An external ventricular drain (EVD) is best described as:

• A. A catheter placed in the cerebral ventricles to drain CSF; must maintain sterile technique, level at tragus, monitor ICP and drainage.
• B. A drain in the subarachnoid space used for antibiotic delivery.
• C. A feeding tube used for nutrition.
• D. A drain in the lumbar spine for analgesia.

Answer: (A)

An external ventricular drain is a catheter placed into the brain’s ventricles to drain cerebrospinal fluid and to monitor intracranial pressure. Its purpose is to reduce raised ICP and allow CSF to be collected for measurement, with the external collection system connected to a transducer for ongoing ICP readings. Maintaining sterile technique is essential to prevent infection, and the drainage system is positioned so its reference level is at the level of the tragus. This height helps regulate the hydrostatic pressure and prevents over- or under-drainage. In clinical use, you continuously assess CSF output and ICP trends, watch for signs of over-drainage (like headaches or subdural collections), and adjust the system accordingly.

The other descriptions refer to different devices or uses: a drain in the subarachnoid space is not the same as an intraventricular external drain and is not primarily for ICP monitoring, a feeding tube is for nutrition, and a lumbar drain is placed in the spine for CSF drainage but serves a different purpose and location than an EVD.