Impact of Propofol Reduction in Anesthesia Induction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Propofol Reduction in Anesthesia Induction (NCT04194151), a randomized phase 4 study. The primary outcome is Systolic Blood Pressure Variation.

2. Clinical Question

The trial asks whether systolic blood pressure responses during anesthesia induction differ according to both the propofol dose and the time between fentanyl and propofol administration. The registry description also identifies time to hypnosis and use of vasoactive drugs as secondary outcomes. The posted record does not include numerical results for these outcomes, so it does not establish the direction or size of any observed differences.

Because dose and timing vary together across the groups, interpretation depends on which group contrasts are reported and how they are analyzed. A difference between groups that vary on both factors would not, by itself, isolate the effect of dose or timing. The registry record does not report a primary-outcome contrast or an analysis that separates these effects.

3. Trial Design

This is a phase 4, randomized, single-masked, parallel-group trial. The registry reports enrollment of 192 and a completed status. The recorded start date is 2017-11-01, and the primary completion date is 2018-10-26. Hospital Central de la Defensa Gómez Ulla is listed as the sponsor.

Patients were assigned to groups defined by the interval between fentanyl and propofol administration and by propofol dose. Fentanyl was administered at 2 μg/kg; propofol followed after 1 minute or 2 minutes at 1 mg/kg, 1,5 mg/kg, or 2 mg/kg. The record describes the allocation as randomized, but does not report the random-sequence method, allocation concealment, or who was masked. The meaning of single masking is therefore not specified in the registry record.

The parallel design means the assigned group is the basis for comparing the recorded outcomes; the record does not describe a crossover. The study summary states that time to hypnosis, defined using bispectral index (BIS<60), and hemodynamic parameters were registered. Blood pressure measurements were described at baseline before fentanyl, pre-intubation after propofol and reaching the BIS threshold, and postintubation 15 seconds after the endotracheal tube was positioned.

The registry lists five outcome measures and two secondary-outcome topics: time to hypnosis and the number of patients who needed a vasoactive drug. It does not report numerical results for the primary outcome in the record. It also does not report the intended primary comparison, the statistical analysis plan, or the sample-size justification. These omissions limit assessment of how the completed study was intended to answer its stated question.

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.

Before assignment: Randomization was prior to data collection. The patient number was assigned by computerized randomizer to the 6 study groups. The collection was systematic from day one of the study, including all patients who met inclusion criteria and accepted participation. Of 192 patients enrolled, 186 met inclusion criteria.

Overall Study

Reasons for not completing this period:

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Systolic Blood Pressure Variation, measured over Baseline before fentanyl administration, pre-intubation after propofol and bispectral index<60 and postintubation 15 seconds after endotracheal tube positioned.

The primary endpoint is systolic blood pressure variation, expressed as a percentage of variation. It describes non-invasive systolic blood pressure change across the study moments: baseline before fentanyl administration, pre-intubation after propofol and BIS<60, and postintubation 15 seconds after endotracheal tube positioning. The registry description says that positive values mean a percentage reduction in systolic blood pressure between the studied moments, while negative values mean a percentage increase. The record does not provide the numerical endpoint results or specify a single pair of moments as the primary contrast.

Blood pressure is recorded in this study as a hemodynamic response to the induction sequence. A percentage-change measure expresses movement relative to a reference measurement rather than only an absolute pressure value. That can help describe change across different moments, but interpretation depends on the exact reference and comparison being used. Since the registry describes multiple moments and does not reduce the endpoint to one comparison, a result for one interval should not be treated as though it represented every interval.

For a continuous endpoint summarized by a mean and standard deviation, the mean describes the group’s average recorded variation, while the standard deviation describes how dispersed individual observations are around that average. The registry record identifies those summary statistics but does not report the estimates. It also does not provide a clinical threshold for interpreting a particular percentage change. Accordingly, the endpoint definition alone cannot establish the magnitude, precision, or practical importance of any group difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is continuous: systolic blood pressure variation is recorded as a percentage, with a mean and standard deviation specified as the summary. General statistical explanation can clarify what those summaries would mean, but the registry record does not report the estimates or the inferential method used for the outcome.

