This drug is used for its osmotic properties to reduce acutely increased intracranial pressure, such as head trauma. Mannitol is often given in a bolus form until a more definitive treatment can be applied.
Mannitol is often used as an acute treatment in primary open angle glaucoma until a more definitive treatment can be used. This medication decreases intraocular pressure by decreasing vitreous humor volume. Mannitol does not cross the blood-ocular barrier and thus exerts oncotic pressure which dehydrates the vitreous.
As mannitol is an osmotic diuretic, it helps promote excretion of substances such as aspirin and barbiturates in overdose situations.
Mannitol is filtered by the kidney glomeruli, but is incapable of being reabsorbed from the renal tubule. This results in decreased water and Na+ reabsorption via its osmotic effect. Consequently, mannitol increases water and Na+ excretion, thereby decreasing extracellular fluid volume.
Mannitol increases tubular fluid osmolarity, which leads to increased Na+ and water flow through the collecting duct, resulting in increased urine flow.
This drug promotes fluid loss and can lead to dehydration if patients are not adequately monitored.
This drug is contraindicated in anuric patients secondary to renal disease. Mannitol does not influence urine production, only enhances existing urine output. If there is no production (as in ARF) you would have hyperosmotic plasma due to mannitol since it would be trapped in that compartment (and thus be of no benefit and possible harm).
Mannitol is contraindicated in CHF because this drug causes the retention of fluid in the plasma. It extracts water from the intracellular compartment and increases blood volume, which can worsen CHF and pulmonary edema.
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