The Effect of Deep Neuromuscular Block on Surgical Condition During Laparoscopic Colorectal Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effect of Deep Neuromuscular Block on Surgical Condition During Laparoscopic Colorectal Surgery (NCT02580188), a randomized phase 4 study. The primary outcome is Number of Participants With Increased Intra-abdominal Pressure (IAP) Alarm as > 15 mmHg.

2. Clinical Question

3. Trial Design

The registry identifies this as a phase 4, randomized, parallel-group trial sponsored by Seoul National University Bundang Hospital. It is marked completed, with a start date of 2015-03-24 and a primary completion date of 2016-06-16. The registry lists quadruple masking. The brief summary instead describes the study as double-blinded, so the masking description is inconsistent within the registry record; further details about who was masked are not reported in the registry record.

Two regimens were compared. The moderate-block group received continuous rocuronium infusion to maintain a train-of-four count of 1–2, followed by neostigmine and glycopyrrolate for reversal at the end of surgery. The deep-block group received continuous rocuronium infusion to maintain a post-tetanic count of 1–2, followed by sugammadex for reversal. The comparison therefore reflects the assigned regimens as described, rather than a difference in block depth alone with all other care held constant.

The enrollment field lists 70 participants, while the brief summary says that 96 patients were randomized. The posted primary outcome lists 32 participants in each outcome group. These entries do not align, and the registry record does not explain the difference. The original sample-size rationale, allocation-concealment procedures, and detailed conduct of randomization are not reported in the registry record. The analysis population and handling of withdrawals are also 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 Number of Participants With Increased Intra-abdominal Pressure (IAP) Alarm as > 15 mmHg, measured over intraoperative, an averrage of 3 hour.

The primary endpoint counts participants with an increased intra-abdominal pressure alarm during the operation. The endpoint title specifies an event as an alarm above 15 mmHg. The entry describes intra-abdominal pressure as maintained at 12 mmHg during pneumoperitoneum and states that pressure was measured with a separate machine connected to the carbon dioxide gas injection line.

This is a binary participant-level outcome: each participant is counted according to whether the event was recorded, rather than by the number of alarms or the duration of elevated pressure. Such an endpoint can make the frequency of an event easy to compare between groups, but it does not by itself describe how high the pressure went, how long an alarm lasted, or the clinical consequences of an alarm. Those details are not reported in the registry record.

The registry gives the timeframe as intraoperative, an average of 3 hour. There is a wording inconsistency: the endpoint title describes an alarm above 15 mmHg, whereas the description says that the pressure alarm was set below 15 mmHg. The record does not clarify this discrepancy, so the endpoint should be interpreted according to the posted label while keeping the ambiguity in mind.

7. Results Posted in the Registry

• Deep Block: 18.8% (6/32) versus 43.8% (14/32) on control; risk difference -25.0 percentage points (95% CI -46.9 to -3.1), risk ratio 0.43 (0.19–0.97); unadjusted two-proportion z-test p = 0.031.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary comparison is between two independent parallel groups. The posted endpoint is a participant count, so the event outcome can be expressed as a group-specific event probability and compared across groups. The registry reports a risk difference, which expresses the difference in event probability on an absolute scale. A negative value for deep block relative to moderate block indicates a lower observed event probability in the deep-block group. General statistical interpretation: the risk difference preserves the direction and absolute scale of a comparison, but its practical importance depends on context that is not quantified in the registry record.

What does a risk difference represent?

A risk difference compares the probability of an event in one group with the probability in another. It is not a count difference, and it does not describe the number of alarms per participant. Here, the posted estimate is -0.25, with deep block designated as the comparison group against moderate block. The sign indicates the direction of the recorded contrast. The registry also supplies event counts and group sizes, which provide the underlying descriptive context for that estimate.

Other measures can describe a binary comparison on a relative scale, such as a risk ratio or odds ratio. The record includes relative measures, but their reported bounds have more than three decimal places and are not reproduced. In general, relative and absolute measures answer different questions: an absolute measure describes a difference in event probability, while a relative measure describes how event probabilities or odds compare proportionally. Neither measure alone determines the clinical importance of the result.

How should the p-value be read?

