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 A Comparison of Desflurane vs. Sevoflurane and the Time to Awakening and the Incidence and Severity of Cough (NCT01202162), a randomized na study. The primary outcome is Time to Awakening.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01202162 |
| Phase | NA |
| Condition | Surgery, Anesthesia |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 85 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Northwestern University |
| Results posted | Yes |
2. Clinical Question
Population
Adults undergoing ambulatory surgery with general anesthesia and a laryngeal mask airway were the intended study population, as described in the registry summary. The registry record does not report further eligibility details or a demographic description of enrolled participants. Enrollment was 85. The primary outcome reports 40 participants in each treatment arm.
Intervention
The intervention was administration of desflurane. The registry summary frames the question around whether desflurane may be associated with faster awakening in short ambulatory cases, while also assessing perioperative cough and quality of recovery.
Comparator
The comparator was administration of sevoflurane. The trial was randomized, double-masked, and parallel-group. The record does not describe the randomization procedure or identify which trial roles were masked.
Primary question
The primary endpoint was elapsed time from turning off the inhalational agent to patient awakening, measured in minutes. The clinical question was whether this time differed between the desflurane and sevoflurane groups. The registry reports a median and inter-quartile range for each group, but does not report a primary-endpoint comparison estimate or statistical test.
3. Trial Design
This was a randomized, double-masked, parallel-group trial comparing desflurane with sevoflurane. The registry lists the phase as NA and the status as completed. Northwestern University is listed as the sponsor. The study start is recorded as 2010-02 and the primary completion as 2012-03. Enrollment was 85.
The registry describes the setting and rationale as ambulatory surgery under general anesthesia with a laryngeal mask airway. Its summary focuses on the practical interest in early recovery and describes perioperative cough, laryngospasm, and quality of recovery as additional concerns. The listed interventions are desflurane and administration of sevoflurane. Arm descriptions specify administration of the corresponding inhaled anesthetic.
The primary endpoint was time to awakening, defined as the time from turning off the inhalational agent until the patient awakened. The registry reports a median and inter-quartile range for each arm, with 40 participants in each arm. The trial record does not explain the difference between overall enrollment and the number reported for this endpoint, nor does it provide a participant flow account.
Secondary outcomes listed in the record include the number of participants who coughed and Quality of Recovery 40. The registry also lists a secondary-outcome assessment of perioperative cough and laryngospasm in its summary, but a numerical laryngospasm result is not reported in the registry record. A numerical Quality of Recovery 40 result is also not reported in the registry record. The record does not report the random sequence method, allocation concealment, masking procedures, eligibility criteria, or details of the anesthesia and surgical protocols.
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 | Desflurane | Sevoflurane |
|---|---|---|
| STARTED | 43 | 42 |
| COMPLETED | 40 | 40 |
| NOT COMPLETED | 3 | 2 |
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 | Desflurane | Sevoflurane | Total |
|---|---|---|---|---|
| Participants analysed | 43 | 42 | 85 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 43 | 42 | 85 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age Continuous | years | 41.2 (SD 8.3) | 39.9 (SD 7.7) | 40.6 (SD 8.1) |
| Sex: Female, Male: Female | Participants | 43 | 42 | 85 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 43 | 42 | 85 |
6. Primary Endpoint
The registry lists the primary outcome as Time to Awakening, measured over Time inhalational agent is turned off to time of patient awakening.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | Elapsed time in minutes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint measures elapsed time in minutes from when the inhalational anesthetic is turned off until the patient awakens. This is a recovery-time measure: it places the starting point at discontinuation of the agent and the endpoint at awakening. The registry identifies the outcome as time to awakening and reports its distribution using a median and inter-quartile range.
As a general statistical point, a median describes the central observation after values are ordered, while the inter-quartile range describes the span from the lower to the upper quartile. These summaries can be useful when a distribution is skewed or includes unusually long times, because the median is less sensitive to extreme values than the mean. The record does not state why this summary was selected, whether the data were skewed, or how awakening was operationally assessed.
The posted medians are 6.8 minutes for desflurane and 11.8 minutes for sevoflurane. The reported inter-quartile ranges are 5.0 to 9.6 and 8.8 to 14.6, respectively. These are separate summaries for the two arms. The registry does not report a treatment-effect estimate, confidence interval, or hypothesis test for the primary endpoint, so the precision of a between-arm contrast cannot be assessed from the posted primary results.
