Incidence of Postoperative Residual Neuromuscular Blockade in Portugal: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Incidence of Postoperative Residual Neuromuscular Blockade in Portugal (NCT03417804), a registered phase not stated study. The primary outcome is Percentage of Patients With Postoperative Residual Neuromuscular Blockade.

2. Clinical Question

The clinical question is descriptive: it concerns the frequency of a defined postoperative finding, rather than whether one anesthetic strategy causes better outcomes than another. Because the study is observational, any associations with reversal agents or intra-operative monitoring would need to be interpreted as associations, not as effects of assigning those practices. The registry identifies the endpoint and timing, but does not provide an outcome value or analysis comparing patient groups.

3. Trial Design

The registry describes an epidemiological, prospective, multicenter observational study conducted in Portugal. Its stated purpose is to determine the incidence of postoperative residual neuromuscular blockade, defined using a train-of-four ratio threshold, at arrival in the post-anesthesia care unit. The record lists the study as completed. The start date is 2018-06-18, and the primary completion date is 2019-07-16.

Eligible participants are described as adults aged at least 18 years who are admitted for elective surgical procedures requiring general anesthesia with neuromuscular blocking agents. The brief description gives n=360, whereas registry enrollment is 366. These are distinct registry entries: the enrollment figure should not be taken as the number with a recorded primary endpoint, because the analyzed population and outcome denominator are not reported in the registry record.

There is no randomized allocation or assigned treatment contrast in this design. The record describes outcomes involving reversal-agent use and intra-operative monitoring, but does not establish that those practices were assigned by the study. Comparisons involving them would therefore be observational. Patient characteristics, clinical decisions and other factors could differ across groups; the registry does not report an adjustment strategy or group-specific estimates that would clarify how such differences were handled.

The primary assessment is scheduled no more than 10 minutes after operating room exit, and is described as an average of 3 consecutive train-of-four stimulations. The registry lists five outcome measures and three named secondary outcomes. It records zero analyses. No study protocol details beyond the registry description, recruitment flow, analysis population, or result estimates are 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 Percentage of Patients With Postoperative Residual Neuromuscular Blockade, measured over No more than 10 minutes after operating room exit.

The primary endpoint is the percentage of patients arriving in the post-anesthesia care unit with a train-of-four (TOF) ratio < 0.9. The assessment is described as the average of 3 consecutive TOF stimulations, made no more than 10 minutes after the patient leaves the operating room. The outcome parameter is a count of participants, although the endpoint description expresses the target as a percentage.

In general, a TOF ratio is a measure derived from responses to a sequence of nerve stimulations. A threshold turns that measurement into a binary classification for this endpoint: a patient either meets the definition of residual blockade or does not. Counting participants who meet the definition can support an estimate of how common the finding is in the observed study population. The percentage is useful for describing frequency, but its interpretation depends on a clearly defined denominator and complete, consistently timed measurement.

The stated timing matters because the endpoint concerns status near arrival in post-anesthesia care, rather than blockade at an unspecified later point. Averaging consecutive stimulations is the measurement procedure specified by the registry. The registry does not report the observed count or percentage, the number assessed, missing measurements, or any uncertainty interval. Consequently, the endpoint definition alone does not establish the observed incidence or its precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a prospective observational study and defines its primary outcome as a count of participants with postoperative residual neuromuscular blockade. The endpoint is also phrased as a percentage. These descriptions are compatible: the count is the number meeting the event definition, while a percentage expresses that count relative to an assessed population. The record does not state the number assessed or the observed count, so neither an estimate nor its precision can be reconstructed.

What does the TOF threshold mean statistically?

As a general statistical idea, a binary endpoint converts a measurement into one of two categories using a specified threshold. Here, the registry defines the event as a TOF ratio < 0.9. The endpoint is not a continuous comparison of TOF values; it is a count of participants classified by that rule. Changing a threshold can change which observations qualify, so the definition is part of the outcome and should be kept distinct from the results. The registry also specifies an average of 3 consecutive stimulations, which describes how the measurement is formed.

For a binary outcome, a frequency estimate is commonly accompanied by an uncertainty interval. In general, a confidence interval communicates the statistical uncertainty around an estimate, rather than guaranteeing that the true value lies within a particular interval. Its width depends in part on the amount of observed information and the frequency of the event. The registry record gives no primary estimate or confidence interval, so the precision of the incidence estimate cannot be assessed.

Why is the design observational?

The study is described as observational and prospective, with no randomized allocation stated. Prospective collection means the study is described as following the population and assessing the outcome according to a planned direction in time; it does not make treatment choices randomized. The record's secondary questions about reversal-agent use and intra-operative monitoring are therefore questions about associations in observed care. In general, patients receiving different care may differ in other ways that are related to the outcome. A causal interpretation would require appropriate design and analysis assumptions, and the registry does not report an analysis plan or adjusted estimates.

