Influence of Anesthetic Technique on Acute and Chronic Neuropathic Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Influence of Anesthetic Technique on Acute and Chronic Neuropathic Pain (NCT02527083), a randomized phase 4 study. The primary outcome is Pain Score, Chronic.

2. Clinical Question

The rationale in the registry summary is that anesthetic technique may affect stress hormone levels during surgery, and that stress hormones may be related to postoperative pain. These statements describe the study’s motivation, not findings from this trial. The study record identifies chronic pain as the main outcome and frames the assessment around pain after surgery, but it does not report group-level pain scores or estimates of differences between anesthetic approaches.

The clinical question therefore has an important distinction between what was intended and what can be concluded from the record. The intended comparison is clear at a broad level: pain after hernia repair under inhalational versus intravenous anesthetic techniques. However, the listed arms include two TIVA variants, and the summary’s mention of propofol does not match those arm descriptions directly. The registry record does not provide a numerical answer about chronic pain or acute pain.

3. Trial Design

This was a completed, randomized, parallel-group Phase 4 study sponsored by VA Pittsburgh Healthcare System. The registry lists the study as single-masked. It does not identify which participants or study personnel were masked, and details about allocation concealment are not reported in the registry record.

The record describes randomization to anesthetic groups. Its brief summary names total intravenous anesthesia maintained with propofol and balanced inhaled anesthesia maintained with sevoflurane. The arm descriptions instead identify BIA, TIVA-K, and TIVA-R. Those descriptions specify sevoflurane for BIA, ketamine for TIVA-K, and remifentanil for TIVA-R. Propofol is also listed among the interventions, but the record does not explain how it relates to the named TIVA arms. This inconsistency means that the specific treatment contrast should be read cautiously.

The registry reports an enrollment of 10 and identifies the study as completed. The recorded start was 2015-01, and primary completion was 2019-06. These dates and the completed status describe the record; they do not establish how long an individual participant was followed. The chronic pain outcome’s stated assessment times extend through 12 months after surgery.

The primary outcome was a continuous pain-intensity score, reported in principle as a mean with standard deviation. The registry names acute pain as a secondary outcome and states that there are two outcome measures. It does not report analysis counts or numerical outcome results in the information. The primary outcome description also notes that statistical differences between techniques were not sought because of the low subject numbers. The registry record does not provide additional detail about the intended statistical methods, recruitment procedures, or the handling of participants who did not complete follow-up.

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: Only 10 subjects were enrolled, and the numbers represented a typical distribution of Inhalational to TIVA use. Because of the low subject numbers, statistical differences between the techniques were not sought.

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 Pain Score, Chronic, measured over 1 month, 3 months, 6 months, 12 months.

The primary endpoint is chronic pain intensity after surgery, measured with the Intensity Score of the Pain Quality Assessment Scale (PQAS). The registry describes assessments at 1 month, 3 months, 6 months, and 12 months after surgery. The scale runs from 0, meaning no pain, to 10, meaning the most intense pain sensation imaginable; higher scores indicate worse pain.

A pain-intensity score gives a numerical description of the reported severity of pain. Summarizing such a continuous measure with a mean and standard deviation can describe the group’s average score and the spread of individual scores around that average. Those summaries alone do not establish whether groups differ, how large a difference may be, or how precisely that difference has been estimated.

Repeated assessment times can describe how pain scores vary over follow-up, but interpreting them jointly requires clarity about the analysis and the handling of incomplete observations. The registry record does not specify a primary assessment time among the listed times or describe a method for combining results across them. Numerical means, standard deviations, and between-group estimates are not reported in the registry record.

The outcome is relevant to the study’s stated aim because it directly measures pain intensity after hernia surgery. The record also lists acute pain as a secondary outcome, but does not provide its measurement details or numerical results in the information available for this analysis.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous measure. For a continuous outcome, a mean describes the group’s average value, while a standard deviation describes the dispersion of values around that mean. The mean and standard deviation answer different descriptive questions: the mean indicates the center of the observed scores, and the standard deviation indicates how much scores vary within the group. Neither statistic alone measures uncertainty about a treatment contrast.

To compare groups, an analysis would ordinarily need to estimate a difference or another contrast and describe its uncertainty. A confidence interval is a range of values compatible with the data and the assumptions of the analysis; its width communicates precision. A narrow interval indicates greater precision than a wide interval. A confidence interval can also help distinguish estimates that are consistent with little difference from those compatible with a range of potentially meaningful differences. These are general statistical principles, not reported findings from this trial. No contrast or confidence interval is reported in the registry record.

