Dexmedetomidine and Propofol for Pediatric MRI Sedation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Dexmedetomidine and Propofol for Pediatric MRI Sedation (NCT03513757), a randomized phase 4 study. The primary outcome is Efficiency of Propofol Dexmedetomidine Sedation Compared With Propofol Infusion.

2. Clinical Question

The trial was randomized and used a parallel-group design. Its stated aim was to compare the two sedation approaches in children having MRI. The registry record lists an enrollment of 40 and reports results for 22 participants in the propofol arm and 18 in the propofol–dexmedetomidine arm. These are the arm-level counts for the primary outcome; the record does not describe how participants without a reported outcome, if any, were handled.

The clinical question is about the time to a recovery-readiness milestone, rather than only the time spent receiving sedation or the duration of the MRI scan. The endpoint begins at anesthesia start and ends when the participant is ready for discharge. It therefore captures a period that includes both the scan-related sedation and the subsequent time until readiness. The record does not define additional discharge criteria.

The study also recorded other outcomes, including medication use, eye opening, oral or enteral intake, and observations after the scan. These may help describe aspects of the sedation and recovery experience, but the primary question remains the comparison of discharge-readiness time. The registry record does not report a formal comparative analysis for that primary outcome, so the posted medians and inter-quartile ranges support a descriptive comparison rather than a definitive inferential conclusion.

3. Trial Design

The registry record describes a completed phase 4, randomized, triple-masked, parallel-group study sponsored by the Medical College of Wisconsin. It lists an enrollment of 40. The study compared propofol infusion with a propofol–dexmedetomidine regimen for sedation during pediatric MRI. The record does not explain who was masked or how masking was maintained, so the meaning of “triple” masking cannot be further specified from this information alone.

The registry’s primary outcome was efficiency of propofol–dexmedetomidine sedation compared with propofol infusion. “Efficiency” was operationalized as time, in minutes, from anesthesia start to readiness for discharge from the department to home or clinic. The outcome was summarized using a median and inter-quartile range. Results were posted for 22 participants in the propofol arm and 18 in the combination arm.

The study summary describes additional medicines that could be used around the MRI, including sevoflurane and nitrous oxide at the start of sedation, lidocaine to reduce pain from propofol injection, and glycopyrrolate to prevent heart rate from decreasing too low. It also says that additional medication could be given if needed to complete the scan. Those co-interventions are relevant when interpreting a comparison of the overall sedation strategies: the groups were not necessarily exposed only to the two medicines named in their arm titles. The available arm descriptions are incomplete, so the full dosing and administration procedures are not reported in the registry record.

The study summary describes recording additional blood pressures and heart rates, observing recovery milestones, and contacting participants after the MRI about behavior, eating, and sleeping. The registry record lists secondary outcomes that include medication use, eye opening, oral or enteral intake, nitrous oxide, and sevoflurane. It does not provide enough detail to establish the full schedule of assessments or the exact definitions used for every outcome.

The registry record lists the study as completed. It does not report the protocol’s sample-size justification, a planned interim analysis, or a statistical analysis plan. Those omissions limit what can be established about the intended analysis, but do not change the descriptive meaning of the results that were posted.

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.

Population: No difference

6. Primary Endpoint

The registry lists the primary outcome as Efficiency of Propofol Dexmedetomidine Sedation Compared With Propofol Infusion, measured over through study completion, an average of 2 hours.

The primary endpoint measures elapsed time from anesthesia start until a participant is ready for discharge from the department to home or clinic. It is reported in minutes. Because it spans the period from the start of anesthesia through recovery to discharge readiness, it is intended to capture more than the time required to administer sedation or complete imaging alone. The registry record describes the endpoint as an efficiency measure for comparing the two sedation approaches.

The record summarizes this outcome with a median and inter-quartile range. A median identifies the middle of the observed distribution, while the inter-quartile range describes the interval from the lower quartile to the upper quartile. These summaries are useful when the distribution may be skewed or when a typical duration is more informative than an average. The registry does not report an estimate of the between-group difference, a confidence interval for that difference, or a p-value for the primary endpoint.