Awakening time is relevant to the stated study question because the registry summary identifies early recovery as a goal in ambulatory surgery. That rationale does not establish that awakening time captures every aspect of recovery. The record also lists quality of recovery as a secondary concern, but its numerical result is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary endpoint summaries are 6.8 minutes for desflurane and 11.8 minutes for sevoflurane. Each is reported as a median, with an inter-quartile range of 5.0 to 9.6 for desflurane and 8.8 to 14.6 for sevoflurane. The posted values describe the observed distributions within each arm. They do not, on their own, provide a formal estimate of the between-arm difference or its uncertainty.
The registry does not report a primary-endpoint comparison estimate, confidence interval, or p-value. It therefore does not establish how precisely the observed arm summaries distinguish the treatments in this trial. The primary endpoint results should be read as descriptive summaries, not as a reported inferential test. The record also does not state whether an analysis adjusted for other variables was planned or conducted.
For the secondary outcome of participants who coughed, the registry reports 4 participants in the desflurane arm and 7 in the sevoflurane arm, with 40 participants at risk in each arm. The posted unadjusted recalculation gives a risk difference of 0.075 for sevoflurane compared with desflurane, with a 95% confidence interval from -0.075 to 0.225 and p = 0.33. The interval includes zero, and its range is compatible with effects in either direction. The results therefore do not support a precise estimate of the difference in cough occurrence. No sponsor-reported analysis is listed for this endpoint.
The posted ratio estimates for cough are also imprecise: the risk ratio is 1.75 with a 95% confidence interval from 0.555 to 5.514, and the odds ratio is 1.909 with a 95% confidence interval from 0.512 to 7.119. These estimates and the risk difference summarize the same small set of event counts in different ways. They should not be treated as independent findings.
The registry lists Quality of Recovery 40 as a secondary outcome, but a numerical result is not reported in the registry record. It also does not post a numerical result for laryngospasm, despite mentioning that outcome in the study summary. The available results consequently offer only a partial account of the secondary questions. The trial's posted results describe the observed data; they do not establish a broad conclusion about the comparative effects of the anesthetics.
9. Statistical Methods Explained
The trial is identified as randomized, double-masked, and parallel-group. These labels describe broad features of the design, but the registry record does not give the procedures behind them. The randomization sequence method, allocation concealment, and the people who were masked are not reported in the registry record. The record likewise does not describe how the masking was maintained or assessed.
What do the primary summaries tell us?
The primary outcome is time to awakening, recorded in minutes from turning off the inhalational agent to awakening. The registry reports a median and inter-quartile range for each arm. A median is a measure of location, while the inter-quartile range describes the central portion of the observed values. As a general statistical explanation, these summaries can describe a distribution without assuming it is symmetric. They do not quantify the uncertainty in a comparison between arms.
The reported median is 6.8 for desflurane and 11.8 for sevoflurane. The inter-quartile ranges are 5.0 to 9.6 and 8.8 to 14.6, respectively. The registry does not identify an inferential method for comparing these values. It does not report a confidence interval or p-value for the primary outcome. No new test can be reconstructed from these summaries alone without making assumptions that are not stated in the record.
How should the cough comparison be read?
For cough, the registry posts counts of participants who coughed and the number at risk in each arm. The recalculated unadjusted comparison expresses the difference in risks as sevoflurane compared with desflurane. Its estimate is 0.075, with a 95% confidence interval from -0.075 to 0.225 and p = 0.33. A risk difference is an absolute contrast between the two observed proportions. A value of zero corresponds to equal risks in the two groups.
As a general statistical explanation, a confidence interval gives a range of values compatible with the data under the method's assumptions. It conveys uncertainty more directly than a point estimate alone. Here the interval includes zero and spans values on both sides of zero, so the observed data do not locate the risk difference precisely. The reported p-value is unadjusted; it does not account for testing multiple outcomes. The registry lists no sponsor-reported analysis for cough, and the recalculation is unadjusted rather than an adjusted model-based result.
The registry also reports a risk ratio of 1.75, with a 95% confidence interval from 0.555 to 5.514, and an odds ratio of 1.909, with a 95% confidence interval from 0.512 to 7.119. As general definitions, a risk ratio compares the risks in two groups as a ratio, while an odds ratio compares their odds. Neither is an absolute difference, and neither should be interpreted as a separate replication of the risk-difference result. The wide intervals indicate that these ratio estimates are also imprecise.
Why does event frequency matter?
