Mannitol produces diuresis by-

Ans. is 'a' i.e., Osmotic effect Mannitol* It is a nonelectrolyte of low molecular weight that is pharmacologically inert.* It raises osmolarity of plasma and tubular fluid.* Blood viscosity is decreased.* Mannitol decreases tubular water and electrolyte reabsorption by -1. Due to osmotic effect, fluid is retained in the lumen of PT.2. Inhibits transport processes in thick ascending limb - most important cause of diuresis.3. Expands ECF (t intravascular volume) - draws water from the intracellular compartment - increases GFR and inhibits renin release.4. Increases renal blood flow, especially to medulla -> medullary hypertonicity is reduced - corticomedullary osmotic gradient is dissipated passive salt reabsortion is reduced.* Uses - Raised IOT (glaucoma), raised ICT, to maintain. GFR and urine flow in impending renal failure, and to counteract low osmolality of plasma/ECF due to rapid hemodialysis.* Contraindications - Acute tubular necrosis (ARF), anuria, pulmonary edema, Acute LVF, cerebral hemorrhage & edema.