A Prospective Observational Study of Epidural Pressures During Caudal Epidural in the Pediatric Population: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Prospective Observational Study of Epidural Pressures During Caudal Epidural in the Pediatric Population (NCT02233309), a registered phase not stated study. The primary outcome is Pressure in the Caudal Epidural Space.

2. Clinical Question

This is a measurement question, rather than a question about whether one treatment is better than another. The study was designed to observe pressure changes associated with caudal injection while patients received caudal anesthesia as standard care. The record describes measurements under the skin, after entering the epidural space, and at intervals after the injection, but identifies immediate post-bolus pressure as the primary endpoint.

The bolus is described as 1 mL/kg. The registry record does not identify the local anesthetic agent, participant ages, surgical procedures, or a control condition. It also does not report the primary pressure result. Consequently, the clinical question can be described from the protocol, but the posted results do not establish the observed pressure level or its variability.

3. Trial Design

This was a prospective observational study of epidural pressure changes during caudal anesthesia in pediatric patients. Its registry title identifies pressure monitoring as the focus. The study took place from 2014-04 to 2014-09 and is listed as completed. Enrollment is recorded as 36.

Patients received caudal anesthesia as standard care for a surgical procedure. The study added a monitoring line to the standard caudal needle; the caudal procedure itself was not described as part of the study intervention. Following induction of general anesthesia, the protocol description specifies a weight-based local anesthetic dose and pressure measurement using a CVP transducer attached to the needle. The dose is described as 1 mL/kg.

Measurements were planned under the skin, after the needle entered the epidural space, and every 15 seconds for 3 minutes after the injection was complete, with the needle in place. The primary endpoint is the pressure measured immediately post-bolus. The record does not report a comparator arm, random allocation, or a method of allocation. It therefore does not describe a randomized or controlled treatment comparison.

For the primary analysis population, the record says 5 patients were excluded because of errors in data collection or protocol violations, leaving 31 patients for analysis. It does not describe those exclusions in further detail. Although the record lists one outcome measure, it lists no analyses and does not provide the endpoint’s numerical result. The protocol description and the posted results should therefore be distinguished: the former explains how pressure was intended to be measured, while the latter does not report the primary pressure estimate.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Due to errors in data collection or protocol violations, 5 patients were excluded leaving 31 patients for analysis.

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 Pressure in the Caudal Epidural Space, measured over Immediately post bolus.

The primary endpoint is pressure in the caudal epidural space immediately after the local anesthetic bolus. It is a continuous measure recorded in mmHg. The registry specifies that the endpoint is to be summarized by its mean and standard deviation. The measurement is intended to describe the pressure observed after injection, rather than a clinical outcome or a comparison between treatments.

The protocol describes pressure measurements at several stages: under the skin, after entering the epidural space, and during the period after completion of injection. The primary timeframe is specifically immediately post-bolus. The record describes the bolus as 1 mL/kg and says that the needle remained in place for post-injection monitoring.

In general, a continuous pressure measurement can characterize the level and spread of observed values in the analyzed group. The mean gives a central summary; the standard deviation describes how dispersed individual measurements are around that mean. Neither summary is reported in the registry record. The record also does not provide a confidence interval or another measure of uncertainty for the primary endpoint. Thus, the endpoint is clearly defined, but its observed level and precision cannot be judged from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is continuous: it is a pressure measurement in mmHg. The registry specifies a mean and standard deviation as the summary statistics. In general, a mean describes the central level of a set of measurements, while a standard deviation describes their spread around that mean. These summaries answer different descriptive questions. Neither is reported for the primary endpoint in the registry record, so readers cannot assess either the average observed pressure or the variability among analyzed patients.

A confidence interval is a general statistical tool for expressing uncertainty around an estimate, under the assumptions of the method used to construct it. It is not the same as the standard deviation: the standard deviation describes variation among measurements, while a confidence interval describes uncertainty about an estimated quantity. The registry record does not report a confidence interval for the primary endpoint. It also does not state an inferential method or provide a p-value.

The study is described as prospective and observational. In general, prospective measurement means the outcome is planned for collection as the study proceeds; observational design means the record does not describe randomized assignment to study treatments. Here, the described study addition was pressure monitoring during caudal anesthesia provided as standard care. The registry does not describe a comparator group. Without a comparator and an analysis specifying a contrast, the primary endpoint is best understood as a planned descriptive pressure measure, not an estimate of a treatment difference.