As a general principle, binary outcomes based on relatively few observed events tend to yield uncertain estimates. A small change in the event count can have a noticeable effect on an estimate, and the confidence interval may remain wide. This is relevant to the posted cough counts. The record does not report a model for the outcome or a covariate-adjusted analysis.
Over-dispersion is a general issue for count data when variability exceeds what a chosen model assumes. It does not apply automatically to every outcome, and the cough result is reported as a binary participant count rather than as a rate of repeated events. The registry does not report an over-dispersion assessment or a count model for these outcomes.
What do the planning figures represent?
The cough planning illustration uses the observed effect as its starting point and specifies a two-sided significance level of 0.05, equal allocation, and a normal approximation. It gives participants per arm for 80% and 90% power at 100%, 75%, and 50% of the observed effect. These are planning illustrations, not observed trial results and not observed power. For example, planning for 75% of the observed effect gives 554 participants per arm for 80% power and 740 participants per arm for 90% power. The registry explicitly distinguishes these calculations from the trial's own design; the trial's sample-size justification is not reported in the registry record.
The record does not report the primary outcome's analysis plan, assumptions about its distribution, missing-data procedures, or analysis population. The statistical methods used by the trial investigators beyond the posted summaries are not reported in the registry record. In particular, a recalculated unadjusted comparison should not be mistaken for a prespecified or sponsor-reported analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary endpoint and multiple secondary outcomes, including participants who coughed and Quality of Recovery 40. Its summary also identifies laryngospasm as an outcome of interest. The record does not report a plan for controlling multiplicity, such as an adjustment to significance thresholds, a prespecified testing sequence, or a distinction between confirmatory and exploratory analyses. Without such information, an unadjusted secondary p-value should be interpreted as a result for that comparison alone, not as evidence that accounts for all outcomes examined.
The cough comparison is reported as unadjusted, with p = 0.33. No sponsor-reported analysis is listed for that endpoint. The primary outcome has no posted comparison test or uncertainty interval. The registry does not report whether the investigators conducted additional analyses that were not included in the posted results.
Missing-data handling is not reported in the registry record. The primary endpoint lists 40 participants per arm, while total enrollment is 85; the record does not explain the participant flow or the availability of the endpoint for enrolled participants. It also does not report exclusions after randomization, withdrawals, or the treatment of incomplete measurements. Therefore, the analysis population and the relationship between enrollment and endpoint denominators are not clear from the posted information.
The record does not report an intention-to-treat definition, a per-protocol population, an imputation method, or sensitivity analyses for missing outcomes. It is not possible to determine from the registry whether missing observations occurred or how they may have affected results. These omissions limit assessment of the robustness and completeness of the reported estimates; they do not establish that any particular analysis was or was not performed.
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 |
|---|---|---|---|
| Desflurane | 0 | 40 | 0.0% |
| Sevoflurane | 0 | 40 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Desflurane | 2 of 40 |
| Sevoflurane | 1 of 40 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Desflurane | Sevoflurane |
|---|---|---|---|
| Laryngospasm | Respiratory, thoracic and mediastinal disorders | 2 of 38 | 1 of 39 |
The registry reports serious adverse events for 40 participants at risk in each arm, with zero serious events in the desflurane group and zero in the sevoflurane group. These are the posted serious-event figures. They describe what was recorded for the participants at risk in the registry's safety reporting, not a guarantee that no serious events occurred outside the reported observation and definitions.
The record separately lists other adverse events: 2 in the desflurane group and 1 in the sevoflurane group, with 40 participants at risk in each. The registry does not provide event terms for these counts in the posted summary, and no serious adverse-event terms are listed. The deaths field is not reported as a numerical value for either group, so mortality information is not reported in the registry record.
As a general statistical point, zero observed serious events in a limited group does not establish that the underlying risk is zero. Safety counts should be interpreted with attention to the number at risk, the event definitions, follow-up, and completeness of reporting. The registry record does not describe the safety follow-up period, event-collection procedures, or how adverse events were attributed to treatment. These figures therefore provide a limited description of reported events rather than a comprehensive comparison of safety.
12. What the Result Does, and Does Not, Mean
The posted primary results describe the observed time-to-awakening distributions in the two randomized groups. The medians are 6.8 minutes for desflurane and 11.8 minutes for sevoflurane, with the reported inter-quartile ranges of 5.0 to 9.6 and 8.8 to 14.6, respectively. These summaries show the values recorded in the trial arms, but the registry does not post a primary comparison estimate or confidence interval. The precision of a treatment contrast is therefore not available from the primary results.
