Should an External Ventricular Drain (EVD) be closed when a patient with a history of hydrocephalus or brain injury is lying flat?

EVD Management During Patient Positioning

No, an EVD should NOT be routinely closed when a patient is lying flat—the EVD should remain open with the drainage level adjusted to maintain appropriate intracranial pressure monitoring and CSF drainage based on the clinical indication. The key is adjusting the reference point (typically the tragus or external auditory meatus) to maintain the prescribed drainage threshold, not closing the system.

Standard EVD Management Principles

The drainage system must remain referenced to a consistent anatomical landmark regardless of patient position. When a patient lies flat versus having the head of bed elevated, the relationship between the drainage collection chamber and the patient's ventricles changes, which affects the hydrostatic pressure gradient and thus CSF drainage 1, 2.

Position-Based Adjustments

• When lowering the head of bed: The drainage chamber must be lowered proportionally to maintain the same pressure threshold relative to the ventricles 3
• The reference point (zero point) should always be leveled to the tragus or external auditory meatus to ensure accurate ICP monitoring and appropriate drainage 1, 4
• Closing the EVD during position changes is unnecessary and potentially harmful as it interrupts ICP monitoring and CSF drainage when the patient may be most vulnerable to pressure changes 2, 4

Clinical Context Matters

For Hydrocephalus Management

• Continuous drainage is the predominant approach used in 94% of institutions for secured aneurysms and 81% for unsecured aneurysms, with the EVD kept open at all times 1
• The drainage level is typically set at 10-20 cm H₂O above the reference point depending on whether the goal is to enhance or minimize CSF drainage 1, 5
• Intermittent drainage strategies exist but are associated with higher complication rates including catheter obstruction and need for replacement 4

Special Circumstance: CSF Hypotension

• In rare cases of documented CSF hypotension (as seen with CSF leaks), the EVD may be kept at a higher threshold or temporarily closed to allow CSF pressure recovery 3
• One case report described maintaining a patient in 5° Trendelenburg position with EVD threshold at 15 mm Hg for CSF hypotension, where minimal EVD output was actually desired 3
• This represents an exceptional clinical scenario, not standard practice

Common Pitfalls to Avoid

• Do not close the EVD during routine position changes—this interrupts critical ICP monitoring and therapeutic CSF drainage 2, 4
• Do not forget to re-level the drainage system after any position change, as failure to adjust creates inappropriate drainage gradients 1, 4
• Do not assume flat positioning requires EVD closure—the drainage threshold should be maintained through proper leveling, not by closing the system 1, 2
• Verify EVD patency if drainage suddenly stops when position changes, as this may indicate catheter obstruction rather than appropriate response to positioning 6, 4

Practical Management Algorithm

1. Before position change: Note current drainage level and ICP
2. During position change: Keep EVD open but clamped temporarily only during active movement if necessary to prevent rapid drainage
3. After position change: Immediately re-level the drainage chamber to the tragus/external auditory meatus at the prescribed height (e.g., 15 cm H₂O)
4. Verify: Check that CSF drainage resumes appropriately and ICP readings are physiologic 1, 4, 5

The fundamental principle is maintaining consistent hydrostatic pressure relationships through proper leveling, not through opening and closing the drainage system 1, 2, 4.