Effects of Neuromuscular Blockade Level and Intra-abdominal Pressure on Surgical Conditions and Cardiopulmonary Responses During Laparoscopic Colon Surgery With the Trendelenburg Position: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Neuromuscular Blockade Level and Intra-abdominal Pressure on Surgical Conditions and Cardiopulmonary Responses During Laparoscopic Colon Surgery With the Trendelenburg Position (NCT02249585), a randomized na study. The primary outcome is Cardiac Index.

2. Clinical Question

3. Trial Design

The registry describes a randomized, triple-masked, parallel trial and lists the study as completed. The recorded enrollment is 131. The phase is listed as NA. The sponsor is Seoul National University Hospital. The study start is recorded as 2014-09 and primary completion as 2016-10.

The arm descriptions identify a reference group receiving conventional neuromuscular blockade with standard abdominal pressure, a group receiving deep blockade with standard pressure, and a group receiving deep blockade with low pressure. The arm-level cardiac-index summaries report 43 participants for the reference group, 44 for the deep-block, standard-pressure group, and 44 for the deep-block, low-pressure group. These are the group sizes attached to the posted endpoint summaries; they should not be taken as a complete account of the analysis population or participant flow.

Randomization and masking are stated, but details of the randomization procedure and the people masked are not reported in the registry record. The registry also does not report allocation concealment, the protocol for implementing pressure or blockade conditions, or whether any planned groups were omitted from the posted arm descriptions. The listed interventions include standard and low abdominal pressure, as well as conventional and deep neuromuscular blockade.

The primary endpoint is a continuous measure, reported as a mean with standard deviation. Cardiac index was measured 30 min after onset of laparoscopy using an arterial waveform analysis system from the radial artery. Five secondary outcomes are listed. The record has six outcome measures, while the registry’s analysis count is 0; detailed information about the trial’s original analysis methods is 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 Cardiac Index, measured over 30 min after onset of laparoscopy.

Cardiac index is the primary endpoint. The registry reports it as a mean continuous measure, with the unit L/min/m^2, at 30 min after onset of laparoscopy. It describes measurement with an arterial waveform analysis system from the radial artery. The posted summaries give a group mean and standard deviation for each listed arm.

In general, cardiac index expresses cardiac output in relation to body surface area. It is used as a measure of cardiovascular function, making it relevant to a study whose stated purpose includes examining cardiac responses during laparoscopic surgery in the Trendelenburg position. The registry record identifies this specific measurement time, but further details about measurement procedures, repeated measurements, or the choice of this time point are not reported in the registry record.

The endpoint is a measurement at a defined time during surgery, rather than a clinical event tracked over time. A difference in group means describes an average contrast; it does not show how individual measurements were distributed or establish why any difference occurred. The outcome should therefore be read alongside its variability and the uncertainty around the estimated contrasts. The posted summary does not by itself describe every aspect of cardiopulmonary function or surgical conditions.

7. Results Posted in the Registry

• DS(Deep Block With Standard Pressure): mean 2.70 versus 2.60 on control; difference 0.10 (95% CI -0.30 to 0.50), standardized effect d = 0.11; z-test p = 0.624.
• DL(Deep Block With Low Pressure): mean 2.70 versus 2.60 on control; difference 0.10 (95% CI -0.26 to 0.46), standardized effect d = 0.12; z-test p = 0.590.

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is summarized with means and standard deviations because cardiac index is treated as a continuous measurement. A mean describes the central value for a group, while a standard deviation describes variability among measurements around that mean. In general, neither statistic alone captures the full distribution; unusual values or asymmetry may affect how well a mean-based comparison represents the data. Distributional details are not reported in the registry record.

What does a mean difference represent?

The comparison estimates are expressed as mean differences against the group receiving conventional blockade with standard pressure. A positive difference means the comparison group’s reported mean is higher than the reference mean; a negative difference would mean it is lower. Both displayed estimates are 0.1. This is an unadjusted contrast in group averages, not a difference adjusted for baseline characteristics or other possible influences. Adjustment methods are not reported in the registry record.

The listed comparisons use the same reference group. The first contrasts deep blockade with standard pressure against conventional blockade with standard pressure. The second contrasts deep blockade with low pressure against that same reference. Since the second contrast changes blockade and pressure together, it does not isolate the effect of low pressure on its own. The record’s arm descriptions do not supply a conventional-block, low-pressure comparison.

