Nitrous Oxide for Pain Management During In-office Transcervical Sterilization: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Nitrous Oxide for Pain Management During In-office Transcervical Sterilization (NCT02312739), a randomized na study. The primary outcome is Change From Baseline in Pain Scale Measurement During and After the Procedure.

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-blind, parallel-group study of in-office transcervical sterilization. Enrollment was 72, and the study status is completed. The phase is listed as NA. The sponsor is the University of New Mexico. The registry dates the study start to 2014-02 and primary completion to 2015-03.

Participants were assigned to one of two pain-management groups. The Vicodin, Lorazepam and Oxygen arm included those oral medications, intramuscular ketorolac at least 30 minutes before the procedure, and oxygen administered via a scented mask. The Placebo Pills and Nitrous Oxide arm included placebo pills, the same stated ketorolac timing, and nitrous oxide administered during the procedure via a scented mask. Both groups were to undergo the in-office procedure.

Random allocation can help make groups comparable at the point of assignment, while masking is intended to reduce influences on care, reporting, or assessment. Those are general design principles; the registry record does not report the randomization method, allocation concealment, or who was masked. It also does not report whether masking was maintained or how the study handled departures from assigned treatment. The listed interventions and arm descriptions identify the intended contrast, but do not establish what each participant actually received.

The registry lists secondary outcomes for anxiety change after the procedure, patient satisfaction on a 5-point Likert scale, and provider ease of insertion on a 0-100mm visual analogue scale. It lists five outcome measures overall, but does not report results for them. Details of eligibility criteria, participant flow, and the number analyzed for each outcome 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

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 Change From Baseline in Pain Scale Measurement During and After the Procedure, measured over At baseline before the procedure, during the procedure after paracervical block injection and after placement of second Essure® coil, and prior to discharge from clinic (approximately 30-45 minutes postprocedure).

The primary endpoint is titled as change from baseline in pain scale measurement during and after the procedure. The registry describes pain assessment using a 0-100mm visual analogue scale, anchored at 0 for no pain and 100 for worst pain imaginable. Assessments were planned at baseline before the procedure, after paracervical block injection, after placement of the second Essure® coil, and before discharge, approximately 30-45 minutes postprocedure.

A pain scale is a way to record a participant’s subjective experience in a consistent form. Repeated measurements can describe pain at different procedural stages and whether reported pain changes from baseline. The registry lists the summary parameter as a mean and the dispersion as a standard deviation. In general, a mean describes the average recorded score, while a standard deviation describes variation among scores around that average.

The endpoint title refers to change from baseline, but the registry record does not report the actual means, standard deviations, changes, or a group contrast at any time point. It also does not specify which time point or summary across time points was intended to provide a single primary comparison. The record explicitly indicates that the primary outcome has several categories or time points and was not reduced to one comparison. Thus the endpoint’s measurement approach is described, but a numerical primary result and its precision are not available in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry gives some information about the planned design and outcome measurement, but little information about the statistical analysis actually used. It lists a mean as the endpoint summary and standard deviation as its dispersion. These describe continuous measurements: the mean locates the average score, and the standard deviation describes how spread out participant scores are around that average. Neither statistic alone establishes a difference between randomized groups.

What a group comparison would describe

In general, a comparison of mean pain scores would estimate how the average recorded pain differed between the assigned groups at a defined point or across a defined set of points. A change-from-baseline comparison would use the relationship between a participant’s baseline score and a later score. The precise contrast matters: comparing scores at one occasion is not necessarily equivalent to comparing changes from baseline, and a summary across repeated occasions requires a stated method. The registry record does not identify the exact contrast used for a primary analysis.

The scale runs from 0 to 100mm, with anchors for no pain and worst pain imaginable. Because the outcome is a subjective scale, the numerical score represents a participant’s recorded report rather than an objective physical measurement. In general, consistent assessment procedures and clear timing help make such scores interpretable. The registry specifies the assessment occasions, but details such as assessor procedures and the handling of incomplete assessments are not reported in the registry record.

Why repeated measures require clarity

Measurements taken from the same participant are generally related to one another. In general, an analysis of repeated observations should account for that within-participant relationship rather than treating every score as independent. A statistical plan might define a primary time point, compare change from baseline at that time, or use a model that includes multiple observations. These are general possibilities, not claims about the method used in this study. The registry record does not report which approach, if any, was used.

