This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for The Use of Bispectral Index Monitoring to Assess Depth of Sedation in Patients With Traumatic Brain Injury (NCT03575169), a registered phase not stated study. The primary outcome is Mean BIS for Population Over 24 Hours.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03575169 |
| Phase | Phase not stated |
| Condition | Traumatic Brain Injury |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 26 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Aberdeen |
| Results posted | Yes |
2. Clinical Question
Population
Patients with traumatic brain injury admitted to Aberdeen ICU and expected to require more than 24 hours of sedation. The registry records enrollment of 26 participants. Further eligibility details and the characteristics of the enrolled participants are not reported in the registry record.
Intervention
The study used a BIS Monitor, a device that produces a processed EEG index. The registry describes an observational assessment of the BIS-reported level of sedation; it does not describe assignment to a treatment or a protocol for changing sedation in response to BIS readings.
Comparator
No comparator group is described. The record does not identify a randomized allocation or a like-for-like control comparison. It therefore does not frame the study as a comparison between two assigned groups.
Primary question
The primary endpoint is the mean BIS for the population over 24 hours. The question is descriptive: what mean BIS level was recorded in sedated patients with traumatic brain injury during that timeframe? The numerical result is not reported in the registry record, so the endpoint’s observed value and precision cannot be assessed from the record.
This framing matters because an observational description can characterize recorded measurements without establishing that the device changed sedation, that a particular BIS value is preferable, or that BIS readings predict clinical outcomes. The registry lists additional measures concerning intracranial pressure, osmotherapy, vasopressor dose, sedative dose, and ICU stay. Their numerical results are not reported in the registry record. The record therefore identifies the intended subject and outcomes, but does not provide results with which to answer questions about the distribution of BIS values or their relationships to other measures.
3. Trial Design
NCT03575169 is recorded as a completed observational study sponsored by the University of Aberdeen. The record gives a start date of 2019-07-01 and a primary completion date of 2022-12-31. It reports enrollment of 26 participants with traumatic brain injury. Its summary describes assessing the BIS-reported level of sedation in patients with traumatic brain injury in the ICU.
The described population consists of patients admitted to Aberdeen ICU with a diagnosis of traumatic brain injury and an expectation that they would require greater than 24 hours of sedation. A BIS Monitor is listed as the study device. The registry does not describe a randomized allocation, a comparator arm, or an intervention intended to assign or alter sedation. The record notes that allocation is not stated and that the arms are not a like-for-like control comparison. The study should therefore be read as observational rather than as a randomized comparison.
The primary outcome is mean BIS over 24 hours, with inter-quartile range specified as the measure of dispersion. The listed secondary outcomes cover mean intracranial pressure, incidence of osmotherapy use, median vasopressor dose, sedative dose, and length of ICU stay over 24 hours. Although the registry identifies these measures, it does not report their numerical results. The record also reports zero analyses. Statistical methods, detailed outcome collection procedures, and the analysis population are not reported in the registry record.
Completion is a status designation, not evidence that results are available in the registry record. Enrollment describes the recorded study size and does not establish how many participants contributed data to each endpoint. Participant flow, exclusions, and outcome-specific denominators are not reported in the registry record. These gaps limit assessment of how completely the registered outcomes were measured and analyzed.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Patients With TBI |
|---|---|
| STARTED | 26 |
| COMPLETED | 26 |
| NOT COMPLETED | 0 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Patients With TBI |
|---|---|---|
| Participants analysed | 26 | |
| Age, Continuous | years | 41 (23.75 to 55) |
| Sex: Female, Male: Female | Participants | 4 |
| Sex: Female, Male: Male | Participants | 22 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Mean BIS for Population Over 24 Hours, measured over 24 hours.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Inter-Quartile Range |
| Unit | BIS value (index) |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the mean BIS value for the population over 24 hours. BIS is described in the registry as a processed EEG value on a scale from 0 to 100, with lower values representing decreased brain activity. The registry also notes that the usual range for general anaesthesia is 40-60. That range is background context in the outcome description; the record does not identify it as a target for this study or as a threshold used in an analysis.
A mean is a summary of the recorded values across the measurement period or population defined by the study. It can describe a central level, while the inter-quartile range, also specified for this endpoint, describes the spread of the middle half of the observations. Reporting both can give a reader information about the typical level and variation, although the mean alone does not reveal the shape of the distribution or whether values changed over time.
