Continuous Subpleural Infusion of Bupivacaine: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Continuous Subpleural Infusion of Bupivacaine (NCT01566838), a randomized na study. The primary outcome is Number of Participants With and Without 30-Day Pain Medication Usage.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. Participants were assigned to receive a subpleural pain catheter with 0.125% bupivacaine alongside standard acute pain management, or standard acute pain management without a pain catheter. The record identifies Inova Health Care Services as sponsor and postoperative pain as the condition.

The intended setting was Inova Fairfax Hospital. The eligibility description covers adults having an isolated thoracoscopic procedure for therapeutic or diagnostic purposes. It lists multiple exclusions, including previous ipsilateral thoracic surgery, a need for operative pleurectomy or pleurodesis, chronic use of pain medication, sedatives or hypnotics, drug allergies, liver or renal dysfunction, a history of peptic ulcerative disease, sleep apnea requiring Bipap, severe chronic obstructive pulmonary disease, inability to consent, and pregnancy. The registry record does not report how many screened patients were excluded or the reasons for any exclusions in the enrolled group.

The record gives an enrollment of 83. Separately, the brief study description says that 86 consented patients would be randomized. These entries describe different aspects of the record: the enrollment field and the stated design plan. The actual number randomized to each arm and the number included in each outcome analysis are not reported in the registry record.

The study start is listed as 2012-10, primary completion as 2015-12, and status as completed. The phase entry is NA. The registry record does not report the randomization sequence method, allocation concealment, or whether any protocol changes occurred. The primary endpoint is described as postoperative pain-medication use through postoperative day 30; listed secondary outcomes include paresthesia, length of stay, return to work, and resumed physical activity.

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

Analysis population for the primary outcome, as defined in the registry: 30-day pain medication usage

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 Number of Participants With and Without 30-Day Pain Medication Usage, measured over Postoperative day 1 through postoperative day 30.

The primary endpoint is the number of participants with and without 30-day pain medication usage. Its stated timeframe is postoperative day 1 through postoperative day 30, and the description identifies the outcome as narcotic pain-medication use. The endpoint therefore concerns whether medication was used during the specified postoperative period, rather than the amount of medication taken or the timing of each dose. Those additional details are not reported in the registry record.

Medication use is a behavioral or treatment-use outcome: it records whether participants used pain medication, as opposed to measuring pain intensity directly. Such an endpoint can be relevant to a trial about postoperative pain management because it captures a component of care after surgery. In general, however, medication use does not by itself describe the full pain experience. Use may be affected by factors beyond pain intensity, and a yes-or-no classification does not show how often medication was taken or how much was used. Those are general interpretive considerations, not additional findings from this trial.

The registry describes a comparison between the randomized groups, but it does not report the number of participants with or without use in either arm. It also does not report an effect estimate or uncertainty interval for this endpoint. As a result, the endpoint can be identified from the record, but the posted results do not establish the observed group contrast or its precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization is intended to assign participants to study arms by a chance-based process. In general, this can reduce systematic differences between groups at assignment, although it does not guarantee that groups will be identical, especially in a trial of limited size. The registry describes the allocation as randomized and the model as parallel. It does not report the method used to generate the allocation sequence, how assignments were concealed before enrollment, or whether randomization was stratified. Those details are not reported in the registry record.

What does the parallel design mean?

In a parallel-group design, participants are assigned to an arm and outcomes are compared across arms. The registry’s arms differ in whether a subpleural catheter delivering 0.125% bupivacaine is added to standard acute pain management. The comparator receives standard acute pain management without the additional catheter. Because masking is listed as none, the record describes the study as unmasked. It does not state whether outcome assessment or data analysis was conducted by people unaware of assignment.

In general, lack of masking can matter when an outcome depends on participant decisions, clinician decisions, or how information is collected. The primary endpoint is medication use, which records whether pain medication was used during the specified period. The record does not explain how use was ascertained, whether it came from participant report or another source, or whether the method was identical across arms. These details would help readers evaluate possible measurement differences, but they are not reported in the registry record.

How should a binary endpoint be understood?

The primary outcome is described as the number of participants with and without 30-day pain medication usage. This is a binary classification at the participant level: participants are counted according to whether the defined use occurred. In general, a comparison can report an absolute difference in proportions or a relative measure, but the best summary depends on the question and the analysis plan. No outcome counts or effect estimates are reported for this endpoint, so no such comparison can be described from the record.

