This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Dexmedetomidine to Prevent Agitation After Free Flap Surgery (NCT01904760), a randomized phase 4 study. The primary outcome is Agitation in PACU.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01904760 |
| Phase | Phase 4 |
| Condition | Agitation, Delirium |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 80 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Peking University |
| Results posted | Yes |
2. Clinical Question
Population
Patients after free flap reconstructive surgery. The registry summary describes reconstruction in patients with maxillofacial tumors and notes concern about postoperative agitation and delirium.
Intervention
Dexmedetomidine by infusion beginning before the operation was completed and continuing until 6:00am the next day.
Comparator
Normal saline placebo, administered on the same stated infusion schedule.
Primary question
How many participants experienced agitation in the post-anesthesia care unit (PACU), with agitation defined as a Riker-Agitation Scale score of 5 or higher?
The trial asked whether dexmedetomidine could reduce emergence agitation and prevent delirium after free flap surgery. The primary outcome named in the registry is agitation in the PACU, measured as a count of participants. The stated endpoint description says patients are kept calm and cooperative in the PACU and defines agitation using the Riker-Agitation Scale. Postoperative delirium is named as a secondary outcome.
The record describes a randomized comparison of dexmedetomidine with saline placebo. It does not report a numerical primary-outcome result or a treatment contrast that can answer how often agitation occurred in each arm. Nor does it report a numerical result for postoperative delirium. Accordingly, the clinical question is clear, but the posted results do not show the magnitude or precision of any difference between the groups.
3. Trial Design
The registry describes a completed, phase 4, randomized, parallel-group trial sponsored by Peking University. Enrollment is listed as 80. The masking designation is quadruple, but the registry record does not identify which roles were masked or describe how masking was maintained. The allocation method is labeled randomized; further details about sequence generation or concealment are not reported in the registry record.
Participants were assigned to dexmedetomidine or saline placebo. The dexmedetomidine regimen is described as 0.5㎍/kg/hr for 1 hour before the operation is completed, followed by 0.2-0.7㎍/kg/hr continuously until 6:00am the next day. The control description gives the same infusion schedule for normal saline 0.9%. Its concentration is annotated as a guess in the registry description, so the exact preparation is not certain from that entry.
The recorded study start is 2013-06 and primary completion is 2013-11. These dates describe the registry record and do not establish when results were analyzed or posted. The registry summary places the study in the setting of free flap reconstruction, particularly surgery associated with maxillofacial tumors. It explains that postoperative head movement may be restricted to protect the microvascular anastomosis and identifies agitation and delirium as concerns in this setting.
The primary outcome is agitation in the PACU. Postoperative delirium is named as a secondary outcome, and the record lists 9 outcome measures overall. The number of analyses listed is 0. No detailed protocol, statistical analysis plan, allocation procedures, masking roles, or analysis-population definitions are reported in the registry record. The design labels therefore describe the trial at a high level, while leaving important operational and analytical details unavailable.
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
| Stage | Dexmedetomidine | Control |
|---|---|---|
| STARTED | 40 | 40 |
| COMPLETED | 39 | 40 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | Dexmedetomidine | Control |
|---|---|---|
| Protocol Violation | 1 | 0 |
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.
| Characteristic | Unit | Dexmedetomidine | Control | Total |
|---|---|---|---|---|
| Participants analysed | 39 | 40 | 79 | |
| Age, Continuous | years | 50.3 (SD 15.0) | 50.6 (SD 12.3) | 50.5 (SD 13.6) |
| Sex: Female, Male: Female | Participants | 18 | 19 | 37 |
| Sex: Female, Male: Male | Participants | 21 | 21 | 42 |
| Region of Enrollment: China | participants | 39 | 40 | 79 |
6. Primary Endpoint
The registry lists the primary outcome as Agitation in PACU, measured over participants will be followed for the duration of PACU stay, an expected average of 12 hours.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants with agitation in the PACU. The registry defines agitation as a Riker-Agitation Scale score of 5 or higher, and states that participants are followed for the duration of their PACU stay, expected to average 12 hours. The endpoint is therefore a binary event for each participant—meeting the stated agitation definition or not—reported as a count within each group.
Such an endpoint is relevant to the study question because the investigators focused on emergence agitation after free flap surgery. In general, a clearly defined threshold turns a scale measurement into a countable outcome and allows the frequency of the event to be compared between randomized groups. This approach also discards some information about the range of scale scores: two participants on different sides of the threshold are classified differently, while variation among scores on the same side does not change the event count.
