Pressure Gradient as a Predictor of Time Needed to Drain Cerebrospinal Fluid Via an External Ventricular Drain

Consensus is lacking on best practices regarding treatment of elevated intracranial pressure. One method is placement of an external ventricular drain to divert cerebrospinal fluid via continuous or intermittent drainage.

To explore the time required for fluid to finish draining at various pressure gradients under high- and low-compliance conditions.

An ex vivo model filled with 6200 mL saline and minimal air (low compliance) or 6050 mL saline and 150 mL air (high compliance) was attached to an external ventricular drain and transducer and then calibrated. The initial pressure in the chamber was set by adding or removing saline, and the buretrol was positioned to the set threshold. The external ventricular drain was then opened. Using different pressure gradients, 84 observations (42 low compliance, 42 high compliance) were obtained to identify the time to the second-to-last drop and the last drop (end of drainage).

The overall mean (SD) time from stopcock opening to last drop was 100.80 (65.84) seconds. The mean low-compliance time was 40.57 (15.83) seconds, and the mean high-compliance time was 161.00 (33.14) seconds (P < .001). Pressure gradient was a predictor of drainage time in both high-compliance (P < .001) and low-compliance (P < .001) conditions. In all 84 trials, fluid diversion was complete within 4.5 minutes (second-to-last drop, 2 minutes 48 seconds).

The results of this study highlight the need to standardize intracranial pressure monitoring practice and further scientific knowledge about the best drainage techniques for patients with acquired brain injury.