The Effects of Dexmedetomidine and Remifentanil on Carotid Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effects of Dexmedetomidine and Remifentanil on Carotid Patients (NCT00335972), a randomized phase 4 study. The primary outcome is Mean Arterial Pressure.

2. Clinical Question

The registry describes a randomized, parallel-group comparison and labels the masking as triple. It does not identify which people or roles were masked. The primary endpoint is a continuous measure, reported as a mean with standard deviation. The registry record does not give a single effect estimate or a statistical comparison for that endpoint, so the direction and precision of any between-group difference cannot be assessed from the primary-outcome information recorded.

The summary refers to postoperative pain and opioid requirements, but the record does not identify the specific results for those questions in the information available. The stated trial question is therefore broader than the primary endpoint alone: mean arterial pressure at specified times addresses one component, while analgesic requirements and hemodynamic control are additional topics named in the summary.

3. Trial Design

This was a Phase 4, randomized, triple-masked, parallel-group trial sponsored by The Cleveland Clinic. The registry lists carotid artery stenosis as the condition and carotid endarterectomy as the surgical setting. The listed enrollment is 142. The record gives a start date of 2006-06 and a primary completion date of 2008-05, and its current status is terminated. The reason for termination is not reported in the registry record.

The two groups were assigned to dexmedetomidine or remifentanil. The remifentanil description specifies an infusion throughout surgery at 0.1-0.2 µg/kg/min, with propofol titrated to keep BIS as close to 45 as clinically practical. The dexmedetomidine description specifies a 0.5-1 µg/kg loading infusion over 20 minutes, followed by an infusion of 0.2 µg/kg/hr until the end of surgery; for patients in renal failure, the loading dose was 0.2 µg/kg. The remaining text about adjusting the dexmedetomidine infusion is incomplete in the registry record.

Random allocation can help balance measured and unmeasured characteristics between groups on average, although it does not guarantee identical groups. A parallel design assigns participants to one group rather than having each participant receive both regimens in sequence. The record does not report the allocation method or concealment details. It labels the trial triple-masked but does not name the masked roles. The registry does not report the reason for the enrollment target, whether enrollment was completed as planned, or the number included in each outcome analysis.

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

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.

6. Primary Endpoint

The registry lists the primary outcome as Mean Arterial Pressure, measured over mean arterial pressure at 15, 30, 45, 60, and 90 minutes after extubation.

The primary endpoint is mean arterial pressure, measured in mmHg. The registry identifies the summary measure as a mean with standard deviation and specifies measurement at 15, 30, 45, 60, and 90 minutes after extubation. Mean arterial pressure is a continuous measure of blood pressure, so group summaries can describe both the average level and the spread of recorded values.

Repeated measurements after extubation can describe how blood pressure changes over the specified postoperative period. Looking at several times can be informative because a group difference might vary over time rather than remain constant. However, the record does not specify whether the primary question was a separate comparison at each time, an overall repeated-measures comparison, or another summary across times.

For interpretation, a mean difference would describe the contrast in average pressure between groups, while a confidence interval would describe the range of values compatible with the data under the analysis assumptions. The registry record does not report numerical means, standard deviations, confidence intervals, or a single treatment contrast for this endpoint. It therefore does not permit an assessment of the size or precision of the primary-outcome difference. The clinical importance of any difference is also not established by the endpoint definition alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Continuous outcomes. Mean arterial pressure is a continuous measure. A group mean describes the central level of the observed measurements, and the standard deviation describes their spread around that mean. The standard deviation is not the same as the uncertainty in the estimated mean or in a between-group difference. A confidence interval for a treatment contrast would convey that uncertainty; no such interval is reported in the registry record.

Between-group contrasts. In a randomized comparison, the main statistical quantity of interest is often the difference in outcome between assigned groups. The difference should be interpreted alongside its uncertainty and the outcome scale. For this trial, the registry record does not report the group means, a contrast, or its confidence interval for the primary endpoint. It also does not state whether the contrast was adjusted for other variables. Without these details, the size, direction, and precision of the effect cannot be assessed.

Repeated measurements. The primary endpoint is assessed at 15, 30, 45, 60, and 90 minutes after extubation. Measurements from the same participant are generally related: a participant's pressure at one time may resemble that participant's pressure at another time. A method that treats all time-specific observations as independent may not represent that relationship appropriately. Repeated-measures methods can account for within-participant correlation, but the particular method used is not reported in the registry record.