When several time points are examined, the choice of the primary comparison affects interpretation. A result at one occasion answers a narrower question than an overall summary across the procedure. If many outcomes or time points are tested, there can also be more opportunities to find a nominally notable result by chance. General statistical practice addresses this concern by prespecifying the main comparison or by using an appropriate multiplicity strategy. The registry record does not report a multiplicity plan, and it does not give a single primary comparison from the listed time points.

Uncertainty and precision

A point estimate describes the estimated group difference, while a confidence interval conveys uncertainty around that estimate under the method used. A narrow interval generally indicates greater precision than a wide one, although interpretation also depends on the scale and the question being asked. A p-value, when used, addresses compatibility between the observed data and a specified null hypothesis under the analysis assumptions; it does not measure the size or clinical importance of an effect. The registry record does not report a primary point estimate, confidence interval, or p-value, so these aspects of the comparison cannot be assessed.

Standard deviations would help describe variability in pain scores within each group, but the values are not reported. Sample size alone cannot replace this information: the precision of an estimate depends on variability and the analysis as well as the number of observations. The registry lists an enrollment of 72, but the number included in each outcome analysis is not reported in the registry record.

Design and analysis are distinct

Randomization is intended, in general, to reduce systematic differences between assigned groups at baseline. Double masking is intended, in general, to limit influences related to knowledge of assignment. These design labels do not tell the reader the exact analysis model, whether the analysis followed assigned groups, or how missing values and protocol deviations were addressed. Those details are not reported in the registry record.

The registry also contains a general description of sample-size planning illustrations based on an observed effect and specified assumptions. No resulting planning figures or observed pain effect are reported in the registry record, and the record does not report the trial’s own sample-size justification. Any sample-size illustration would be a planning aid, not observed power or evidence that the study detected a particular effect. Since the primary result needed to anchor such an illustration is not reported, no numerical planning interpretation can be made from the posted results.

10. Multiplicity, Missing Data and Analysis Populations

The primary pain outcome includes measurements at multiple occasions, while the registry notes that it was not reduced to one comparison. The record also lists several secondary outcomes: change in anxiety after the procedure, patient satisfaction, and provider ease of insertion. When multiple outcomes or time points are analyzed, general statistical practice distinguishes a prespecified primary question from additional exploratory comparisons. This helps readers judge which result is the main test and how to interpret a collection of estimates.

The registry record does not report a multiplicity adjustment, a hierarchy among outcomes, or a plan for selecting a primary time point. It also does not report an analysis plan or an explanation of whether the listed secondary outcomes were analyzed. The five outcome measures are listed, but their results are not reported. These gaps limit interpretation of any potential pattern across outcomes; they do not establish that a particular adjustment was necessary or omitted in the actual study.

Missing-data methods and analysis populations are also not reported in the registry record. The number with available pain measurements at each occasion, reasons for missing assessments, and any methods used to address missing values are not specified. The record does not say whether participants were analyzed according to randomized assignment, according to treatment received, or under another definition. Without those details, it is not possible to determine how incomplete observations or treatment deviations might affect the comparison.

General statistical interpretation depends on knowing both the outcome definition and the population included in its analysis. The registry describes the planned measurement occasions and lists enrollment, but does not provide participant flow or an outcome-specific analysis count. Consequently, the extent to which the posted endpoint reflects all randomized participants cannot be assessed.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists 30 participants at risk in the Vicodin, Lorazepam and Oxygen group and 34 in the Placebo Pills and Nitrous Oxide group for both serious and other adverse events. It records 0 serious adverse events and 0 other adverse events for each group. These are the posted counts, not evidence that every possible adverse outcome was assessed or reported in the same way.

The death counts are not reported in the registry record. No serious adverse event terms are listed. The record does not describe how adverse events were defined, how actively they were collected, the observation period for safety, or whether all enrolled participants were included in the safety counts. Those omissions matter when interpreting a zero count: it is a registry entry for the recorded categories and denominators, not a complete characterization of safety.

The safety figures should be read separately from the primary pain question. They do not provide information about the magnitude or precision of the pain comparison, which is not reported. Nor do the listed counts by themselves establish that there were no events outside the registry’s reported categories or observation procedures.

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

The registry record establishes that a completed randomized, double-blind, parallel-group trial was registered to compare two approaches to pain management during in-office transcervical sterilization. It describes a primary pain measure, repeated assessment occasions, and three secondary outcomes. It also records enrollment of 72 and provides group-level adverse-event counts.

What it does not establish is the primary comparative result. No pain scores, changes from baseline, group differences, confidence intervals, or p-values are reported in the registry record. Thus, the direction, size, and precision of any difference between the assigned groups cannot be determined from these posted results. The investigators’ hypothesis about nitrous oxide is not evidence that the hypothesis was confirmed.