The propofol arm had a median of 98 minutes, with an inter-quartile range of 86 to 115 minutes. The propofol–dexmedetomidine arm had a median of 77 minutes, with an inter-quartile range of 64 to 102 minutes. These are descriptive summaries for the posted groups. They do not, by themselves, establish the size or precision of a treatment contrast. The inter-quartile ranges also describe variation among participants within each arm, rather than uncertainty in the estimated difference between arms.

Readiness for discharge is a practical recovery milestone, but its interpretation depends on how readiness was assessed. The record gives the endpoint description but does not report detailed discharge criteria or the method used to ensure consistent assessment across participants.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a median and inter-quartile range describe?

A median is a measure of the center of a distribution. It is the point that divides ordered observations into a lower and an upper portion. The inter-quartile range runs from the lower quartile to the upper quartile and describes the middle half of the observations. Together, these summaries communicate a typical observed value and the spread of individual results without requiring a symmetric distribution.

For the primary endpoint, the registry reports a median of 98 minutes and an inter-quartile range of 86 to 115 minutes in the propofol arm. For the propofol–dexmedetomidine arm, it reports a median of 77 minutes and an inter-quartile range of 64 to 102 minutes. The ranges are not confidence intervals. They do not express how precisely the median, or a difference between medians, has been estimated. The registry does not report a confidence interval or p-value for the primary comparison.

What is a confidence interval?

In general, a confidence interval is a range of values compatible with an estimate under a specified statistical method and its assumptions. It expresses uncertainty about an estimated quantity; it is not a range containing a stated proportion of individual participant outcomes. For binary secondary outcomes, the registry posts confidence intervals for risk differences. A wide interval indicates that the posted data are compatible with a broad range of possible contrasts. An interval that includes no difference does not prove that the groups are equivalent; it indicates that the data do not rule out no difference under that interval method.

The secondary risk-difference intervals are -0.067 to 0.319 for nitrous oxide and sevoflurane, and -0.229 to 0.179 for sleep pattern. These intervals include no difference and extend to values in both directions. They therefore reflect uncertainty about the direction and size of the contrasts. The record does not provide a formal primary-endpoint interval, so the same precision assessment cannot be made for the primary outcome.

What does an unadjusted p-value tell the reader?

In general, a p-value describes how unusual the observed data, or data more extreme, would be under a specified null hypothesis and statistical model. It is not the probability that the null hypothesis is true, and it does not describe the size or practical importance of an effect. The secondary comparisons are marked as unadjusted. That means their p-values do not account for the possibility of chance findings across multiple outcomes or comparisons. They should be interpreted cautiously and alongside the effect estimates and confidence intervals.

The registry does not report a p-value or inferential test for the primary endpoint. As a result, a reader cannot use the posted primary outcome to assess statistical evidence against a null hypothesis using the registry’s reported analysis. The arm-level medians remain informative as descriptive summaries, but they do not replace an analysis of the contrast.

Why can small studies produce uncertain estimates?

In general, estimates from studies with limited information can be sensitive to the outcomes of a small number of participants. This can lead to wide confidence intervals and substantial uncertainty in estimated effects. A non-significant result is not evidence that two approaches are identical, and an apparently notable estimate may also be imprecise. The arm-level outcome counts in this study are modest, and the intervals posted for secondary comparisons are broad enough to include a range of possible effects.

The registry also includes planning illustrations based on observed effects. These are not observed power calculations and do not describe what the trial was designed to detect. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the effect to detect is defined as a stated fraction of the observed effect. These calculations are illustrations for planning a future study. They depend on assumptions and on the observed estimate, which itself may be uncertain. The trial’s own sample-size justification is not reported in the registry record.

How should co-interventions and outcome definitions be considered?

The study summary describes possible use of nitrous oxide and sevoflurane at the start of sedation, lidocaine to reduce pain from propofol injection, and glycopyrrolate to prevent heart rate from decreasing too low. It also states that additional medications could be administered if required to complete a scan. These medicines and decisions may be part of the practical sedation strategy, but the full protocol is not reported. A comparison between arm assignments may therefore represent the overall care strategies used in the study rather than an isolated pharmacologic contrast between two medicines.

