Mannitol osmolarity effects

General:

• Mannitol is an Osmotic diuretic
• 6 carbon sugar
• Dose: 0.25-1.0 g/kg
• Filtered at the glomerulus, but does not get significant reabsorption in the proximal tubule. This osmotically prevents passive water reabsorption that would occur with the active Na+ reabsorption in the proximal tubule
• Rapidly acting, therefore this acutely raises plasma/extracellular osmolarity
• Leads to hyperosmolality, hyponatremia, hypokalemia.

Uses:

• Prophylaxis against ARF in high risk patients (rhabdomyolysis, massive trauma, hemolytic reactions, severe jaundice, cardiac/major vascular surgery)
• Transplant surgery
• Acute reduction of intraocular pressure
• Acute reduction of intracranial pressure/cerebral edema
• Forced diuresis to remove toxic substances (acute drug overdose)

Caution:

• Causes a transient and rapid intracellular to extracellular water shift
• This can cause fluid overload leading to CHF and pulmonary edema
• Transient hyponatremia
• Mild/moderate transient increase in plasma potassium
• Be careful giving large boluses too rapidly. May be advisable to give large bolus in divided doses over ½ hour or longer