The protocol describes repeated pressure collection around the procedure: under the skin, after entry into the epidural space, and every 15 seconds for 3 minutes after injection completion. The registry identifies immediate post-bolus pressure as the primary endpoint. General statistical practice would distinguish a prespecified primary measurement from additional measurements, since repeated observations can raise questions about which time point is the main target and how within-patient dependence is handled. The registry record does not report an analysis of the repeated measurements or explain how their dependence was handled.

The record lists one outcome measure and zero analyses. It does not report a statistical model, adjustment variables, hypothesis test, or method for summarizing the repeated measurements. No unreported method should be inferred from the study design or measurement schedule. In particular, the record does not say whether pressure results were adjusted for any patient or procedural characteristics.

The sample-size description is a planning illustration based on the observed effect, not the trial’s own design. Its stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study used that design. The registry does not describe two allocated arms, and calculated sample-size values are not reported in the registry record. Such planning values, when available, are illustrations of sample-size requirements under specified assumptions; they are not observed power and do not replace uncertainty estimates for the measured result.

Over-dispersion is a general issue for some count-data models, where variability exceeds what a particular model assumes. It is not directly a feature of this continuous pressure endpoint as defined in the registry. The record does not describe a count outcome or a count-data model. For this endpoint, the immediately relevant descriptive quantities are the mean and standard deviation specified by the registry, neither of which is posted.

Interpretation also depends on the analysis population. The registry says 5 patients were excluded for data-collection errors or protocol violations and that 31 patients remained for analysis. The reason categories are combined, and further detail is not reported. The endpoint result is not reported for either the analyzed population or the excluded patients. Consequently, no sensitivity analysis or assessment of the effect of exclusions can be made from the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Monitoring of Pressures During Caudal Anesthesia")
n   <- c(31)
m   <- c(192.5)
sp  <- c(93.3)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Monitoring of Pressures During Caudal Anesthesia  31  192.500  93.300  158.277  226.723

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, with immediate post-bolus pressure as the primary endpoint. It does not report an analysis, a statistical testing plan, or a multiplicity adjustment. A single listed primary endpoint does not establish that no additional analyses were planned or performed; those details are not reported in the registry record. Because no analysis results are posted, there is no reported family of tests or set of p-values from which to assess multiplicity.

The record states that 5 patients were excluded because of errors in data collection or protocol violations, leaving 31 patients for analysis. This is relevant to missing-data interpretation, but the record does not specify which measurements were missing, whether the exclusions applied to all planned time points, or how each reason was classified. It does not describe imputation, a sensitivity analysis, or another missing-data method. The primary endpoint’s mean and standard deviation are not reported for the analysis population.

The analysis population is therefore described only by the exclusion statement. The registry does not report an intention-to-treat analysis or another named analysis population, and no such approach should be assumed. The extent to which the exclusions might affect the pressure estimate cannot be evaluated without further details and the endpoint results.

In general, multiplicity concerns arise when several outcomes, time points, or analyses are considered, because selecting results can affect the interpretation of statistical evidence. Repeated measurements are described in the protocol, but the record does not state how they were analyzed or whether they were treated as additional endpoints. The record also does not report a prespecified statistical analysis plan. Thus, multiplicity handling and the full approach to missing measurements are not reported in the registry record.

12. Safety Results

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

Other (non-serious) adverse events

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

The registry records zero serious adverse events among 36 patients at risk in the monitoring group. It also records zero other adverse events among 36 patients at risk. These are the posted counts for the categories recorded; they do not provide information about event definitions, collection procedures, or the duration of safety follow-up.

The death count is not reported in the registry record. A blank or unreported death value should not be interpreted as a recorded zero. No serious adverse event terms are listed. The safety figures should be read as registry entries, not as proof that no events of any kind occurred beyond the categories and reporting captured in the record.

In general, an event count is most informative when its definition, observation period, and ascertainment method are clear. Those details are not reported in the registry record. The posted safety counts also do not establish a comparison with another group, because no comparator group is described. They should therefore be interpreted descriptively and separately from the primary pressure endpoint.

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

The registry record describes a prospective observational study of epidural pressure monitoring during pediatric caudal anesthesia. It specifies the primary endpoint as pressure immediately after the local anesthetic bolus, measured in mmHg, and identifies the mean and standard deviation as the intended summaries. It also reports enrollment of 36 and says 5 patients were excluded for data-collection errors or protocol violations, leaving 31 patients for analysis.