The record gives the outcome definition and observation setting but does not report the numbers of participants meeting the definition in either arm. It also does not report a treatment-effect estimate or its uncertainty. The record lists several outcome measures, and its notation indicates that the primary outcome has several categories or time points and was not reduced to one comparison. Consequently, the stated endpoint can be described, but its between-group result cannot be interpreted numerically from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central limitation for interpreting the trial is that the registry record does not contain a single numerical comparison for the primary endpoint. It identifies the outcome as agitation in the PACU and defines the event, but does not report the number of participants with agitation by treatment group, an estimated contrast, a confidence interval, or a p-value. The number of analyses listed is 0. Thus, the posted record does not establish the direction, size, or precision of a primary-outcome difference.
The record notes that the primary outcome has several categories or time points and was not reduced to one comparison. That matters because a stated outcome definition is not, by itself, a result. Without the group-specific counts and an identified comparison, readers cannot tell whether the observed event frequency was higher, lower, or similar in either arm. They also cannot assess how compatible the data are with a range of possible treatment effects.
Postoperative delirium is listed as a secondary outcome, but no numerical delirium result is reported in the registry record. The record lists 9 outcome measures overall, while only agitation and postoperative delirium are described in the available outcome information. The other outcome details and their findings are not reported in the registry record. No adjustment for multiple outcomes, repeated assessments, or multiple comparisons is described.
The adverse-event entries report 0 serious events and 1 other event in each group, with 40 at risk in each group. These counts should be read as descriptive registry entries, not as proof that the groups have identical safety profiles. The record does not provide event descriptions, statistical comparisons, or a death count. Sparse counts also make it difficult to characterize uncommon harms from a study of this size.
In general, an estimate is more informative when accompanied by an uncertainty interval, because the interval conveys the range of effects reasonably compatible with the data under the analysis. Neither an estimate nor an interval for the primary outcome is reported. The enrollment and design labels do not substitute for such results. The record therefore supports a description of the research question and methods at a broad level, but not a conclusion about the observed efficacy or the precision of a treatment effect.
9. Statistical Methods Explained
The registry labels the study randomized and parallel. In a randomized trial, assignment is intended to make the groups comparable on average with respect to characteristics measured and unmeasured at baseline. This is a general rationale for randomization, not evidence that the allocation process was implemented without problems in this trial. The sequence-generation method, concealment procedures, baseline characteristics, and any checks for departures from the planned allocation are not reported in the registry record.
What does a binary endpoint represent?
The primary outcome is recorded as a number of participants, and its meaning is participants with an event. The event is agitation defined by a Riker-Agitation Scale score of 5 or higher during the PACU stay. In general, this converts each participant’s assessment into an event indicator: the participant either meets the threshold or does not. Group counts can then be used to estimate event frequencies and compare them. The registry record does not report those primary counts or a statistical comparison, so no effect measure can be interpreted from the posted results.
In general, binary outcomes can be compared using measures such as a difference in event probabilities or a relative measure. Each answers a different question: an absolute contrast describes a change in event frequency, while a relative contrast describes how event frequency compares proportionally. These measures require group-specific event data and a clearly stated analysis. Neither a new estimate nor a re-calculation is possible from the available primary-outcome information. No primary-outcome confidence interval or p-value is reported in the registry record.
What does masking tell the reader?
The masking label is quadruple. Masking can reduce the influence of knowledge of assignment on participant experience, care decisions, outcome assessment, or analysis, depending on which roles are masked. In general, the designation alone does not show how masking was implemented or whether it remained intact. The registry record does not name the masked roles, describe the placebo’s appearance or administration, or report an assessment of masking. Those details should not be inferred from the label.
How should the follow-up window be understood?
The primary endpoint is assessed during the PACU stay, with an expected average duration of 12 hours. This specifies the intended clinical setting and approximate observation period, but it does not give each participant’s actual time under observation. In general, differences in observation time can affect the chance of detecting an event when follow-up durations vary. The record does not provide participant-level follow-up durations, a time-to-event analysis, or a method for handling differing PACU stays. The endpoint is described as a count of participants with an event, not as a time-to-event measure.
The intervention description specifies an infusion that starts before the operation is completed and continues until 6:00am the next day. The control description gives the same schedule. The record does not report treatment adherence, interruptions, crossovers, or how deviations were handled. It also does not describe whether outcomes were assessed at multiple specified time points or how any repeated assessments informed the primary comparison.
