ADVERSE EFFECTS

The major adverse effects of mannitol include:

• Hyponatremia/hypernatremia. Osmotic agents are associated with an initial phase of hyponatremia, which results from the systemic efflux of intracellular fluid in response to extracellular hyperosmolality (“pseudohyponatremia”). As free water is excreted with mannitol in the urine, hypernatremia follows, which can cause mental status changes, headache, lethargy, and nausea.
  
• Hyperkalemic acidosis. As water is drawn out of cells, the intracellular concentrations of potassium and protons can rise, prompting their efflux through membrane channels. Hyperkalemic acidosis may persist in patients with poor renal function, who cannot eliminate the excess extracellular potassium or protons.
  
• Pulmonary edema owing to the expansion of extracellular volume