Intracranial Pressure Monitoring via External Ventricular Drain: Are We Waiting Long Enough Before Recording the Real Value?

BACKGROUND External ventricular drain (EVD) is a standard approach for both monitoring intracranial pressure (ICP) and draining cerebrospinal fluid (CSF) for patients with subarachnoid hemorrhage. Documenting an accurate ICP value is important to assess the status of the brain, which would require the EVD system to be leveled properly and closed to CSF drainage for an adequate period. It is suggested that a minimum period of 5-minute EVD closure is needed before documenting a true ICP; however, there is no commonly agreed upon standard for documenting ICP. To obtain an insight into how well the intermittent EVD clamping procedure is performed for ICP documentation, we conducted a retrospective analysis of ICP recordings obtained through EVD from 107 patients with subarachnoid hemorrhage. METHODS The EVD was kept open for continuous CSF drainage and then intermittently closed for ICP documentation. For each EVD closure, mean ICP, standard deviation of ICP, duration of EVD closure, and time interval between 2 adjacent EVD closures were studied. The total number of EVD closures was calculated for each patient. We developed an algorithm to evaluate whether ICP reached a new equilibrium before the EVD was reopened to drainage. The percentage of EVD closures that reach the equilibrium was calculated. RESULTS The 107 patients had 32 755 EVD closures in total, among which 65.9% instances lasted less than 1 minute and only 16.3% of all the EVD closure episodes lasted longer than 5 minutes. The median duration of each EVD closure was 25 seconds (interquartile range, 10.2 seconds to 2.33 minutes). Only 22.9% of the EVD closures reached ICP equilibrium before EVD reopening. CONCLUSION A standard guideline and proper training are needed for bedside nurses, and a potential tool that can render ICP trend at a proper scale at bedside would help clinicians correctly document ICP.