Processed EEG measures are used to summarize a signal as an index. In general, such an index can help describe sedation-related observations, but interpretation depends on the measurement context and on how readings were collected. The registry does not report the observed mean BIS, the inter-quartile range, measurement frequency, or the endpoint’s participant-level data. The endpoint’s numerical result and precision are therefore not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies a descriptive primary endpoint, but it does not report the endpoint result. The mean BIS over 24 hours and its inter-quartile range are not reported in the registry record. Consequently, the posted record cannot establish the level of BIS observed in this group, how variable individual readings were, or how precisely the population’s average was estimated. It also does not report a confidence interval, test statistic, or p-value for this outcome.
Enrollment is recorded as 26. That number should not automatically be treated as the denominator for every outcome: the record does not report outcome-specific participant counts or how many participants contributed BIS data. Nor does enrollment show whether all measurements were complete. The analysis population and participant flow are not reported in the registry record.
The study is observational, and no like-for-like control comparison is described. Its purpose, as stated in the registry summary, is to assess the BIS-reported sedation level among ICU patients with traumatic brain injury. This design can describe measurements in the enrolled group, but without a defined comparison it cannot estimate a between-group effect. It also does not, by itself, establish whether a measurement caused a change in care or whether a particular reading led to a clinical outcome.
The record lists secondary outcomes relating to intracranial pressure, osmotherapy, vasopressor dose, sedative dose, and length of ICU stay. Their numerical results are not reported in the registry record. There are no analyses reported, so associations between BIS and these measures cannot be evaluated from the record. The presence of an outcome in a registration does not itself show that it was measured successfully or that a result was observed.
The registry describes lower BIS values as representing decreased brain activity and gives a usual general anaesthesia range of 40-60. These descriptions explain the index but do not establish what values occurred in this study or define a study-specific target. Without the recorded outcome distribution, it is not possible to compare the observed measurements with that context. The absence of a posted result should be interpreted as unavailable evidence in the registry record, not as a finding that the endpoint had no variation or that an effect was absent.
The study’s completed status and the listed enrollment provide context about the registered project, but do not substitute for reported results. A careful reading separates the study question and planned outcomes from evidence: the registry describes what was to be assessed, while the quantitative findings and their uncertainty are not reported in the registry record.
9. Statistical Methods Explained
The registry gives the primary endpoint as a mean BIS over 24 hours and identifies inter-quartile range as its dispersion measure. It does not report the statistical analysis used to calculate or compare these quantities. The following explanations are general statistical context, not a description of an analysis confirmed in the registry.
What does a mean describe?
General: The arithmetic mean combines observed values into a single measure of central tendency. It can be useful when the research question concerns an average level, but it can be influenced by unusually high or low observations. It also compresses the data: different patterns of readings can have the same mean. In a repeated-measure setting, the interpretation depends on whether the mean is calculated over all readings, first within each participant and then across participants, or by another approach. The registry does not report which approach was used for the BIS endpoint.
What does the inter-quartile range add?
General: The inter-quartile range describes the span from the lower quartile to the upper quartile, containing the middle half of observations. It conveys spread in a way that is less affected by extreme values than the full range. It does not show every observation, identify outliers on its own, or indicate how precisely a population quantity has been estimated. For repeated readings, its meaning also depends on whether the observations represent readings or participant-level summaries. That detail is not reported in the registry record.
Why does the study design matter?
General: In an observational study, measurements are recorded without the random assignment that would define a randomized comparison. Descriptive summaries can characterize the enrolled population, but differences or associations can be affected by participant characteristics, clinical decisions, timing, and other factors. A causal interpretation requires design and analysis features that address these issues. The registry does not report a comparator or an analysis plan that would support such an interpretation. It describes an assessment of BIS-reported sedation levels, not a randomized test of a sedation strategy.
What would precision information contribute?
General: A confidence interval describes a range of estimates compatible with the data under a specified statistical method and assumptions. It helps distinguish the estimated value from its uncertainty. A standard error or interval does not remove bias from measurement, selection, or study design. No confidence interval or other precision estimate for the primary outcome is reported in the registry record, and no primary result is posted. Precision therefore cannot be judged from the record.
How should count and continuous outcomes be approached?