What can be inferred from the planning assumptions?
The registry describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. This is a planning framework, not a report of the trial’s original sample-size justification. The record does not give the trial’s own design rationale or identify a prespecified effect used to plan enrollment. Planning calculations are not observed power and do not replace an analysis of the trial results. No numerical planning outputs are reported in the record.
In general, a significance level sets a threshold for evaluating data against a null hypothesis under specified assumptions; it does not measure the probability that a treatment works. A confidence interval, when reported, conveys uncertainty around an estimated effect. Neither concept can supply a missing treatment estimate. Since the registry lists 0 analyses and does not report a numerical primary comparison, readers cannot evaluate the trial’s statistical evidence for the primary question using the posted results.
What analysis details remain unavailable?
The analysis population is not reported in the registry record. It is therefore not possible to determine whether the intended analysis included all randomized participants, only participants who received assigned treatment, or another defined group. The handling of missing outcome measurements, protocol deviations, and withdrawals is also not reported. In general, these choices can affect which participants contribute to an estimate and how robust the estimate is to missing data. No model specification, covariate adjustment, subgroup analysis, or sensitivity analysis is listed in the record. The absence of these details limits assessment of the statistical methods beyond the broad design and endpoint description.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 9 outcome measures and identifies agitation in the PACU as the primary outcome and postoperative delirium as a secondary outcome. The remaining outcome definitions and results are not reported in the registry record. It also lists 0 analyses and indicates that the primary outcome has several categories or time points and was not reduced to one comparison. No single numerical primary-outcome contrast is available.
When a study evaluates multiple outcomes, time points, or comparisons, there can be more opportunities for apparently notable results to occur by chance. In general, a prespecified statistical plan can clarify which comparison is primary and whether any adjustment or hierarchy is used. The registry record does not report a multiplicity strategy, a hierarchy among outcome measures, or an analysis plan explaining how categories or time points were handled. It is not possible to determine whether multiplicity was addressed in another document or analysis.
Missing-data procedures and analysis populations are also not reported in the registry record. The record does not state how missing agitation assessments, withdrawals, or deviations from assigned treatment were handled, nor does it define an intention-to-treat or other analysis population. In general, missingness can affect the interpretation of outcome frequencies when the chance of an unavailable measurement is related to participant status or treatment. Without the relevant counts and methods, the potential effect of missing data cannot be evaluated. These reporting gaps limit assessment of both the analysis and the reliability of any unreported treatment comparison.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Dexmedetomidine | 0 | 40 | 0.0% |
| Control | 0 | 40 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Dexmedetomidine | 1 of 40 |
| Control | 1 of 40 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Dexmedetomidine | Control |
|---|---|---|---|
| hypotension in PACU | Vascular disorders | 0 of 39 | 1 of 40 |
| bradycardia in PACU | Cardiac disorders | 1 of 40 | 0 of 40 |
The registry’s adverse-event entries list 0 serious events among 40 at risk in the dexmedetomidine group and 0 among 40 at risk in the control group. It lists 1 other event among 40 at risk in each group. The record does not provide descriptions of the other events, and no serious-event terms are listed. A death count is not reported in the registry record.
These are descriptive counts. They do not show that the groups have identical risks, and they do not establish that either intervention is safe or unsafe. In general, a zero count means that no event of the specified type was recorded in the listed group; it does not prove that such an event cannot occur. A small number of observed events also gives limited information about uncommon outcomes.
The record does not report a statistical safety comparison, uncertainty intervals, severity details for the other events, or information about how adverse events were collected and attributed. The entries should therefore be interpreted narrowly as the counts recorded, rather than as a complete characterization of comparative safety.
12. What the Result Does, and Does Not, Mean
The registry record establishes the intended question and gives a broad description of a randomized, parallel comparison between dexmedetomidine and saline placebo after free flap reconstructive surgery. It defines the primary event as agitation in the PACU, based on a Riker-Agitation Scale score of 5 or higher, and names postoperative delirium as a secondary outcome. These details help readers understand what the trial was designed to investigate.
The record does not report a single numerical result for the primary outcome or a numerical result for delirium. It does not provide group-specific primary event counts, an effect estimate, a confidence interval, or a p-value. The posted data therefore do not establish whether agitation or delirium differed between groups, by how much, or with what precision. A treatment effect should not be inferred from the study title, hypothesis, intervention description, or enrollment figure.