The unadjusted p-value is 0.031. In general, a p-value describes how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, nor does it measure the probability that the result will replicate. The word unadjusted matters because the registry does not report a multiplicity adjustment for this comparison. It also does not report the detailed statistical model or test used to obtain the p-value, so those specifics are not reported in the registry record.

A p-value should be read with the estimated effect and its confidence interval. A threshold-based interpretation alone discards information about direction and magnitude. The estimate and interval describe the scale and uncertainty of the comparison; the p-value is a separate summary of compatibility with a null model. The registry record does not state a prespecified threshold for statistical significance or provide a statistical analysis plan.

What does the confidence interval add?

In general, a confidence interval gives a range of estimates that are compatible with the data under the method used to construct it. It makes uncertainty visible rather than presenting the point estimate as exact. For the posted risk difference, both interval limits are below zero, with the upper limit near zero. That pattern indicates that the interval includes estimates of a small difference as well as estimates farther from zero in the same direction. The interval does not account for possible bias from missing data, outcome misclassification, or inconsistencies in the registry entries.

General explanation: interval width is affected by the amount of information in the data and by variation in the outcome. A less precise estimate generally has a wider interval. The record does not report an interval-construction method, any adjustment for covariates, or a model specification, so those methodological details are not reported in the registry record.

Why can event counts be informative but incomplete?

Counts show how many participants had the recorded event in each displayed group. They are useful for checking the direction of the comparison and understanding its observed basis. Counts alone do not convey uncertainty, which is why the effect estimate and confidence interval matter. They also cannot answer questions about timing, repeated alarms, or severity, because the endpoint is reported as the number of participants with an event and no further event-level detail is included.

The registry presents 32 participants in each primary-outcome group, but other parts of the record report different enrollment information. This inconsistency limits confidence about how the outcome groups relate to the overall randomized population. The registry record does not explain whether the outcome counts reflect all randomized participants, an analysis subset, or another analysis population. That information is not reported in the registry record.

What is not established by these methods?

The displayed comparison is unadjusted, and no analyses are listed in the registry. The record does not report covariate adjustment, subgroup analyses, a method for handling missing observations, or an approach to repeated measurements. It also does not report whether the primary outcome definition and analysis were set before results were examined. Without those details, the posted statistics can be described as the recorded unadjusted comparison, but the broader analytical process cannot be reconstructed from the registry record.

General statistical explanation: randomization is intended to make treatment groups comparable on average, but it does not eliminate every concern about conduct, measurement, missingness, or selective reporting. Interpretation still depends on a clear endpoint, reliable outcome ascertainment, and a well-described analysis population. The record's inconsistencies in masking, enrollment, and endpoint wording are relevant when assessing how securely the statistical comparison answers the intended question.

10. Confidence Intervals and Precision

The posted risk difference is -0.25, and its confidence interval lies entirely below zero. This gives a range of values compatible with the analysis that favors a lower event probability in the deep-block group, while the endpoint's wording and the analysis population remain uncertain. The interval's upper boundary is close to zero, so the data are also compatible with a comparatively small difference. The lower boundary is farther from zero, reflecting that larger differences in the same direction are also compatible with the analysis.

Confidence intervals describe statistical uncertainty under the method used; they do not include every source of uncertainty. They cannot correct for an unclear event definition, possible missing data, or inconsistencies in the registry record. The record does not report the interval method or details of the analysis population. Thus the interval should be understood as precision for the posted comparison, not as a full measure of uncertainty about the study's conduct or the endpoint's meaning.

General explanation: narrower intervals indicate greater precision, while wider intervals indicate less precision. Precision is distinct from whether an effect is important in practice. The registry record does not provide a threshold for a clinically meaningful risk difference, so the reported interval cannot establish whether values within its range would be important to patients or clinicians.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed effect, not a report of the trial's original design calculation. The listed figures are participants per arm, not total participants or total events. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Each planning row uses a stated fraction of the observed effect as the effect to detect. The trial's own original design assumptions are not reported in the registry record.

