The underlying pathology of the patient is also taken into consideration when determining the height of the collecting system. In the setting of an unsecured aneurysmal subarachnoid hemorrhage, the initial height of the collecting system is set “high” such that CSF is not drained too quickly in order to avoid rapid change in the transmural pressure across the aneurysm wall, which may predispose to rebleeding.

After the desired height (cmH2O) of the collection system is determined, management of the EVD essentially becomes a nursing responsibility. Drainage can be continuous at a set level, fixed volume per desired time (i.e., every hour), or as needed according to ICP elevations. ¹⁾.