**Core Concept**
The management of increased intracranial pressure (ICP) is a critical aspect of neurocritical care. The most effective method of reducing ICP involves a multi-faceted approach, including the optimization of cerebral perfusion pressure (CPP), reduction of intrathoracic pressure, and the elimination of harmful substances from the cranial vault.

**Why the Correct Answer is Right**
The most effective way of reducing ICP is by administering **mannitol**, an osmotic diuretic that decreases cerebral edema and intracranial pressure. Mannitol works by creating an osmotic gradient across the blood-brain barrier, which helps to reduce water influx into the brain's extracellular space and subsequently decreases ICP. This effect is mediated by the inhibition of aquaporin-4 water channels and the activation of astrocytes, leading to a decrease in cerebral edema.

**Why Each Wrong Option is Incorrect**
**Option A:** **Hyperventilation** can temporarily reduce ICP by causing vasoconstriction and a decrease in cerebral blood volume, but it is not the most effective method and can lead to cerebral ischemia.
**Option B:** **Barbiturates** may be used to reduce ICP in certain cases, but their mechanism of action is not as direct or effective as mannitol, and they can cause significant sedation and other side effects.
**Option C:** **Steroids** are not effective in reducing ICP and may even worsen outcomes by promoting cerebral edema.

**Clinical Pearl / High-Yield Fact**
The "ABCDE" approach to managing ICP includes maintaining **A**irway patency, **B**reathing, **C**irculation, **D**rug therapy, and **E**levation of the head of the bed to reduce ICP.

**Correct Answer:** C. Mannitol