Combined Electroencephalogram, Magnetic Resonance Imaging-Positron Emission Tomography of Dexmedetomidine Induced Sleep: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Combined Electroencephalogram, Magnetic Resonance Imaging-Positron Emission Tomography of Dexmedetomidine Induced Sleep (NCT01485380), a na na study. The primary outcome is Number of Participants With Changes in the Brains Default Mode Network..

2. Clinical Question

3. Trial Design

The registry identifies this as a completed, single-group study sponsored by Massachusetts General Hospital. Enrollment was 20. The listed phase is NA, allocation is NA, and masking is NONE. These entries do not describe a randomized, masked comparison between treatment groups. The active study arm is the only arm described.

The study investigated dexmedetomidine-induced sedation using EEG and MRI-PET. The arm description says participants were to undergo two brain MRI-PET scans in addition to high-density EEG acquisition. It identifies the first scan as baseline and begins to describe the second scan, but that description is cut off in the registry record. The primary outcome description refers to BOLD signals in awake, unconscious, and recovery states, and compares changes during sedation with baseline.

The registry lists a start of 2012-09, primary completion of 2013-07, and status COMPLETED. These dates describe the recorded study timeline; they do not, by themselves, provide information about the timing or conduct of statistical analyses.

There is no reported parallel control arm, random allocation, or masking. The stated comparison is instead against baseline within the study’s sedation-related observations. A baseline comparison can describe changes across conditions in the measured participants, but it is not equivalent to a concurrent control group. The protocol details, including the complete scan sequence, are not reported in the registry record. Nor is the method used to determine the enrollment target reported in the registry record.

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

Analysis population for the primary outcome, as defined in the registry: All 17 participants were analyzed. Blood oxygen level depended (BOLD) signals during the awake (n = 16), unconscious (n = 16), and recovery (n = 15) states were included in the final data set.

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Changes in the Brains Default Mode Network., measured over 1.5hrs.

The primary endpoint is titled “Number of Participants With Changes in the Brains Default Mode Network.” It is a count of participants, rather than a continuous estimate of the size of a brain-signal change. The outcome description specifies changes in the Default Mode Network during loss and recovery of consciousness under dexmedetomidine-induced sedation compared with baseline. These changes were to be assessed using blood oxygen level dependent (BOLD) signals in the awake, unconscious, and recovery states. The stated timeframe is 1.5hrs.

A participant count can make an outcome easier to interpret as the number meeting a defined condition. However, the registry record does not specify the operational threshold or decision rule used to classify an individual as having a change. It also does not report the endpoint result. Without the classification rule and the observed count, readers cannot determine how the endpoint was applied or how many participants met it.

EEG and MRI-PET are described as the measurement approaches used to investigate brain activity. The endpoint specifically describes changes assessed through BOLD signals; it does not provide a numerical BOLD change, uncertainty interval, or statistical test. Those results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods are difficult to evaluate because the registry describes the primary outcome but does not report an analysis. The record lists zero analyses. It does not specify a statistical test, model, effect estimate, confidence interval, or p-value. The concepts below explain what such methods would mean in general; they do not describe methods confirmed for this study.

What does a participant count measure?

The primary outcome is a count of participants classified as having changes in the Default Mode Network. In general, a count endpoint requires a rule for deciding whether each participant meets the outcome definition. That rule might rely on a threshold or another prespecified criterion, but the registry record does not state which rule was used. A count alone also does not show the size or direction of a signal change. Those distinctions matter because a threshold-based classification can summarize whether a criterion was met while omitting information about how far measurements moved or how variable they were.

The registry identifies BOLD signals in three states as the basis for assessing change. It gives the state-specific numbers included in the final data set, but does not explain the participant-level processing, how observations were compared across states, or how signals were converted into the endpoint count. Those methods are not reported in the registry record.

What would an estimate and confidence interval add?

In general, an estimate describes the observed quantity of interest, while a confidence interval communicates uncertainty around that estimate under the assumptions of the analysis. For a participant-count outcome, a report might give the observed count and, where appropriate, an interval for a proportion or another specified effect measure. The choice depends on the research question and analysis plan. No count, effect measure, or interval for the primary endpoint is reported in the registry record, so readers cannot assess its magnitude or precision.

A confidence interval is not a guarantee that the true value lies within a particular interval. It is a statistical summary whose interpretation depends on the method and assumptions used to construct it. Those assumptions and methods are not available for this endpoint in the registry record.

How should a p-value be understood?