The safety entries give limited descriptive counts: no serious events are listed in either group and one other event is listed in each. These observations do not establish equivalence or rule out uncommon harms. The registry does not provide event details or a comparative safety analysis.
In general, a randomized design can support a causal comparison when allocation, follow-up, outcome assessment, and analysis are appropriately conducted. The design label alone is not enough to assess those conditions, and the methods needed to judge them are not fully reported in the registry record. The findings cannot be generalized beyond what the record reports, and the absence of a numerical outcome result prevents assessment of the magnitude and uncertainty of any effect. The appropriate interpretation is therefore limited: the registry describes a clinical question and study design, but the posted results do not answer the primary statistical question.
13. Why This Trial Matters Statistically
This trial is statistically relevant because its clinical question concerns a defined event in a specific postoperative setting, and it uses a randomized comparison. The registry describes agitation after free flap reconstructive surgery as the primary concern and specifies a threshold on the Riker-Agitation Scale. Clear endpoint definitions are important because they establish what is counted and when the event is considered present.
The record also illustrates why a design description and a result are different kinds of evidence. Randomization, parallel groups, and quadruple masking describe intended features of the study. They do not provide the observed event counts or quantify uncertainty. Without a reported primary comparison, readers cannot determine the direction or magnitude of an effect or assess its precision, regardless of the trial’s stated hypothesis.
Multiplicity and reporting are also important. The record lists 9 outcome measures but does not describe a strategy for managing multiple outcomes, categories, or time points. It reports 0 analyses and notes that the primary outcome was not reduced to one comparison. Those details leave the reader unable to identify a single inferential result corresponding to the primary question.
Finally, the limited adverse-event counts demonstrate the distinction between observed events and broader safety conclusions. Counts can be reported accurately while still leaving substantial uncertainty about less common events and comparative risk. In general, clear reporting of denominators, endpoint definitions, analysis populations, missing data, estimates, and uncertainty allows readers to evaluate what a trial contributes. Several of these elements are not reported in the registry record, so the statistical contribution available from the posted results is chiefly the study’s question and high-level design rather than an estimate of treatment effect.
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.
A key trial-specific limitation in the registry record is the absence of a single numerical comparison for the primary outcome. Although agitation is defined and the endpoint is named, the record does not report the number of participants meeting the definition in each group or any estimate of the between-group contrast. The note that the primary outcome has several categories or time points and was not reduced to one comparison makes the intended primary analysis difficult to identify.
The outcome description gives an expected average PACU stay of 12 hours, but actual observation duration and assessment timing are not reported. The registry does not state how many participants had complete assessments, whether any measurements were missing, or how missingness was handled. Analysis-population definitions, withdrawals, adherence, and protocol deviations are also not reported.
Other trial-specific details remain unclear. The registry labels the study quadruple-masked without identifying the masked roles. It does not describe the randomization sequence or concealment procedures. The saline concentration entry is qualified as a guess, and the record does not provide further clarification. Postoperative delirium is listed as a secondary outcome but has no numerical result in the record. Although 9 outcome measures are listed, the other outcome descriptions and results are not reported there.
The adverse-event information is limited to event counts and at-risk denominators. Serious-event terms are not listed; descriptions of the other events, a death count, and a comparative safety analysis are not reported in the registry record. These gaps do not show that the trial methods were inadequate, but they prevent readers from assessing several important aspects of conduct, analysis, and interpretation using the registry record alone.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Dexmedetomidine to Prevent Agitation After Free Flap Surgery — NCT01904760.
- Registry record last updated 2014-11-13; status last verified 2014-11.
- Results first posted 2014-11-13.
- 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.
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18. Record Summary
The registry describes a completed, phase 4, randomized, quadruple-masked, parallel-group trial sponsored by Peking University, with enrollment listed as 80. It compares dexmedetomidine infusion with saline placebo after free flap reconstructive surgery. The primary outcome is agitation in the PACU, defined as a Riker-Agitation Scale score of 5 or higher; postoperative delirium is listed as a secondary outcome.
The record lists 9 outcome measures and 0 analyses. It notes that the primary outcome has several categories or time points and was not reduced to one comparison. No numerical primary-outcome result, treatment-effect estimate, confidence interval, or p-value is reported in the registry record. The adverse-event entries list 0 serious events and 1 other event in each group, with 40 at risk in each group; a death count is not reported. The posted record therefore describes the research question and broad design but does not provide a numerical answer to the primary comparison.