ESP Block for Post Cesarean Analgesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for ESP Block for Post Cesarean Analgesia (NCT05664958), a non-randomized phase 4 study. The primary outcome is Postoperative Oxycodone Consumption 0- 48 Hours After Cesarean Delivery.

2. Clinical Question

3. Trial Design

This completed study is listed as phase 4, with a parallel model and non-randomized allocation. It is described as a pilot case-control study with a prospective and a retrospective component. The prospective component was open label; the registry lists no masking. The study description says women undergoing elective cesarean delivery under spinal or combined spinal epidural anesthesia would be approached for participation.

The planned prospective arm consisted of 30 subjects receiving the ESP block, and the planned retrospective arm consisted of 120 historical controls receiving the same multimodal analgesic regimen without a truncal block. Cases were to be matched to historical controls in a 1:4 ratio by age, race, history of prior cesarean delivery, and insurance status. The registry lists enrollment of 150. Matching is part of the study description; the registry record does not report whether matching was completed as planned or how it was implemented in analysis.

The intervention arm is described as standard-of-care analgesia with an ESP block, while the control arm is described as standard-of-care analgesia. The brief summary specifies liposomal bupivacaine in the block and also lists bupivacaine among the interventions. The registry record does not report further procedural details in the information available for interpretation.

Because controls were historical and allocation was not randomized, differences between groups could reflect factors other than the block. Planned matching addresses the listed characteristics, but the registry record does not report whether other characteristics were adjusted for or how residual differences were assessed. Study start is recorded as 2023-04-17, primary completion as 2023-11-09, and status as completed. Completion status does not itself establish that outcome results or analysis details are available 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

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 Postoperative Oxycodone Consumption 0- 48 Hours After Cesarean Delivery, measured over 0-48 hours after cesarean delivery.

The primary endpoint is total dose of rescue oxycodone used in mg from 0-48 hours after cesarean delivery. It focuses on opioid rescue medication rather than all aspects of pain experience or the entire analgesic regimen. The endpoint is specified as a median with an inter-quartile range, so its intended summary emphasizes the distribution's central value and spread rather than a mean and standard deviation.

Rescue opioid consumption can serve as a measure of postoperative analgesic use: it records how much oxycodone was taken within the defined interval. It is not, by itself, a direct measure of pain intensity, patient satisfaction, or overall recovery. Consumption can also be influenced by pain, prescribing and administration practices, patient preferences, ability to request medication, and other care factors. These are general considerations when interpreting an opioid-use endpoint; the registry record does not report how these factors were measured or addressed.

The stated primary endpoint is distinct from the listed secondary outcomes, which include opioid consumption at 24 hours, time to first opioid rescue medication, pain-score area under the curve, nausea and vomiting, rescue antiemetic and antipruritic use, pruritus, and the number not receiving rescue opioids. The registry record does not report numerical results for the primary endpoint. It also does not report group medians, inter-quartile ranges, or an estimated between-group contrast. Therefore, the endpoint definition is available, but its observed result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary summary describe?

The primary endpoint is a quantitative measure: total rescue oxycodone consumption in mg during 0-48 hours after cesarean delivery. The registry specifies a median and inter-quartile range. In general, the median describes the center of an ordered set of observations, while the inter-quartile range describes the spread across its middle portion. These summaries can be useful when values are skewed or include a long tail, because a few high observations can influence a mean more strongly than a median. The registry record does not report the observed summaries, so their values and the distribution's shape cannot be assessed.

What would a comparison estimate mean?

For a quantitative endpoint, an analysis might compare groups using a difference in central tendency, a model-based estimate, or another prespecified contrast. The interpretation depends on the estimator and its assumptions. A confidence interval, in general, expresses the statistical uncertainty around an estimated effect under the method used; it is not a guarantee that the true effect lies within its limits. A p-value, if reported, would describe how incompatible the observed data are with a specified null model under the test assumptions. Neither a confidence interval nor a p-value is reported for the primary endpoint in the registry record.

The registry identifies the endpoint summary as a median with inter-quartile range, but does not report the statistical test or model used to compare arms. It also does not report whether the analysis used a matched-pair or matched-set approach, whether it accounted for matching in a regression model, or how covariates were handled. These details matter because a descriptive comparison of group medians and an adjusted estimate answer related but not identical questions.

Why does the design affect the statistical reading?

Random allocation is one way to reduce systematic differences between comparison groups, on average. This study is explicitly listed as non-randomized, and its control group is historical. The prospective cases and retrospective controls may therefore differ for reasons related to time, patient selection, care delivery, or recorded characteristics. Matching was planned by age, race, history of prior cesarean delivery, and insurance status. In general, matching can improve comparability on measured matching factors, but it does not automatically control factors that were not measured or not included in matching.

