Continuous Nerve Block Block vs Combination of Single Block Plus Intravenous Lidocaine for Postoperative Pain.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Continuous Nerve Block Block vs Combination of Single Block Plus Intravenous Lidocaine for Postoperative Pain. (NCT04208516), a randomized phase 4 study. The primary outcome is Opioid Consumption After Surgery.

2. Clinical Question

3. Trial Design

NCT04208516 is a phase 4, randomized, parallel-group, active-comparator study of postoperative pain management. Its official title describes a prospective, randomized, active-comparator, open-label, non-inferiority study. The registry also lists single masking; who was masked and how that designation relates to the open-label description are not reported in the registry record. Allocation is listed as randomized. The study status is terminated.

The two treatment strategies are continuous nerve blocks and single nerve blocks plus intravenous lidocaine infusion. The surgical context determines whether the block is Erector Spinae Plane or Quadratus Lumborum. The record describes the former for unilateral thoracic surgery and the latter for major abdominal surgery. It also lists lidocaine IV, ropivacaine 0.5% injectable solution, dexamethasone, and dexmedetomidine as interventions. The available arm descriptions are incomplete, so the full regimen, timing, and treatment implementation are not reported in the registry record.

Registry enrollment is 17. For the primary outcome, the posted results show 7 participants in the continuous nerve blocks arm and 7 in the single nerve blocks plus IV lidocaine arm. The record does not explain the difference between the enrollment figure and the outcome-group counts. Study start is listed as 2021-05-26 and primary completion as 2022-08-18. The reasons for termination and whether it affected recruitment, follow-up, or analysis are not reported in the registry record.

The primary outcome is mean opioid consumption, expressed in oral morphine equivalents, 24 hours after surgery. The registry lists 16 secondary outcomes, including opioid consumption, pain after surgery, and local anesthetic consumption. The exact outcome-specific analyses and their results are not reported in the registry record. No primary-outcome analysis is listed.

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: For 3 patients under the abdominal portion of this study, Erector Spinae Blocks were performed rather than Quadratus Lumborum Blocks. There are various anatomic reasons why a different block would be considered when performing the actual block. This study was analyzing Quadratus Lumborum Blocks for abdominal surgery, as such, the results from the patients who had Erector Spinae Blocks for abdominal surgery were excluded.

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 Opioid Consumption After Surgery, measured over 24 hours after surgery.

The primary endpoint is opioid consumption during the 24 hours after surgery, with opioids converted to oral morphine equivalents (OME). The registry describes the measure as a mean and reports a standard deviation for each arm. OME expresses different opioid medications on a common scale, allowing consumption to be summarized despite use of different drugs. The record does not describe the conversion procedure in further detail.

Opioid consumption is used as an outcome because it quantifies medication use during a defined postoperative period. It is distinct from a pain rating: consumption reflects administered opioid amounts, while a pain score records a patient's reported pain at a specified assessment. The registry lists pain after surgery among the secondary outcomes, but does not provide those results in the posted data.

The posted mean is 34.93 OME in the continuous nerve blocks arm, with standard deviation 31.32, and 46.5 OME in the single nerve blocks plus IV lidocaine arm, with standard deviation 33.37. Each arm has 7 participants. These are descriptive summaries. The record does not report a confidence interval, p-value, adjusted estimate, or formal test for the primary outcome. The time window is 24 hours after surgery; results for later periods are not part of this primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the mean describe?

The primary endpoint is a continuous measure: opioid consumption converted to OME over the 24 hours after surgery. A mean summarizes the central level of consumption within each arm. The registry reports means of 34.93 and 46.5 OME, with standard deviations of 31.32 and 33.37, respectively. A mean is useful for describing a group, but it does not show the full distribution of observations or how much uncertainty there is about the comparison between groups.

What does the standard deviation describe?

General statistical explanation: a standard deviation describes the spread of observations around a mean. Larger spread means individual values vary more widely around that group average. The reported standard deviations are substantial relative to the means, which cautions against interpreting either mean as representative of every participant. A standard deviation is not a confidence interval and does not directly quantify uncertainty in the difference between groups.

What would a confidence interval add?

General statistical explanation: a confidence interval gives a range of estimates compatible with the observed data under a specified method. For a treatment comparison, an interval would help show both the estimated contrast and its precision. The registry record does not report a confidence interval for the primary comparison. Without one, readers cannot evaluate the range of comparative effects supported by the posted outcome summaries.

What is specific to non-inferiority?

General statistical explanation: a non-inferiority study asks whether an intervention is not unacceptably worse than a comparator according to a prespecified margin. The margin is a clinically and statistically important design choice: it defines the boundary for the claim. A result is not established as non-inferior merely because group means look similar or because a conventional test fails to find a difference. The record states a non-inferiority objective but does not report the margin, the analysis used to assess it, or a formal conclusion. Thus, the posted summaries cannot be interpreted as a non-inferiority finding.