There is more than one reasonable way to frame a repeated-measures question. Separate analyses can compare groups at each time. A joint model can assess the pattern across times, and a prespecified summary can represent change over the interval. These approaches answer different questions and can produce different estimates. The record does not state which approach defined the primary analysis, whether one time point was designated as especially important, or whether results at all listed times were intended to be interpreted separately.

Uncertainty and significance. A confidence interval represents a range of effect values compatible with the observed data under the model and its assumptions. A narrow interval indicates greater precision than a wide interval, but precision alone does not determine clinical importance. A significance test addresses compatibility with a specified null hypothesis under a statistical model; it does not measure the size of an effect. No primary-outcome p-value, confidence interval, or treatment estimate is reported in the registry record, so a significance-based conclusion cannot be drawn from the recorded primary-outcome information.

Multiplicity. Testing several outcomes or several time points increases the opportunity for at least one apparently notable result to arise by chance. A prespecified analysis plan may identify a primary comparison or use an adjustment strategy to account for multiple testing. The registry lists three outcome measures and six analyses, and notes that the primary outcome has several time points or categories and is not reduced to one comparison. A multiplicity strategy, if any, is not reported in the registry record. General statistical practice is to interpret a set of related comparisons in light of the analysis plan rather than selecting a single result after seeing the data.

Randomization and masking. Randomization is intended to reduce systematic differences in prognostic characteristics between groups. It does not eliminate chance imbalances, and its success cannot be assessed from the allocation label alone. The record identifies the trial as randomized but does not report the allocation sequence method or concealment procedure. The triple-masking label indicates that masking was used, but the record does not identify which roles were masked or how masking was maintained. Masking can reduce the influence of expectations on care, measurement, or assessment, depending on who is masked and how outcomes are assessed.

Planning illustrations. The registry-associated sample-size illustrations are described as planning calculations based on the observed effect, with two-sided significance level 0.05, equal allocation, and a normal approximation. They represent participants per arm for 80% or 90% power under the stated effect-fraction assumptions; they are not observed power and do not describe the trial's original design justification. The record does not report the trial's own sample-size justification. A planning illustration is conditional on its assumptions and should not be read as a guarantee that a future study will detect an effect.

Analysis populations and missingness. The listed enrollment does not tell readers how many participants contributed to each endpoint analysis. The registry record does not report the analysis population definition, outcome-specific denominators, missing measurements, or the method used to handle missing data. These details matter because an analysis using only observed measurements can be affected if missingness is related to outcomes or treatment assignment. The record also does not report whether analyses followed assigned treatment groups or another population definition.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint is recorded at 15, 30, 45, 60, and 90 minutes after extubation, and the registry notes that it has several time points and is not reduced to one comparison. The record lists three outcome measures and six analyses. Conducting multiple comparisons can make chance findings more likely across a family of tests. A prespecified primary contrast or an adjustment for multiple testing can help clarify how the evidence should be interpreted, but the multiplicity approach is not reported in the registry record.

Missing-data information is also not reported in the registry record. The record does not give the number of participants contributing data at each time point, reasons for missing measurements, or methods for handling missing values. Repeated-measures outcomes may have different amounts of available data at different times. If participants with missing observations differ systematically from those with observed observations, the analyzed data may not represent the original randomized groups in the same way.

The analysis populations are not described. The record does not say whether the primary analysis included everyone as randomized, only participants who received the assigned intervention, or another defined group. The listed enrollment of 142 is not an outcome-specific analysis denominator. The registry record also does not report a statistical analysis plan or explain how the six analyses relate to the three outcome measures.

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.

The adverse-event record lists Remifentanil with 71 at risk for serious events and 0 affected; it also lists 71 at risk for other events and 0 affected, with 0 deaths. For Dexmedetomidine, it lists 68 at risk for serious events and 0 affected; it also lists 68 at risk for other events and 0 affected, with 0 deaths. These are the registry's recorded counts.

A recorded zero means that no affected participants are entered for that event category in the registry record. It does not establish that the true risk is zero, and it does not show that the groups have equal safety. Rare events can be difficult to characterize from a trial, and the precision of a risk estimate depends on the amount and completeness of safety information. The record does not report confidence intervals for these counts, event definitions, or additional details about the safety-analysis population. No serious-event terms are listed.

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

The record establishes that the trial compared dexmedetomidine with remifentanil in a randomized, parallel-group study of patients undergoing carotid endarterectomy. It identifies mean arterial pressure at specified times after extubation as the primary endpoint and records adverse-event counts for each group. It does not report a single primary-outcome comparison or the numerical results needed to describe the size, direction, and precision of a difference.

