Caudal Block Versus Local Wound Infiltration for Inguinal Procedures: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Caudal Block Versus Local Wound Infiltration for Inguinal Procedures (NCT04590027), a registered phase not stated study. The primary outcome is Comparison of Analgesia Quality Between the Two Groups.

2. Clinical Question

3. Trial Design

The registry describes a single-centre prospective observational study comparing caudal block with local wound infiltration for inguinal procedures in young children. It lists University Hospital Tuebingen as the sponsor, an enrollment of 86, a start date of 2014-02-01, a primary completion date of 2015-06-30, and a status of COMPLETED.

Because allocation is not stated and the study was not randomized, the groups should not be treated as if they were assigned by chance. The record does not explain how clinicians or participants came to receive one approach rather than the other. If treatment choice was related to patient characteristics, procedure features, clinician preference, or other factors, those differences could also be related to postoperative pain. An observed group contrast could therefore reflect a mixture of treatment and selection effects.

The registry identifies pain-score comparison as the primary outcome and lists set up time, rescue medication, and neurological outcome as secondary outcomes. The primary pain assessments are scheduled from arrival on the postoperative care unit through arrival on the ward and later postoperative time points, up to 24h. The study is observational; the record does not report a protocol for controlling confounding or a plan for adjusting the comparison. The exact enrollment flow, group allocation process, participant characteristics, and analysis populations are not reported in the registry record. The total enrollment should not be used to infer the group denominators for a particular analysis.

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.

Before assignment: Causes for exclusion from the study No return of Questionaire (n=31) Not meeting criteria for anaesthesia (n=3)

Overall Study

Reasons for not completing this period:

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 Comparison of Analgesia Quality Between the Two Groups, measured over Arrival on postoperative care unit (PCU), arrival ward, 1h, 2 h 3h, 4h, 5h, 6h, 12h. 24h,.

The primary endpoint is analgesia quality assessed with a Visual Analog Score (VAS), a continuous pain measure with a minimum of 0 for no pain and a maximum of 10 for worst pain. The registry specifies comparison of the mean scores between the caudal block and local infiltration groups. Assessments are listed at arrival on the postoperative care unit (PCU), arrival on the ward, 1h, 2 h, 3h, 4h, 5h, 6h, 12h, and 24h.

Repeated assessments can describe pain at different points in postoperative recovery rather than relying on a single measurement. They may also show whether group patterns differ over time. However, interpretation depends on knowing which time point or summary was designated for the principal comparison, how repeated measurements were handled, and how missing scores were addressed. Those analysis details are not reported in the registry record.

The record defines a two point difference of mean pain scores as clinically meaningful for establishing superiority of one procedure. That threshold gives a clinical reference for interpreting a mean contrast; it does not establish that such a contrast occurred. The group means, standard errors, confidence intervals, and statistical test results are not reported in the registry record. Thus, the endpoint's scale and intended clinical benchmark are described, but its observed result cannot be evaluated from the registry information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical details available for this study are limited. The registry identifies the primary measure as a continuous score, specifies means and standard errors as the summary format, and describes a clinically meaningful difference. It does not report the analysis model, test, estimates, or uncertainty for the primary outcome. The concepts below explain how such analyses are generally interpreted; they do not describe undocumented procedures as if they were used in this trial.

What does a mean describe?

A mean summarizes the average score in a group. For a bounded pain scale, it can be useful for comparing average reported pain, but it does not describe every participant's experience. Participants may have scores clustered near the average or spread across a wider range. A mean alone does not reveal that distribution, the presence of unusual observations, or how many scores were available at each assessment.

The registry reports the parameter as a mean and the dispersion label as standard error. Standard error describes the precision of an estimated mean, rather than the spread of individual scores. It generally becomes smaller when an estimate is based on more information and individual observations are not highly variable. It should not be read as though it were a range containing most individual participants' scores. The record does not include numerical standard errors for the pain outcome.

How would a group contrast be read?

A comparison of group means estimates the difference in average scores. The sign depends on the order used to subtract one group mean from the other, so interpretation requires knowing the reported contrast's direction. For this scale, higher values represent worse pain and lower values represent less pain. A numerical contrast would need to be interpreted with its uncertainty, not just its sign or a test result.

A confidence interval is a general way to express uncertainty around an estimate. It gives a range of values that are reasonably compatible with the observed data under the analysis assumptions. It is not a guarantee that the true effect lies within that particular interval, and it does not account for biases caused by study design or measurement. A confidence interval for a mean contrast could help assess whether the evidence is compatible with no difference, with a clinically meaningful difference, or with a range of possibilities. Such an interval is not reported in the registry record.

Why does the observational design matter?