Why does the analysis population matter?

General statistical explanation: randomized trials can report results for different analysis populations, depending on how participants are classified and which observations are included. In non-inferiority research, the selected population and treatment adherence can affect interpretation. The registry record does not report whether the primary outcome analysis included all randomized participants, participants who received treatment, or another population. It also does not report adherence, exclusions, or the handling of missing outcome data. Readers therefore cannot determine how the analysis set was formed.

How should random variation be considered?

Random allocation is listed, which is intended to support fair comparison by assigning treatment strategies without choosing them according to participant characteristics. In a small trial, chance differences between groups can nevertheless occur. The registry does not report baseline characteristics or an adjusted analysis that could help readers assess group balance. The posted arm summaries alone do not show whether other factors differed between groups.

Why can over-dispersion matter?

General statistical explanation: when a continuous outcome varies widely between individuals, the mean can be estimated less precisely, particularly with limited observations. A statistical model that assumes less variation than the data actually contain may understate uncertainty. The posted standard deviations show considerable spread, but the registry record does not describe a model, variance assumption, or robust method. No claim about the suitability of a particular model can be made from the reported summaries.

What can be said about recalculation?

The registry result data give arm-level means and standard deviations, but do not give a formal primary comparison or enough reported analysis detail to establish its inferential result. No recalculated comparative estimate, p-value, or confidence interval is reported in the registry record. The interpretation should remain descriptive rather than substituting a newly calculated test for the sponsor's analysis.

What about planning calculations?

General statistical explanation: sample-size planning uses assumptions about the effect to detect, outcome variability, allocation, and the chosen error rates. A planning illustration based on an observed effect is not observed power and does not establish that a completed study had adequate power. The record describes a planning approach using a two-sided significance level of 0.05, equal allocation, a normal approximation, and fractions of the observed effect. The numerical planning results and the trial's own sample-size justification are not reported in the registry record. It is therefore not possible to assess the planned or achieved power from the 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("Continuous Nerve Blocks", "Single Nerve Blocks Plus IV Lidocaine Infusion")
n   <- c(7, 7)
m   <- c(34.93, 46.5)
sp  <- c(31.32, 33.37)
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  Continuous Nerve Blocks  7  34.930  31.320  5.964  63.896
CARM  Single Nerve Blocks Plus IV Lidocaine Infusion  7  46.500  33.370  15.638  77.362

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 16 secondary outcomes, including repeated listings for opioid consumption and pain after surgery, as well as local anesthetic consumption. Testing multiple outcomes or time points can increase the chance of observing apparently notable findings by chance. General statistical explanation: multiplicity methods can control or otherwise address this issue, but the appropriate method depends on which outcomes and comparisons were prespecified. The multiplicity strategy is not reported in the registry record.

The record does not report the statistical analysis plan, the hierarchy of primary and secondary analyses, or whether any secondary outcomes were considered exploratory. It also does not provide results for the listed secondary outcomes in the posted data. Consequently, no secondary-outcome conclusions or multiplicity-adjusted interpretation can be drawn.

Missing-data handling is not reported in the registry record. The posted primary outcome groups each include 7 participants, while registry enrollment is 17; the record does not explain the relationship between these figures or whether any participants lacked outcome data. There is no reported description of exclusions, withdrawals, imputation, or sensitivity analyses. Without this information, it is not possible to assess how missing observations may have affected the estimates.

The analysis population is also not reported in the registry record. It is unclear whether the reported summaries reflect all randomized participants or another set. This matters for understanding both the treatment comparison and the non-inferiority objective. No account of treatment adherence or protocol deviations is reported. These omissions limit interpretation of the posted means and prevent assessment of whether the analysis followed the intended trial plan.

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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: abnormal lidocaine blood level (14.3%).

The registry reports serious adverse events for the two treatment groups. In the continuous nerve blocks group, 0 of 7 participants are listed as affected by a serious adverse event; in the single nerve blocks plus IV lidocaine group, 1 of 7 is listed as affected. The record lists 0 deaths in each group. These are event summaries for the reported groups, not estimates of comparative safety with quantified uncertainty.

The registry lists “Abnormal Lidocaine Blood Level” as a serious adverse event term, at 14.3%. The record does not identify which group this term belongs to in the term listing, nor does it report a causal relationship to treatment. The group-level serious-event figures should not be used to infer causation or to compare risk precisely, particularly given the small group counts.

Other, non-serious adverse events are listed separately: 1 of 7 participants in the continuous nerve blocks group and 0 of 7 in the single nerve blocks plus IV lidocaine group. The registry does not provide additional detail about the event, severity, timing, or relatedness. No broader safety conclusion can be drawn from these limited summaries.

