Ultrasound-guided Intermediate Cervical Plexus Block: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ultrasound-guided Intermediate Cervical Plexus Block (NCT02794974), a non-randomized na study. The primary outcome is Local Anesthetic Supplementation (Frequency).

2. Clinical Question

3. Trial Design

The registry record describes a completed, parallel-group, non-randomized study of ultrasound-guided intermediate cervical plexus block for carotid endarterectomy. The listed start was 2016-05 and primary completion was 2017-08. Enrollment was 29. The record classifies masking as none and phase as not applicable. The sponsor is Helios Research Center.

The two groups share the intermediate cervical plexus block and the facial nerve block of the cervical branch. The group titled “With Perivascular Block” also received a perivascular block; the group titled “Without Perivascular Block” did not. The listed interventions are cervical plexus block, facial nerve block, and perivascular block. The registry description gives the drugs and amounts for each of the two group regimens.

Because allocation was non-randomized, group assignment may be related to participant characteristics, clinical circumstances, or other factors. The record does not describe how allocation was determined, whether the groups were comparable at baseline, or whether any statistical adjustment was planned. Those details are not reported in the registry record. Therefore, even if an outcome contrast were available, it would need to be interpreted as an association between group membership and outcome rather than as an unconfounded causal effect.

The parallel structure means participants are described in one group or the other, rather than moving between regimens. The record does not report the number enrolled in each group for the primary endpoint, the eligibility criteria beyond the stated condition, or the study setting details. It also does not report a protocol, a sample-size justification, or an account of interim analyses. A completed status indicates the registry record marks the study as completed; it does not supply missing outcome values or establish what analyses were conducted.

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:

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 Local Anesthetic Supplementation (Frequency), measured over intraoperatively.

The primary endpoint is the frequency of participants needing intraoperative supplementation of prilocaine 1% by the surgeon. Its unit is participants, and the registry description expresses the outcome as a number of participants who needed supplementation, with a percentage notation. In practical terms, the measure records whether the initial anesthetic regimen was accompanied by a need for additional local anesthetic during the operation.

This outcome is used to characterize the adequacy of the anesthetic approach in relation to additional local-anesthetic use. It is a binary participant-level outcome: a participant either needed supplementation or did not, according to the registry description. The group-level frequency would usually be interpreted alongside the number of participants assessed in each group. Those primary-endpoint denominators, event counts, and percentages are not reported in the registry record.

The registry lists the timeframe as intraoperatively. It does not provide an operational definition for the decision to supplement, specify who made that decision beyond identifying the surgeon, or describe criteria for recording an event. It also does not give the numerical comparison between groups or an uncertainty interval. Consequently, the endpoint’s definition can be described, but the extent or precision of any group difference cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study’s primary outcome is a participant-level binary measure: whether supplementation with prilocaine 1% was needed intraoperatively. General: binary outcomes are often summarized by counting participants with the event and relating that count to the number assessed. The resulting proportion can describe frequency, while a comparison between groups can be expressed in several ways. The registry record does not report the counts, denominators, comparative estimate, or uncertainty measure for this endpoint, so no such quantity can be interpreted for this study.

What does non-randomized allocation imply?

The record classifies allocation as non-randomized. General: random allocation is intended to balance measured and unmeasured participant characteristics across groups on average. Without random allocation, the groups can differ for reasons that also relate to the outcome. An observed difference may therefore reflect the intervention, differences in who received each regimen, or both. Statistical adjustment can address measured differences when appropriate information is collected, but it cannot automatically remove unmeasured confounding.

The registry record does not report how participants were assigned, the baseline characteristics of each group, or any planned adjustment strategy. It is not possible to determine whether the investigators accounted for group differences or how they handled possible confounding. The comparison should consequently be read as non-randomized, rather than as if treatment assignment had been randomized.

How should an estimate and its precision be read?

General: a point estimate gives a single summary of an observed contrast, while a confidence interval communicates its statistical uncertainty under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but an interval does not by itself resolve bias from non-randomized allocation, measurement decisions, or missing data. Statistical significance is also not the same as clinical importance.

No estimate, confidence interval, or p-value for the primary endpoint is reported in the registry record. The reader cannot assess whether the data are compatible with a small or large difference, or whether the estimate is precise. Nor can an unadjusted comparison be reconstructed from the record because the primary event counts and group denominators are absent.

What do the planning assumptions mean?