The primary endpoint is described as readiness for discharge, but detailed criteria and assessment procedures are not reported in the registry record. The record also does not specify the analysis population, how missing observations were handled, or whether the analysis followed the randomized assignment regardless of treatment received. These details matter because they help determine how reproducible and interpretable the estimated comparison is.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists multiple secondary outcomes, including medication doses or use, eye opening, oral or enteral intake, and sleep pattern. It reports comparative estimates for some binary outcomes but does not report an approach to multiplicity. When many outcomes are examined, the chance of obtaining one or more apparently notable results by chance can increase. Statistical approaches can control or describe that issue, but the record does not say that any such approach was used. The secondary p-values are unadjusted and should therefore be treated as exploratory rather than as a set of independent confirmatory tests.

The record does not report which secondary outcomes were designated as key, whether a hierarchy was prespecified, or how the investigators planned to interpret outcomes with missing or incomplete observations. The analysis population is not reported. It is therefore not possible to establish from the registry record whether results were analyzed according to randomized assignment, according to treatment received, or using another population definition.

Missing-data handling is also not reported. The arm-level primary outcome counts are posted, but the registry does not explain whether all randomized participants contributed to that outcome, why the posted counts differ by arm, or whether any observations were unavailable. No assumption about the missingness mechanism or its effect on the estimates can be justified from the record. In general, missing outcomes can affect both the precision and the interpretation of a comparison, especially if their availability is related to treatment assignment or participant recovery.

The registry record does not report an interim-analysis plan, an analysis plan for the primary comparison, or a sample-size justification. It also does not state whether any sensitivity analyses were conducted. These are reporting gaps, not evidence that the analyses were improperly conducted. They do mean that readers cannot assess whether the posted analyses followed a prespecified plan or how robust the results are to alternative assumptions.

These limitations are particularly relevant when considering the secondary results. Without an analysis population, missing-data details, and a multiplicity plan, the posted comparisons cannot be interpreted as a comprehensive or definitive account of all planned outcomes. The primary outcome’s descriptive summaries remain readable, but the record does not provide the additional information needed for a full inferential assessment.

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.

Most frequent non-serious adverse event terms

The registry reports 0 serious adverse events and 0 deaths in the propofol arm, and 0 serious adverse events and 0 deaths in the propofol–dexmedetomidine arm. These figures describe what was recorded in the study groups; they do not establish that serious events are impossible or that the regimens have no safety risks. With a limited number of participants, uncommon events may not be observed.

Other adverse events were reported for 13 of 22 participants in the propofol arm and 10 of 18 participants in the propofol–dexmedetomidine arm. The record does not list serious adverse-event terms, and the serious-event counts are zero in both groups. It does not provide a detailed breakdown of the other adverse events, their severity, timing, or relationship to study medication in the information available for this summary.

These safety figures are descriptive. They are not a formal test of whether the groups differ in safety, and the record does not report a comparative analysis for adverse events. The absence of reported serious events should be interpreted in the context of the study’s limited size and the registry’s level of detail. The counts do not support a broad conclusion about safety beyond the events recorded in this trial.

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

The primary results describe observed time to readiness for discharge in two randomized arms. The posted median is 98 minutes for propofol and 77 minutes for propofol–dexmedetomidine. Their inter-quartile ranges describe the spread of participant times within each arm. These summaries make the observed pattern visible, but the registry record does not report a formal primary comparison, a confidence interval for a contrast, or a primary-outcome p-value.

Accordingly, the posted results do not establish how precisely the groups differ in discharge-readiness time. They do not show that the combination regimen causes a shorter time, nor do they establish that the groups are equivalent. A causal interpretation would require a reported analysis that accounts for the randomized comparison and its uncertainty, along with sufficient information about the analysis population, missing data, and outcome assessment.

The study’s randomized design is relevant because randomization is intended to make groups comparable on average at the start of a trial. However, randomization alone does not supply an effect estimate or resolve reporting gaps. The registry record describes additional medicines that could be used during sedation and permits additional medication if needed to complete a scan. The full protocol and analysis details are not reported, so the posted comparison should be understood as a description of the study’s assigned strategies and recorded outcomes.

The secondary outcomes provide further observations, but they are not a replacement for the primary analysis. Their unadjusted comparisons are uncertain and are subject to the interpretive problems that arise when multiple outcomes are examined. They can contribute context, but should not be treated as independent proof of a treatment effect.

