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 Efficacy of Liposomal Bupivacaine Versus 0.25% Bupivacaine for Laparoscopic Urologic Surgery (NCT02222129), a randomized phase 4 study. The primary outcome is Total Opioid Consumption Measured in Intravenous Morphine Equivalents During the Postoperative Hospital Stay.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02222129 |
| Phase | Phase 4 |
| Condition | Pain, Postoperative |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 206 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Knight, Richard, M.D. |
| Results posted | Yes |
2. Clinical Question
Population
Patients undergoing robotic-assisted or laparoscopic urologic surgery. The registry record does not report further eligibility details or a demographic profile for the participants in the primary outcome groups.
Intervention
Surgical-site infiltration of liposomal bupivacaine at the wound sites.
Comparator
Surgical-site infiltration of 0.25% bupivacaine at the wound sites.
Primary question
How did total opioid consumption during the postoperative hospital stay compare between the groups, measured in intravenous morphine equivalents? The registry reports group medians and inter-quartile ranges, with a Wilcoxon (Mann-Whitney) comparison.
The trial addressed whether the choice of local anesthetic infiltration was associated with a difference in opioid use during hospitalization after laparoscopic urologic surgery. The registry describes the study as a prospective, randomized comparison and states that local injection was given at all wound sites. The primary outcome focuses on cumulative opioid consumption over the hospital stay, rather than pain scores alone or opioid use at a single time point.
Visual Analog Pain Scores, Length of Hospital Stay, and Time to First Opioid Use were listed as secondary outcomes. The primary outcome summary reports a median of 17.3 mg of morphine equivalents for the bupivacaine group and 15.0 mg for the liposomal bupivacaine group. The reported comparison has p = 0.39. These figures describe the posted results; they do not by themselves establish the size or precision of a treatment effect. A confidence interval for the between-group difference is not reported in the registry record.
3. Trial Design
NCT02222129 is recorded as a completed, randomized, phase 4 trial with a parallel-group model and single masking. The registry identifies Knight, Richard, M.D. as the sponsor. The recorded start is 2012-12, and primary completion is recorded as 2013-12. Enrollment is listed as 206.
The trial compared surgical-site infiltration of 0.25% bupivacaine with infiltration of liposomal bupivacaine in patients undergoing robotic-assisted or laparoscopic urologic surgery. The brief summary describes a prospective randomized comparison intended to determine which method reduced postoperative opioid use the most. The specific process used to generate the allocation sequence, conceal assignments, or maintain masking is not reported in the registry record. The identity of the masked parties is also not reported in the registry record.
The primary outcome was total opioid consumption measured in intravenous morphine equivalents during the postoperative hospital stay. The recorded timeframe says data were recorded during the hospital stay, typically less than 5 days, and tabulated from the electronic medical record, typically within 30 days of hospital discharge.
The primary outcome results list 94 participants in the bupivacaine group and 97 in the liposomal bupivacaine group. The registry does not explain the difference between those primary outcome group counts and the enrollment figure. It does not report whether the primary analysis followed intention-to-treat, per-protocol, or another analysis-population definition.
The listed secondary outcomes were Visual Analog Pain Scores, Length of Hospital Stay, and Time to First Opioid Use. Although those outcomes are named, their numerical results are not reported in the registry record. Details such as eligibility criteria, procedure mix, dose, timing of infiltration, follow-up beyond the hospital stay, and the operational definitions for secondary outcomes 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
| Stage | Bupivacaine | Liposomal Bupivacaine |
|---|---|---|
| STARTED | 100 | 106 |
| COMPLETED | 100 | 106 |
| NOT COMPLETED | 0 | 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.
Population: Six patients were excluded from the 0.25% bupivacaine group: one for seizures; four for NSAID and/or PCA use; and one for incomplete data. Nine patients were excluded from the liposomal bupivacaine group; one for remaining intubated overnight; four for surgical complications; three for a hospital stay \>5 days due to ileus; and one for NSAID use.
