Remifentanil Only vs. Midazolam and Meperidine During Elective Colonoscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Remifentanil Only vs. Midazolam and Meperidine During Elective Colonoscopy (NCT01693185), a randomized phase 4 study. The primary outcome is The Recovery Time.

2. Clinical Question

The clinical question is about recovery time in the setting of elective colonoscopy, rather than a broad comparison of all aspects of sedation. The registry describes a randomized, parallel-group comparison, with 27 participants represented in each arm's posted primary outcome. The record does not report further details about screening eligibility, the clinical setting beyond elective colonoscopy, or the characteristics of participants enrolled.

The intervention contrast is between remifentanil as the only active study drug and the conventional combination identified in the record as midazolam plus meperidine. Placebos for the other drugs are listed in each arm description. The registry does not report additional detail about how the study drugs were administered beyond the dose descriptions recorded for the two regimens.

Recovery was defined using the Aldrete score, which evaluates respiration, oxygen saturation, consciousness, circulation, and activity. The primary measure is the elapsed time to the specified recovery threshold, not a direct measure of pain, recall, distress, or endoscopist satisfaction. Those topics appear among the named secondary outcomes, but the record contains numerical arm results for only two secondary outcomes.

3. Trial Design

The registry classifies the study as a randomized, single-masked, parallel-group, phase 4 trial. The listed enrollment is 60, and the status is completed. The recorded start is 2012-12, with primary completion in 2013-02. Konkuk University Medical Center is named as the sponsor.

Participants were assigned to one of two regimens: remifentanil alone or midazolam and meperidine. The posted primary outcome has 27 participants in each arm. Although the registry lists an enrollment of 60, the reason the primary-outcome arm counts do not account for the full enrollment is not reported in the registry record. The record does not explain whether this reflects missing outcome data, exclusions, a difference between enrollment and analysis populations, or another reason, so none of those explanations can be assumed.

Single masking is the masking classification recorded, but the record does not specify who was masked or how masking was maintained. It also does not report the randomization sequence method, allocation concealment, or whether the groups were balanced on baseline characteristics. These details matter when assessing how assignment was implemented and whether knowledge of treatment could have affected outcome assessment.

The primary outcome was time from completion of colonoscopy to achievement of an Aldrete score of 10 in the recovery unit. The registry specifies assessment every 5 minutes after colonoscopy through 30 min. The primary analysis reported in the record used the Wilcoxon (Mann-Whitney) method. The registry does not report a detailed statistical analysis plan, a protocol document, or an explanation of how measurements recorded at the scheduled assessment times were converted into the posted recovery-time summaries.

While the registry lists 60 participants as the enrollment, the posted primary outcomes include 27 per arm. A difference between those counts is important for interpreting the evidence: the analyzed population may not be the same as the enrolled population, but the reason and any participant flow are not reported in the registry record. The results therefore describe the posted arm data, with the relationship to the full enrollment left unclear.

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: The exclusion criteria were applied. If a patient was excluded after recruitment and enrollment into the study, the following new patient assumed the status of the excluded patient.

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.

Population: Patients with ASA PS class 1 or 2 undergoing elective colonoscopy under monitored anesthesia care

6. Primary Endpoint

The registry lists the primary outcome as The Recovery Time, measured over every 5 minutes after completing colonoscopy up to 30 min.

The primary endpoint is recovery time, measured as the time from completion of colonoscopy until a participant achieved an Aldrete score of 10 in the recovery unit. The Aldrete score combines assessments of respiration, oxygen saturation, consciousness, circulation, and activity. A score of 10 represents the endpoint threshold specified by the registry; it is not a measure of just one physiological feature.

The registry says this outcome was assessed every 5 minutes after colonoscopy up to 30 min. The summary is reported as a median with an inter-quartile range (IQR). A median describes the middle of the observed ordered values, while the IQR describes the span from the lower to the upper quartile and gives information about the spread of the central portion of the observations. These summaries are useful when values may be skewed or when a few long recovery times could pull an arithmetic mean away from the typical observed value.