Random allocation is one way trials seek to make comparison groups similar, on average, with respect to measured and unmeasured baseline factors. This study is described as observational, and allocation is not stated. Treatment selection may therefore be associated with clinical or procedural characteristics that also affect pain scores. An unadjusted comparison would describe the groups as observed, but could not isolate the effect of the analgesia approach from those other influences.

Adjustment is a general statistical method for accounting for measured covariates. Its usefulness depends on which variables were collected, whether they were measured adequately, and how the model was specified. Adjustment cannot resolve unmeasured confounding simply by being performed. The registry record does not report whether the primary comparison was adjusted, which covariates were considered, or what model was used.

How should measurements over time be considered?

The endpoint is assessed at several postoperative time points. Repeated scores from the same participant are usually related to one another, so treating each measurement as fully independent can understate uncertainty. General approaches can model within-participant correlation or define a summary across time, but each approach answers a somewhat different question. The registry record does not report how repeated measurements were analyzed, whether each time point was tested separately, or whether a single time point was prioritized in the analysis.

Standard errors and confidence intervals depend on the analysis assumptions. For example, methods that assume a particular distribution or variance structure can be unreliable when those assumptions do not fit the data. A suitable repeated-measures method can account for correlation, while a model may need to handle unequal variability or other departures from its assumptions. These are general considerations, not claims about the method used in this study.

What do the planning illustrations mean?

The registry's 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. The illustration considers detecting a stated fraction of the observed effect. Such calculations are planning aids: they describe how a future study might be sized under specified assumptions. They are not observed power and do not establish that the current study had adequate power. The record does not report the trial's own sample-size justification, and numerical planning results should not be treated as outcome findings.

More generally, planning calculations depend on the effect chosen, the outcome's variability, the statistical test, allocation, significance criterion, and assumptions about missing data and analysis. If those assumptions differ from what is observed, the planning estimate may not describe the study's actual precision. Since the registry record does not report the primary outcome estimates or their uncertainty, the precision achieved for the pain comparison cannot be judged.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies four outcome measures and records two analyses, but does not report how many outcome comparisons or time-point tests were performed, which analyses were primary in practice, or whether any multiplicity adjustment was used. Multiplicity arises when several hypotheses are tested or several outcomes are examined. In general, conducting many tests can increase the chance of finding a nominally unusual result even when there is no true effect. Adjustments or a prespecified hierarchy can help address that issue, but the registry record does not document such a plan.

The primary pain endpoint includes assessments at multiple postoperative times. If each time point is analyzed separately, interpretation should account for the number and relationship of those comparisons. Alternatively, a repeated-measures model or a prespecified summary can address the trajectory or an overall contrast, but those approaches answer different questions. The analysis strategy for the listed assessments is not reported in the registry record.

Missing data are also important for repeated pain scores. Scores may be absent for reasons related to recovery, care processes, or participant characteristics; the effect of missingness depends on the circumstances and the analysis. The record does not report the amount or pattern of missing pain data, how missing measurements were handled, or whether sensitivity analyses were conducted.

Analysis populations are not specified. The record does not say which participants were included in each outcome analysis or whether exclusions were made. Without this information, readers cannot determine whether the analyzed groups correspond to all enrolled participants or to a subset with available measurements. These omissions limit assessment of both bias and precision.

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.

Most frequent non-serious adverse event terms

The adverse-event record lists serious adverse events for 30 participants at risk in the caudal block group, with 0 affected, and for 22 participants at risk in the local infiltration group, also with 0 affected. Deaths are listed as 0 in both groups. For other, non-serious adverse events, the record lists 2 affected among 30 at risk in the caudal block group and 3 affected among 22 at risk in the local infiltration group.

These counts describe what the registry reports; they do not establish that the groups had equivalent safety. A zero count means no event was recorded in the listed group denominator, not that the possibility of an event is absent. With limited information about event definitions, ascertainment, follow-up, and missing safety data, the counts cannot provide a full safety comparison. The registry lists no top serious adverse-event terms. It does not report whether the at-risk groups include all enrolled participants or how they relate to the analysis populations.

The adverse-event figures should be kept separate from the pain endpoint. They do not indicate which approach produced lower pain scores, and the observational design does not support a causal safety conclusion from these counts alone.

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

The registry record establishes that a prospective observational study compared caudal block with local wound infiltration for inguinal procedures in young children. It defines postoperative VAS pain scores as the primary outcome, describes the score's range, and states that a two point difference between mean scores was considered clinically meaningful. It also identifies secondary outcome topics and reports adverse-event counts.

Those design details do not show the observed comparative pain result. The record does not report group scores, an estimated difference, uncertainty intervals, or a statistical test result. It is therefore not possible to say from the registry record whether the groups had similar or different average pain scores, whether any contrast met the stated clinical benchmark, or how precisely a contrast was estimated.

