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EVD Height Position Drainage — FRCA Final MCQ

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ModerateNeuroanaesthesiaEVD Height Position DrainageFRCA Final

A 65-year-old man in ICU has an EVD (external ventricular drain) for obstructive hydrocephalus. The drain is set to drain at 10 cmH2O above the external auditory meatus. The nurse repositions the patient 15 cm head-up. What effect does this have on CSF drainage if the drain height is not readjusted?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: D — Increased CSF drainage (overdrainage risk)

If the patient's head is raised but the EVD drainage point is not adjusted upward correspondingly, the pressure gradient between the ventricles and the drainage point increases (because the drainage point is now relatively lower than intended relative to the ear). This causes INCREASED CSF drainage, with risk of overdrainage (ventricular collapse, subdural haematoma, upward herniation). The drainage height must ALWAYS be referenced to the external auditory meatus (tragus) and readjusted whenever the patient's head position changes. This is a common and dangerous nursing/medical error.

Reference: NACCS – 2023 – Neurocritical care guidelines; Brain Trauma Foundation – 2016 – TBI guidelines