For randomized trials, an assigned comparator can help balance prognostic factors on average. That logic does not apply as an automatic guarantee in an observational comparison. Statistical adjustment can address measured differences under its assumptions, but cannot ensure removal of unmeasured confounding. The registry does not state which covariates were collected, whether adjustment was done, or how missing covariate data were treated. The secondary outcomes therefore cannot be interpreted as treatment effects from the information in the record.

What can a planning illustration tell a reader?

In general, a sample-size calculation is a planning exercise: it describes the amount of information that might be needed for a chosen effect and statistical assumptions. A planning illustration based on an observed effect is not the trial's original design justification and is not evidence that the study had a particular probability of detecting an effect. Such illustrations are not observed power. The registry does not report its own sample-size justification, and no particular planning output or observed effect is stated in the record. Any planning scenario should therefore be read as conditional on its assumptions, not as a result of this study.

For a binary outcome, a planning calculation depends on assumptions about the event frequency, the effect to detect, allocation, significance level and statistical approximation. The stated assumptions for the illustrative calculations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. The record does not describe a randomized two-arm study, so those assumptions do not establish that the clinical study used equal allocation or had two assigned arms. They are calculation assumptions rather than design details.

Why does uncertainty matter?

General statistical interpretation should distinguish the point estimate from its uncertainty and from the study's design. A percentage, if reported, would describe the observed population under the endpoint definition. A confidence interval would indicate sampling uncertainty under the interval method. Neither alone resolves measurement error, selection, missing outcomes, or differences between the study population and other settings. Here, the registry provides no incidence estimate and no interval, so readers cannot assess either the observed frequency or its statistical precision.

The primary outcome is measured shortly after operating room exit, at no more than 10 minutes, according to the registry. That operational window supports a focused description of postoperative status at a particular time. It does not by itself answer how long a finding persists, whether it changes later, or whether it is associated with other clinical outcomes. Those questions would require additional outcome definitions and reported analyses, which are not given in the registry record.

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("Patients Proposed for Elective Surgical Procedures")
n      <- c(366)
events <- c(20)
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  Patients Proposed for Elective Surgical Procedures  366  20  5.5  3.4  8.3  3.6  8.3  3.6  8.3

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including the primary outcome and named secondary outcomes concerning severe residual blockade, reversal-agent use, and intra-operative monitoring. It records zero analyses. The registry record does not report a statistical plan describing which comparisons were confirmatory, how outcomes were prioritized beyond the primary designation, or whether any multiplicity adjustment was planned or used.

In general, testing multiple hypotheses can increase the chance of obtaining at least one apparently notable result by chance if each is interpreted without accounting for the set of tests. Adjustment procedures can address some forms of this problem, but the appropriate approach depends on the questions and analysis plan. No test results or adjustment methods are reported, so multiplicity cannot be evaluated from the record.

Missing-data handling is also not reported in the registry record. There is no description of the number of participants with a successful primary measurement, the reasons measurements may be absent, or how missing endpoint values were treated. Because the endpoint is a percentage, its denominator is essential; the enrollment entry of 366 does not establish how many participants contributed to that outcome.

The analysis population is not reported in the registry record. The record does not specify whether analyses included all enrolled participants, only those with an evaluable measurement, or another defined group. It also does not report protocol deviations, exclusions, or a participant flow account. These omissions limit interpretation of representativeness, denominator choice, and the potential effect of missing observations on the estimated incidence.

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: pulmunary thromboembolism (0.3%), severe residual neuromuscular blockade (0.3%).

The registry lists adverse-event entries for the group titled Patients Proposed for Elective Surgical Procedures. It records 366 participants at risk for serious adverse events and 2 affected, with 366 at risk for other adverse events and 10 affected. Deaths are recorded as 0. These are the entries in the adverse-event record; they are not the primary outcome incidence.

The registry also identifies Pulmunary thromboembolism and Severe residual neuromuscular blockade among the top serious-event terms, each listed as 0.3%. The first term is spelled Pulmunary in the record. The registry does not provide further event-level detail, timing, attribution, or a comparison group for these terms.

In general, an adverse-event count describes events recorded under the registry's reporting conventions. It does not, by itself, establish that an event was caused by a treatment, procedure, or study participation. This study is observational, and the record does not provide an attribution assessment or comparative safety analysis. The serious-event figures should therefore be read as descriptive registry entries, not as causal estimates or as evidence about relative safety.

The terms and counts also have different roles from the primary endpoint. The primary outcome uses a specified TOF threshold at a specified postoperative time; serious adverse events are recorded separately. The registry does not explain how the serious-event terms overlap with the primary endpoint or with other adverse events, so those categories should not be combined or treated as interchangeable.

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

The study asks a clinically focused descriptive question: how often a defined TOF finding is present shortly after elective surgery under general anesthesia involving neuromuscular blocking agents. The record makes the definition explicit, including the < 0.9 threshold, the average of 3 consecutive stimulations, and measurement no more than 10 minutes after operating room exit. This clarity helps readers understand what the intended endpoint represents.

However, the record does not report the observed primary outcome count or percentage. It therefore does not establish the frequency of residual blockade in the enrolled or assessed population. It also does not report a confidence interval, participant flow, or an evaluable denominator. The outcome cannot be judged as common or uncommon, and its precision cannot be assessed from the registry record.

