Highlights
In severe traumatic brain injury (TBI), intracranial pressure (ICP) crises guide urgent treatment decisions, yet the standard bedside method may not always reflect the underlying electronic signal.
In this post hoc BOOST II analysis, only 47% of bedside-defined “minimalist” ICP episodes were confirmed by concurrent electronic data during the 5-minute qualifying window.
Many bedside-labeled episodes had electronically measured ICP values below the treatment threshold for most or all of the episode, raising concerns about temporal mismatch and episode-definition variability.
The authors argue for real-time, open-source, synchronized electronic definitions of ICP crises to improve both bedside care and research reproducibility.
Clinical background and unmet need
Intracranial hypertension remains one of the most important secondary insults after severe TBI. Elevations in ICP can reduce cerebral perfusion pressure, worsen ischemia, and contribute to poor neurological outcome. As a result, ICP is a central target in neurocritical care, and treatment algorithms often escalate from first-tier measures such as head positioning, sedation, analgesia, cerebrospinal fluid drainage, and ventilator adjustments to more aggressive interventions when pressure remains elevated.
Despite decades of use, there is still no universally standardized way to define an “ICP crisis.” In day-to-day practice, clinicians often interpret a bedside monitor, respond to trends, and decide whether a threshold has been crossed long enough to require action. In research settings, however, precise definitions matter. Outcome studies, treatment trials, and quality metrics all depend on whether an episode truly represents sustained intracranial hypertension or only a brief, artifact-prone, or already-resolving rise in pressure.
This distinction is not merely semantic. If bedside identification overcalls episodes, clinicians may appear to treat more “crises” than actually exist in the continuous signal. If it undercalls them, meaningful exposure to intracranial hypertension may be missed. The BOOST II trial provided a valuable dataset to explore this problem because it combined routine bedside management with background-collected continuous electronic ICP data.
Study design and methods
This was a post hoc analysis nested within the Brain Tissue Oxygen Monitoring and Management in Severe Traumatic Brain Injury II (BOOST II) randomized trial. The parent trial enrolled patients with severe TBI across 10 U.S. intensive care units. For the present analysis, 70 of the 110 randomized patients had complete datasets suitable for concordance assessment.
The investigators focused on “minimalist” bedside ICP episodes, defined as episodes lasting 60 minutes or less and requiring only tier 1 treatments. These episodes made up 83% of the isolated ICP episodes in BOOST II, making them clinically important because they represent the most common real-world crisis pattern. Bedside clinicians identified 509 minimalist episodes using a practical bedside criterion: 5 minutes of bedside ICP at or above 20 mm Hg, termed B-ICP5.
The central comparison was with background-collected electronic ICP data. For the same defining 5-minute window, the authors assessed whether electronic ICP also reached 20 mm Hg or higher, termed E-ICP5. They then examined the full episode average electronic ICP (E-ICPAVG) and the maximal electronic ICP during the episode (E-ICPMAX) to understand whether the bedside-labeled event corresponded to sustained or transient pressure elevation.
The analysis was observational and post hoc. It did not test a therapeutic intervention, but rather the concordance between routine bedside episode recognition and continuously sampled electronic data. The study also attempted to explore confounding explanations such as whether discordant episodes were brief, first in a sequence, or easily controlled. However, the authors note that temporal synchrony between bedside and electronic datapoints could not be fully evaluated.
Key findings
Among the 509 minimalist bedside ICP episodes, only 47% were confirmed by electronic data during the 5-minute defining window. In other words, more than half of the episodes that clinicians considered to meet the bedside threshold were not simultaneously corroborated by the continuous electronic signal at the same threshold level.
The 241 episodes considered concordant, meaning both bedside and electronic measurements met the threshold during the defining period, still showed an important nuance. In 38% of these concordant events, the average electronic ICP across the entire episode was below 20 mm Hg. This suggests that even when the opening segment aligned, sustained intracranial hypertension was not always present throughout the episode.
The 286 discordant episodes were more revealing. These were defined by bedside ICP of at least 20 mm Hg for 5 minutes, but electronic ICP below 20 mm Hg during that same period. Within this group, 76% had an average electronic ICP below 20 mm Hg for the entire episode, and 31% had both average and maximal electronic ICP values below 20 mm Hg. That pattern argues against sustained physiologic intracranial hypertension in a substantial fraction of events treated at the bedside.
The investigators tested several plausible explanations for discordance, including whether these were especially brief episodes, the first episode in a series, or events that were easily controlled. These analyses did not offer a clear explanation. The most important unresolved issue was temporal asynchrony: because bedside assessments and electronic datapoints were not perfectly synchronized, some apparent mismatches may reflect timing differences rather than true disagreement.
From a clinical standpoint, the study suggests that current bedside methods may be adequate for urgent response but less reliable as a precise research-grade definition of an ICP crisis, especially for the most common type of short, low-intensity episode.