Accordingly, the registry information does not show whether mean arterial pressure differed between groups, whether any difference was consistent across measurement times, or how uncertain the estimates were. It also does not establish results for the summary's questions about hemodynamic control or PACU analgesic requirements. A stated trial objective is not evidence that the objective was met, and an absence of a reported comparison is not evidence of no effect.

The zero adverse-event counts should likewise be read as recorded counts rather than as proof of no risk or equivalent safety. The number at risk is reported for each group, but event definitions, safety-analysis details, and uncertainty estimates are not reported in the registry record.

The record also does not report the reason for termination, the reason for the enrollment target, missing-data handling, the primary analysis population, or a multiplicity strategy. These gaps limit assessment of both the reliability and the scope of the posted information. A fuller interpretation would require outcome estimates with uncertainty, clear analysis methods, and details about the participants included in each analysis. The trial's design and endpoint description alone cannot establish clinical benefit or harm.

13. Why This Trial Matters Statistically

This trial illustrates why a clear endpoint definition is only one part of interpreting a clinical comparison. The registry specifies a continuous primary measure, its unit, the summary statistic, and several assessment times after extubation. Those details help identify what was intended to be measured. They do not, by themselves, convey the observed group difference or how precisely it was estimated.

The multiple measurement times also make the statistical question important. A series of separate comparisons and a single analysis of the full trajectory do not answer exactly the same question. Without knowing which analysis was designated primary and how multiple comparisons were handled, readers cannot determine how to interpret a selected result across times. This is a general issue in trials with repeated outcomes.

The record further distinguishes trial design information from outcome evidence. Randomization and masking describe intended protections against bias; the label alone does not show how well those protections were implemented. Similarly, enrollment and adverse-event counts do not replace an outcome analysis. This distinction is especially useful when a registry entry identifies a study objective but does not present one interpretable primary-outcome comparison.

Finally, the status of terminated and the absence of a stated reason underline the importance of reporting trial completion and analysis details. Without the reason for termination, participant flow, missingness, and analysis populations, the context for the recorded results remains incomplete. These are statistical reporting questions, not grounds for inferring why the study ended or what its unreported outcome results would have been.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation of the registry information for interpreting the primary endpoint is that it does not report a single comparison or numerical results for mean arterial pressure. Although the measurement times and summary type are identified, group means, standard deviations, treatment contrasts, confidence intervals, and p-values are not reported in the registry record. The magnitude, direction, and precision of the primary result therefore cannot be evaluated.

The record identifies multiple measurement times but does not report the primary analysis method or how repeated measurements were handled. It also does not report whether or how multiplicity was addressed. The number of participants contributing measurements at each time, missing-data reasons, and missing-data methods are not reported in the registry record. These omissions make it difficult to assess the robustness of any time-specific finding.

Other limitations include the absence of an analysis-population definition, allocation-method details, and identification of the roles covered by triple masking. The registry status is terminated, but the reason is not reported. The listed enrollment cannot be assumed to be the number analyzed for every endpoint. The dexmedetomidine arm description is incomplete in its final infusion-adjustment text, and the record does not provide results for the additional questions about hemodynamic control and PACU analgesic requirements.

The adverse-event entries provide counts but do not include uncertainty estimates or further event definitions. These limitations concern what can be learned from the registry record; they do not establish that the trial lacked additional information elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Effects of Dexmedetomidine and Remifentanil on Carotid Patients — NCT00335972.
• Registry record last updated 2017-08-11; status last verified 2017-08.
• Results first posted 2017-08-11.
• 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 NCT00335972 as a Phase 4, randomized, triple-masked, parallel-group trial sponsored by The Cleveland Clinic. It lists enrollment of 142, a start date of 2006-06, primary completion in 2008-05, and status as terminated. The study compares dexmedetomidine with remifentanil during carotid endarterectomy.

The primary endpoint is mean arterial pressure in mmHg, summarized as a mean with standard deviation at 15, 30, 45, 60, and 90 minutes after extubation. The registry record does not provide a single primary-outcome comparison or numerical results for those times. It lists three outcome measures and six analyses. Recorded serious events, other events, and deaths are zero in both groups, with the group-specific at-risk counts stated in the safety information. The reason for termination, analysis populations, missing-data methods, and multiplicity approach are not reported in the registry record.