Venous drainage

Outflow obstruction is the most easily missed cause of a rising ICP, and the cheapest to fix. Cerebral venous blood leaves via the jugular system, and anything that impedes it raises intracranial volume directly.

Head-up positioning of about 30° aids drainage.
Keep the head midline; neck rotation kinks jugular outflow.
Check that collars and tube ties are not compressing the neck.
High intrathoracic pressure — coughing, ventilator dyssynchrony, high PEEP in a hypovolaemic patient — transmits backward and impedes drainage.

Before escalating to osmotherapy, it is worth confirming that none of these is the actual problem.