The cough result is a separate secondary comparison. Its unadjusted estimate is uncertain, and its confidence interval includes values on either side of no difference. That finding does not resolve the primary question, nor does the primary endpoint resolve the cough question. Each outcome addresses a different aspect of the study.
The registry does not report numerical results for Quality of Recovery 40 or laryngospasm. Consequently, the posted record does not provide a complete assessment of the additional recovery and perioperative outcomes described in the study summary. It also does not report details needed to assess missing data, analysis populations, or multiplicity.
These limitations mean that the posted numbers should be understood as a partial statistical record of a completed randomized trial. They do not establish that either anesthetic is better or worse overall, and they do not support medical advice. A conclusion about the broader clinical question would require consideration of the trial's complete methods and results, as well as evidence beyond this registry record.
13. Why This Trial Matters Statistically
This trial illustrates why a randomized design and a complete statistical report serve different purposes. Randomization is a design feature intended, in general, to support fair comparisons between groups. The registry identifies the study as randomized and double-masked, but does not describe the specific procedures or provide a primary inferential comparison. The design labels alone do not reveal the precision of the estimated treatment effect.
The primary endpoint is reported with distributional summaries that are meaningful for time measurements, but the registry does not include a comparison estimate or confidence interval. This highlights the difference between describing each arm and quantifying the uncertainty in a contrast. Readers can see the group summaries, but cannot assess the precision of the primary treatment comparison from the posted primary results.
The cough outcome demonstrates another statistical issue: small event counts can lead to uncertain estimates. Its point estimate is accompanied by a confidence interval that spans both directions, and the comparison is unadjusted. This makes the uncertainty and the multiplicity context important parts of interpretation, rather than relying on a single point estimate or p-value.
Finally, a registry may identify outcomes that do not have numerical results in the posted record. Here, Quality of Recovery 40 and laryngospasm are named in the record, but their numerical results are not reported in the registry record. This limits the ability to evaluate the full outcome set and to understand how the reported primary measure relates to broader recovery. The trial is therefore a useful example of why transparent outcome reporting, analysis details, and uncertainty estimates matter in clinical research.
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.
Several limitations are specific to the information posted for this trial. The primary endpoint is summarized by arm, but the registry does not report a treatment-effect estimate, confidence interval, or p-value. As a result, the primary result's statistical precision cannot be assessed from the registry record. The inter-quartile ranges describe the observed distributions but are not a substitute for uncertainty around a between-group contrast.
The registry's total enrollment is 85, while the primary endpoint lists 40 participants per arm. The record does not explain this relationship, describe participant flow, or identify the analysis population. It is not possible to determine whether the difference reflects missing observations, exclusions, or another feature of reporting. Missing-data procedures and sensitivity analyses are not reported in the registry record.
Some outcomes discussed in the study summary do not have numerical results posted. In particular, numerical findings for Quality of Recovery 40 and laryngospasm are not reported in the registry record. This prevents an assessment of the full set of recovery and perioperative outcomes described by the investigators. The record also does not specify how awakening was defined operationally beyond the stated time interval.
Details of randomization, masking, treatment administration, eligibility, follow-up, and analysis methods are not reported in the registry record. The record does not give a sample-size justification or multiplicity plan. The cough comparison is an unadjusted recalculation, rather than a listed sponsor analysis. Together, these reporting gaps limit assessment of precision, robustness, and completeness; they do not show that the underlying trial necessarily lacked these procedures.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Comparison of Desflurane vs. Sevoflurane and the Time to Awakening and the Incidence and Severity of Cough — NCT01202162.
- Registry record last updated 2013-11-25; status last verified 2013-10.
- Results first posted 2013-07-25.
- 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 record describes a completed, randomized, double-masked, parallel-group trial sponsored by Northwestern University. It compared desflurane with sevoflurane in ambulatory surgery using a laryngeal mask airway. Enrollment was 85, and the study dates are recorded as 2010-02 to 2012-03.
The primary outcome was time from turning off the inhalational agent to awakening. The registry posts arm-specific medians and inter-quartile ranges, but no primary comparison estimate or test. Secondary information includes participant counts for perioperative cough and adverse events. Numerical results for Quality of Recovery 40 and laryngospasm are not reported in the registry record. Details of the analysis plan, missing-data procedures, and multiplicity handling are also not reported.