Bilateral Continuous Erector Spinae Blocks for Post-Sternotomy Pain Management: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bilateral Continuous Erector Spinae Blocks for Post-Sternotomy Pain Management (NCT04567407), a na phase 4 study. The primary outcome is Analgesic Requirement.

2. Clinical Question

3. Trial Design

This is a phase 4, interventional, single-group study sponsored by Boston Children's Hospital. The registry record lists the study as completed, with a start date of 2020-09-22 and a primary completion date of 2022-01-22. Enrollment is listed as 45. The study is described as open label, with no masking and allocation recorded as not applicable.

All enrolled patients were to receive bilateral erector spinae blocks, with catheters for postoperative local anesthetic infusion. The intervention is identified as bilateral erector spinae blocks using ropivacaine. The study summary places the blocks in the context of postoperative analgesia for children and adolescents undergoing cardiac surgery via sternotomy as part of an Early Recovery After Surgery program.

Because there is only one group, the design does not compare outcomes between people assigned to the blocks and a concurrent control group. The study can describe outcomes recorded among participants receiving the intervention, but a difference attributable to the intervention cannot be estimated from a randomized between-group comparison. The registry record does not report a comparator group or a controlled allocation procedure.

The registry record lists 11 outcome measures, including duration of mechanical ventilation or intubation, postoperative intensive care and hospital stay, median pain scores, and time to first mobilization. It lists 0 analyses. Numerical results for the primary endpoint are not reported in the registry record. Further details about the planned statistical analysis are not reported 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 Analgesic Requirement, measured over 24hours postop.

The primary endpoint is total opiate equivalents, expressed in mg/kg, at 24hours postop. The registry record identifies the endpoint as analgesic requirement and specifies a mean as its summary measure, with standard error as the dispersion measure. This endpoint describes the amount of opioid medication received relative to body weight over the specified postoperative period.

Medication use is one way to characterize postoperative analgesic requirements. In general, a summary expressed as a mean uses the values across participants to describe an average, while a standard error describes the estimated sampling variability of that mean. The standard error is not the spread of individual participants' medication requirements; that spread is described by other measures, such as a standard deviation.

The registry record does not report the mean, its standard error, a confidence interval, or participant-level observations for this endpoint. It therefore does not permit a numerical description of the recorded analgesic requirement or its precision. It also does not report details such as the specific opioid conversion method or the handling of medication received outside the stated time frame. These details should not be inferred from the endpoint name alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical methods must be interpreted in light of the study structure: this is an open-label, single-group study with no concurrent comparator. The registry record identifies the primary endpoint and its summary format, but does not report the numerical endpoint result or a detailed analysis plan. The concepts below explain what the listed statistical terms mean in general; they do not establish which additional procedures the investigators used.

What does a mean describe?

In general, the mean is an average of measured values. For the primary endpoint, the intended measure is total opiate equivalents in mg/kg at 24hours postop. A mean can provide a concise description of the group's average recorded requirement, but it does not show how values vary across individuals. If values are unevenly distributed or include unusually high observations, the mean may be influenced by those features. The registry record does not report the distribution of individual endpoint values, so those features cannot be assessed.

What does the standard error convey?

In general, the standard error describes the sampling uncertainty of an estimated mean. It concerns how much the estimated mean would vary across repeated samples under an appropriate statistical model; it is not a direct measure of the range or spread of individual participants' values. A standard deviation, in contrast, describes variation among individual observations. The registry record names standard error as the dispersion measure for the primary endpoint but does not report its value. The endpoint's precision therefore cannot be evaluated from the posted record.

How would a confidence interval help?

In general, a confidence interval gives a range of values compatible with an estimate under the assumptions of the interval procedure. It conveys uncertainty more directly than a point estimate alone. A narrow interval indicates greater statistical precision than a wide interval, although precision does not by itself establish clinical importance or eliminate bias. The registry record does not report a confidence interval for the primary endpoint. No interval can be reconstructed from the available information without adding data or making assumptions.

Why does the single-group design matter?

A treatment effect is usually a contrast between outcomes under different treatment conditions. In a randomized comparison, the groups can provide estimates of those contrasting outcomes, with random allocation intended to balance factors that could otherwise distort the comparison. This study has no randomized or concurrent control group. Its primary endpoint can describe the intervention group if a result is reported, but the design does not estimate a between-group treatment contrast. It cannot, on its own, distinguish the intervention's contribution from other influences on postoperative medication use.

