EEG Studies of Sevoflurane-Induced General Anesthesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for EEG Studies of Sevoflurane-Induced General Anesthesia (NCT03503578), a na phase 2 study. The primary outcome is Frequencies At Which Changes in Alpha, Theta, and Slow-Delta Wave Power Were Observed From Baseline During Sevoflurane-induced General Anesthesia.

2. Clinical Question

In broad terms, the study is intended to characterize electrical brain activity during induction of anesthesia and to examine how anesthetic drugs act in the brain. The EEG provides a way to record changing electrical signals over time. The registry’s outcome focuses on spectral power changes and the frequencies associated with those changes, rather than on a clinical outcome or a direct comparison of treatment effects. The research question is therefore descriptive and physiological as recorded, not a test of whether one regimen is superior to another.

3. Trial Design

This is a completed phase 2 study sponsored by Massachusetts General Hospital. The registry lists a start date of 2018-05-01 and a primary completion date of 2018-08-01. It describes the study as a single-group model, with allocation listed as NA and masking listed as none. These design details do not describe a randomized, blinded, parallel-group comparison.

The registry names the EEG Dynamics group and says EEG data would be collected from patients receiving sevoflurane, and sevoflurane and ketamine together. It lists both drugs as interventions. The record does not state how many patients received each exposure, whether the exposures were given in a fixed sequence, or whether every patient contributed data under both conditions. Those details are important for interpreting any within-person or between-condition contrast, but they are not reported in the registry record.

Enrollment is listed as 12, and the primary outcome description says EEGs of 12 patients were analyzed. The outcome timeframe is approximately 60 minutes. The registry identifies one primary outcome measure but lists no statistical analyses. It does not report a formal control condition, an allocation procedure, masking of EEG assessment, or a prespecified model for comparing the exposure conditions.

Consequently, the design information supports reading the study as an EEG characterization during sevoflurane-induced anesthesia, with ketamine also included in the intervention description. It does not support treating the named exposure conditions as randomized arms or interpreting their results as a controlled causal contrast. Details such as inclusion criteria, participant demographics, dose and timing, and the rationale for enrollment are not 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

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 Frequencies At Which Changes in Alpha, Theta, and Slow-Delta Wave Power Were Observed From Baseline During Sevoflurane-induced General Anesthesia, measured over Approximately 60 minutes.

The primary endpoint is the frequency, measured in Hz, at which changes from baseline in EEG spectral power were observed during sevoflurane-induced general anesthesia. The description highlights alpha, theta, and slow-delta wave power, while also referring to other spectral frequencies. The assessment is tied to loss of responsiveness and has an approximate timeframe of 60 minutes.

EEG spectral power describes how signal energy is distributed across frequencies. Examining frequency-specific changes can characterize patterns of brain electrical activity associated with an anesthetic state. In general, this type of measurement can help describe physiological dynamics that are not captured by a single clinical event alone. It does not, by itself, establish that a particular frequency change caused loss of responsiveness or that a drug regimen produced a beneficial clinical effect.

The registry says the reported frequency values represent findings for all 12 participants, but it does not include the actual values, a participant-level distribution, or an estimate of variability. It also does not explain whether the endpoint is a list of frequencies, a selected frequency per spectral band, or another aggregation of the EEG observations. Thus, the endpoint’s stated measurement and purpose can be described, but its numerical result and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is framed as a frequency measurement rather than a single treatment-effect estimate. Frequencies are expressed in Hz, and the endpoint description concerns changes from baseline in spectral power at sevoflurane-induced loss of responsiveness. In general, spectral analysis separates an EEG signal into frequency components and examines how signal power is distributed across those components. The registry names alpha, theta, and slow-delta activity, along with other frequencies, but does not provide the measured frequency values.

This distinction matters when interpreting statistical summaries. A treatment contrast usually compares a defined outcome between conditions or groups. A frequency characterization may instead report which frequencies were associated with observed changes. The registry does not explain how the observations were reduced to the stated outcome, whether the result is a set of frequencies or a selected value, or how variability across participants was represented. Without that information and the numerical findings, the magnitude and precision of the EEG pattern cannot be reconstructed.

In general, a confidence interval communicates uncertainty around an estimated quantity, using a statistical method and assumptions. A narrow interval would indicate greater precision than a wide interval, but neither can be judged without the estimate and interval. The registry record lists no confidence interval, standard error, or other dispersion measure for the primary outcome. It also lists no analysis. Consequently, there is no inferential result from which to evaluate statistical evidence or precision.

Over-dispersion is a general concern for count outcomes when observed variation exceeds what a simple count model assumes. It is not possible to determine from this record whether over-dispersion is relevant to the primary endpoint: the outcome is described as a frequency in Hz, not as a count with a reported distribution. More generally, an analysis should match the measurement scale and structure of the data. The record does not identify a statistical model, distributional assumptions, or a method for handling repeated EEG observations.

