Analysis Of Normal High-Frequency Intracranial Pressure Values And Treatment Threshold In Neurocritical Care Patients: Insights Into Normal Values And A Potential Treatment Threshold (Vol 77, Pg 1150, 2020)

Importance Intracranial pressure (ICP) elevation is a compartment syndrome that impairs blood flow to the brain. Despite the importance of ICP values in neurocritical care, normal ICP values and the precise ICP threshold at which treatment should be initiated remain uncertain. Objective To refine our understanding of normal ICP values and determine the ICP threshold most strongly associated with outcome. Design, Setting, and Participants Prospective observational study (2004-2010), with outcomes determined at hospital discharge. The study included neurocritical care patients from a single level I trauma center, San Francisco General Hospital. Three hundred eighty-three patients had a traumatic brain injury with or without craniectomy; 140 patients had another indication for ICP monitoring. Consecutive patients were studied. Data analyses were completed between March 2015 and December 2019. Exposures Five hundred twenty-three ICP-monitored patients. Main Outcomes and Measures A computer system prospectively and automatically collected 1-minute physiologic data from patients in the intensive care unit during a 6-year period. Mean ICP was calculated, as was the proportion of ICP values greater than thresholds from 1 to 80 mm Hg in 1-mm Hg increments. The association between these measures and outcome was explored for various epochs up to 30 days from the time of injury. A principal component analysis was used to explore physiologic changes at various ICP thresholds, and elastic net regression was used to identify ICP thresholds most strongly associated with Glasgow Outcome Scale score at discharge. Results Of the 523 studied patients, 70.7% of studied patients were men (n = 370) and 72.1% had a traumatic brain injury (n = 377). A total of 4090964 1-minute ICP measurements were recorded for the included patients (7.78 years of recordings). Intracranial pressure values of 8 to 9 mm Hg were most commonly recorded and could possibly reflect normal values. The principal component analysis suggested state shifts in the physiome occurred at ICPs greater than 19 mm Hg and 24 mm Hg. Elastic net regression identified an ICP threshold of 19 mm Hg as most robustly associated with outcome when considering all neurocritical care patients, patients with TBI, and patients with TBI who underwent craniectomy. Intracranial pressure values greater than 19 mm Hg were associated with mortality, while lower values were associated with outcome in surviving patients. Conclusions and Relevance This study provides insight into what normal ICP values could be. An ICP threshold of 19 mm Hg was robustly associated with outcome in studied patients, although lower ICP values were associated with outcome in surviving patients.This study investigates associations between intracranial pressure values and outcomes in neurocritical care patients.Questions In neurocritical care patients, what intracranial pressure values are normal and what intracranial pressure threshold is most strongly associated with Glasgow Outcome Scale score at hospital discharge? Findings In this observational study, intracranial pressure values of 8 to 9 mm Hg were most commonly recorded and could reflect normal values. An intracranial pressure threshold of 19 mm Hg was robustly associated with outcome in studied patients, although lower intracranial pressure values were associated with outcome in surviving patients. Meaning This study provides insight into what normal intracranial pressure values may be and suggests that threshold values lower than 20 mm Hg should be studied in future prospective studies.