Recovery time is used to describe how quickly participants reached the prespecified recovery criterion. It should be distinguished from a measure of overall sedation quality, patient experience, or safety. The registry does not report a primary-outcome confidence interval, and it does not explain how the scheduled assessment times were handled when determining the recorded time to the threshold. Such details would help readers judge the precision and measurement resolution of the endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary result is summarized with a median and inter-quartile range and tested using the Wilcoxon (Mann-Whitney) method. This is a rank-based method for comparing observations between two independent groups. Rather than requiring the outcome to follow a normal distribution, it compares the relative ordering of values across groups. In general, this can be useful for outcomes such as recovery time when the distribution may be skewed. A rank test is not automatically a test of medians alone: its interpretation depends on the shapes of the group distributions as well as their location.

The reported primary p-value is p < 0.001. In general, a p-value describes how unusual data at least as incompatible with a null hypothesis would be if that null hypothesis and the test assumptions held. It does not measure the probability that the null hypothesis is true, the probability that the result will reproduce, or the clinical importance of the observed separation. The registry does not report a primary confidence interval or a detailed account of assumptions and implementation for the rank test.

The median and IQR complement the rank-test result by describing the observed values on the time scale of the outcome. The median is a measure of central location; the IQR indicates the range containing the central half of the observations. Reporting both helps readers see the observed distributional spread rather than relying on a single test statistic. The registry specifies outcome assessment every 5 minutes through 30 min, but it does not describe how that schedule was incorporated into the exact recorded recovery times. The assessment schedule may affect the granularity of recorded times, but further interpretation of that issue requires details not reported in the registry record.

What do the secondary risk differences describe?

The secondary comparisons include unadjusted risk differences. A risk difference is the difference between the proportions of participants with an outcome in the two groups, expressed on the absolute probability scale. The stated contrast is midazolam and meperidine relative to remifentanil. A positive estimate indicates a higher observed proportion in the former group; a negative estimate indicates a lower observed proportion. This describes direction, not causation by itself, and the uncertainty interval is important to interpretation.

For the frequent-pain outcome, the unadjusted risk difference is 0.111 and its 95% confidence interval runs from -0.102 to 0.324. The interval spans the value of no difference and includes both negative and positive values. In general, a confidence interval represents uncertainty about the effect estimate under the method's assumptions; it is not a range containing a fixed proportion of individual participant outcomes. The p-value of 0.311 is consistent with substantial uncertainty about this comparison. The record does not report a sponsor analysis for this outcome.

For the recall-related outcome, the unadjusted risk difference is -0.518 and its 95% confidence interval runs from -0.707 to -0.330, with p < 0.001. The interval lies below no difference for the stated contrast. These are unadjusted secondary calculations from the posted arm counts, and they should not be treated as equivalent to a prespecified primary analysis. The registry names several secondary outcomes, but numerical results are posted for only two of them. It does not report whether these analyses were prespecified in a detailed statistical plan or whether any multiplicity procedure was used.

What do the planning illustrations mean?

The registry's primary-outcome description says a pilot study measured recovery in 10 patients in each of groups-MM and -R before the present study. It reports means and standard deviations of 22.5 ± 9.5 and 7.5 ± 9.2 min, respectively, and says the intended difference to distinguish was 7.5 min, described as half of the observed difference. This is the sample-size rationale recorded for the trial. Further details of the original calculation are not reported in the registry record.

For the frequent-pain outcome, planning illustrations use two-sided significance level 0.05, equal allocation, and a normal approximation. The listed participants per arm are 206 for planning for 100% of the observed effect, 347 for 75% of the observed effect, and 737 for 50% of the observed effect for 80% power. For 90% power, the corresponding listed numbers are 275, 464, and 986 participants per arm. These are planning illustrations based on the observed effect and the stated assumptions, not the observed power of this trial and not evidence that those sample sizes were enrolled. In general, sample-size calculations depend on the assumed effect and design conditions; smaller effects generally require more participants to detect with a given target power.

For any outcome, over-dispersion means the observed variation exceeds what a statistical model assumes. In general, this can make uncertainty estimates too narrow if the model does not account for the extra variability. The primary endpoint is analyzed with a rank-based method, and the registry does not report an over-dispersion model. The general concept is relevant when interpreting model-based analyses, but there is no basis in the registry record to claim that over-dispersion occurred in this trial.

The registry does not report a complete statistical analysis plan, the analysis populations, a missing-data procedure, adjustment for baseline covariates, or a multiplicity strategy. In general, these details indicate how analyses were selected and how uncertainty was handled. Their absence from the record means the analysis cannot be independently assessed on those points; it does not establish that particular procedures were or were not used outside what is recorded.

