Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is the best way to accomplish external draining of CSF via an external ventricular drain (EVD)?

1. Drain continuously until fully drained

2. Drain a few drops per minute and close the drain after 5 minutes or less

3. Drain until clear fluid is observed

4. Drain using a constant flow until pressure normalizes

The correct answer is: Drain a few drops per minute and close the drain after 5 minutes or less

The most effective method for external draining of cerebrospinal fluid (CSF) via an external ventricular drain (EVD) involves controlled drainage rather than continuous or excessive rates. Draining a few drops per minute and closing the drain after a short time helps regulate the removal of CSF while minimizing the risk of complications, such as significant fluctuations in intracranial pressure (ICP). This approach allows for the careful monitoring of both the volume of CSF being removed and the patient's neurological status. Maintaining a balance is crucial; too rapid drainage can lead to hypotension, which may cause further complications or damage. Additionally, this method reduces the risk of over-drainage, which can precipitate a condition known as subdural hematoma or cause the brain to collapse due to negative pressure if CSF is removed too quickly. While continuous drainage or draining until clear fluid is observed might seem efficient, these methods lack the careful controls necessary to maintain homeostasis in intracranial pressure and could lead to adverse outcomes. Therefore, the selected method promotes safety and patient stability during the procedure.