Remifentanil Versus Dexmedetomidine for Post-Cardiac Surgery Patients With Noninvasive Ventilation Intolerance: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Remifentanil Versus Dexmedetomidine for Post-Cardiac Surgery Patients With Noninvasive Ventilation Intolerance (NCT03395886), a registered phase not stated study. The primary outcome is Number of Participants With NIV Failure.

2. Clinical Question

The clinical question concerns sedation in post-cardiac surgery patients who cannot tolerate NIV, and compares two drug regimens used in that setting. The study is described as prospective and observational. It is therefore a comparison between groups observed in a cohort, not a randomized comparison. The registry does not state how patients were allocated to the groups.

The stated primary endpoint is a count of participants with NIV failure, rather than a measure of the duration of NIV or a continuous sedation score. A secondary outcome is the number of participants with NIV mitigation. The endpoint definitions and time frame are intended to make the comparison clinically interpretable, but the registry record does not provide group counts for either outcome. As a result, it does not support an estimate of the difference between the observed groups for the primary clinical question.

3. Trial Design

The registry describes a prospective, observational cohort study of remifentanil versus dexmedetomidine for post-cardiac surgery patients with NIV intolerance. The condition listed is cardiac surgery. The record identifies Shanghai Zhongshan Hospital as sponsor, gives a study start date of 2018-01-01 and a primary completion date of 2019-03-31, and lists the study status as completed. Enrollment is recorded as 90.

The two treatment groups are described as receiving continuous infusions. For remifentanil, the listed starting dose is 0.05 μg/kg/min and the maximum is 0.12 μg/kg/min. For dexmedetomidine, the listed starting dose is 0.5 μg/kg/h and the maximum is 1 μg/kg/h. In both descriptions, dosing is adjusted according to sedation satisfaction, with a target NIV-intolerance score of 1-2. These are descriptions of the planned regimens; the registry does not report the doses participants actually received.

The comparison is not randomized, and the record does not state how treatment assignment occurred. Consequently, the groups should not be read as a like-for-like control comparison. Differences between groups could reflect treatment as well as differences in patient characteristics or clinical circumstances. The registry does not report details that would establish whether such differences were measured or adjusted for.

The listed primary outcome is the number of participants with NIV failure, assessed 72 hours after initiation of sedation. NIV failure is defined as reintubation or death in the course of the study. A secondary outcome is the number of participants with NIV mitigation. Although the record lists two outcome measures and two analyses, group results and analysis details beyond the stated primary comparison 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

Analysis population for the primary outcome, as defined in the registry: Summary statistics are expressed as numbers and percentages and compared between groups by Chi-square test.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With NIV Failure, measured over 72 hours after the initiation of sedation.

The primary endpoint is the number of participants with NIV failure during the stated assessment period, 72 hours after initiation of sedation. The registry defines NIV failure as reintubation or death in the course of the study. It describes the endpoint as a participant count, with the planned presentation expressed as numbers and percentages for comparison between groups.

A binary endpoint of this kind classifies each participant according to whether the event occurred. It can be useful when the clinical question concerns the occurrence of an important event rather than the amount of time spent in a particular state. In this study, combining reintubation and death into the definition creates a single outcome for the comparison. The registry does not report separate counts for the components, so the relative contribution of reintubation and death to any group result cannot be assessed from the record.

The fixed assessment time gives the outcome a stated window for interpreting the comparison. However, the registry does not provide group-specific counts, percentages, an effect estimate, or uncertainty measures for this endpoint. It is therefore not possible to describe the observed primary outcome comparison or its precision from the registry record. The secondary outcome, number of participants with NIV mitigation, is listed, but its result is also not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary: participants are counted according to whether they experienced NIV failure. The registry defines failure as reintubation or death in the course of the study and gives the assessment time as 72 hours after sedation begins. For a binary outcome, group summaries commonly include the event count and the proportion of participants who experienced the event. The registry describes numbers and percentages as the summary statistics, but does not report the primary outcome values.

What does the stated Chi-square test assess?

The registry says the groups are to be compared by a Chi-square test. In general, this test assesses whether categorical outcome patterns differ between groups, by comparing observed counts with counts expected under a no-association model. It is a test of evidence against that model, not a measure of the size or clinical importance of a difference. The test result alone would not convey how precisely the group contrast is estimated. Interpretation also depends on the counts and the suitability of the test assumptions. Those counts and the test result are not reported in the registry record, so the comparison cannot be checked or interpreted from the available outcome information.

For this outcome, useful descriptive information would include the number of participants with NIV failure and the group denominator for each arm. An effect estimate could express the group contrast, and a confidence interval could communicate its uncertainty. A confidence interval is a range of values compatible with the data under the assumptions of the method; it is not a guarantee that the true value lies in that range. No primary-outcome counts, effect estimate, or confidence interval are reported in the registry record. No numerical comparison should be inferred from enrollment or from the adverse-event fields.

Why does the observational design matter?