The 80% power column describes the planned number of participants per arm for a design with an 80% chance of detecting the specified effect under the stated assumptions, if that effect and those assumptions hold. The 90% power column describes the corresponding planning target for a 90% chance. These are design quantities, not guarantees about what a future study will find. This is not observed power.

The rows that plan for 100%, 75%, and 50% of the observed effect illustrate how the assumed effect size changes the planning requirement. A smaller effect is harder to distinguish from random variation under the same general framework, so planning for a smaller effect requires more participants per arm. The curve presents the same general relationship visually; it should be read as an illustration tied to these assumptions, not as a separate result from the trial.

Because the calculation uses the observed effect, it should not be treated as independent confirmation of that effect or as evidence that the completed trial had a particular probability of success. The record does not report the original target sample size rationale, and the enrollment figures elsewhere in the record are inconsistent. Those limitations are separate from the stated planning assumptions.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.438; treatment proportion p₁ = 0.188; average p̄ = 0.312.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6555 = 1.2848.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6312 = 0.5312.
4. n = (1.2848 + 0.5312)² / (-0.2500)² = 52.8, rounded up to 53 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.4375                          # control proportion
p1 <- 0.1875                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(2580188)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 53 (80% power), 71 (90% power)
 75% of observed effect: n per arm = 100 (80% power), 133 (90% power)
 50% of observed effect: n per arm = 235 (80% power), 314 (90% power)
power.prop.test: 52.8 
Simulated power at n = 53 per arm: 0.813 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry posts one primary outcome in the results represented and lists zero posted analyses. It also lists zero posted secondary outcomes. The brief summary mentions surgical rating score, but no secondary outcome results for that measure are posted in the registry record. A mention in a summary does not establish how that outcome was defined, analyzed, or interpreted.

The record does not report a multiplicity plan, whether multiple comparisons were prespecified, or whether any adjustment was made for examining more than one outcome or analysis. The reported p-value is unadjusted. Without a statistical analysis plan, it is not possible to determine from the registry record how the primary outcome was prioritized relative to other possible measures or analyses. The record also does not report interim analyses or stopping rules.

Missing-data handling is not reported in the registry record. The results do not state whether any primary-outcome values were unavailable, how participants with missing outcomes were handled, or whether sensitivity analyses were conducted. The analysis population is not reported in the registry record; specifically, the record does not say whether the displayed comparison follows all randomized participants or a defined subset.

The mismatch among the enrollment field, brief summary, and primary outcome group sizes makes the analysis population particularly important, but the registry does not resolve it. Nor does the record explain the difference between its quadruple-masking classification and the summary's double-blinded description. These gaps do not change the posted numbers, but they limit the ability to assess how analyses were selected and how completely the comparison represents the randomized groups.

14. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists serious adverse event figures for groups labeled Group M and Group D. For each group, the number at risk is 35, and the number affected by a serious adverse event is 0. The entry also reports 0 for other affected participants in each group. No deaths are reported in the adverse-event fields.

These are the posted counts for the registry's adverse-event categories. They should not be read as proof that no adverse events occurred: the displayed serious-event figures concern events meeting the registry's serious category, and the other category is also reported as zero affected. The record does not provide event descriptions, definitions, follow-up duration, or further detail about collection and reporting. The adverse-event groups are labeled differently from the primary-outcome arms, and the registry record does not explain that labeling.

General statistical explanation: zero recorded events in a group does not establish that the underlying event risk is zero. Interpretation depends on the amount of observation, event definitions, and completeness of reporting. The record's adverse-event entry alone cannot characterize safety across all possible outcomes or establish a causal relationship between a regimen and an event.

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

The posted result describes a difference in the recorded frequency of an intraoperative pressure-alarm outcome between two assigned regimens. The primary outcome lists 14 participants with the event in the moderate-block group and 6 in the deep-block group, with 32 participants in each group. The risk-difference estimate is -0.25, and the unadjusted p-value is 0.031. The confidence interval is entirely below zero, although its upper limit is close to zero.

This result does not by itself establish that block depth alone caused the difference. The assigned regimens also differed in the reversal drug used at the end of surgery. Nor does the result establish a difference in surgical rating score or other outcomes: although the brief summary refers to a surgical rating score, secondary results are not posted in the registry record.