What does a mean describe?

For a continuous measure, the mean is the arithmetic average of the recorded values in a group. It gives a central summary, not a description of every participant’s measurement. Two groups can have similar means while their individual observations vary substantially, or their means can differ while the distributions overlap. The mean alone also does not show whether a difference is concentrated in a subgroup or is broadly distributed across observations.

The endpoint’s percentage scale and sign definition are important to reading a mean. Positive values are defined as a reduction in systolic blood pressure, and negative values as an increase between studied moments. Any comparison should identify the moments and reference involved. The registry lists baseline, pre-intubation, and postintubation measurements but does not state one primary pairwise interval in the description.

What does a standard deviation describe?

In general, a standard deviation describes the spread of observations around their mean, in the same measurement units. A small standard deviation indicates that observations are relatively clustered around the average; a larger one indicates greater dispersion. It is not the uncertainty of the mean itself, and it does not show the range of observed values. The registry identifies standard deviation as the dispersion measure but does not report its values.

How should uncertainty be assessed?

In general, a confidence interval describes a range of estimates compatible with the data and the specified statistical procedure. Its width conveys precision: a narrower interval indicates greater precision under that procedure, while a wider interval indicates less. A confidence interval is not a guarantee that the true value lies inside its particular limits. The registry record does not report confidence intervals for the primary endpoint, so its precision cannot be assessed from the outcome results.

A hypothesis test, when used, evaluates data against a specified null hypothesis under model assumptions. A p-value does not measure the probability that a treatment effect is true, and it does not quantify the size or practical relevance of a difference. The record does not report p-values or the test used for the primary outcome. The significance level in the sample-size assumptions is a planning input and does not establish which inferential procedure was used for the completed analysis.

Why does the group structure matter?

The randomized groups combine two design factors: the interval between fentanyl and propofol and the propofol dose. A comparison may therefore involve a change in timing, dose, or both. A model that estimates separate factor effects or an interaction would answer a different question from a simple comparison between two combined regimens. The registry does not report the primary contrast, model, or whether an interaction was assessed. No particular analytic approach can be attributed to the trial from this record.

Measurements were described at baseline, pre-intubation, and postintubation. Repeated measurements within a participant are generally statistically related; they are not equivalent to independent observations. General methods for repeated measurements account for that dependence when estimating changes across time. The record does not state whether the analysis used a repeated-measures model, analyzed changes between selected moments, or applied another method. Nor does it say whether baseline blood pressure was used as a covariate.

Distributional assumptions also matter. A normal approximation is explicitly mentioned among the planning assumptions, but that does not demonstrate that the completed-outcome analysis used a normal model or that its assumptions were checked. General model assessment would consider the outcome’s distribution and the pattern of residual variation. The registry record does not report diagnostic checks or a rationale for any model choice.

What does the planning illustration mean?

The stated illustration uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It is based on the observed effect, while the target effect is a stated fraction of that observed effect. The illustration is not the same as a prospective sample-size justification: the registry does not report the trial’s own design calculation. It is also not observed power. Sample-size illustrations indicate what would be planned under their assumptions; they do not show the probability that the completed study detected an effect, nor do they replace estimates and confidence intervals.

For a time-to-event outcome, event-based planning can be expressed in terms of total events, whereas other planning approaches may express participants per arm. The registry’s planning note makes that distinction. The listed secondary outcome is time to hypnosis, but the record does not say that it is a time-to-event analysis or report an event-based result. Its scale and analysis method are not specified beyond its name.