Historical comparisons can also face differences in measurement and documentation. Prospective outcome collection and retrospective record review may capture exposure, outcomes, or covariates differently. The registry record does not report how data were abstracted, whether measurements were harmonized, or how missing historical records were treated. These issues do not establish that bias occurred; they identify potential sources of uncertainty when interpreting a non-randomized comparison.

How should planning calculations be distinguished from analysis?

The record describes assumptions for planning illustrations: two-sided significance level 0.05, equal allocation between arms, normal approximation, and effects defined as stated fractions of the observed effect. It also notes that time-to-event illustrations use total event counts, while other illustrations use participants per arm. These are planning conventions, not evidence that the study used the same procedure for its outcome analysis. Equal allocation is an illustration assumption and differs from the described planned matching ratio of 1:4.

A sample-size calculation asks how much information might be needed under specified assumptions to detect a target effect with a chosen operating characteristic. It does not show whether the completed study achieved that precision, and a calculation based on an observed effect does not provide independent confirmation of the effect. Planning calculations are not observed power. The registry record does not report the numerical sample-size illustrations, the observed effect used for them, or the trial's own sample-size justification.

The registry record lists no analyses. It does not report an inferential method, an adjustment strategy, an interim analysis, or a prespecified statistical analysis plan. In the absence of these details and outcome estimates, readers cannot determine whether the planned matching was incorporated into inference, whether multiplicity was addressed, or how statistical uncertainty was quantified. General statistical methods can clarify what such choices mean, but they cannot recover methods or results that are not reported.

What do zero event counts establish?

Zero recorded events mean that the registry lists no events in the stated categories for the groups and at-risk counts shown. In general, an absence of recorded events does not demonstrate absence of risk. The interpretation depends on how events were defined, how actively they were sought, the follow-up period, and the completeness of reporting. These details are not reported in the registry information for the safety entries. The event counts should therefore be read as registry-reported counts, not as a comprehensive estimate of safety or as proof of equivalence between groups.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and secondary outcomes addressing opioid use, time to first rescue medication, pain scores, nausea and vomiting, antiemetic use, pruritus, antipruritic use, and whether rescue opioids were received. Considering multiple outcomes can raise a multiplicity issue: when many hypotheses are tested, the chance of at least one apparently unusual result can increase. This is a general statistical concern, not a statement that a particular adjustment was required or used in this study.

The registry record does not report a multiplicity strategy, a hierarchy for secondary endpoints, or which outcomes were formally tested. It also lists no analyses. The order in which outcomes are registered does not establish how they were handled analytically. Without a reported plan and results, the evidential status of any secondary finding cannot be assessed.

Missing-data handling is also not reported in the registry record. It does not describe missing primary endpoint observations, completeness of retrospective records, exclusions, imputation, or sensitivity analyses. Missingness can affect interpretation when the chance that an observation is absent is related to the outcome or to group membership. This is a general issue; the registry information does not establish that missing data occurred or identify its extent.

The analysis population for the primary outcome is not reported in the registry record. The endpoint's population field is empty, and no analysis results are listed. The registry does not explain whether analyses included all enrolled participants, only participants with observed outcome data, or another defined set. Enrollment and the at-risk counts listed for safety do not establish the denominator used for the primary endpoint. The statistical interpretation is consequently limited to the design and endpoint definitions that are reported.

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 5% reporting threshold.

The registry lists no serious adverse events and no other adverse events for either arm. For ESP Block, the at-risk count is 30 for serious events and 30 for other events; for Control, it is 120 for each category. Deaths are listed as 0 in both arms. These are the safety counts recorded in the registry, not a comparison adjusted for differences between groups.

Zero recorded events do not prove that risk is absent. In general, event counts depend on definitions, surveillance, the period of observation, and reporting completeness. The registry information does not specify the adverse-event observation period or provide a detailed account of event collection. The non-randomized design also means the groups should not be treated as exchangeable for safety comparisons merely because both have zero listed events.

The figures should be read narrowly: the registry reports zero events in the stated categories for the listed at-risk groups. They do not establish that the intervention and control have equal safety, and they do not provide evidence about events outside the registry's recorded categories or period. No medical conclusion follows from these entries alone.

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

The study asks a clinically relevant statistical question: how postoperative rescue oxycodone consumption over 0-48 hours compares between women receiving an ESP block with the standard-of-care analgesic regimen and historical controls receiving the regimen without a truncal block. The registry defines the outcome and records a completed study. It does not report the group outcome values or the comparison, so it does not establish the observed direction, size, or precision of a difference.