A p-value, when calculated under a specified statistical model, describes how unusual data at least as incompatible with a null hypothesis would be if that hypothesis and the model’s assumptions held. It does not measure the probability that the null hypothesis is true, the size of an effect, or whether an effect matters clinically. The registry record reports that statistical differences between techniques were not sought because of the low subject numbers, and it provides no p-values. No inferential conclusion should be reconstructed from descriptive information that is not reported.

The pain score is measured at 1 month, 3 months, 6 months, and 12 months. Repeated observations from the same participant are generally related rather than independent. General methods for repeated measures account for this within-person relationship and can estimate patterns over time, but the particular method depends on the outcome structure, study aims, and data completeness. The registry record does not identify a repeated-measures method, a primary time point for inference, or a plan for interpreting results across the assessment times.

When outcomes are examined at multiple times, or when several outcomes and comparisons are considered, the chance of finding at least one apparently notable result can increase if each is tested separately. Multiplicity methods address this issue by defining which comparisons are primary and, where appropriate, adjusting inference across a family of tests. This is a general statistical concern. The registry record does not report a multiplicity strategy, and the absence of reported analyses means there is no set of p-values to evaluate for adjustment.

Randomization is intended to make assigned groups comparable on average with respect to factors that could affect outcomes. In a small study, randomization does not guarantee that the realized groups are balanced on every relevant characteristic. It also does not remove the need to report how allocation was generated, concealed, and analyzed. The record says the study was randomized, but further details on sequence generation, concealment, and the identity of those masked are not reported in the registry record.

Analysis populations also matter. An intention-to-treat analysis generally retains participants in their randomized groups, while other approaches may restrict analyses according to treatment received or outcome availability. These approaches can answer different questions and can be affected differently by deviations and missing observations. The registry record does not identify an analysis population or explain how participants with missing measurements or deviations from assigned treatment were handled.

The registry notes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such calculations estimate the number of participants per arm needed under stated assumptions for a planned power target and target effect. They are planning aids, not observed power, and do not show that a study had a particular probability of detecting an effect after it was completed. The registry does not report its own sample-size justification. The posted assumptions also do not resolve the record’s ambiguity about the number and identity of the anesthetic comparisons.

The registry explicitly states that statistical differences between techniques were not sought because of the low subject numbers. That statement should take priority over treating planning illustrations as evidence of an inferential analysis. A planning calculation cannot replace observed estimates, uncertainty intervals, or a clearly described analysis. Because numerical outcome summaries and analysis results are not reported in the registry record, the magnitude and precision of any pain difference remain unknown.

10. Multiplicity, Missing Data and Analysis Populations

The primary chronic pain outcome is listed at 1 month, 3 months, 6 months, and 12 months, and acute pain is listed as a secondary outcome. The registry states that there are two outcome measures, but does not specify whether each time point was treated as a separate test, whether one time point was designated as primary for inference, or how multiplicity across outcomes and times was addressed. A multiplicity plan is not reported in the registry record.

This matters because repeated testing can increase the chance of an apparently unusual result even when there is no underlying difference. General approaches include selecting a primary comparison in advance or adjusting inference across a defined family of comparisons. Without the statistical plan and reported analyses, it is not possible to assess whether or how such an approach was used. The record also says statistical differences between techniques were not sought.

Missing-data procedures are not reported in the registry record. The record does not state how many outcome measurements were available at each assessment time, whether participants missed follow-up, or how incomplete observations were handled. This prevents assessment of whether the reported outcome summaries, if any, would represent all randomized participants or a subset with available measurements.

The analysis population is also not reported in the registry record. It is not clear whether analyses were intended to follow randomized assignment, actual anesthetic received, or another definition. The registry provides no analysis counts and no numerical outcome analyses. Consequently, readers cannot determine the extent to which the reported study outcomes, beyond the enrollment statement, reflect all randomized participants or complete follow-up.

11. Safety Results

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

Deaths

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 serious adverse events for BIA, TIVA-K, and TIVA-R. Each listed group has 6 participants at risk for serious adverse events, with 0 affected in each group. The death count is 0 in each listed group. The record does not list serious adverse-event terms.

For other adverse events, the listed at-risk counts differ by group: 6 for BIA, 2 for TIVA-K, and 2 for TIVA-R. The affected count is 0 in each group. These figures should be read with their group-specific denominators rather than as a comparison of rates; they are counts recorded in the registry, not estimates of comparative risk.

Zero recorded events does not establish that an intervention is free of risk. In a small study, uncommon events may not occur among the participants observed, and the record does not provide detailed event descriptions, collection procedures, or a broader safety analysis. The safety figures therefore describe what the registry records for these groups and do not support a general claim about safety.

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

This study addresses a clinically relevant statistical question: whether pain after inguinal hernia repair differs according to anesthetic technique. It identifies chronic pain intensity as the primary outcome and lists repeated assessments through 12 months. Those elements describe the question the study intended to address, not the answer to it.