Finally, statistical interpretation requires knowing which participants contributed to each outcome, how missing observations were handled, and whether the stated analysis followed randomized assignment. Those details are not reported in the registry record. Without the numerical estimates and methods, the design and endpoint descriptions can be explained, but the statistical strength of the outcome findings cannot be evaluated.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and identifies systolic blood pressure variation as the primary outcome, with time to hypnosis and the number of patients who needed a vasoactive drug listed as secondary outcomes. The primary endpoint description includes multiple measurement moments and does not reduce them to one comparison. The record does not state which contrasts were prespecified, how many comparisons were tested, or whether any procedure was planned to control the chance of false-positive findings when making multiple comparisons. Multiplicity handling is not reported in the registry record.

In general, testing multiple outcomes, time points, or group contrasts can increase the chance that at least one apparently unusual result occurs by chance. Adjusting for multiplicity can address that issue, but the appropriate approach depends on the questions and analysis plan. The record does not report an adjustment method, a testing hierarchy, or whether results were intended to be confirmatory or exploratory. No claim about such procedures can be made from the available registry description.

The record also does not describe missing-data counts, reasons for missingness, imputation, or sensitivity analyses. Missing outcome measurements can affect both the estimate and its uncertainty, especially if the chance of missingness is related to the participant’s condition or recorded response. General statistical practice distinguishes these possibilities, but the registry does not provide enough information to determine what applied in this trial.

Although the study is described as randomized, the analysis population is not specified. The registry record does not state whether analyses followed the randomized assignment regardless of adherence, included only participants with recorded outcomes, or used another population definition. It also does not report exclusions from analysis or participant flow by outcome. These omissions limit assessment of the relationship between randomization and the reported analyses.

There is no reported statistical analysis plan, interim-analysis information, or adjustment strategy in the record. Their absence from the registry record should not be interpreted as proof that a procedure was or was not used; it means the record does not establish it.

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 1% reporting threshold.

Most frequent non-serious adverse event terms

The adverse-event record lists serious events as zero in each of the six named time-dose groups. Deaths are also recorded as zero in each group. These are registry counts, not estimates of the probability of an event, and they do not establish that an event is impossible. The record does not report event definitions, severity criteria, observation duration, or detailed event narratives.

The same entries list other adverse events separately from serious adverse events. The recorded other-event counts are 4 for the 2 Minute - 2 mg/kg Group, 1 for the 2 Minute - 1,5 mg/kg Group, 0 for the 2 Minute - 1 mg/kg Group, 2 for the 1 Minute - 2 mg/kg Group, 3 for the 1 Minute - 1,5 mg/kg Group, and 0 for the 1 Minute - 1 mg/kg Group. These counts should not be confused with the serious-event counts. The record does not provide descriptions of these other events or a basis for judging their clinical relevance.

Counts need context to support comparisons: the recorded at-risk group sizes differ, and no event-rate analysis or uncertainty interval is reported in the registry record. The event counts alone do not establish whether groups differ in safety, and the zero serious-event entries should not be read as evidence of equivalent safety.

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

The registry record establishes that the trial was designed to compare propofol dose and the interval after fentanyl during anesthesia induction, with systolic blood pressure variation as the primary outcome. It describes how positive and negative endpoint values are interpreted and identifies time to hypnosis and use of vasoactive drugs as secondary outcomes. This information clarifies the research question and measurement plan.

The record does not provide numerical primary-outcome results, secondary-outcome estimates, confidence intervals, or statistical test results. Consequently, it does not establish whether the groups differed, the size or direction of any difference, or how precisely an estimate was measured. It cannot support a conclusion that any dose or interval had a larger or smaller blood pressure response.

The design varies both propofol dose and fentanyl-to-propofol timing across groups. Without a reported contrast and analysis, a difference between groups cannot be attributed specifically to one factor. The registry record also does not report enough about missing outcomes, analysis populations, or adjustment for multiple comparisons to assess those aspects of the results.

The safety entries record zero serious adverse events and zero deaths in each group, alongside separate counts for other adverse events. These are descriptive counts in the registry record, not proof that serious harms cannot occur or that safety is the same between groups. No event-rate comparison or uncertainty estimate is reported.

