How does mannitol cause transient volume expansion?

How does mannitol cause transient volume expansion?

Mannitol being an osmotically active agent draws fluid from the extravascular compartment into the vascular compartment. This causes transient volume expansion and may cause pulmonary edema if the cardiac or renal status is compromised. But if the renal status is good, this extra fluid is soon excreted as mannitol is an osmotic diuretic as well. This property of mannitol is used therapeutically to treat cerebral edema, though caution has to be exercised in those with co-existing renal or cardiac disease.