Even a reported statistical difference would need careful interpretation. Statistical evidence concerns compatibility between data and a model or hypothesis; it does not by itself establish clinical importance. The stated threshold offers a clinical reference, but judging whether an estimate is important would require the estimate and its uncertainty. Conversely, an imprecise estimate would not prove that the approaches are equivalent.

The study's observational design also matters. Without randomized allocation, differences between groups could reflect factors that influenced treatment choice as well as differences associated with the analgesia approach. Any causal interpretation would depend on adequate measurement and handling of those factors, and the registry record does not describe such an analysis.

The safety counts are limited observations, not a comprehensive demonstration of comparative safety. The reported zero serious events and death counts should be understood within the stated denominators and available registry detail. Overall, the record describes the question and some study characteristics, but it does not provide the outcome estimates needed to answer the comparative effectiveness question or establish a treatment effect.

13. Why This Trial Matters Statistically

This study illustrates why a clear endpoint definition and a reported estimate are both needed to interpret a clinical comparison. The registry specifies a VAS scale, its endpoints, postoperative assessment times, and a two point threshold defined as clinically meaningful. These details help readers understand what the investigators intended to measure and how they framed clinical importance.

At the same time, the registry record does not report the pain results. Without group means and an estimated contrast, the endpoint definition cannot tell readers which group had higher or lower average scores. Without a measure of uncertainty, readers cannot assess precision. A clinically meaningful threshold is useful only when it can be compared with an observed estimate and its uncertainty.

The observational design makes the distinction between description and causal inference especially important. A measured difference between groups, if reported, would not automatically be attributable to the analgesia approach because allocation was not stated and treatment was not randomized. Baseline characteristics and treatment-selection processes would be relevant to interpreting any contrast.

The record also highlights the importance of reporting repeated-measurement methods, missing-data handling, analysis populations, and multiplicity procedures when outcomes are recorded across several time points. These choices affect what question an estimate answers and how much confidence readers can place in its precision. They are not reported in the registry record.

Finally, the adverse-event counts demonstrate why denominators and event definitions belong beside counts. The registry supplies group-specific at-risk counts and affected counts, but does not provide the surrounding detail needed for a comprehensive safety comparison. The study is therefore useful for understanding the planned comparison and its reporting gaps, while its registry information does not establish a comparative pain or safety result.

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 the registry record does not report the primary pain outcome results. Group means, standard errors, between-group estimates, confidence intervals, and p-values are absent. The stated clinical threshold therefore cannot be assessed against an observed difference.

The study is observational, and allocation is not stated. This leaves treatment-selection mechanisms and potential confounding unclear. The registry does not report participant characteristics that would help assess group comparability, nor does it describe any adjustment strategy. The title refers to young children, but an age range and detailed eligibility criteria are not reported in the registry record.

The pain outcome is measured at several postoperative times, but the record does not explain whether each time point was analyzed separately, whether an overall summary was used, or how correlation between repeated scores was handled. The handling of missing measurements, exclusions, and analysis populations is also not reported. These details are needed to assess whether the analysis matches the stated question and whether its precision could be affected by incomplete follow-up.

The record lists secondary outcomes and records four outcome measures and two analyses, but does not describe the full statistical plan or any approach to multiplicity. It also does not report the trial's own sample-size justification. The planning illustration based on an observed effect should not be mistaken for evidence about the study's actual power or precision.

Safety interpretation is limited by the absence of fuller information about event definitions, ascertainment, follow-up, and the relationship between at-risk denominators and the enrolled population. The counts alone cannot establish comparative safety. Taken together, these gaps mean the registry supports a description of design, endpoint definitions, and selected safety counts, but not a complete evaluation of the primary clinical comparison.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Caudal Block Versus Local Wound Infiltration for Inguinal Procedures — NCT04590027.
• Registry record last updated 2021-07-14; status last verified 2020-08.
• Results first posted 2021-07-14.
• 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 record describes a completed, single-centre prospective observational study sponsored by University Hospital Tuebingen, with enrollment of 86 and study dates from 2014-02-01 to 2015-06-30. It compares caudal block with local wound infiltration for inguinal procedures in young children. Allocation is not stated, and the comparison was not randomized.

The primary outcome is mean postoperative VAS pain score, assessed from arrival on the postoperative care unit through 24h. The scale ranges from 0 for no pain to 10 for worst pain, and a two point difference was defined as clinically meaningful. Secondary outcomes include set up time, rescue medication, and neurological outcome.

Group pain results and analysis details are not reported in the registry record. Adverse-event counts are listed by group, including 0 serious events and 0 deaths in each group. The record does not provide enough outcome information to assess the comparative pain result or its precision.