What parameter is routinely monitored to guide CSF drainage and assess brain status when an EVD is in place?

• A. Blood glucose.
• B. Oxygen saturation.
• C. Intracranial pressure (ICP) readings and drainage volume.
• D. Serum calcium.

Answer: (C)

Intracranial pressure measurements along with the drainage volume are routinely monitored with an external ventricular drain to guide how much CSF to drain and to track brain status. ICP tells you whether intracranial pressure is elevated and when drainage is needed to prevent herniation, while the drainage volume shows how much CSF you’ve removed and helps prevent overdrainage and monitor trends in CSF production. Together, they provide real-time insight into the patient’s intracranial physiology. Blood glucose, oxygen saturation, and serum calcium matter for overall care, but they do not directly guide CSF drainage or reflect intracranial dynamics in the context of an EVD.