Table: What the BOOST II concordance analysis suggests
Episode type | Definition | Main finding | Interpretation
Concordant episodes | B-ICP5 ≥ 20 mm Hg and E-ICP5 ≥ 20 mm Hg | 241 episodes; 38% had E-ICPAVG < 20 mm Hg | Even “confirmed” episodes were not always sustained across the full event
Discordant episodes | B-ICP5 ≥ 20 mm Hg but E-ICP5 < 20 mm Hg | 286 episodes; 76% had E-ICPAVG < 20 mm Hg; 31% had E-ICPAVG and E-ICPMAX < 20 mm Hg | Many bedside crises may not represent true sustained intracranial hypertension
Overall minimalist episodes | ≤60 minutes and tier 1 treatment only | Only 47% confirmed by electronic data in the defining window | Routine bedside episode labeling may overcall or misclassify many common events
Expert commentary and interpretation
This analysis addresses a practical but underappreciated problem in neurocritical care: the difference between a clinically actionable bedside impression and a rigorously defined physiologic event. In a busy ICU, clinicians must act on what they see in real time. Bedside recognition is therefore valuable, especially when rapid treatment can prevent secondary brain injury. However, bedside thresholds may incorporate clinical context, waveform interpretation, transient artifacts, and evolving treatment effects in ways that are difficult to reproduce retrospectively.
The BOOST II data suggest that the most common ICP episode phenotype is not always captured consistently by current bedside conventions. This matters because many observational studies and quality initiatives rely on counted episodes as if they were objective, discrete events. If the same threshold can yield different conclusions depending on whether the source is a bedside note or a continuous recording, then comparisons across studies become less reliable.
At the same time, the findings should not be interpreted as evidence that bedside clinicians are “wrong” in a simplistic sense. Several factors can create apparent discordance. Transducer drift, waveform damping, transient patient movement, line leveling issues, intermittent waveform artifacts, and delays between observation and documentation can all contribute. The study also could not fully resolve the timing relationship between clinician recognition and electronic sampling. In practice, a clinician may correctly recognize a rising ICP trend before the formal electronic criterion is captured, or may intervene just as the pressure is already falling.
Another important point is that many ICU treatment decisions are made before or independent of a rigid threshold. A patient with worsening examination, agitation, poor compliance, or concerning imaging may receive therapy even if a continuous 5-minute threshold is not clearly met. Thus, “episode” definitions are both clinically and methodologically imperfect proxies for the decision-making process.
The authors’ suggestion to develop open-source, real-time, temporally synchronized electronic definitions is especially compelling. Such tools could standardize event capture, reduce misclassification, and enable better comparison across centers and trials. They may also support more nuanced phenotyping, such as duration-burden metrics, pressure-time integral, waveform-based thresholds, and individualized autoregulation-informed triggers rather than a single fixed number alone.
Clinical implications and future directions
For clinicians, the immediate implication is not to abandon bedside ICP monitoring, but to recognize that the way episodes are documented may not faithfully reflect sustained physiology in all cases. This is particularly relevant when counting treatment-responsive episodes, benchmarking ICU performance, or interpreting trial endpoints.
For researchers, the study highlights the need for standardized definitions that are operationally precise and reproducible. Future work should ideally pair bedside annotations with synchronized high-resolution signals and include transparent algorithms for episode onset, offset, artifact handling, and pressure thresholding. Incorporating additional variables such as cerebral perfusion pressure, brain tissue oxygenation, imaging findings, and neurologic examination could also create a more clinically meaningful definition of intracranial crisis.
There is also a broader methodological lesson. Neurocritical care has increasingly sophisticated data streams, yet many endpoints still depend on human interpretation of dynamic physiologic processes. As machine-assisted monitoring becomes more available, the field will need consensus around what counts as an event, how it is measured, and when it is acted upon.
Conclusion
The BOOST II concordance analysis raises a significant challenge to conventional bedside identification of ICP crises in severe TBI. In the most common short, low-tier episode type, bedside-defined events were often not confirmed by continuous electronic data, and many “confirmed” episodes still did not show sustained elevation across the full episode. These findings do not negate the clinical value of bedside judgment, but they do suggest that current episode definitions may be too imprecise for research-grade phenotyping and possibly for some treatment frameworks.
The field now needs temporally synchronized, transparent, and ideally open-source electronic definitions of ICP crisis that better distinguish transient fluctuations from true sustained intracranial hypertension. Such refinement could improve trial design, outcome interpretation, and ultimately the precision of care for patients with severe TBI.
Funding and clinicaltrials.gov
The article reports data from the Brain Tissue Oxygen Monitoring and Management in Severe Traumatic Brain Injury II (BOOST II) randomized trial. The abstract provided does not specify funding details or a clinicaltrials.gov identifier. Those items should be confirmed directly from the full publication or trial record before formal citation in regulatory or academic materials.
References
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3. Chesnut RM, Temkin N, Carney N, et al. A trial of intracranial-pressure monitoring in traumatic brain injury. N Engl J Med. 2012;367(26):2471-2481.
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