| Characteristic | Unit | Bupivacaine | Liposomal Bupivacaine | Total |
|---|---|---|---|---|
| Participants analysed | 94 | 97 | 191 | |
| Age, Customized: Age | years | 63 (53 to 69) | 62 (52 to 68) | 63 (53 to 68) |
| Sex: Female, Male: Female | Participants | 37 | 34 | 71 |
| Sex: Female, Male: Male | Participants | 57 | 63 | 120 |
| Race/Ethnicity, Customized: Hispanic | participants | 45 | 55 | 100 |
| Race/Ethnicity, Customized: White | participants | 41 | 32 | 73 |
| Race/Ethnicity, Customized: African American | participants | 5 | 6 | 11 |
| Race/Ethnicity, Customized: Asian/Pacific Islander | participants | 0 | 1 | 1 |
| Race/Ethnicity, Customized: Unknown | participants | 3 | 3 | 6 |
| Region of Enrollment: United States | participants | 94 | 97 | 191 |
| BMI | kg/m2 | 28.9 (25.6 to 34.8) | 28.2 (25.5 to 32.8) | 28.7 (25.6 to 33.3) |
6. Primary Endpoint
The registry lists the primary outcome as Total Opioid Consumption Measured in Intravenous Morphine Equivalents During the Postoperative Hospital Stay, measured over All data was recorded during the patient's hospital stay, typically less than 5 days. All data was tabulated from the electronic medical record, typically within 30 days of discharge from hospital..
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | mg (morphine equivalents) |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is total opioid consumption during the postoperative hospital stay, expressed in milligrams of intravenous morphine equivalents. This measure combines opioid use recorded during the admission on a common scale. Such a measure can be used to compare overall opioid exposure across groups even when opioid use involves different drugs or doses, provided that the conversion to morphine equivalents is applied consistently. The registry does not describe the conversion procedure.
The endpoint is summarized using the median and inter-quartile range. The median identifies the middle of the observed distribution, while the inter-quartile range describes the central spread of the observations. These summaries are often useful when individual values are not symmetrically distributed or when unusually high observations could make the mean less representative of a typical participant. This is general statistical context; the registry does not state why this summary was selected.
The outcome covers the admission rather than a fixed follow-up interval for every participant. The registry notes that hospital stays were typically less than 5 days, but does not report the range of stay lengths or explain how length of stay was handled in the analysis. Because consumption accumulates during hospitalization, the endpoint describes recorded inpatient use over each participant’s stay, not opioid use over a common period after discharge.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted median total opioid consumption was 17.3 mg of intravenous morphine equivalents in the bupivacaine group and 15.0 mg in the liposomal bupivacaine group. The reported inter-quartile ranges were 8.3 to 30.5 mg and 6.7 to 27.0 mg, respectively. These summaries show the observed distributions’ central values and central spreads. The ranges overlap substantially, but overlap between inter-quartile ranges is not itself a formal test of a difference.
The registry reports a Wilcoxon (Mann-Whitney) comparison with p = 0.39. In general, a p-value describes how compatible the observed data are with a specified null hypothesis under the assumptions of the test. It is not the probability that the null hypothesis is true, and it does not quantify the probability that a treatment is beneficial or harmful. The registry does not provide a confidence interval for a difference or another effect estimate, so the precision of the between-group contrast cannot be assessed from the reported primary analysis alone.
The p-value is not below the conventional two-sided significance level of 0.05 used in the registry’s stated sample-size assumptions. That planning assumption does not establish that the same threshold governed the trial’s reported analysis: the registry does not report the primary analysis’s prespecified significance level or full statistical plan. The reported p-value should therefore be read as the result of the analysis identified in the record, not as evidence about an unreported analysis plan.
The group medians are descriptive summaries, while the Wilcoxon (Mann-Whitney) test assesses a rank-based comparison of observations. In general, that test does not directly test a difference between medians unless additional assumptions about the shapes of the group distributions are appropriate. Individual observations and detailed distributional information are not reported in the registry record. The test result therefore cannot be translated into a precise median difference from the information available.
The result does not establish that the groups are equivalent. A non-significant test can reflect a small or uncertain difference, and without a confidence interval it is difficult to determine which effect sizes remain compatible with the result. The registry record does not report an equivalence or non-inferiority margin, and it does not report an analysis designed to establish equivalence.
Interpretation is also limited by the endpoint’s inpatient timeframe, the absence of reported detail about missing outcome data and analysis populations, and the lack of posted numerical results for the named secondary outcomes. The summary is specific to the participants and procedures represented in this trial record; the registry does not provide enough detail to evaluate how broadly the findings apply to other surgical settings.
