Does intracranial pressure vary based on external ventricular drainage? A real-world clinical observation study

Background: External ventricular drains (EVDs) are placed in patients with increased intracranial pressure (ICP) to serve as a cerebrospinal fluid (CSF) pressure flow diverter and ICP monitor. EVD management practice among institutions and practitioners varies greatly, with little evidence supporting ideal ICP recording and CSF drainage practice. Objective: This study's aim is to determine variations in ICP across 21 min before and after CSF drainage. Methods: Thirty adult patients with EVDs were consented for a real-world observational study. As per the institution guidelines, each patient's drain was levelled to the tragus and zeroed. The EVD was then clamped for 10 min, opened to drain for 1 min, and clamped again for another 10 min. ICPs were then recorded immediately, at 30 s, 1 min, 5 min, and 10 min after drain clamp. Each patient was eligible for up to 10 separate observation events, limited to one observation per shift. Results: We observed 226 independent drain-clamping events among 30 participants. The most common indication for EVD placement was to monitor and treat a mass-occupying lesion (n = 28). The patients had a mean age of 54.8 (15.9) years, including 12 (41%) females and 17 (59%) males. Fifty-one percent of CSF was characterised as clear, followed by serosanguinous, serous, and sanguineous characterisations. One minute of CSF drainage decreased ICP from 10.30 to 9.20, an average of 1.1 mmHg lower (p < 0.05). Conclusion: The ICP measurement practice is not standardised among clinicians. ICP variations ranged from negative numbers to well above the normal range, whereas no clinical changes in patient exam were seen. Drainage of CSF decreases ICPs momentarily, and the effects of drainage do not last long. Further studies are needed to evaluate the safest approach to EVD management and ICP recording practice.