mannitol induced "rebound" increase in ICP

Q: How mannitol can induce a "rebound" increase in Intra Cranial Pressure (ICP)?

Answer:  Mannitol is the most commonly used osmotic diuretic in neurosurgical ICUs to reduce ICP. It is frequently given every six to eight hours. When given in repeated doses, mannitol may enter the brain through a damaged blood-brain barrier and reverses the osmotic gradient resulting in a "rebound" increase in ICP. Mannitol therapy can be monitored or curtailed when serum sodium goes >150 mEq, serum osmolality rises >320 mOsm, or there is any evidence of evolving acute tubular necrosis (ATN). Also, mannitol can acutely drop systemic blood pressure resulting in decreased cerebral perfusion pressure (CPP).

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References:

1. Jafar JJ, Johns LM, Mullan SF. The effect of mannitol on cerebral blood flow. J Neurosurg 1986; 64:754. 

2. Kaufmann AM, Cardoso ER. Aggravation of vasogenic cerebral edema by multiple-dose mannitol. J Neurosurg 1992; 77:584.