9. Statistical Methods Explained
The registry identifies the primary comparison method as Wilcoxon (Mann-Whitney), and reports p = 0.39. The endpoint is summarized by group median and inter-quartile range. No confidence interval or numerical estimate of the difference between groups is reported in the registry record.
What does the Wilcoxon (Mann-Whitney) test compare?
In general, the Wilcoxon rank-sum test, also known as the Mann-Whitney test, compares the ranks of observations from two independent groups. Rather than comparing group means directly, it uses the ordering of the observations across the combined groups. This can make it useful when an outcome is skewed or does not fit assumptions commonly used for a mean-based comparison. That is general statistical context; the registry does not report the rationale for choosing this test.
The test is sometimes described informally as a test of medians, but that description can be misleading. A difference in medians is one possible way for the distributions to differ. The rank-based test can also respond to differences in spread or shape. Treating its result as a test specifically of medians requires assumptions about the distributions that are not documented in the registry record.
For this trial, opioid consumption is reported as medians with inter-quartile ranges. Those summaries help describe the typical level and central spread, but they do not contain enough information to reproduce the rank-based test. The participant-level outcome values and the rank calculations are not reported in the registry record.
What do the median and inter-quartile range describe?
In general, the median is the midpoint of an ordered set of observations. The inter-quartile range spans the central half of the observations and gives an indication of their spread. These measures can be informative for outcomes with a long upper tail, because a small number of large values may strongly influence the mean while having less influence on the median. This is a general feature of the statistics, not a claim about the shape of this trial’s unreported participant-level data.
The reported median was 17.3 mg in the bupivacaine group, with an inter-quartile range of 8.3 to 30.5 mg. In the liposomal bupivacaine group, the median was 15.0 mg, with an inter-quartile range of 6.7 to 27.0 mg. The inter-quartile ranges describe within-group spread; they are not confidence intervals for the medians or for a treatment contrast.
How should the p-value be read?
In general, a p-value measures how unusual data at least as incompatible with a null model as the observed data would be, if that model and the test assumptions held. The reported p = 0.39 does not mean there is a 39% chance that the groups are the same. Nor does it give the probability that the observed contrast arose by chance in a general, assumption-free sense. A p-value does not report the magnitude or clinical importance of a contrast.
The registry does not provide a confidence interval for the primary comparison. A confidence interval would show a range of effect estimates compatible with the observed data under a specified method, and would convey uncertainty about the magnitude and direction of the contrast. Without that interval or another effect estimate, the p-value alone gives a limited account of precision.
What can the planning assumptions tell readers?
The record describes sample-size assumptions for planning illustrations: a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. These assumptions describe illustrations based on the observed effect, not the trial’s own design rationale. The protocol’s sample-size justification is not reported in the registry record. A planning illustration is not observed power and cannot establish the probability that the completed trial detected an effect.
In general, planning estimates depend on the assumed effect size and variability, the significance threshold, allocation, and analysis method. If an observed effect is used to plan for a later study, the result is conditional on that effect estimate and may not reflect the true effect. No numerical planning estimates are discussed in this explanation.
What remains unknown about the analysis?
The registry does not report whether the analysis was prespecified, the exact handling of missing primary outcome data, or whether any covariate adjustment was used. It does not identify the analysis population. It also does not describe checks of model or test assumptions, a method for confidence intervals, or an approach to multiple comparisons. These omissions limit assessment of how the reported p-value was obtained and how robust it is to analytic choices.
The general statistical concepts above explain what the named method and summaries usually represent. They do not fill in unreported details of the trial’s statistical plan or participant-level data.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| Wilcoxon (Mann-Whitney) | not reported | 0.390 |
The registry’s own reported primary analysis is the Wilcoxon (Mann-Whitney) comparison, with p = 0.39. It reports group medians and inter-quartile ranges but does not report a between-group effect estimate or confidence interval. A separate recalculated comparison is not reported in the registry record.
Without participant-level data or enough summary information to reconstruct the rank-based test, the sponsor’s reported test cannot be independently reproduced from the posted medians and inter-quartile ranges alone. Those summaries do not identify all the ranks used by the test. The reported p-value should therefore be treated as the registry’s analysis result, while recognizing that the underlying calculation cannot be checked from the posted summaries.