10. Analyses Reported by the Sponsor

The registry reports the primary comparison as a Wilcoxon (Mann-Whitney) analysis with p < 0.001. The median and IQR in each arm are also posted. No recalculated primary estimate or confidence interval is reported, so the primary result is best described using the sponsor's posted analysis rather than an alternative calculation. The record does not report a numerical effect estimate from that test.

The secondary risk differences and their confidence intervals are unadjusted recalculations from the posted arm counts. The registry does not list sponsor-reported analyses for those secondary outcomes. These recalculations provide an absolute-scale description and uncertainty interval, but they do not replace a prespecified analysis or account for potential multiplicity. There is no discrepancy flagged between a sponsor estimate and a recalculation in the registry record.

Accordingly, the primary result remains the sponsor-reported rank-test result. The recalculated secondary comparisons can help describe the posted counts, but their unadjusted status and the absence of a reported analysis plan should be kept in view. A p-value from a recalculation should not be presented as though it were an analysis reported by the trial sponsor.

11. Multiplicity, Missing Data and Analysis Populations

The record lists one primary outcome and five secondary outcomes. Numerical results appear for the primary outcome and two secondary outcomes. The registry does not report whether the secondary outcomes were all prespecified in a protocol, how many comparisons were planned, or whether a multiplicity adjustment was used. With multiple outcomes, the chance of observing at least one apparently unusual result can increase when each comparison is assessed separately. In general, multiplicity procedures are used to control that risk, but no specific procedure can be attributed to this trial from the registry record.

Repeated assessment is also part of the primary outcome description: recovery was assessed every 5 minutes after colonoscopy up to 30 min. The record does not say whether the inferential analysis used only a single summary per participant, how exact times were assigned between scheduled assessments, or whether any repeated measurements were modeled. It reports the final primary summaries and a Wilcoxon (Mann-Whitney) test, but not a fuller account of the data structure or analysis implementation.

The posted primary results include 27 participants in each arm, while the registry enrollment is 60. The record does not explain the difference, identify exclusions, or state how many participants were randomized, treated, or included in each analysis. It also does not report a missing-data method, the amount or pattern of missing data, or whether an intention-to-treat population was used. These omissions prevent assessment of whether missing outcomes or exclusions could have influenced the posted results.

The registry does not report baseline balance, a detailed protocol, a statistical analysis plan, or the handling of protocol deviations. These details would help distinguish planned analyses from exploratory ones and assess the consequences of incomplete follow-up. Their absence does not establish that analyses were changed or that data were missing; it means those possibilities cannot be evaluated from 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 5% reporting threshold.

The registry reports 0 serious adverse events among 27 participants in the remifentanil arm and 0 among 27 participants in the midazolam-and-meperidine arm. It also reports 0 other adverse events among 27 participants in each arm. No serious-event terms are listed. The death counts are not reported in the registry record.

These figures describe the adverse-event counts recorded for the posted groups. A count of zero means no events of that category were recorded for the stated group in the registry results; it does not establish that no adverse events could occur, nor does it by itself demonstrate equivalence between the regimens. The counts are also based on the posted arm sizes, whose relation to the listed enrollment of 60 is not explained.

The record does not give definitions of serious and other adverse events, information about collection and follow-up procedures, or details about whether all randomized participants were included in safety monitoring. Without those details and the unreported death counts, the safety information is limited. It should be read as a report of the recorded counts, not as a comprehensive estimate of comparative safety.

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

The posted results show that, in this randomized comparison of elective colonoscopy regimens, the remifentanil group had a lower median time to the Aldrete score of 10 than the midazolam-and-meperidine group. The reported rank-test p-value is p < 0.001. The medians and IQRs describe the observed recovery-time distributions, while the p-value provides evidence of a difference in their rank distributions under the test assumptions.

The result does not, on its own, establish the size or precision of a population effect. There is no primary confidence interval in the registry record, and the outcome counts shown for the primary endpoint do not account for the listed enrollment without an explanation. The full analysis population and handling of missing data are not reported. Those limitations matter when judging how reliably the posted sample represents the randomized groups.