General: A continuous measure such as BIS or dose can be summarized using measures of location and spread, while an event outcome such as whether osmotherapy was used is often summarized using counts and proportions. The appropriate analysis depends on how each outcome is defined, its distribution, the observation period, and whether measurements are repeated or clustered within participants. These general considerations do not establish which models or summaries were used in this study. The registry lists several outcome types but reports no analyses.
What is over-dispersion?
General: In count-data analysis, over-dispersion occurs when variability is greater than a model assumes. If not addressed, uncertainty estimates can be too small and tests can appear more decisive than warranted. Whether this issue applies depends on the data and model. The registry record does not report a count-data model, model diagnostics, or the underlying observations, so no conclusion about over-dispersion can be drawn for this study.
What can a planning illustration say?
General: A sample-size planning illustration estimates the number of participants needed under specified assumptions, such as an effect size, significance level, allocation, and model approximation. It is not an observed result, and it is not observed power. The registry record does not report the study’s own sample-size justification or design assumptions. No sample-size illustration can establish that the enrolled study was adequately powered for its actual outcomes, particularly without a posted effect estimate and analysis.
The registry states that there are zero analyses. It does not report model specifications, handling of repeated observations, adjustment variables, missing-data methods, or inferential tests. These are not details that can be inferred from the endpoint labels. As a result, statistical interpretation must remain at the level of the study description: the registered question is identifiable, but the analysis and numerical evidence are not available in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome and several secondary outcomes. It does not report a multiplicity strategy, such as prioritizing a limited set of secondary tests, adjusting significance thresholds, or treating secondary findings as exploratory. Because zero analyses are reported, the record does not show whether any outcome testing took place or how multiple questions would have been handled.
Multiplicity is a general concern when many hypotheses are tested: the chance of at least one apparently notable finding can increase as the number of tests grows. The appropriate response depends on the study’s aims and analysis plan. No such plan is reported in the registry record, so it is not possible to determine how multiplicity was considered or whether formal testing was intended.
Missing-data handling is also not reported in the registry record. The record does not state whether any BIS readings or secondary outcome observations were missing, how missingness was defined, or whether participants with incomplete data were included in particular analyses. Enrollment of 26 does not establish the denominator for any endpoint or imply complete follow-up.
The record does not define an analysis population beyond its description of patients admitted to Aberdeen ICU with traumatic brain injury who were expected to require greater than 24 hours of sedation. It does not report participant flow, exclusions, or outcome-specific denominators. Without these details, readers cannot assess whether the analyzed participants, if analyses were conducted, differed from the enrolled group. The absence of these methods and results limits reproducibility and makes it inappropriate to infer a complete-case, intention-to-treat, or other analysis approach.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Patients With TBI | 0 | 26 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Patients With TBI | 4 of 26 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Patients With TBI | 0 of 26 |
The registry’s adverse-event record lists 26 patients with traumatic brain injury at risk, with 0 serious adverse events and 0 other adverse events. It also lists 4 deaths. These are registry counts; they do not establish that the device caused, prevented, or had no relationship to any event. The record does not provide event terms for serious adverse events.
The time period and collection procedures for these safety figures are not reported in the registry record. It is not clear from the posted information whether the counts cover the full study period, a defined observation window, or only a specified reporting interval. Nor does the record explain how deaths were classified in relation to adverse events. The count of deaths should therefore be reported as recorded, without assigning a cause or interpreting it as a device-related outcome.
Zero recorded events does not prove that no events occurred outside the reporting definitions or observation process. Likewise, the number at risk should not be assumed to be the denominator for every outcome without further detail. The safety figures are descriptive registry entries and should be read alongside the missing event definitions, timing, and attribution information.
12. What the Result Does, and Does Not, Mean
This record establishes that an observational study was registered to assess BIS-reported sedation levels in ICU patients with traumatic brain injury. It identifies a primary endpoint, mean BIS over 24 hours, specifies inter-quartile range as its dispersion measure, and lists additional outcomes. It also records enrollment of 26 and a completed status.
It does not report the numerical primary outcome or the results of the listed secondary outcomes. It does not provide an analysis, confidence interval, or statistical test. Consequently, the registry record cannot show what BIS values were observed, how variable those measurements were, or how precisely an average was estimated. Nor can it show whether BIS readings were associated with intracranial pressure, osmotherapy, vasopressor dose, sedative dose, or ICU stay.