The registry record does not report numerical pain scores, group summaries, treatment contrasts, confidence intervals, or p-values. It therefore does not show the direction, magnitude, or precision of a difference in chronic pain. It also does not provide numerical results for the listed acute pain outcome. The statement that statistical differences were not sought because of low subject numbers further cautions against interpreting this as a formal test establishing a difference or lack of difference.

The absence of reported statistical significance is not evidence that the anesthetic approaches have equivalent effects. Equivalence or non-inferiority requires a defined margin and an analysis designed to address that question; such information is not reported in the registry record. Likewise, without numerical estimates and uncertainty intervals, the record cannot show that any possible difference is small or clinically unimportant.

The intervention descriptions require care. The brief summary identifies propofol-based TIVA and sevoflurane-based BIA, whereas the arm descriptions list TIVA-K and TIVA-R as separate TIVA variants. The record does not reconcile those descriptions, so the exact treatment contrast cannot be fully interpreted from the registry record alone.

The available safety counts record no serious adverse events or deaths in the listed groups, but those counts should not be taken as proof of absence of risk. Overall, the registry describes a small completed study and its intended outcome assessments, while leaving the numerical efficacy results and several details needed for statistical interpretation unreported.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its stated question involves a potentially long-term outcome measured repeatedly after surgery. Follow-up at 1 month, 3 months, 6 months, and 12 months can describe pain at different stages, but repeated measurement requires a clearly specified analysis and transparent reporting of available observations. Those details are not reported in the registry record.

The enrollment of 10 and the explicit statement that statistical differences between techniques were not sought shape what can reasonably be inferred. A small study can provide descriptive information, but without reported outcome estimates it cannot quantify the observed pain pattern or the uncertainty around a comparison. The record does not provide the information needed to assess whether a possible difference is clinically important or whether estimates are precise.

The record also illustrates why intervention descriptions must align across the summary and arm definitions. The mention of propofol-based TIVA differs from the named TIVA-K and TIVA-R arms. Clear descriptions of randomized groups are essential for understanding which contrast an estimate represents and for interpreting whether results apply to a particular anesthetic strategy.

Finally, planning calculations and observed results answer different questions. A sample-size illustration based on an observed effect is not observed power and does not substitute for an estimate with uncertainty. The registry’s stated decision not to seek statistical differences should remain central when interpreting any planning material. In this record, the statistical value lies mainly in clarifying the intended question and the limits of the information available, rather than establishing a numerical treatment comparison.

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.

The most important limitation for interpretation is that numerical primary and secondary outcome results are not reported in the registry record. Without group means, standard deviations, contrasts, or uncertainty estimates, neither the direction nor magnitude of any pain difference can be assessed. The record also states that statistical differences were not sought because of the low subject numbers.

The enrollment was 10, and the chronic pain outcome has assessments at 1 month, 3 months, 6 months, and 12 months. The registry does not report how many outcome measurements were available at each time, how missing data were handled, or which analysis population was used. These omissions limit assessment of the completeness and representativeness of follow-up information.

The anesthetic descriptions are not fully aligned. The brief summary describes TIVA maintained with propofol and BIA maintained with sevoflurane, while the arm descriptions list BIA, TIVA-K, and TIVA-R. The record does not clarify the relation between propofol and the two named TIVA arms, making the precise randomized contrasts uncertain.

Further statistical details are not reported in the registry record, including the identity of those masked, allocation concealment, the method for analyzing repeated assessments, and any approach to multiplicity. The record also does not report a sample-size justification. These limitations prevent a fuller evaluation of design and analysis choices, beyond the stated randomized, single-masked, parallel design and the stated lack of statistical comparisons.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Influence of Anesthetic Technique on Acute and Chronic Neuropathic Pain — NCT02527083.
• Registry record last updated 2025-12-31; status last verified 2021-05.
• Results first posted 2025-12-31.
• 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

The registry identifies NCT02527083 as a completed, randomized, single-masked, parallel-group Phase 4 study sponsored by VA Pittsburgh Healthcare System. It reports an enrollment of 10, with a recorded start of 2015-01 and primary completion in 2019-06.

The stated aim was to examine anesthetic technique and pain after inguinal hernia repair. Chronic pain intensity measured by the PQAS is the primary outcome, with assessments at 1 month, 3 months, 6 months, and 12 months; acute pain is listed as a secondary outcome. The record states that statistical differences between techniques were not sought because of low subject numbers.

The registry lists no serious adverse events or deaths in the named groups. Numerical pain results, statistical comparisons, missing-data procedures, analysis populations, and a detailed statistical plan are not reported in the registry record. The anesthetic descriptions also differ between the brief summary and arm descriptions.