In general, a p-value summarizes how incompatible observed data are with a specified null hypothesis, given the test’s assumptions. It does not measure the probability that the null hypothesis is true, the probability that the findings occurred by chance, or the clinical importance of a result. A p-value is interpretable only alongside the exact comparison, statistical test, and analysis population. None of these inferential results is reported for the primary outcome.

What can a baseline comparison establish?

As a general design concept, comparing measurements with baseline can characterize within-participant changes across conditions. Repeated measurements can account for some stable differences between people when the analysis is designed to do so. However, a baseline comparison is not the same as a randomized comparison with a concurrent control group. Without such a group, changes over time or other influences cannot automatically be separated from changes associated with the study condition. This describes a limitation of the comparison structure, not an explanation of any particular unreported finding.

The registry identifies a single-group study and names baseline as the reference for the primary outcome. It does not report whether a paired statistical method was used, how repeated observations were modeled, or whether other covariates were included. Those details are not reported in the registry record.

What do planning illustrations mean?

Planning sample-size illustrations are hypothetical calculations, not observed study findings. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a fraction of the observed effect. Those assumptions do not describe the listed single-group study design. The registry record does not report the study’s own sample-size justification or statistical plan, and the planning assumptions should not be treated as the protocol’s design decisions.

In general, a sample-size calculation addresses the chance of detecting an effect of a chosen size under specified assumptions. It does not show whether the study actually observed that effect. “Observed power” is not a substitute for an effect estimate and its uncertainty; after data collection, the estimate and interval are more informative for interpreting precision. Any planning illustration is not an observed power result, and no trial-specific statistical interpretation can be recovered from the stated assumptions alone.

Over-dispersion is a general concern when count data vary more than a chosen statistical model expects. If present, it can make standard errors and uncertainty estimates too small under an unsuitable model. The registry does not report a count model or enough outcome information to assess whether over-dispersion is relevant to the endpoint analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Active Study Arm")
n      <- c(17)
events <- c(16)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Active Study Arm  17  16  94.1  71.3  99.9  73.0  99.0  72.7  98.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and zero analyses. It does not report a statistical analysis plan, a list of secondary outcomes, or any planned adjustment for multiple testing. Multiplicity refers, in general, to the increased chance of false-positive findings when many hypotheses or outcomes are tested. With no analysis results or testing plan reported, it is not possible to determine whether multiplicity was an issue or how it was handled. The number of listed outcome measures alone does not establish the full set of analyses that may have been considered.

The stated analysis population is all 17 participants. The registry also says that BOLD signals in the final data set included the awake (n = 16), unconscious (n = 16), and recovery (n = 15) states. The record does not explain why the state-specific counts are not the same as the total analyzed population, whether the same participants contributed data across states, or how any unavailable observations were handled. These details are not reported in the registry record.

Missing-data methods matter because results can depend on whether data are absent and on the assumptions made about that absence. In general, an analysis may use only available observations, make assumptions about the missing values, or use another prespecified approach. The registry record does not say which approach was used, whether observations were excluded, or whether any sensitivity analysis was performed. The stated counts should therefore be read as descriptions of the data included for each state, not as evidence about the reasons for differing counts or the robustness of the findings.

The record does not report a prespecified analysis population definition beyond the statement that all 17 participants were analyzed. Further details about eligibility for each outcome analysis are not reported in the registry record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists 20 participants at risk in the active study arm and records 0 serious adverse events and 0 other adverse events. These figures describe the counts entered in the registry for this group. The deaths entry is null, which means deaths are not reported in the registry record; it should not be interpreted as a reported count of zero.

A zero recorded count does not, by itself, establish that an event was impossible or that the intervention is free of risk. In general, safety counts depend on the period of observation, event definitions, ascertainment, and reporting. The registry entry does not provide enough detail to evaluate those features, including the exact safety observation period or event-coding procedures. Those details are not reported in the registry record.

The study is single-group, with no separate control group described. Therefore, the listed safety counts do not offer a randomized between-group comparison. They should be read as registry-reported counts for the active study arm, not as evidence about comparative safety. The record also does not list serious adverse event terms. A blank list of terms is not a substitute for a detailed safety narrative.

13. What the Result Does, and Does Not, Mean

The record establishes that a completed single-group study investigated brain activity during dexmedetomidine-induced sedation using EEG and MRI-PET. Its primary question concerned the number of participants with changes in the Default Mode Network during loss and recovery of consciousness compared with baseline, based on BOLD signals in awake, unconscious, and recovery states. The record also identifies the participant counts included for each state.