The study’s observational design and lack of a described comparator are important to interpretation. The record does not provide a randomized comparison of monitoring strategies or sedation approaches. It therefore cannot establish that use of the monitor changed clinical management or caused a particular outcome. A descriptive study may help characterize measurements, but the registered question and the posted evidence must be kept distinct.
The general anaesthesia range noted in the endpoint description is context for the index, not a reported study finding or a study-specific threshold. The record does not say that it was used to guide care or define success. Likewise, the zero adverse-event counts do not establish absence of risk or attribution, especially because event definitions and timing are not reported.
In short, the registry describes what the study set out to observe, but the quantitative findings needed to interpret the observed BIS levels are not reported in the registry record. This is an absence of posted results, not evidence that a particular result was null or that the device was ineffective or effective.
13. Why This Trial Matters Statistically
This study matters statistically because it highlights the distinction between a registered measurement question and an inferential comparison. The primary endpoint is a mean BIS over 24 hours, a descriptive summary of a processed EEG index. With the result and its inter-quartile range, readers could assess the recorded level and variation. Without those values, the record communicates the intended measurement but not the evidence obtained.
The observational setting is also central. Sedation measurements in an ICU arise in a clinical context, and an observational assessment does not assign participants to contrasting strategies. A descriptive summary can be useful for characterizing a population, but it does not isolate the effect of monitoring from other influences. The absence of a comparator is therefore not a minor reporting detail; it defines what kind of question the design can address.
The record also illustrates why outcome definitions and denominators matter. It lists outcomes with different forms, including continuous measures, a measure of incidence, and length of stay, but does not report outcome-specific counts or analyses. Without those details, readers cannot evaluate missingness, distribution, precision, or whether analytic choices were appropriate for each measure.
Finally, a completed registry status and a recorded enrollment do not replace posted outcome data. Statistical interpretation requires results and enough methodological detail to understand how they were obtained. Here, those elements are not reported in the registry record. The appropriate conclusion is limited: the project was registered as an observational assessment of BIS-reported sedation in patients with traumatic brain injury, while its quantitative findings cannot be evaluated from the posted record.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
A central limitation is that the registry does not report the numerical value of the primary endpoint or the inter-quartile range. It also does not report numerical findings for the listed secondary outcomes. No statistical analyses are reported, so estimates, uncertainty, and relationships among outcomes cannot be assessed.
The description of the study population is brief. It identifies patients with traumatic brain injury admitted to Aberdeen ICU and expected to require greater than 24 hours of sedation, but further eligibility criteria and participant characteristics are not reported in the registry record. Although enrollment is recorded as 26, participant flow, exclusions, and endpoint-specific denominators are not reported. The number contributing to each outcome is therefore unknown.
The record does not describe how often BIS readings were collected, how the 24-hour mean was constructed, or how repeated observations were handled. It does not report details about the measurement process or how missing readings were addressed. These omissions limit interpretation of the endpoint even if its result were available.
No comparator or randomized allocation is described, and the record explicitly notes that the arms are not a like-for-like control comparison. The findings, if reported, would need to be interpreted within that observational design. The registry also does not report a statistical analysis plan, sample-size justification, multiplicity approach, or method for handling missing data.
Safety reporting has its own limits: event terms are not listed, and the timing and attribution of the adverse-event and death counts are not described. These gaps do not establish that the study had a particular bias or that events were missed; they mean the relevant assessment cannot be made from the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Use of Bispectral Index Monitoring to Assess Depth of Sedation in Patients With Traumatic Brain Injury — NCT03575169.
- Registry record last updated 2026-08-10; status last verified 2023-01.
- Results first posted 2026-08-10.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT03575169 is a completed observational study sponsored by the University of Aberdeen. The registry records enrollment of 26 participants, a start date of 2019-07-01, and a primary completion date of 2022-12-31. The study concerns BIS-reported sedation levels in ICU patients with traumatic brain injury who were expected to require greater than 24 hours of sedation.
The primary outcome is mean BIS over 24 hours, with inter-quartile range specified. Listed secondary outcomes concern intracranial pressure, osmotherapy use, vasopressor dose, sedative dose, and ICU stay. The record reports zero analyses and does not report numerical outcome results, an analysis plan, or outcome-specific denominators.
The adverse-event entry lists 0 serious adverse events, 0 other adverse events, and 4 deaths among 26 at risk. Event terms, timing, and attribution are not reported. The record describes no randomized comparator, so it supports identification of the intended observational question but not a controlled estimate of a monitoring effect.