The lack of masking is also relevant to how outcomes are collected and interpreted. Medication administration is a recorded clinical outcome, while pain scores involve assessment and reporting. In general, awareness of treatment can influence the behavior of participants or assessors, depending on the outcome and study procedures. The registry record does not report methods intended to reduce such influences, and no specific effect of open-label conduct should be assumed.

What do the planning illustrations mean?

General sample-size calculations estimate the number of participants needed to detect a specified effect under stated assumptions. The planning illustrations associated with the posted material use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are described as based on the observed effect, with the effect to detect expressed as a stated fraction of that observed effect. Those assumptions do not describe this trial's single-group design, and the illustrations are not a retrospective measure of observed power. A sample-size calculation is a planning aid, not evidence that an effect was detected or that an outcome estimate is precise.

For time-to-event outcomes, a general method such as the Schoenfeld approach expresses planning in terms of the total number of events. Other planning calculations may express the number of participants per arm. These conventions describe calculation outputs, not additional observations from this study. The registry record does not report a sample-size justification for the trial's own design, so the rationale for enrollment of 45 is not reported in the registry record.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. When a model assumes less variability than is present, its uncertainty estimates may be too small, which can make results appear more precise than they are. This issue is relevant only when a suitable model and data indicate it; it should not be presumed for this study. The registry record does not report a model for the primary outcome or information that would establish whether over-dispersion is present.

The posted information does not include a reported primary estimate, standard error, confidence interval, or analysis details sufficient to evaluate model assumptions. Accordingly, statistical interpretation is limited to the design and endpoint definitions. No significance claim, adjusted analysis, or estimate of treatment effect can be drawn 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("Bilateral Erector Spinae Blocks")
n   <- c(40)
m   <- c(0.6)
sp  <- c(0.06)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Bilateral Erector Spinae Blocks  40  0.600  0.379  0.479  0.721

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 11 outcome measures, including the primary analgesic-requirement endpoint and secondary outcomes covering mechanical ventilation or intubation, postoperative intensive care and hospital stay, median pain scores, and time to first mobilization. It lists 0 analyses. The record does not report a plan for controlling multiplicity, such as designating a hierarchy among secondary outcomes or adjusting for multiple statistical tests. It is therefore not possible to determine how the investigators intended to handle the chance of false-positive findings across several outcomes or repeated assessments.

Several median pain-score outcomes are listed, but their specific time points and the relationships among those measures are not reported in the registry record. The record also does not report a detailed analysis plan specifying which outcomes would be analyzed, what statistical tests or models would be used, or whether analyses would be adjusted for participant characteristics.

Missing-data methods and the amount of missing outcome information are not reported in the registry record. The analysis population for the primary endpoint is also not reported. Although enrollment is listed as 45, the registry record does not establish how many participants contributed data to each outcome, whether any participants were excluded from an analysis, or how incomplete measurements were handled. These omissions limit the ability to assess the representativeness and precision of any outcome estimate, even if a numerical result were available.

These are gaps in the registry record, not evidence that a particular procedure was or was not used outside the record. No imputation method, sensitivity analysis, or multiplicity adjustment should be assumed.

12. 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 40 participants at risk for serious adverse events, with 0 affected, and 40 participants at risk for other adverse events, with 10 affected. It also lists 0 deaths. The serious-event terms are not listed in the registry record. These counts describe the entries posted for this study; they do not establish that every possible event was assessed or that events were caused by, or unrelated to, the intervention.

Enrollment is listed as 45, while the at-risk denominators in the adverse-event record are 40. The registry record does not explain why these counts differ. The safety figures should therefore be interpreted using the stated denominators and not treated as if they necessarily cover all enrolled participants. The record also does not report further information about the timing, duration, severity, or individual descriptions of the other adverse events.

A count of 0 serious adverse events in the posted record is not proof that serious events are impossible or that the intervention is risk-free. It is a description of what the registry record reports for the listed at-risk group. Likewise, the count of 10 participants with other adverse events does not, by itself, establish a causal relationship. No comparison group is available to provide a concurrent reference rate.

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

The registry record documents a completed, open-label, single-group study of bilateral continuous erector spinae blocks using ropivacaine for postoperative analgesia in children and adolescents undergoing cardiac surgery via sternotomy. It identifies total opiate equivalents in mg/kg at 24hours postop as the primary endpoint and specifies that the mean and standard error were the intended summary measures.

The posted information does not include a numerical result for that primary endpoint. It therefore does not show the group's average analgesic requirement or how precisely that average was estimated. The record also does not report a comparator group, a treatment-effect estimate, a confidence interval, or a statistical test result. The evidence available from the registry record cannot establish whether the intervention changed opioid requirements relative to another approach.