The planning illustration is described as using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It is based on the observed effect, with the effect to detect expressed as a stated fraction of that observed effect. General: a sample-size calculation estimates the amount of information that might be needed to detect a specified effect under chosen assumptions. Such a calculation depends on the assumed effect and the analysis model. It is a planning exercise, not a result observed in participants.

The registry record does not report the numerical primary effect needed to evaluate those planning illustrations, nor does it report the numerical planning outputs. The record explicitly distinguishes the illustration from the trial’s own design. These calculations must not be interpreted as evidence that the study had a particular probability of detecting an effect, or as observed power. Sample-size planning cannot substitute for reported outcome estimates and their uncertainty.

How should the safety counts be interpreted statistically?

The safety summary lists zero serious adverse events and zero other adverse events in each group, with 14 participants at risk per group, and zero deaths in each group. General: an observed count of zero means no event was recorded in the listed group and denominator during the reported assessment; it does not establish that the underlying event risk is zero. With limited information about follow-up, definitions, and ascertainment, the precision of safety conclusions cannot be judged. The registry record does not provide those additional details.

What is not available for assessing the analysis?

The record does not report a statistical analysis plan, outcome-specific analysis methods, model specification, covariate adjustment, handling of missing observations, or rules for excluding participants from analyses. It lists five outcome measures and five analyses, but gives no corresponding primary outcome estimates. General: when those details are absent, the reader cannot verify whether analyses were prespecified, whether the analysis population matched the enrolled population, or whether all planned outcomes are represented. These are reporting limitations, not proof that a particular method was or was not used.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Cervical Plexus and Facial Nerve Block", "Cervical Plexus, Perivascular and Facial Nerve Blo")
n      <- c(14, 14)
events <- c(11, 7)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Cervical Plexus and Facial Nerve Block  14  11  78.6  49.2  95.3  52.4  92.4  51.9  92.2
ARM  Cervical Plexus, Perivascular and Facial Nerve Blo  14  7  50.0  23.0  77.0  26.8  73.2  26.6  73.4

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists five outcome measures and five analyses. It identifies the primary measure as intraoperative local-anesthetic supplementation and lists hoarseness, cough, and dysphagia as secondary outcomes. Numerical results for these outcomes and the remaining listed measures are not reported in the registry record. The record does not describe whether any multiplicity adjustment was planned or performed.

General: when several outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase if each is assessed separately. Multiplicity procedures can account for that issue, but they may not be necessary for every descriptive analysis. Without a statistical plan or reported testing strategy, it is not possible to determine how the study handled multiple outcomes. The record’s count of analyses alone does not establish that every analysis was a significance test.

Missing-data procedures are not reported in the registry record. It does not state whether primary outcome data were complete, how missing observations were handled, or whether any sensitivity analysis was used. Analysis populations are also not described: the record does not say which participants were included in each outcome analysis or whether any participants were excluded after enrollment.

These absences matter because outcome denominators, missingness, and analysis-population definitions help readers understand who contributed to each result and whether comparisons might be affected by incomplete data. The total enrollment is 29, while the adverse-event summary lists 14 participants at risk in each group. The record does not explain the relationship between those figures, and the adverse-event denominators should not be assumed to be the primary-endpoint denominators.

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.

The adverse-event summary lists zero serious adverse events among 14 participants at risk in the group without a perivascular block, and zero among 14 participants at risk in the group with a perivascular block. It also lists zero other adverse events in each group and zero deaths in each group. No top serious-event terms are listed.

These figures describe what the registry record reports for its listed groups and denominators. General: zero recorded events is not the same as proof of zero risk. A small number of observed events, including none, provides limited information about uncommon harms, especially when the duration and completeness of follow-up are unclear. The registry record does not report the adverse-event collection period, definitions, or ascertainment procedures.

The safety denominators are not necessarily the denominators for the primary endpoint. The record lists total enrollment as 29 but does not explain the relation between that enrollment and the 14 participants at risk in each adverse-event group. No rates or comparisons should be inferred beyond the recorded counts. These figures alone cannot establish that the regimens have equivalent safety or that adverse events were absent outside the reported assessment.

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

The registry record makes clear what comparison the study was designed to describe: a regimen with an added perivascular block versus a regimen without that block, with both groups receiving the recorded cervical plexus and facial nerve blocks. Its primary endpoint concerns whether the surgeon needed to supplement anesthesia with prilocaine 1% during the operation. That outcome is relevant to the study’s stated question about anesthetic quality, but the registry record does not report its group counts or comparative result.