In general, an estimate and its uncertainty are needed to judge how compatible the data are with different possible effects. A statistically distinguishable difference, if reported, would still need to be interpreted in context, including its size, the measurement scale, and the study’s limitations. Conversely, an imprecise estimate would not establish that the groups were equivalent. No such distinctions can be made without the relevant results.

The record also does not report how many participants contributed to each outcome, how missing measurements were handled, or what analysis method was used. These omissions restrict the ability to assess the robustness of any result because the result itself and its analytical context are unavailable. The adverse-event counts describe the registry entries for the listed groups, but do not answer the primary pain question.

Accordingly, the appropriate reading is narrow: the registry documents a trial designed to investigate a comparative pain-management question, but its posted results do not permit a conclusion about the primary pain contrast. This is a statement about the information in the registry record, not a claim about results that may be available elsewhere.

13. Why This Trial Matters Statistically

This trial raises a statistical issue common in clinical research: a well-defined question and randomized design are not enough to interpret an effect if the comparative outcome is not reported. The record describes the assignment groups and the pain scale, but provides no primary estimate or measure of uncertainty. Readers therefore cannot judge the magnitude, direction, or precision of the intended comparison.

It also illustrates why outcomes measured at several occasions need clear analytical definitions. Baseline, post-block, post-coil, and pre-discharge scores may answer different questions. A prespecified primary time point or an explicit repeated-measures summary can clarify which contrast is central. The registry’s note that the endpoint was not reduced to one comparison makes that issue visible, while the absence of a reported analysis leaves the resolution unknown.

Other important statistical details include the analysis population, missing-data handling, and multiplicity plan. These details help distinguish a planned analysis from an exploratory one and show how the evidence was assembled. They are not reported in the registry record. Their absence, alongside the missing primary results, prevents a full assessment of the trial’s statistical evidence.

The case also shows the value of separating design information from findings. Randomization and masking describe intended safeguards against bias; they do not substitute for outcome estimates. Similarly, adverse-event counts and enrollment describe aspects of the record, but cannot fill the gap in the pain comparison. Statistical interpretation depends on transparent reporting of the result, its uncertainty, and the methods connecting the observations to the conclusion.

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 central limitation of interpreting this trial from the registry record is that the primary comparative pain result is not reported. The record gives the measurement scale and timing, but no group estimates, changes, variability, confidence interval, or p-value. This prevents assessment of the observed effect and its precision.

The endpoint spans several occasions, and the registry notes that it was not reduced to one comparison. The primary estimand, or precise quantity intended to answer the main question, is not reported in the registry record. It is therefore unclear which time point or combination of measurements would represent the principal comparison. The record also does not report the statistical model or whether repeated measurements were accounted for.

Participant flow, outcome-specific analysis counts, and analysis populations are not reported. The number of participants with complete measurements at each occasion and the handling of missing data are also not reported in the registry record. Consequently, the extent of missing outcome information and its possible influence cannot be assessed.

The registry identifies the trial as randomized and double blind, but does not report the randomization procedure, allocation concealment, who was masked, or whether masking was maintained. It does not report a statistical analysis plan, multiplicity approach, or sample-size justification. These are limitations of the available record; their absence does not establish how the study was conducted in practice.

Finally, the listed adverse-event counts lack reported definitions, collection procedures, and observation details, and death counts are not reported in the registry record. The posted safety figures should therefore be interpreted as limited registry entries rather than a complete assessment of safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Nitrous Oxide for Pain Management During In-office Transcervical Sterilization — NCT02312739.
• Registry record last updated 2016-07-06; status last verified 2016-05.
• Results first posted 2016-07-06.
• 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

NCT02312739 is a completed randomized, double-blind, parallel-group study sponsored by the University of New Mexico. The registry lists enrollment of 72, a start date of 2014-02, and primary completion in 2015-03. The comparison was between Vicodin, Lorazepam, ketorolac, and oxygen, and placebo pills, ketorolac, and nitrous oxide during in-office transcervical sterilization.

The primary outcome concerned pain measured on a 0-100mm visual analogue scale at baseline and several procedural or post-procedural occasions. Anxiety change, patient satisfaction, and provider ease of insertion were also listed as secondary outcomes. The registry record does not report the primary pain comparison or results for the secondary outcomes. It lists 0 serious and 0 other adverse events in each reported group; death counts are not reported in the registry record.