A binary measure also compresses detail. It does not, by itself, show the amount or frequency of medication used, the timing of use, or the reported pain score. The record lists postoperative pain scores among secondary outcomes in the design description, but it does not provide those results. Interpretation should therefore stay with the measure as defined rather than treating medication use as a direct measurement of pain severity.

What can uncertainty measures tell readers?

In general, an effect estimate describes the observed contrast between groups, while a confidence interval describes uncertainty around that estimate under the chosen method. The interval’s width is important: a point estimate without an interval can make precision difficult to judge. A hypothesis test and its p-value address a related but different question, and a p-value does not state the probability that a treatment effect is true. Here, the registry record does not report an estimate, confidence interval, or p-value for the primary outcome. The sponsor’s own analysis, if available elsewhere, is not reported in the registry record; no recalculated estimate can be made from the posted outcome information.

The sample-size assumptions describe a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. They state that the effect to detect is a specified fraction of the observed effect. No calculated planning counts are reported in the registry record. Such calculations, when available, are planning illustrations rather than observed power. They depend on assumptions about the effect and analysis and should not be mistaken for evidence about the trial’s outcome or the probability that a result is correct.

Why do analysis details matter?

Statistical results depend on how the endpoint is coded, which participants are included, and how incomplete records are handled. For example, an analysis restricted to participants with complete outcome records can differ from an analysis that uses all randomized participants under a stated missing-data approach. These are general methodological considerations. The registry record does not report the analysis population, the number with missing endpoint data, or the method used to address missingness.

The registry record lists no analyses and does not provide a statistical plan. It is therefore not possible to confirm which model, comparison measure, confidence level, or hypothesis-testing procedure was used for the primary outcome. Nor can readers assess whether the reported analysis followed a prespecified plan. These omissions do not establish that a particular method was or was not used; they mean the method is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The record lists a primary endpoint and several secondary outcomes, including 7-day paresthesia, length of stay, 30-day incidence of paresthesia, return to work, and resumed physical activity. The brief design description also mentions postoperative pain scores and hospital and length of stay. The record does not report how the secondary outcomes were defined in detail, which outcomes were analyzed, or whether any adjustment was planned for multiple comparisons.

In general, examining multiple outcomes can increase the chance that at least one result appears notable by chance, depending on the testing approach. A prespecified hierarchy or multiplicity adjustment can help define how evidence across outcomes is interpreted. The registry record does not report a multiplicity strategy, so it is not possible to determine whether secondary comparisons were adjusted, prioritized, or treated as exploratory. The lack of a reported strategy does not prove that no strategy was used.

The registry lists no analysis results. It does not report the numbers analyzed for the primary outcome, missing outcome counts, reasons for missingness, or a missing-data method. It also does not report whether analysis followed randomized assignment or was limited to participants with observed data. These details matter because missing outcomes and choices about analysis populations can affect estimates and their uncertainty.

Accordingly, readers cannot assess whether all prespecified outcomes were reported, whether outcome definitions changed, or whether analyses were selected after results were examined. The registry record does not report these matters. The completed status and the listed outcome names alone are not enough to establish the analysis process.

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 adverse-event entries report 0 serious events and 0 other events for the On-q Pump group, with 41 participants at risk. For Standard of Care, the entries report 0 serious events and 0 other events, with 42 participants at risk. These are the registry’s reported event counts for the listed groups.

Zero events in the posted fields should be read narrowly. They mean that the record lists no serious or other events in those entries; they do not establish that every possible harm was actively assessed, that all events were captured, or that the groups have identical safety profiles. The registry record does not provide the event definitions, collection procedures, follow-up completeness, or detail about how the at-risk counts were determined. The deaths fields are null, so deaths are not reported in the registry record; null should not be interpreted as a reported zero.

In general, safety counts are most informative when readers can see the event definitions, observation period, group denominators, and completeness of reporting. The listed entries do not provide enough detail to evaluate those features. They also do not replace the trial’s primary medication-use endpoint, which has no reported outcome counts in the registry record.

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

The registry record supports a description of the study question and design: a randomized, unmasked, parallel comparison after thoracoscopy of a subpleural catheter delivering 0.125% bupivacaine alongside standard acute pain management versus standard acute pain management without an additional catheter. Its primary endpoint is pain-medication use from postoperative day 1 through postoperative day 30.