The record does not report a recalculated effect estimate that can be compared with the sponsor’s analysis. It also does not provide a discrepancy indication. There is consequently no competing recalculation to reconcile with the reported result. The absence of a confidence interval remains important: the reported p-value provides a test result but does not show the precision of a treatment-effect estimate.
11. Multiplicity, Missing Data and Analysis Populations
The primary outcome is total opioid consumption during the postoperative hospital stay. The registry also names Visual Analog Pain Scores, Length of Hospital Stay, and Time to First Opioid Use as secondary outcomes. Numerical results for these secondary outcomes are not reported in the registry record. The record lists four outcome measures and one analysis, but does not explain how outcomes were selected for analysis or reporting.
When a trial assesses multiple outcomes or makes multiple statistical comparisons, the chance of at least one false-positive result can increase. Statistical methods can address that issue, but the registry does not report whether a multiplicity adjustment was planned or applied. It also does not report a hierarchy of outcomes, a testing sequence, or how the primary outcome was distinguished from any additional analyses. No correction or adjustment should be assumed from the available information.
Information about missing data is limited. The primary outcome group summaries list 94 participants for bupivacaine and 97 for liposomal bupivacaine, while overall enrollment is listed as 206. The record does not explain the difference between these figures, state whether any primary outcome values were missing, or describe how missing values were handled. It does not report whether all randomized participants were analyzed in their assigned groups.
The analysis population is not reported in the registry record. In general, intention-to-treat analysis retains participants in their randomized groups, while per-protocol approaches may exclude participants based on post-randomization events or adherence. Which approach was used can affect interpretation, particularly when exclusions or missing outcomes differ between groups. The record does not provide enough information to classify the reported analysis as intention-to-treat, per-protocol, or another approach.
The record also does not describe imputation, sensitivity analyses for missingness, or procedures for handling participants discharged before outcome capture. These details matter because the endpoint accumulates during each participant’s hospital stay and is recorded from electronic medical records. The available description does not establish whether outcome ascertainment or completeness was comparable across groups.
12. 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 |
|---|---|---|---|
| Bupivacaine | 0 | 100 | 0.0% |
| Liposomal Bupivacaine | 0 | 106 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Bupivacaine | 0 of 100 |
| Liposomal Bupivacaine | 0 of 106 |
The serious adverse event summaries list 100 participants at risk in the bupivacaine group and 106 in the liposomal bupivacaine group, with 0 serious adverse events affected in each group. The summaries also list 100 and 106 participants at risk, respectively, for other adverse events, with 0 affected in each group. Deaths are not reported in the registry record.
These figures describe what the registry lists; they should not be interpreted as proof that no adverse events occurred outside the recorded summaries or as a complete safety assessment. The registry does not provide serious adverse event terms, and no top serious event terms are listed. It does not report the adverse-event collection period, event definitions, ascertainment procedures, or a narrative explaining the relationship between these safety group counts and the primary outcome group counts.
The at-risk counts in the safety summaries differ from the participant counts listed for the primary outcome. The registry does not explain the difference. Safety figures and efficacy outcome counts can reflect different recording or analysis populations, but the specific reason in this trial is not reported in the registry record. Zero affected in the posted categories should therefore be read narrowly as a registry summary, not as evidence that the interventions have no safety risks.
13. What the Result Does, and Does Not, Mean
The registry reports a median total inpatient opioid consumption of 17.3 mg of intravenous morphine equivalents in the bupivacaine group and 15.0 mg in the liposomal bupivacaine group. The reported Wilcoxon (Mann-Whitney) test yielded p = 0.39. These are the central descriptive results and test result available for the primary endpoint.
The result does not show that the interventions are equivalent. Establishing equivalence would require an explicit equivalence margin and an analysis designed to evaluate whether the difference lies within that margin; neither is reported in the registry record. A non-significant p-value is not evidence that any possible difference is small enough to be unimportant. Because a confidence interval or other contrast estimate is not reported, the range of plausible differences cannot be evaluated from the registry summary.
The figures also do not, on their own, establish a clinically important difference. A statistical test and a measure of clinical importance answer different questions. The registry does not report a threshold for a clinically meaningful change in opioid consumption, and the primary outcome is limited to use during the postoperative hospital stay. It does not describe opioid use after discharge.