The result also does not establish a difference in every other dimension of sedation or colonoscopy experience. The pain and recall outcomes are secondary, and the registry does not provide numerical results for all named secondary measures. The posted secondary comparisons are unadjusted, and the record does not describe a multiplicity strategy. They should not be treated as confirmation of the primary finding or as a complete assessment of patient experience.

More generally, a statistical comparison in one trial describes the data collected under its design and analysis. It does not establish that the same results would apply to other populations, procedures, or clinical settings. The registry record identifies diagnostic colonoscopy screening and elective colonoscopy, but does not report enough participant or setting detail to assess broader applicability. The result is evidence about the recorded comparison, not a recommendation about which regimen should be used.

14. Why This Trial Matters Statistically

This trial illustrates how an endpoint definition shapes statistical interpretation. Recovery was operationalized as time until reaching an Aldrete score of 10, a threshold based on several domains. That makes the outcome more specific than an unstructured impression of recovery, while also making the exact scoring and assessment schedule important to understanding the recorded time.

It also demonstrates why distributional summaries and an appropriate comparison method should be read together. Median and IQR summaries describe the observed recovery times, while the Wilcoxon (Mann-Whitney) test compares the ordering of observations between groups. The reported p-value is informative about evidence against a no-difference model, but it is not a substitute for an effect estimate with an uncertainty interval. The absence of a primary confidence interval makes the precision of the primary comparison harder to judge.

The record also highlights the value of transparent participant accounting. Enrollment is listed as 60, while the primary outcome summaries include 27 participants in each arm. Without a participant flow or explanation, readers cannot determine why those numbers differ or how the analyzed participants relate to all enrolled participants. Clear reporting of analysis populations and missing data would support a more complete appraisal.

Finally, secondary outcomes require context. A trial can report multiple outcomes, but nominal results from a subset have less interpretive weight when the multiplicity plan and numerical results for all named outcomes are unavailable. This record offers a useful example of separating the primary question from secondary observations, and of distinguishing sponsor-reported inference from unadjusted calculations based on posted counts.

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.

The main trial-specific limitation is the unexplained difference between the listed enrollment of 60 and the 27 participants per arm in the primary results. The registry does not report participant flow, analysis-population definitions, or reasons for any participants not represented in those results. Consequently, the impact of exclusions or missing outcomes cannot be assessed.

For the primary endpoint, the registry reports medians, IQRs, and a Wilcoxon (Mann-Whitney) p-value, but no confidence interval or effect estimate from the test. The assessment schedule is stated as every 5 minutes through 30 min, yet the record does not explain how this schedule translated into the exact recovery-time values analyzed. The absence of these details limits assessment of the primary estimate's precision and measurement process.

The record identifies the trial as single-masked but does not say who was masked, how masking was implemented, or how randomization and allocation concealment were carried out. Baseline participant characteristics are not reported in the registry record for this record. These omissions leave important aspects of design conduct and group comparability unclear.

Numerical results are available for only two of the five named secondary outcomes. The secondary risk-difference analyses are unadjusted, and the registry does not state whether multiplicity was addressed or whether the analyses were prespecified. Interpretation of secondary findings is therefore limited. The registry also does not report the statistical analysis plan, missing-data methods, detailed safety definitions, or death counts. These are reporting gaps; they do not prove that the trial lacked procedures that are simply not described in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Remifentanil Only vs. Midazolam and Meperidine During Elective Colonoscopy — NCT01693185.
• Registry record last updated 2014-06-18; status last verified 2014-05.
• Results first posted 2014-06-18.
• 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

NCT01693185 is a completed, randomized, single-masked, parallel-group, phase 4 trial sponsored by Konkuk University Medical Center. It lists enrollment of 60 and compares remifentanil alone with midazolam and meperidine during elective colonoscopy. The primary outcome is time to an Aldrete score of 10 after colonoscopy, assessed every 5 minutes up to 30 min.

The posted primary results include 27 participants per arm. Median recovery time was 0 minutes (IQR 0 to 10) with remifentanil and 30 minutes (IQR 15 to 30) with midazolam and meperidine; the reported Wilcoxon (Mann-Whitney) comparison was p < 0.001. The record does not explain the relationship between the listed enrollment and the posted primary arm counts.

The registry names five secondary outcomes, with numerical results posted for two. It reports zero serious and zero other adverse events in each group, while death counts are not reported. Details of participant flow, missing-data handling, multiplicity, and the full statistical analysis plan are not reported in the registry record.