As a result, the record does not establish whether supplementation was more or less frequent in either group, how large a difference might have been, or how precisely any difference was estimated. The secondary outcomes are named, but their results are also not reported in the registry record. The available safety figures describe zero recorded serious events, other events, and deaths in groups with 14 participants at risk each; they do not establish that the regimens are equally safe or free of risk.

The design also limits causal interpretation. Because allocation was non-randomized, potential group differences could affect the comparison. Baseline characteristics, allocation procedures, and adjustment methods are not reported in the registry record. Even a numerical contrast would therefore need to be interpreted with caution and in light of possible confounding.

General: a study’s conclusion depends not only on the question it set out to ask, but also on complete outcome reporting, appropriate analysis, and a design that supports the intended inference. The registry entries identify the intended comparison and some safety counts, but do not provide the primary outcome evidence needed to judge the central question. The record supports describing the design and the limits of the available statistics; it does not support a conclusion that one regimen is superior, inferior, or equivalent.

14. Why This Trial Matters Statistically

This study illustrates a common statistical distinction between a clearly stated clinical question and a result that can be evaluated. The registry identifies an outcome that can be counted at the participant level: the need for intraoperative supplementation of prilocaine 1%. It also specifies the two regimens sufficiently to show that the perivascular block is the component that differs. Yet the outcome counts, denominators, and comparative estimate are not reported in the registry record. Without them, readers cannot quantify the central contrast.

The non-randomized design is also important. General: when treatment assignment is not random, treatment groups may differ in factors related to outcomes. That creates a challenge for causal interpretation even when an outcome comparison is reported. In this record, the allocation process, baseline group characteristics, and adjustment methods are not reported, so the degree of that challenge cannot be assessed.

The safety summary offers a second statistical lesson: zero observed events in the listed groups are not proof of zero risk. Counts need context, including the denominator and the period over which events were monitored. The record gives adverse-event denominators of 14 per group but does not describe the duration or procedures for collection, and it does not explain their relationship to total enrollment.

Finally, the record shows why an outcome list and an analysis count do not replace outcome estimates. It identifies five outcome measures and five analyses, but numerical results for the primary and secondary measures are not reported. Statistical interpretation needs transparent estimates and information about their precision, alongside the design and analysis details. Where those details are not reported, the appropriate conclusion is that the comparison cannot be evaluated from the registry record, rather than filling gaps with assumptions.

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 most direct limitation is that the primary endpoint result is not reported in the registry record. Counts needing supplementation, group denominators, percentages, a comparative estimate, and an uncertainty interval are not available. The listed secondary outcomes—hoarseness, cough, and dysphagia—also lack numerical results in the registry record. Therefore, outcome patterns and precision cannot be assessed.

Non-randomized allocation is an additional limitation for comparing groups. The registry record does not describe the allocation process, baseline characteristics, potential confounders, or adjustment methods. It is not possible to assess whether the groups were similar or whether statistical methods addressed measured differences. No causal interpretation can be justified from design information alone.

Other methodological details are not reported in the registry record, including a statistical analysis plan, sample-size justification, primary endpoint analysis method, missing-data handling, analysis populations, and interim analyses. The registry’s planning illustration is described as separate from the trial’s own design, and its numerical inputs and outputs are not reported in the registry record. The report also does not give an operational definition for supplementation or explain how that event was recorded.

For safety, the record lists zero serious events, zero other events, and zero deaths in each group, with 14 participants at risk per group. It does not state the follow-up duration, event definitions, or ascertainment procedures, and it does not explain the relationship between those denominators and the total enrollment of 29. The safety counts should therefore be read as limited reported observations, not as comprehensive evidence about risk.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Ultrasound-guided Intermediate Cervical Plexus Block — NCT02794974.
• Registry record last updated 2018-12-19; status last verified 2018-11.
• Results first posted 2018-08-16.
• 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, parallel, non-randomized study of ultrasound-guided intermediate cervical plexus block for carotid endarterectomy in people with internal carotid artery stenosis. It lists enrollment of 29, no masking, a start of 2016-05, and primary completion in 2017-08.

Both groups received an intermediate cervical plexus block and a facial nerve block of the cervical branch. One group also received a perivascular block. The primary outcome was the number of participants needing intraoperative supplementation with prilocaine 1%. Hoarseness, cough, and dysphagia were listed as secondary outcomes.

Primary and secondary outcome results are not reported in the registry record. The adverse-event summary lists zero serious events, zero other events, and zero deaths in each group, with 14 participants at risk per group. Non-randomized allocation, absent outcome estimates, and unreported analysis details limit interpretation of the comparison.