The trial is described as a single-group study, with allocation listed as NA and no masking. The intervention description includes sevoflurane and a combination of sevoflurane and ketamine, but no formal comparison method is recorded. In general, a causal comparison requires a clear definition of the conditions being contrasted and an analysis that accounts for how participants entered or experienced those conditions. If the same participants contributed data in multiple conditions, a paired analysis might be relevant; if different participants contributed to different conditions, other methods could be needed. The registry does not report which structure applies, so no particular comparison method should be assumed.

The sample-size assumptions recorded for planning illustrations specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not a description of the study’s actual design. The record describes a single-group study and does not report a formal two-arm comparison. Any planning illustration based on those assumptions should therefore not be read as the trial’s sample-size justification or as observed power. The registry does not report the protocol’s sample-size rationale.

Power is a design concept describing the probability that a planned analysis will detect an effect of a specified size under stated assumptions. It is not a measure of how likely a result is true, and a post hoc calculation based on an observed effect is not observed power. The record does not report a trial-specific power analysis or enough numerical outcome information to assess one. Planning calculations can illustrate hypothetical requirements under their assumptions, but they cannot replace an analysis of the study’s actual EEG data.

Multiplicity is a general concern when many outcomes, frequency bands, time points, or analytic choices are examined. If several hypotheses are tested, the chance of at least one false-positive result can increase unless the analysis addresses that issue. The registry names several spectral bands and other frequencies, yet it does not report the number of tested frequencies, a prespecified testing hierarchy, or any multiplicity adjustment. No claim about adjustment or selective reporting can be made from this information alone.

Missing-data methods also depend on how many observations are absent, why they are absent, and which analysis population is intended. The record says EEGs of 12 patients were analyzed, but it does not describe missing recordings, exclusions, incomplete time series, or data-quality criteria. It does not identify an intention-to-treat or per-protocol population. The absence of those details limits assessment of selection and completeness; it does not establish that data were missing or that they were complete.

Finally, the posted safety counts and the EEG endpoint answer different questions. Adverse-event counts describe recorded safety events in the listed group, while the primary endpoint concerns EEG frequencies. Neither the event counts nor the endpoint definition provides a substitute for the other, and no statistical relationship between them is reported. The overall methods information is insufficient to reproduce an inferential analysis, but it does identify what was intended to be measured and several important design details and omissions.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure, but its description refers to changes in several EEG spectral bands, including alpha, theta, and slow-delta, as well as other frequencies. Multiple frequency components can create multiplicity concerns if each is tested or selected from the data. In general, testing many related hypotheses can increase the chance of a false-positive finding unless the analysis plan addresses the family of tests. The registry does not report a multiplicity strategy, a prespecified hierarchy of spectral outcomes, or how frequency selection was handled.

The registry lists no statistical analyses. It therefore does not report the tests used, whether analyses were adjusted, or how any estimates were calculated. The outcome description gives a timeframe of approximately 60 minutes but does not specify how EEG measurements over that period were summarized or modeled. These methodological details are not reported in the registry record.

The record states that EEGs of 12 patients were analyzed. It does not describe whether any enrolled patients lacked usable EEG data, whether recordings or time points were incomplete, or how data quality and exclusions were handled. Missing-data methods and the reasons for any missing observations are not reported in the registry record. The analysis population is not given a formal label, and the registry does not describe an intention-to-treat or per-protocol approach.

These omissions do not establish that multiplicity was unaddressed or that data were missing. They mean that readers cannot determine the planned handling of multiple frequency findings, the completeness of the measurement process, or the population represented by a formal statistical analysis from the registry record.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

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

For the EEG Dynamics group, the registry lists 12 at risk for serious adverse events and reports zero serious adverse events. It also lists 12 at risk for other adverse events and reports zero other adverse events. Deaths are listed as zero. These are the posted registry counts; they should be read as reported event totals for the listed group, not as a complete account of every possible safety outcome.

The registry record does not provide additional event details, definitions, attribution to a particular drug, or a description of the safety observation and reporting procedures. It also does not give a separate safety breakdown for sevoflurane alone versus sevoflurane combined with ketamine. The counts therefore do not establish comparative safety between those exposure conditions, and the zero counts do not show that an adverse event could not occur. They describe only what is recorded for this study group.

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

The registry record identifies a study of EEG dynamics during sevoflurane-induced general anesthesia and describes an outcome based on frequencies associated with changes in spectral power from baseline. It also names ketamine in the intervention description. This establishes the subject and measurement of the study, but the record does not report the observed frequency values. The size, direction, and precision of the EEG findings therefore cannot be described from the recorded information.