These results are specific to the participants and procedures recorded in this trial. The registry record does not report enough information to assess how well its findings apply to other settings, patient groups, MRI procedures, or sedation protocols. The figures therefore support a careful description of this study, not a general recommendation about clinical care.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between descriptive results and a comparative analysis. It reports a median and inter-quartile range for its primary endpoint in each arm, which allows readers to see the observed center and spread of discharge-readiness times. But an arm-by-arm summary is not the same as an estimated contrast with uncertainty. Without a reported primary comparison, readers cannot assess the precision of the difference using the registry record alone.

The trial also illustrates why the choice of summary should match the outcome. Time to readiness is reported using medians and inter-quartile ranges, while some secondary outcomes are binary and reported using risk differences and confidence intervals. These approaches answer different questions. A confidence interval around a risk difference cannot be used to infer the uncertainty in the primary time outcome, and overlap between inter-quartile ranges is not a substitute for a direct test or interval for a contrast.

Its secondary outcomes show another important statistical issue: multiplicity. When several measures are examined, unadjusted results are more appropriately treated as exploratory unless a prespecified strategy supports confirmatory interpretation. The record does not report such a strategy. Nor does it report an analysis population or missing-data approach. Those details are central to understanding what participants contributed to the estimates and how complete the evidence is.

The planning illustrations are also a useful reminder that sample-size calculations depend on assumptions. These calculations use observed effects and stated planning assumptions, so they are not evidence of achieved power and do not describe the study’s original design rationale. Their value is in illustrating possible future-study requirements under particular assumptions, not in deciding whether the present results are conclusive.

Overall, the record presents useful trial-level descriptive information while leaving key inferential and design details unreported. That contrast helps readers distinguish what the data directly describe from what would require a fuller statistical analysis.

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 registry record leaves several limitations specific to this trial. It gives arm-level primary summaries but does not report a comparative analysis, confidence interval, or p-value for the primary endpoint. The outcome is defined as time from anesthesia start to readiness for discharge, but detailed criteria for readiness and information about who assessed it are not reported. This makes it difficult to judge how consistently the endpoint was measured.

The arm descriptions are incomplete. The study summary mentions additional medications and allows additional medication if needed to complete the scan, but the full protocol and the distribution of co-interventions by arm are not reported. Consequently, the registry record does not allow readers to determine whether differences in medication use or clinical management influenced observed recovery times.

The reported primary-outcome counts differ between the arms, but the record does not explain the relationship between the enrollment figure and the outcome counts, or describe whether any participants were excluded from the primary analysis. The analysis population and missing-data handling are not reported. This prevents assessment of whether all randomized participants were included and whether missing outcomes could have affected the comparison.

The record also does not report a sample-size justification, a primary analysis plan, an interim-analysis plan, a multiplicity approach, or sensitivity analyses. It is therefore unclear which analyses were planned in advance and how the study’s precision was anticipated. The secondary comparisons are unadjusted, and the record does not establish a hierarchy among outcomes.

Finally, information needed to judge generalizability is limited. The listed conditions identify a broad range of reasons for MRI, but eligibility criteria, age range, and detailed clinical characteristics are not reported. These omissions do not invalidate the posted observations, but they narrow the conclusions that can be drawn from them.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Dexmedetomidine and Propofol for Pediatric MRI Sedation — NCT03513757.
• Registry record last updated 2020-02-21; status last verified 2020-02.
• Results first posted 2020-02-21.
• 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 record describes a completed, randomized, triple-masked, parallel-group phase 4 study of pediatric MRI sedation, sponsored by the Medical College of Wisconsin. It lists enrollment of 40 and compares propofol infusion with a propofol–dexmedetomidine regimen.

The primary endpoint was time from anesthesia start to readiness for discharge, summarized by arm as a median and inter-quartile range. The posted medians were 98 minutes for propofol and 77 minutes for propofol–dexmedetomidine. The registry does not report a formal primary comparison or its uncertainty.

Several secondary outcomes are listed, with unadjusted comparisons posted for selected binary outcomes. Serious adverse events and deaths were recorded as 0 in each arm. Important details—including the primary analysis plan, analysis population, missing-data handling, multiplicity strategy, and sample-size justification—are not reported in the registry record.