Random assignment, when used, aims to make treatment groups comparable in expectation with respect to both measured and unmeasured characteristics. This study is described as observational, and the registry says allocation was not stated. The groups therefore cannot be assumed to have been comparable at baseline. In general, factors associated with both treatment choice and outcome can confound an observational comparison. Adjustment methods may help address measured differences, but they cannot automatically remove bias from unmeasured or poorly measured factors. The registry does not report whether covariate adjustment was performed, what variables were considered, or how missing covariate information was handled.

The listed primary comparison is between remifentanil and dexmedetomidine, but the registry explicitly notes that the arms are not a like-for-like control comparison. This qualification limits causal interpretation: an observed difference, if reported, would describe the groups as analyzed and would not on its own establish that the sedative caused the difference. Because the group outcome results are absent, even a descriptive contrast is unavailable.

What can a sample-size illustration tell a reader?

A planning illustration based on an observed effect is different from a prospective sample-size justification. The registry’s stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is expressed as a fraction of the observed effect. These assumptions describe a planning exercise, not the original design or an observed treatment effect. The registry does not report a sample-size justification for the study. The numerical planning results are not reported in the registry record.

In general, sample-size calculations describe how much information a hypothetical study might need under chosen assumptions. They do not establish the probability that the completed study’s result is true, and a retrospective calculation is not “observed power.” Planning values also depend on the effect size assumed, the outcome rate, allocation, statistical test, and other design choices. The equal-allocation assumption in the planning illustration should not be confused with the actual group sizes recorded in the adverse-event data.

How should event counts and uncertainty be read?

For binary outcomes, the count is the number of participants with the event, while the denominator is the number assessed or at risk in that group. The proportion depends on both. Small event counts can produce imprecise estimates, and a confidence interval helps show the range of uncertainty around an estimate. These are general principles; the registry does not provide primary-outcome counts or an interval for this study. The adverse-event count fields are separate information and cannot replace the endpoint-specific event data.

Multiplicity refers to making several outcome or subgroup comparisons, which can increase the chance of at least one apparently notable finding when many tests are considered. The record lists a primary outcome and a secondary outcome, but does not report a multiplicity strategy. The number of analyses listed does not reveal whether adjustments were planned, whether all analyses were conducted, or how findings were prioritized beyond identifying the primary endpoint. Those details are not reported in the registry record.

10. Exact Estimates for Each Arm

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

R code and output

arm    <- c("Remifentanil Group", "Dexmedetomidine Group")
n      <- c(52, 38)
events <- c(10, 8)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Remifentanil Group  52  10  19.2  9.6  32.5  10.8  31.9  10.8  32.0
ARM  Dexmedetomidine Group  38  8  21.1  9.6  37.3  11.1  36.3  11.1  36.5

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies NIV failure as the primary outcome and the number of participants with NIV mitigation as a secondary outcome. It lists two outcome measures and two analyses. The actual results for these endpoints are not reported in the registry record, and the record does not explain whether additional comparisons, subgroup analyses, or model-based analyses were planned or conducted.

When multiple outcomes or comparisons are tested, the chance of at least one result appearing unusual by chance can increase. Statistical methods can address this issue, for example by adjusting the threshold for interpretation or by defining a hierarchy of outcomes in advance. These are general approaches; the registry does not report a multiplicity adjustment or a detailed analysis hierarchy. It does identify a primary outcome, but that designation alone does not establish how other analyses were handled.

Information about missing outcome data is also not reported in the registry record. The record does not state how many participants had outcome information available, how missing observations were handled, or whether any sensitivity analysis examined the impact of missingness. It also does not describe the analysis population, such as whether analyses included all enrolled participants, only participants receiving the assigned treatment, or another defined group. These details matter because the analysis population and missing-data approach can affect the interpretation of a group comparison.

The registry describes a Chi-square test for the primary endpoint, but does not provide further details about the statistical analysis plan, model adjustments, or assumptions checked. No interim analyses or sample-size justification are reported in the registry record. Without these details and the endpoint results, readers cannot assess the completeness of the analysis or determine how multiplicity and missing data may have influenced the reported evidence.

12. 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.

The adverse-event fields list 52 participants at risk in the remifentanil group and 38 in the dexmedetomidine group. They report zero participants affected by serious adverse events in each group and zero affected by other adverse events in each group. The same group sizes are listed for both adverse-event categories.

The record also lists deaths of 6 in the remifentanil group and 4 in the dexmedetomidine group. These death counts are reported in the adverse-event information. The registry does not state the time window or further analysis context for these counts in those fields, so they should not be interpreted as a treatment comparison or assumed to correspond exactly to the primary endpoint assessment period.

Zero recorded participants affected in an adverse-event category does not by itself establish that no adverse events occurred outside the registry’s recorded definitions or reporting process. The record does not provide event descriptions, severity details beyond the serious-event category, attribution to treatment, or a fuller account of monitoring. The death counts also should not be combined with the serious or other adverse-event counts. Safety results and the primary NIV failure outcome are distinct data; the primary endpoint’s group-specific results are not reported in the registry record.