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

The result record offers descriptive information about opioid consumption after surgery in a randomized comparison of continuous nerve blocks with single nerve blocks plus IV lidocaine. The reported mean OME is 34.93 for continuous nerve blocks and 46.5 for single nerve blocks plus IV lidocaine during the 24 hours after surgery. The reported standard deviations are 31.32 and 33.37, and each arm has 7 participants. These figures show the observed group summaries, not the precision or statistical significance of a treatment contrast.

The study was designed with a stated non-inferiority objective. However, the registry record does not report the non-inferiority margin, the formal comparative analysis, a confidence interval, or a conclusion. Consequently, the posted summaries do not establish whether the single-block-plus-lidocaine strategy met the study's non-inferiority criterion. They also do not establish that one strategy is superior, equivalent, or clinically interchangeable with the other.

The record describes a terminated study and lists enrollment of 17. It does not explain how the enrollment figure relates to the 7 participants reported in each primary-outcome group, why the study was terminated, or whether all intended analyses were completed. Missing-data methods and the analysis population are not reported. Those uncertainties limit the conclusions that can be drawn from the results.

More generally, a trial result is interpreted through the estimate, its uncertainty, its design, and the completeness of the analysis—not by comparing means alone. The posted means are an observation from the reported groups. They do not show the full range of patient-level outcomes, establish a mechanism, or determine whether the observed pattern would persist in a larger or different population.

14. Why This Trial Matters Statistically

This trial raises a statistical question that is more specific than whether two observed means differ. The stated aim is non-inferiority: assessing whether a single nerve block followed by IV lidocaine can remain within an acceptable boundary relative to a continuous nerve block. That question depends on a prespecified margin and an uncertainty interval, neither of which is reported in the registry record. The distinction matters because a non-significant difference, if one had been reported, would not by itself demonstrate non-inferiority.

The study also illustrates the importance of separating descriptive summaries from inferential evidence. Means and standard deviations communicate the observed levels and variability in each group, while a comparative estimate with uncertainty would address how precisely the data distinguish between strategies. The posted group counts are small, and the record does not report the primary comparison or its precision. Interpretation should therefore remain limited to the reported summaries.

The trial's terminated status and the unexplained relationship between enrollment and the outcome-group counts are relevant to transparency. A reader needs to know which participants contributed to the primary outcome, how missing data were handled, and whether the planned analysis was completed. Those details are not reported in the registry record. The limitations are particularly important when the research question relies on prespecified design choices such as a non-inferiority margin.

Finally, the record demonstrates why outcome definitions and time windows matter. Opioid consumption in OME during the 24 hours after surgery is a specific endpoint; it is not interchangeable with pain ratings, later opioid use, or other recovery measures. The registry lists secondary outcomes, but their results are not reported in the posted data. Statistical interpretation must stay within the endpoint and evidence that the record actually documents.

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 primary comparative analysis is not reported in the registry record. Although arm-level means and standard deviations are available, there is no confidence interval, p-value, adjusted estimate, or stated conclusion for the primary endpoint. The non-inferiority margin is also not reported, so the central design criterion cannot be evaluated.

The study is marked terminated, but the reason and consequences of termination are not reported in the registry record. Enrollment is listed as 17, whereas the primary outcome summaries give 7 participants in each arm. The record does not explain this difference or identify whether the posted groups include all randomized participants. It also does not describe missing observations, withdrawals, exclusions, or treatment adherence.

Details that would help interpret the comparison are absent, including baseline characteristics, the analysis population, the statistical model, and the handling of outcome distributions. The arm descriptions are incomplete, and the registry does not give full treatment-delivery details. The record labels the study open-label in its official title while also listing single masking; the masked party and how masking was implemented are not reported.

The registry lists 16 secondary outcomes, but their results and the approach to multiplicity are not reported. Safety summaries are limited, and the relationship of the listed serious adverse event term to a particular group or treatment is not specified. These limitations mean the results support only a cautious description of the posted outcome summaries, not a broad comparative or safety conclusion.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Continuous Nerve Block Block vs Combination of Single Block Plus Intravenous Lidocaine for Postoperative Pain. — NCT04208516.
• Registry record last updated 2023-09-13; status last verified 2023-08.
• Results first posted 2023-09-13.
• 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

NCT04208516 is a phase 4 randomized, parallel-group, active-comparator study with a stated non-inferiority objective. It compares continuous nerve blocks with single nerve blocks plus IV lidocaine for postoperative analgesia in thoracic or major abdominal surgery. The record lists enrollment of 17 and status terminated. The official title describes the study as open-label, while the registry lists single masking.

The primary endpoint is mean opioid consumption in OME during the 24 hours after surgery. The posted results report 34.93 OME, with standard deviation 31.32, for continuous nerve blocks and 46.5 OME, with standard deviation 33.37, for single nerve blocks plus IV lidocaine. Each arm has 7 participants. The registry does not report a formal comparative analysis, non-inferiority margin, or confidence interval. Reasons for termination, missing-data handling, and the analysis population are not reported in the registry record.