in the face of decompensation that already occurred even at a lower preload --> increased LAP (PCWP) with further decompensation --> exacerbation of pulmonary venular transudation.
I just read in UW that in high doses it elevates the hydrostatic pressure by pulling water out of the cells
But it must first elevate oncotic pressure in order to pull water out of said cells.
My understanding is Mannitol is an osmotic diuretic-> increases plasma osmolarity->water and potassium come out of the interstitium& cells to compensate for this increase in osmolarity (wonder why potassium comes out)-> decrease in ICF+ increase in ECF(->if major increase in ECF-> increase in hydrostatic pressure-> pulm.edema).
Pls correct if its wrong
how would it increase oncotic pressure if the proteins are getting diluted?