The available design information helps explain what a future reported estimate would need to be interpreted alongside. Allocation was non-randomized, the control group was historical, and matching was planned on age, race, history of prior cesarean delivery, and insurance status. Those features may make a comparison informative, but they cannot by themselves exclude confounding, temporal changes, selection differences, or measurement differences. The registry record does not report the analysis details needed to assess how those concerns were addressed.

The record also cannot establish whether any observed difference, if reported elsewhere, would be attributable to the block. A non-randomized comparison can identify an association between group and outcome, while causal interpretation requires assumptions about comparability and measurement. Those assumptions and supporting analyses are not reported in the registry record.

The zero adverse-event counts are a limited description of recorded safety events, not proof of no risk or equal safety. Likewise, completion status and enrollment do not indicate that the primary result is available or precisely estimated. The main conclusion is about reporting: the registry record specifies the study question and methods at a broad level, but does not report the primary outcome result needed to answer the comparative question.

13. Why This Trial Matters Statistically

This trial illustrates why design details matter as much as an outcome label. The primary endpoint is clearly framed as postoperative rescue oxycodone use over a defined interval, but the comparison is non-randomized and uses historical controls. A statistical contrast in this setting would need to be interpreted in light of matching, possible differences over time, and the extent to which measurement and care were comparable. Those are central questions for clinical researchers reading observational comparisons embedded in a pilot study.

It also illustrates the distinction between a registered endpoint and a reported finding. A registry can describe what investigators intended to measure without presenting the observed data or the analysis. Here, the registry record does not report group summaries, an effect estimate, or uncertainty for the primary endpoint. This leaves the clinical question unresolved from the posted registry results, regardless of the study's completed status.

The listed adverse-event counts offer another useful lesson in restraint. Zero events in the registry is not equivalent to evidence that risks are equal or absent; the meaning depends on ascertainment, definitions, follow-up, and completeness. Those details are not reported in the registry information.

Finally, planning illustrations should not be mistaken for evidence about the completed study's precision. The planning assumptions use equal allocation and a normal approximation, while the study description specifies historical controls and planned 1:4 matching. Keeping design assumptions, analysis methods, and observed results separate is essential when evaluating what a small pilot comparison can establish. The registry record gives enough information to identify these interpretive issues, but not enough to quantify the comparative outcome.

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 principal limitation for interpreting the primary endpoint is that its results are not reported in the registry record. There are no group medians or inter-quartile ranges, no contrast, and no uncertainty estimate. Without those elements, neither the magnitude nor the precision of the primary comparison can be assessed.

The non-randomized, historical-control design limits causal interpretation. Matching was planned on age, race, history of prior cesarean delivery, and insurance status, but the record does not say whether matching was completed, how matched sets were analyzed, or whether other covariates were considered. Historical controls may also differ from prospective cases in care practices, selection, documentation, or other factors. The registry information does not establish whether such differences occurred or how they were handled.

The prospective component was open label, and the registry lists no masking. The record does not report whether this affected outcome collection, medication requests, or clinical management. The primary endpoint is medication consumption, which can reflect multiple influences beyond pain intensity; the registry does not report how these influences were measured. Details about missing observations, analysis populations, and retrospective data completeness are not reported in the registry record.

The registry lists zero serious and other adverse events, but does not specify the safety observation period or event-collection procedures in the information available. It also does not report an analysis plan, multiplicity handling, or inferential methods. These are reporting limitations: their absence from the registry record does not prove that the study team did not address them, but prevents readers from evaluating them from this record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: ESP Block for Post Cesarean Analgesia — NCT05664958.
• Registry record last updated 2025-02-05; status last verified 2025-02.
• Results first posted 2025-02-05.
• 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 describes a completed phase 4, parallel, non-randomized pilot study of an ESP block with liposomal bupivacaine for post-cesarean analgesia. The prospective arm was planned for 30 subjects, with 120 historical controls described for the retrospective arm; cases were to be matched in a 1:4 ratio on specified characteristics. The primary endpoint is total rescue oxycodone consumption in mg from 0-48 hours, summarized by median and inter-quartile range.

The registry record does not report primary outcome values, a statistical comparison, or analysis methods. It lists zero serious and other adverse events in both arms and zero deaths. These entries do not establish a comparative efficacy or safety conclusion. The design and endpoint are described, but the posted registry results do not provide the evidence needed to determine the observed primary-outcome difference or its precision.