The study’s single-group designation and allocation listed as NA do not support a randomized comparison. The registry does not specify the number of patients under each exposure condition or how the conditions were sequenced. As a result, the record does not establish a contrast between sevoflurane alone and sevoflurane with ketamine, nor can it isolate the effect of either drug. The EEG outcome is a physiological measurement, not by itself evidence of a clinical benefit or a causal mechanism.

The reported safety counts are zero serious adverse events, zero other adverse events, and zero deaths in the listed group. These counts are limited to the registry’s recorded group and categories. They do not supply comparative safety estimates or detailed information about event assessment.

In general, a study can contribute descriptive information even when a registry record does not report an inferential analysis. Here, however, the missing numerical EEG values and absence of listed statistical analyses prevent evaluation of how consistent or precise the frequency findings were. Conclusions should remain within the scope of the recorded details: the study examined EEG spectral changes during anesthesia, but the registry record does not provide enough results to quantify those changes or compare drug conditions.

13. Why This Trial Matters Statistically

This study illustrates how a clinical research question can focus on a physiological signal rather than a conventional clinical endpoint. EEG spectral power represents electrical activity across frequencies, and characterizing changes from baseline can describe brain activity during anesthetic induction. The outcome’s focus on alpha, theta, slow-delta, and other frequencies makes the measurement potentially multidimensional, which raises questions about how findings are selected, summarized, and compared.

The registry also illustrates why design labels matter. A single-group study with allocation listed as NA is not equivalent to a randomized comparison. Although both sevoflurane and sevoflurane with ketamine appear in the intervention description, the record does not provide the condition-specific allocation or comparison procedure needed to interpret a treatment contrast. Without those details, physiological characterization should not be recast as evidence of comparative drug effects.

Statistically, a defined outcome is only one part of a useful result. Readers also need the observed values, an account of variation, and a clear analysis method to assess magnitude and precision. The registry provides an outcome definition and states that EEGs of 12 patients were analyzed, but it lists no statistical analyses and does not report the frequency results. This limits what can be inferred, regardless of the study’s completion status.

The record is a useful reminder that transparency includes reporting how complex measurements are reduced to interpretable outcomes. Frequency selection, repeated observations, multiplicity, and data completeness can all affect interpretation. The registry does not resolve these issues, so its contribution is chiefly to identify the study question and measurement framework rather than to support a quantitative conclusion.

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.

The main limitation for interpreting this study from the registry record is the absence of numerical primary outcome results. The endpoint description identifies frequency changes in EEG spectral power, but it does not report the frequencies observed. There is also no measure of variability or uncertainty, and no listed statistical analysis. Accordingly, the size and precision of the findings cannot be assessed.

The design information is limited for evaluating drug conditions. The study is described as single group, allocation is listed as NA, and masking is listed as none. The intervention description includes sevoflurane and sevoflurane with ketamine, but the registry does not say how many patients contributed to each exposure, whether participants experienced both conditions, or how the conditions were administered in relation to one another. It does not report a formal comparator or a procedure for estimating a contrast.

The outcome description names several spectral bands and other frequencies, while the record does not specify how the EEG observations were summarized, how frequencies were selected, or how repeated measurements were handled. Multiplicity procedures, missing-data methods, data-quality rules, and the analysis population are not reported in the registry record. These gaps limit reproducibility and assessment of potential selection or analytic choices.

The registry provides little detail about the participants beyond the statement that EEGs of 12 patients were analyzed. Eligibility criteria, participant characteristics, drug doses and timing, and the rationale for enrollment are not reported. The safety listing gives event counts but no event definitions, attribution, or separate condition-level results. These limitations restrict interpretation of both the physiological outcome and the safety record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: EEG Studies of Sevoflurane-Induced General Anesthesia — NCT03503578.
• Registry record last updated 2019-10-24; status last verified 2019-10.
• Results first posted 2019-10-24.
• 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.

18. Record Summary

NCT03503578 is a completed phase 2 study titled “EEG Studies of Sevoflurane-Induced General Anesthesia,” sponsored by Massachusetts General Hospital. The registry lists a start date of 2018-05-01, a primary completion date of 2018-08-01, enrollment of 12, a single-group model, allocation listed as NA, and no masking.

The study describes EEG data collection during sevoflurane anesthesia and during sevoflurane with ketamine. Its primary outcome concerns frequencies associated with changes from baseline in alpha, theta, slow-delta, and other EEG spectral power at loss of responsiveness, over approximately 60 minutes. The registry says EEGs of 12 patients were analyzed, but does not report numerical frequency results or statistical analyses.

The EEG Dynamics group has zero serious adverse events, zero other adverse events, and zero deaths recorded. The registry does not describe a formal comparison between the exposure conditions or provide detailed analysis, missing-data, or multiplicity methods.