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

The registry record shows that a prospective observational cohort was conducted to compare remifentanil and dexmedetomidine in post-cardiac surgery patients with NIV intolerance. It describes how the infusions were intended to be administered and defines NIV failure as reintubation or death, assessed 72 hours after sedation began. The primary endpoint is clinically interpretable as a participant-level event count, and the record states that a Chi-square test was planned for comparing groups.

However, the registry does not report the primary outcome counts or percentages, a group comparison, or an uncertainty interval. It also does not report the result for NIV mitigation. Therefore, the posted record cannot show whether the observed primary outcome was more common in either group, how large any difference was, or how precisely it was estimated. Completion status and the enrollment figure do not answer those questions.

The adverse-event data report zero participants affected by serious adverse events and zero affected by other adverse events in both groups, alongside death counts of 6 and 4. These entries are limited to the information recorded in those fields. They do not provide a complete account of adverse events, establish treatment attribution, or replace the missing outcome-specific results.

Even if group outcome results were available, the observational design would limit causal conclusions. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Any observed association could reflect differences between the patients or circumstances in the groups as well as treatment. Details about adjustment for confounding, missing data, analysis populations, and multiplicity are not reported in the registry record. The study can be described as a comparison of two sedation approaches in this cohort, but the available record does not establish that one approach caused better or worse outcomes.

14. Why This Trial Matters Statistically

This study raises a practical statistical question: how to compare two sedation approaches when the clinical outcome is a participant-level event following cardiac surgery and NIV intolerance. The registry defines a clear primary endpoint, states its assessment time, and identifies the planned summary as counts and percentages. Those details are important because an outcome definition and observation window determine what a comparison represents.

Its observational design also makes it a useful example of why study labels matter. A comparison of two groups is not automatically a randomized treatment comparison. Without stated random allocation, baseline comparability cannot be assumed, and causal interpretation requires caution. Statistical adjustment can address some measured differences in general, but the registry does not report whether such adjustment was used. This makes transparency about design and analysis central to evaluating the evidence.

The record also illustrates the difference between knowing a study was completed and having enough results to assess its primary question. Enrollment, drug regimens, and adverse-event fields do not reveal the group-specific NIV failure results. Without endpoint counts and uncertainty measures, neither the size nor precision of the central comparison can be described. The missing result is consequential for statistical interpretation, regardless of the study’s completion status.

Finally, the separate reporting of safety fields and the primary endpoint shows why outcome definitions and analysis contexts should not be conflated. Death appears in the definition of NIV failure and is also listed in the adverse-event data, but the registry does not provide endpoint-specific component counts or a clear matching time window for the death entries. A reader needs those distinctions to interpret each statistic correctly. The record makes the comparison question visible, while leaving key evidence needed to answer it unreported.

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 principal limitation for interpreting this trial from the registry record is that group-specific results for the primary endpoint are not reported. Without those counts, percentages, or a comparison estimate, the observed NIV failure result and its precision cannot be assessed. The result for the secondary outcome, number of participants with NIV mitigation, is also not reported.

The study is observational, allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison. Potential differences between groups could affect outcomes independently of the sedative used. The registry does not report baseline characteristics, methods for controlling confounding, or adjusted estimates. It is therefore not possible to assess the extent to which the comparison accounted for differences between participants.

Other analysis details are missing from the registry record. These include the analysis population, outcome data completeness, methods for handling missing data, any multiplicity strategy, and any interim analyses. The record does not report a sample-size justification. It gives planning assumptions for an illustration, but does not report the numerical planning results. The stated Chi-square test is not accompanied by outcome counts or a test result, so its application and assumptions cannot be evaluated.

The adverse-event information is limited: it records zero participants affected by serious events and zero affected by other events in each group, as well as death counts of 6 and 4. The time window and analysis context for those death counts are not stated in those fields, and the record does not provide detailed event descriptions or attribution. These limitations prevent a fuller interpretation of safety or comparison with the primary endpoint.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Remifentanil Versus Dexmedetomidine for Post-Cardiac Surgery Patients With Noninvasive Ventilation Intolerance — NCT03395886.
• Registry record last updated 2019-11-29; status last verified 2019-08.
• Results first posted 2019-11-29.
• 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

The registry record identifies NCT03395886 as a completed prospective observational cohort study sponsored by Shanghai Zhongshan Hospital. It lists cardiac surgery as the condition, enrollment of 90, a start date of 2018-01-01, and a primary completion date of 2019-03-31.

The study compares remifentanil with dexmedetomidine for post-cardiac surgery patients with NIV intolerance. The primary outcome is the number of participants with NIV failure, defined as reintubation or death and assessed 72 hours after sedation begins. A secondary outcome is the number of participants with NIV mitigation. The primary comparison is described as using a Chi-square test.

The record does not report results for either outcome. Adverse-event fields list zero participants affected by serious and other adverse events in both groups, with death counts of 6 for remifentanil and 4 for dexmedetomidine. Because the comparison is observational and allocation is not stated, causal interpretation would require caution even if outcome results were available.