The record does not report the primary outcome counts, an estimated group contrast, a confidence interval, or a statistical test. It therefore does not show whether medication use differed between the arms, in which direction, or with what precision. Trial completion is a status entry, not a result. Likewise, the fact that the design was randomized does not itself reveal the outcome.

In general, a trial result is interpreted by considering the observed effect, its uncertainty, the outcome definition, and the conduct and analysis of the study. A result about whether medication was used would not, by itself, describe all aspects of postoperative pain, the amount of medication taken, or every secondary outcome. The registry record does not provide the information needed to make those broader assessments.

The safety entries list zero serious and zero other events in both groups, with the reported at-risk counts. Those entries should be interpreted as registry counts, not as proof that no unrecorded events occurred or that risks are the same. The record does not describe adverse-event ascertainment in enough detail to support a broader safety conclusion.

Overall, the registered question is identifiable, but the posted results are insufficient to establish an observed primary effect or its precision. No treatment recommendation or conclusion about clinical benefit follows from the information reported in the registry record.

13. Why This Trial Matters Statistically

This trial raises a useful statistical distinction between a clearly stated clinical question and a result that can be evaluated quantitatively. The registry describes random assignment, the intervention and comparator, and a primary endpoint focused on medication use through postoperative day 30. Those details identify what the study was designed to compare. They do not supply the outcome data needed to estimate the comparison.

For clinical researchers, the distinction matters because a completed trial record can still leave key questions unanswered. Arm-specific event counts, an effect estimate, and an uncertainty interval are needed to understand both the direction and precision of a binary endpoint comparison. Without them, neither the magnitude of a difference nor the range of values compatible with the data can be assessed. A design description cannot stand in for results.

The record also illustrates why outcome definitions and analysis reporting matter. Medication use is not the same measure as pain intensity, and a count of participants with use does not describe dose or frequency. The listed secondary outcomes broaden the study’s intended scope, but their results and the approach to multiple comparisons are not reported. This limits the conclusions readers can draw from the registry entry.

Finally, the difference between the enrollment field and the planned randomized number in the brief description makes transparent reporting of participant flow important. The record does not explain the difference or provide arm-specific analysis populations. Clear reporting of randomization, exclusions, follow-up, missing data, and analysis would help readers assess how closely results correspond to the intended comparison. These are general reporting considerations; the missing details are not reported in the registry record.

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 for interpretation is that the registry record does not report primary outcome counts or a primary comparison estimate. Without those results, the magnitude, direction, and precision of the registered endpoint cannot be assessed. The record also lists no analysis results, so the statistical approach used for the primary comparison is not reported in the registry record.

The enrollment field lists 83, while the brief study description states that 86 consented patients would be randomized. The registry record does not explain this difference, give the number assigned to each arm, or describe participant flow from screening through analysis. The adverse-event entries include at-risk counts by group, but these do not establish the analysis population for the primary endpoint.

The record does not report the randomization method, allocation concealment, outcome-assessment procedures, or whether any outcome assessors or analysts were masked. Masking is listed as none, but further detail about outcome ascertainment is not reported in the registry record. This is relevant because the primary outcome concerns medication use and the record does not specify how use was measured.

The endpoint description does not report medication amount, frequency, or detailed classification rules. The record also does not report missing-outcome counts, reasons for missingness, or the method used to handle missing data. Secondary outcomes are listed, but their detailed definitions and results are not reported. No multiplicity strategy or statistical analysis plan is reported in the registry record.

These limits concern what can be evaluated from the registry record. They do not establish that the trial failed to collect the information or that particular methods were not used; the relevant details are simply not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Continuous Subpleural Infusion of Bupivacaine — NCT01566838.
• Registry record last updated 2017-12-20; status last verified 2017-12.
• Results first posted 2016-08-04.
• 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

NCT01566838 is a completed, randomized, unmasked, parallel-group trial sponsored by Inova Health Care Services. It compares a subpleural catheter delivering 0.125% bupivacaine alongside standard acute pain management with standard acute pain management without an additional catheter after thoracoscopy. The registry enrollment is 83; the brief design description states that 86 consented patients would be randomized.

The primary endpoint is the number of participants with and without pain-medication use from postoperative day 1 through postoperative day 30. The record lists secondary outcomes concerning paresthesia, length of stay, return to work, and resumed physical activity. The posted registry record does not report primary outcome counts, an effect estimate, a confidence interval, or analysis results. Adverse-event entries list zero serious and zero other events in each group, while deaths are not reported in the registry record.