The findings should not be extended automatically to other procedures, patient populations, or settings. The record identifies robotic-assisted or laparoscopic urologic surgeries but does not provide detailed eligibility criteria, procedure-specific results, or participant characteristics. It also does not report numerical results for the listed secondary outcomes. The primary summary therefore cannot describe pain scores, time to first opioid use, or hospital stay results.
Overall, the posted data describe the observed inpatient opioid consumption summaries and a non-significant rank-based comparison. They provide limited information about the magnitude and precision of any group difference and do not establish equivalence, clinical importance, or results beyond the outcomes and population details recorded.
14. Why This Trial Matters Statistically
This trial is statistically informative because it illustrates the difference between describing group outcomes and estimating a treatment contrast precisely. Medians and inter-quartile ranges show the central location and spread of opioid consumption within each group. The Wilcoxon (Mann-Whitney) p-value provides a rank-based comparison. Neither element alone provides a confidence interval for the magnitude of the between-group difference.
The choice of summary is relevant for an outcome such as total opioid consumption, for which the distribution may be asymmetric. In general, medians and inter-quartile ranges can describe such distributions without relying on a mean and standard deviation. However, they cannot fully characterize the data or reproduce a rank-based test. Participant-level observations or additional statistical output would help readers assess distribution shape and the stability of the comparison.
The trial also highlights the importance of transparent reporting around analysis populations and missing outcomes. Enrollment is listed as 206, while primary outcome group counts are reported separately. The reason those figures differ is not reported. Without an explanation, readers cannot determine how outcome availability, exclusions, or analysis-population choices relate to the randomized trial.
Finally, the registry names several secondary outcomes but does not report their numerical results or a multiplicity strategy. Reporting the outcome hierarchy, analysis population, missing-data handling, and confidence intervals would make the evidence easier to assess. These are general reporting considerations; the registry record does not establish which methods were used beyond the analysis it identifies.
15. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary results are summarized without participant-level data, a confidence interval, or a between-group effect estimate. The p-value and group summaries therefore do not show the precision of the contrast or permit independent reproduction of the reported Wilcoxon (Mann-Whitney) test. The registry does not report the distribution of individual opioid consumption values.
The record does not explain why the primary outcome group counts are 94 and 97 when enrollment is listed as 206. It does not report whether outcome data were missing, why any randomized participants may not appear in the primary summaries, or which analysis population was used. This prevents a clear assessment of completeness and the handling of participants after randomization.
Details needed to understand the procedures are also limited. Eligibility criteria, participant characteristics, the mix of urologic procedures, the specific infiltration dose and timing, and the identity of those masked are not reported in the registry record. Without those details, applicability to particular clinical settings cannot be evaluated fully.
The registry does not provide numerical findings for the listed secondary outcomes, report a multiplicity strategy, or describe a prespecified statistical analysis plan. It does not explain the conversion method for morphine equivalents or report how hospital stay duration may affect the cumulative endpoint. Safety information is limited to the posted affected counts; event definitions, ascertainment period, and deaths are not reported.
These limitations concern what the registry record reports. They do not establish that the trial did not collect or analyze the information, only that it is not reported in the registry record.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Efficacy of Liposomal Bupivacaine Versus 0.25% Bupivacaine for Laparoscopic Urologic Surgery — NCT02222129.
- Registry record last updated 2015-04-16; status last verified 2015-04.
- Results first posted 2015-04-16.
- 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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19. Record Summary
NCT02222129 is a completed randomized phase 4 parallel-group trial comparing surgical-site infiltration of 0.25% bupivacaine with liposomal bupivacaine for robotic-assisted or laparoscopic urologic surgery. The primary endpoint was total opioid consumption in intravenous morphine equivalents during the postoperative hospital stay.
The posted median was 17.3 mg in the bupivacaine group and 15.0 mg in the liposomal bupivacaine group. The registry reports inter-quartile ranges of 8.3 to 30.5 mg and 6.7 to 27.0 mg, respectively, and a Wilcoxon (Mann-Whitney) p-value of 0.39. A confidence interval for the between-group contrast is not reported in the registry record.
Important details remain unreported, including the analysis population, missing-data handling, the reason for the difference between enrollment and primary outcome group counts, and numerical results for the listed secondary outcomes. The posted primary result describes the registry’s reported comparison but does not establish equivalence or quantify the precision of a treatment effect.