The endpoint is not completely clear because its title describes an alarm above 15 mmHg while its description says the pressure alarm was set below 15 mmHg. The registry also gives conflicting information about enrollment and masking. Those issues do not permit a different result to be inferred, but they affect how confidently the recorded comparison can be mapped onto a precisely defined outcome and study population.

The result should therefore be read as an unadjusted statistical comparison of the posted counts, with the stated uncertainty and record limitations. The registry does not report a clinical-importance threshold, a complete analysis plan, missing-data handling, or an analysis population. Statistical evidence of a difference is not the same as evidence about the practical importance of that difference. The posted data do not establish what would happen in other settings or populations.

16. Why This Trial Matters Statistically

This trial illustrates why the estimand and the treatment contrast need to be clear before interpreting a group comparison. The intended contrast concerns deep versus moderate neuromuscular block, but the arm descriptions also specify different reversal drugs. Statistically, the estimate compares the recorded regimens as a whole. Attributing the observed contrast to one component alone would go beyond the comparison described in the registry.

It also illustrates the value of reading event counts, an effect estimate, a confidence interval, and a p-value together. Counts show the observed basis of the result; the risk difference gives an absolute-scale contrast; the interval communicates uncertainty; and the unadjusted p-value describes compatibility with a null model under assumptions. None of these summaries substitutes for the others, and none supplies a clinical-importance threshold that the registry does not report.

Finally, the record demonstrates that statistical interpretation depends on data-definition and reporting quality as well as numerical analysis. The endpoint wording, enrollment entries, and masking descriptions are not fully consistent. The absence of a reported analysis population, missing-data approach, and multiplicity plan limits assessment of the result's analytical context. These are not merely formatting issues: they determine what population and outcome the displayed estimate can be understood to represent.

For biostatisticians and clinical researchers, the central lesson is to separate what the estimate says from what the registry does not document. The posted comparison has a clear direction and a reported interval, but its scope is bounded by the record's definitions and omissions. A precise description of the contrast and a transparent account of the analysis population are essential complements to the numerical result.

17. 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.

Several limitations are specific to this registry record. First, the endpoint title describes increased intra-abdominal pressure as an alarm above 15 mmHg, while the endpoint description states that the alarm was set below 15 mmHg. The record does not reconcile these statements. It also gives the timeframe as intraoperative, an average of 3 hour, without further detail about how the measurement period was defined.

Second, the record contains inconsistent participant information: the enrollment field lists 70, the brief summary says 96 patients were randomized, and the primary outcome reports 32 participants in each group. No explanation of these differences is reported in the registry record. It is therefore not possible to establish from these entries how the displayed outcome groups relate to the full randomized population.

Third, masking is listed as quadruple in the trial-design fields, whereas the brief summary says double-blinded. The identities of the masked parties and any practical masking procedures are not reported in the registry record. The arm descriptions also pair different block targets with different reversal drugs, limiting interpretation as an isolated comparison of block depth.

Finally, the registry does not report detailed eligibility criteria, baseline characteristics, missing-data handling, the analysis population, an analysis plan, or a multiplicity approach. It posts no secondary outcome results, despite the summary's mention of surgical rating score. These omissions limit assessment of generalizability, robustness, and the full set of outcomes considered.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: The Effect of Deep Neuromuscular Block on Surgical Condition During Laparoscopic Colorectal Surgery — NCT02580188.
• Registry record last updated 2019-03-13; status last verified 2019-03.
• 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.

21. Record Summary

The registry describes a completed, randomized, parallel-group phase 4 trial of deep versus moderate neuromuscular block during elective laparoscopic colorectal surgery, sponsored by Seoul National University Bundang Hospital. Its primary posted outcome is the number of participants with an increased intra-abdominal pressure alarm. The primary outcome lists 14 events among 32 participants in the moderate-block group and 6 among 32 in the deep-block group, with a risk difference of -0.25 and an unadjusted p-value of 0.031.

The interpretation is limited by inconsistent descriptions of the endpoint threshold, enrollment, and masking. The registry record does not report the original sample-size rationale, analysis population, missing-data handling, or multiplicity plan. No secondary outcome results are posted in the record.