Thus, the available record supports a description of trial design, intended measurements, and recorded adverse-event counts. It does not provide the outcome evidence needed to determine the comparative statistical findings or their precision. That distinction is important: knowing what a trial set out to measure is not the same as knowing what its results showed.

13. Why This Trial Matters Statistically

This trial is statistically notable because it varies two components of an induction sequence: propofol dose and the interval after fentanyl. That structure makes the exact comparison important. A contrast between groups that differ in both factors cannot automatically isolate the contribution of either one. A clearly reported analysis would need to connect its estimates to the specific dose, timing, or combined-regimen question being asked.

The primary outcome is recorded across multiple induction moments, with a defined sign convention for percentage change. This illustrates why endpoint definitions matter: the direction of a numeric value depends on how the change is encoded, and a result for one pair of moments may not characterize the response across every measured moment. The registry description lists the moments but does not identify a single primary interval comparison.

The case also shows why statistical conclusions depend on more than a design label or enrollment figure. Randomization describes how groups were assigned, but interpretation also requires outcome estimates, measures of uncertainty, analysis methods, and information about missing data and the analysis population. These details are not reported in the registry record.

Finally, the record includes serious and other adverse-event counts that are distinct types of information. Zero recorded serious events is a descriptive observation; it is not an estimate with precision and does not demonstrate equivalence. Separating event counts from comparative inference helps prevent overinterpretation. The trial’s statistical relevance lies in the structure of its question and the need to align claims with the specific estimates and methods actually reported.

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 most direct limitation for interpreting the registry record is the absence of numerical primary-outcome results. The record identifies systolic blood pressure variation, its sign convention, and the measurement moments, but does not report group means, standard deviations, contrasts, confidence intervals, or test results. The direction, magnitude, and precision of the primary findings therefore cannot be assessed.

The record does not define one primary comparison among the baseline, pre-intubation, and postintubation measurements. Since the groups differ by both dose and timing, an unspecified contrast also leaves unclear which component of the induction sequence an estimate would address. The analytic model and any assessment of dose-by-timing interaction are not reported.

Further limitations include the absence of a statistical analysis plan, details of randomization and concealment, and an explanation of who was masked. The record does not describe participant characteristics, outcome-specific analysis populations, missing observations, exclusions, or sensitivity analyses. The number of outcome measures is reported, but multiplicity procedures and the prespecification of detailed contrasts are not.

The serious-event entries are counts without event descriptions, follow-up context, or comparative uncertainty estimates. Other adverse-event counts are also not described in detail. They should therefore be interpreted as registry entries rather than a complete account of safety or a formal comparison among groups.

Finally, the planning assumptions describe an illustration based on the observed effect, not the trial’s own design justification. The record does not report the original sample-size rationale or the numerical planning outputs described by those assumptions. These gaps limit both reproducibility and the extent to which readers can evaluate the statistical evidence.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Impact of Propofol Reduction in Anesthesia Induction — NCT04194151.
• Registry record last updated 2020-08-12; status last verified 2020-08.
• Results first posted 2020-08-12.
• 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

The registry identifies NCT04194151 as a completed phase 4 randomized, single-masked, parallel-group study sponsored by Hospital Central de la Defensa Gómez Ulla. Enrollment was 192. The recorded start date is 2017-11-01, and the primary completion date is 2018-10-26.

The study examined propofol dose and the interval after fentanyl during anesthesia induction. The primary outcome was systolic blood pressure variation, with measurements described at baseline, pre-intubation, and postintubation. Time to hypnosis and the number of patients who needed a vasoactive drug were listed as secondary outcomes.

The registry record does not report numerical primary or secondary outcome findings, confidence intervals, or inferential test results. It records zero serious adverse events and zero deaths in each group, alongside separate counts of other adverse events. Important details about analysis methods, missing data, multiplicity, and analysis populations are not reported in the registry record.