A patient is admitted to the intensive care unit after sustaining a closed head injury. The physician orders mannitol IV. The nurse would expect which of the following after administration of mannitol?

Increased urinary output


• Mannitol is an osmotic diuretic. It makes the blood serum hypertonic, which pulls fluid from the intracellular (and intracranial) space to balance it out. This, in turn, increases the osmotic pressure of the glomerular filtrate, inhibiting reabsorption of water and electrolytes, so the patient eliminates excess fluid through urination. The therapeutic effect is decreased cerebral edema and decreased intracranial pressure.

• Diuresis and reduced intracranial pressure (ICP) should begin 30-60 minutes after IV administration as fluid is pulled into the vascular space.

• Effectiveness is evaluated by monitoring intracranial pressure (which should decrease) and urinary output (which should increase).

• Mannitol is contraindicated in patients with dehydration, anuria, active intracranial bleeding, or severe pulmonary edema or congestion.

• Adverse effects may include headache, pulmonary edema, tachycardia, thirst, nausea, hyper or hypokalemia, hyper or hyponatremia, and transient volume expansion.

• Mannitol does not affect WBC count or body temperature. 

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