It does not report the primary endpoint result. Readers cannot tell from the registry record how many participants met the outcome definition, what the measured changes were, or how uncertain any estimate may be. The absence of a reported result is not a finding of no change. It also is not evidence that no analysis was conducted outside the registry record.

The single-group structure means the stated comparison is with baseline, rather than with a concurrent randomized control group. In general, a baseline comparison can describe changes among measured participants, but by itself does not isolate the cause of those changes. The record does not provide a statistical analysis that would quantify the comparison or its uncertainty.

The study’s safety entries report 0 serious adverse events and 0 other adverse events among 20 participants at risk. The deaths entry is not reported in the registry record. These entries are limited to what the registry records and do not establish a complete safety profile.

Overall, the available information supports understanding the study’s objective, design, measurement approach, and reported analysis population. It does not support a quantitative conclusion about the primary outcome, its statistical significance, or the size and precision of any change.

14. Why This Trial Matters Statistically

This study is statistically notable because its central question connects measurements across different modalities and states of consciousness. The registry describes EEG acquisition alongside MRI-PET scans and identifies BOLD signals as the basis for assessing changes in the Default Mode Network. Such a question requires clear definitions of the measured change, the comparison with baseline, and the participant-level rule used to count an outcome. The registry record does not provide those analytic details.

The design also illustrates the distinction between a within-study baseline comparison and a randomized control comparison. A baseline reference can be useful for describing how measurements differ across conditions within participants. It does not automatically control for other changes over time or establish that observed differences are attributable only to the condition under study. That distinction is important when interpreting results from a single-group design.

The stated analysis population deserves attention as well. The record reports that all 17 participants were analyzed, while state-specific BOLD data counts are 16 for awake, 16 for unconscious, and 15 for recovery. Without an explanation of those counts or the missing-data approach, the scope of the data contributing to each state comparison remains unclear.

Finally, a registry outcome description is not a results report. The record identifies the primary question but gives no endpoint count, effect estimate, confidence interval, or inferential test. This demonstrates why design and outcome definitions are necessary but insufficient for judging statistical evidence: readers also need transparent results, analysis methods, and uncertainty estimates.

15. 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.

Several limitations are specific to the information recorded for this study. The arm description is incomplete: it identifies a baseline MRI-PET scan and starts to describe a second scan, but the remainder is not available in the registry record. The complete sequence of study procedures is therefore not reported in the registry record.

The primary outcome is expressed as the number of participants with changes in the Default Mode Network, but the criterion for classifying a participant as having a change is not stated. The record does not provide an observed count, a measure of the magnitude of BOLD changes, or an uncertainty estimate. The endpoint result and the method for deriving it are not reported in the registry record.

The record states that all 17 participants were analyzed, while the BOLD data counts differ by state. It does not explain the state-specific counts, whether the same participants contributed data across states, or how observations not represented in a state were handled. Missing-data methods and sensitivity analyses are not reported in the registry record.

The study is listed as single-group, with allocation NA and masking NONE. No separate randomized control group is described. This limits interpretation of a baseline comparison as a causal contrast. The statistical plan, analysis methods, sample-size justification, and any interim analyses are not reported in the registry record. The registry’s planning assumptions are not evidence that those assumptions were used in the study.

Safety entries are also limited: the registry records adverse-event counts but does not provide detailed event terms or the observation period. The deaths entry is not reported in the registry record. These limitations prevent a full assessment of outcome precision, analysis robustness, and safety reporting from the recorded information alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Combined Electroencephalogram, Magnetic Resonance Imaging-Positron Emission Tomography of Dexmedetomidine Induced Sleep — NCT01485380.
• Registry record last updated 2019-01-08; status last verified 2019-01.
• Results first posted 2014-10-10.
• 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.

19. Record Summary

NCT01485380 is a completed, single-group study sponsored by Massachusetts General Hospital. The registry lists enrollment of 20, a start of 2012-09, and primary completion of 2013-07. Dexmedetomidine-induced sedation was studied using EEG and MRI-PET.

The primary outcome concerns the number of participants with Default Mode Network changes during loss and recovery of consciousness compared with baseline, assessed using BOLD signals. The record states that all 17 participants were analyzed, with awake (n = 16), unconscious (n = 16), and recovery (n = 15) data in the final data set. The endpoint result and statistical analyses are not reported in the registry record.

The registry records 0 serious adverse events and 0 other adverse events among 20 participants at risk. Deaths are not reported in the registry record.