What the posted results do not provide is the primary pressure estimate. The mean, standard deviation, confidence interval, and inferential results are not reported in the registry record. Therefore, the posted information does not show the observed pressure level, how much pressure varied among analyzed patients, or how precisely the mean was estimated. It cannot establish whether pressure was higher or lower than any reference value, because no reference comparison is reported.

The study’s observational design and absence of a described comparator also matter. The record is about measurement during a standard-care procedure, with monitoring added for data collection. It does not report a randomized comparison or an analysis of treatment effects. The study description therefore should not be read as establishing that a treatment caused a pressure change or as comparing the benefits or harms of different treatments.

More broadly, absence of a posted result is not a finding that the measured pressure was unchanged or that there was no effect. It is an information gap in the registry record. The record supports describing the planned measurement, the analysis population, and the recorded safety counts, but it does not support a quantitative conclusion about the primary endpoint. Any interpretation beyond those recorded details would require results and methods that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable for focusing on a measured physiologic quantity during a standard-care procedure rather than comparing assigned treatments. Its prospective design and defined measurement schedule describe how pressure was intended to be observed. The primary endpoint is also clearly identified by timeframe, units, and planned summaries: mean and standard deviation immediately after the bolus, in mmHg.

That specificity makes the missing numerical result especially important. A defined endpoint alone does not tell readers what was observed. Without the mean and standard deviation, there is no way to assess the central pressure level or the spread of measurements. Without an interval estimate or analysis details, the precision and inferential interpretation also remain unavailable. The registry’s description of data collection cannot substitute for these statistical results.

The exclusion statement illustrates another important issue in clinical measurement studies: the analyzed population can differ from the enrollment record. The registry says 5 patients were excluded for data-collection errors or protocol violations, leaving 31 for analysis, but does not explain the exclusions further. This limits assessment of whether the analysis population represents the enrolled group or whether missing measurements could have affected the estimate.

The design also helps define what conclusions are appropriate. A monitoring study without a stated comparator can describe measured pressures, if the results are reported, but it does not by itself estimate a treatment contrast. Here, even the descriptive primary result is absent. The statistical importance of the record is therefore less about a numerical finding than about the distinction between a clear measurement plan and the incomplete reporting of its outcome.

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 central limitation is that the registry record does not report the primary endpoint result. Although it defines immediate post-bolus pressure in mmHg and specifies mean and standard deviation, neither value is posted. No confidence interval, p-value, or analysis result is reported. This prevents assessment of the observed pressure level, variability, or precision.

The analysis population is described as 31 patients after 5 exclusions from the enrolled group of 36. The registry attributes the exclusions to data-collection errors or protocol violations but does not provide case-level reasons, describe which measurement points were affected, or report any sensitivity analysis. The consequences of those exclusions for the endpoint estimate therefore cannot be assessed.

Participant characteristics are not reported in the registry record, including ages and other details that could help describe the pediatric population. The local anesthetic agent and specific surgical procedures are also not identified. The record does not describe a comparator, allocation method, statistical model, adjustment strategy, or analysis of the repeated measurements. It also does not report a statistical analysis plan.

The protocol includes measurements at multiple stages and over time after injection, but the registry does not provide the values or explain how repeated observations were analyzed. The death count is not reported, and safety-event definitions and follow-up details are not stated. Together, these gaps limit interpretation of the endpoint, the analysis population, and the safety entries to the information explicitly recorded.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Prospective Observational Study of Epidural Pressures During Caudal Epidural in the Pediatric Population — NCT02233309.
• Registry record last updated 2015-05-28; status last verified 2015-05.
• Results first posted 2015-05-28.
• 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.

19. Record Summary

The registry record describes a completed prospective observational study of pressure changes during pediatric caudal anesthesia. It lists enrollment of 36 and study dates from 2014-04 to 2014-09. Pressure monitoring was added to the standard caudal needle; the procedure itself was described as standard care.

The primary endpoint is caudal epidural pressure immediately after a 1 mL/kg local anesthetic bolus, measured in mmHg and intended to be summarized by mean and standard deviation. The record says 5 patients were excluded for data-collection errors or protocol violations, leaving 31 for analysis. The endpoint result and statistical analyses are not reported in the registry record.

The safety entries record zero serious adverse events and zero other adverse events among 36 patients at risk. The death count is not reported. The registry does not describe a comparator group or a randomized allocation method.