The record does not test an assigned intervention against a randomized control. Reversal-agent use and intra-operative monitoring are listed as subjects of secondary association outcomes, not as randomized strategies. Even if group differences were available, an observational association would not by itself show that a practice caused a difference; patient characteristics and clinical circumstances could also be related to both practice and outcome. The registry provides no such group estimates or adjustment details.

Completion status indicates that the study is registered as completed, not that all results are present in the record. The design and endpoint can be described, but the primary finding and secondary analyses cannot. The adverse-event entries provide separate descriptive counts and terms, not a substitute for the primary incidence result or a causal safety comparison.

In general, a study's relevance beyond its participants also depends on who was enrolled, how measurements were obtained, and how closely other settings resemble the study population and care context. The registry describes adult elective-surgery patients in Portugal, but gives no site-level, demographic, or case-mix detail. Accordingly, the record supports understanding of the intended question and measurement approach, but not conclusions about incidence, causal effects, or applicability to populations not described.

14. Why This Trial Matters Statistically

This study illustrates why an endpoint definition and an outcome estimate are different kinds of information. The registry states exactly how postoperative residual neuromuscular blockade was to be classified: a TOF ratio < 0.9, based on an average of 3 consecutive stimulations, assessed no more than 10 minutes after operating room exit. That operational detail makes the intended measurement interpretable. But without the observed count, denominator, or percentage, it cannot answer the central descriptive question.

The record also highlights the role of study design in interpreting comparisons. Questions about reversal agents and intra-operative monitoring may be important, but the study is observational and does not describe randomized assignment. Any association between a practice and the outcome would need to be considered alongside potential differences in patients and clinical circumstances. Naming an association outcome does not establish that it was analyzed or that a causal effect was estimated.

For statistical readers, the gap between registry enrollment and the described study population reinforces the need for transparent participant flow. Enrollment is 366, while the brief description specifies n=360. Without a reported analysis population and endpoint denominator, neither number should be silently treated as the number contributing to an incidence estimate. Reporting the number assessed and the handling of missing measurements would be necessary to evaluate the denominator and possible selection effects.

Finally, the registry records five outcome measures but zero analyses. This distinction matters: a set of registered questions is not the same as a set of reported estimates. Results, uncertainty intervals, analysis methods and missing-data handling are needed to assess statistical strength. The available record is informative about the intended clinical question and measurement, but leaves the key empirical result unavailable.

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.

A central limitation of the registry record is that it does not report the primary outcome result. The incidence count, percentage, denominator, and uncertainty interval are not reported in the registry record. This prevents assessment of both the observed frequency and how precisely it was estimated.

The study description gives n=360, while enrollment is 366. The record does not explain this difference or provide participant flow. It does not state how many people were eligible, enrolled, measured, excluded from analysis, or missing a TOF assessment. The actual analysis population is not reported in the registry record, so the enrollment figure cannot be treated as the endpoint denominator.

The study is observational, and the registry does not report how differences in patient characteristics or care decisions were addressed in analyses of reversal-agent use or monitoring. It does not provide adjusted or unadjusted association estimates, covariate definitions, or methods for confounding control. Consequently, the planned secondary questions cannot be evaluated, and any possible association could not be interpreted causally from this record.

The registry specifies a measurement window and a threshold, but does not report additional measurement-quality information, such as the distribution of measurements or agreement across assessors. It also does not report the detailed protocol, site-specific enrollment, population characteristics, or outcome ascertainment procedures beyond the primary endpoint description. These omissions constrain evaluation of measurement consistency and applicability.

Finally, five outcome measures are listed, but no analyses are recorded. The statistical analysis plan, multiplicity approach, missing-data methods, and sample-size justification are not reported in the registry record. The planning assumptions associated with illustrative calculations do not replace the study's own design rationale. Together, these limitations mean the registry supports a description of the intended study, but not a substantive estimate of its primary result or its statistical robustness.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Incidence of Postoperative Residual Neuromuscular Blockade in Portugal — NCT03417804.
• Registry record last updated 2021-07-06; status last verified 2021-06.
• Results first posted 2021-07-06.
• 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

NCT03417804 is a completed, prospective, multicenter observational study in Portugal sponsored by Centro Hospitalar do Porto. The registry lists enrollment of 366. The brief description concerns adults aged at least 18 years undergoing elective procedures requiring general anesthesia with neuromuscular blocking agents and specifies n=360.

The primary outcome is the percentage of patients arriving in the post-anesthesia care unit with a TOF ratio < 0.9, measured as an average of 3 consecutive stimulations no more than 10 minutes after operating room exit. The registry lists five outcome measures, three named secondary outcomes, and zero analyses.

The observed primary result, denominator, analysis population, statistical plan, and missing-data approach are not reported in the registry record. Adverse-event entries list 2 serious events, 10 other events, and 0 deaths in the group titled Patients Proposed for Elective Surgical Procedures; the record separately lists two serious-event terms at 0.3% each.