The study's single-group design allows outcomes among participants receiving the blocks to be described if results are reported. It cannot, by itself, separate the effect of the blocks from other influences on postoperative pain management and recovery. The open-label design is another feature to consider, particularly for outcomes that involve assessment or reporting, such as pain scores. The registry record does not report numerical results for those secondary outcomes or their assessment time points.

The safety entries report 0 serious adverse events among 40 participants at risk, 10 participants with other adverse events among 40 at risk, and 0 deaths. The record does not explain why the adverse-event denominators differ from the enrollment of 45, and the entries do not provide a controlled comparison or establish causality.

These limitations concern what can be concluded from the posted record. They do not establish that the study's results were negative, nor do they establish a beneficial or harmful effect. The numerical primary endpoint result and its uncertainty are not reported in the registry record.

14. Why This Trial Matters Statistically

This trial is statistically notable because the clinical question concerns an intervention delivered in a setting where postoperative analgesia and recovery are relevant, while the registered design is single group and open label. Those design features determine the kind of evidence the study can provide. They permit description of outcomes among participants receiving bilateral erector spinae blocks, but they do not provide the randomized contrast needed to estimate an effect relative to a concurrent control group.

The primary endpoint is clearly framed as a continuous measure: total opiate equivalents in mg/kg at 24hours postop, summarized as a mean. That makes the choice and reporting of uncertainty important. A mean alone would describe a group average, while a standard error or confidence interval would help readers assess its precision. The registry record identifies standard error as the dispersion measure but does not report its numerical value or the endpoint mean.

The record also illustrates why enrollment, analysis populations, and safety denominators should be distinguished. Enrollment is listed as 45, while the safety record uses 40 participants at risk for each adverse-event category. Without an explanation of the difference, readers cannot assume the same participants contributed to every outcome. The analysis population and missing-data methods are not reported in the registry record.

Finally, a list of multiple outcomes raises questions about outcome selection, timing, and multiplicity. The record lists 11 outcomes but no analyses, and does not report a statistical plan for interpreting them together. Transparent numerical results and methods would be needed to assess uncertainty, missingness, and the consistency of findings across outcomes. The current registry information supports a careful account of design and reporting limits, rather than a conclusion about comparative effectiveness.

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 main design limitation is the absence of a concurrent control group. Because the study is single group and allocation is listed as not applicable, it cannot estimate a randomized between-group contrast. Postoperative outcomes may reflect several aspects of care and recovery, and the design does not separate those influences from the intervention. The open-label conduct also means that participants and assessors were not masked, although the registry record does not establish how this affected any specific outcome.

The primary endpoint's numerical result is not reported in the registry record. Its mean, standard error, confidence interval, and analysis population are not available in the posted information. This prevents assessment of the estimate's magnitude and precision. Numerical results for the listed secondary outcomes are also not reported in the registry record, as are their specific assessment times for the repeated median pain-score outcomes.

The registry record lists enrollment of 45 but gives adverse-event at-risk denominators of 40. It does not explain this difference. Information about missing observations, participant exclusions, or outcome-specific denominators is not reported. Missing-data handling and sensitivity analyses are also not reported in the registry record.

The record lists 11 outcome measures and 0 analyses, but does not report how outcomes were prioritized, how multiplicity was handled, or which statistical methods were used. A sample-size justification for the trial's own single-group design is not reported in the registry record. Planning illustrations based on an observed effect and a two-arm assumption should not be read as a design justification or as observed power for this study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Bilateral Continuous Erector Spinae Blocks for Post-Sternotomy Pain Management — NCT04567407.
• Registry record last updated 2023-10-17; status last verified 2023-09.
• Results first posted 2023-10-17.
• 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 phase 4 interventional study sponsored by Boston Children's Hospital. It lists enrollment of 45, a start date of 2020-09-22, and a primary completion date of 2022-01-22. The study is open label and single group, with allocation listed as not applicable.

The intervention is bilateral erector spinae blocks using ropivacaine, with catheters for postoperative local anesthetic infusion. The population is children and adolescents undergoing cardiac surgery via sternotomy in an Early Recovery After Surgery program. The primary endpoint is total opiate equivalents in mg/kg at 24hours postop, summarized as a mean with standard error.

The record lists 11 outcome measures and 0 analyses. A numerical result for the primary endpoint is not reported in the registry record. Safety entries list 0 serious adverse events among 40 at risk, 10 participants with other adverse events among 40 at risk, and 0 deaths. The difference between enrollment and the adverse-event denominators is not explained.