How should the confidence intervals be read?

In general, a confidence interval describes the range of effect estimates reasonably compatible with the data and the calculation method. It communicates uncertainty around an estimate rather than the range of individual participant measurements. Both intervals for the mean differences span zero, meaning the data are compatible with no average difference as well as with differences in either direction. The intervals are unadjusted recalculations from the posted summary statistics. Their interpretation depends on the assumptions used in that calculation; the registry does not describe a separate sponsor confidence-interval method.

What does a p-value contribute?

The reported unadjusted p-values are 0.624 and 0.59. In general, a p-value measures how unusual data at least as incompatible with a specified null model would be if that model and the calculation assumptions held. It is not the probability that the null model is true, and it does not measure clinical importance. Because these are unadjusted p-values, they do not account for testing multiple endpoints or comparisons. The record does not report a multiplicity plan or a prespecified threshold for interpreting results.

The posted means, standard deviations, and comparison summaries support a straightforward comparison of group averages. The registry record does not report the handling of missing measurements, the analysis population, checks of model assumptions, or methods for adjustment. Consequently, the recalculated contrasts should not be mistaken for a fully specified trial analysis. No sponsor analysis for cardiac index is described in the registry record, and the reported analysis count is 0.

Why do variability and standard errors matter?

In general, the standard error reflects the uncertainty in an estimated group mean or contrast, whereas the standard deviation reflects variability among individual observations. Standard errors are influenced by both measurement variability and the amount of information contributing to an estimate. The posted arm summaries include standard deviations, while the comparison calculations use the group summaries to estimate uncertainty in the mean differences. The exact recalculated standard errors are not needed to understand the central point: the confidence intervals are broad enough to include both negative and positive mean differences.

The comparison data also include pooled standard deviations and standardized-effect calculations. In general, a pooled standard deviation combines variability information across groups, and a standardized effect expresses a mean difference relative to a variability scale. Such measures can help place a contrast in context, but they do not replace the outcome’s original units or its confidence interval. The exact standardized-effect values and pooled standard deviations are not because the mean-difference estimates and intervals are more directly interpretable in the endpoint’s units.

What assumptions underlie planning illustrations?

The sample-size illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect targeted is a stated fraction of the observed effect, and the illustrations are based on that observed effect rather than the trial’s original design. In general, a normal approximation uses a mathematical model for the sampling distribution of an estimate. Its suitability depends on design and data conditions, which the registry record does not describe in detail. The record does not report the assumptions used for the trial’s original design or its sample-size justification.

These calculations have a planning purpose: they indicate the per-arm sample size associated with the stated target effect and power under the listed assumptions. They do not establish what the trial was designed to detect, and they do not account for unreported features such as missing data, multiplicity, or departures from the planning assumptions. They should be interpreted separately from the observed endpoint results.

10. Confidence Intervals and Precision

The mean-difference estimates are small in the endpoint’s reported units, but their precision is limited. For each comparison, the confidence interval crosses zero and extends to both negative and positive values. This means that the posted summaries do not tightly pin down the direction or magnitude of the average contrast. The intervals are unadjusted recalculations based on the reported group summaries.

A confidence interval is not a statement that individual measurements fall inside its bounds. It describes uncertainty about the estimated mean difference under the calculation method. In general, a narrower interval indicates greater precision, while a wider interval leaves more possible values compatible with the data. Here, the intervals allow a range that includes no mean difference and contrasts in either direction. Their breadth should be considered alongside the point estimates rather than relying on the point estimates alone.

The group standard deviations are 1.0, 0.9, and 0.7, and the arm summaries report 43, 44, and 44 participants, respectively. These summaries provide context for the uncertainty, but they do not resolve limitations in the analysis information. The registry record does not report the amount of missing endpoint data, whether all randomized participants contributed to these summaries, or a prespecified precision target. It also does not report an adjusted analysis that might produce a different estimate or interval.

The unadjusted p-values, 0.624 and 0.59, are consistent with the intervals spanning zero, but p-values and intervals answer related rather than identical questions. A p-value does not tell readers how wide the range of plausible differences is. For assessing precision, the confidence intervals are more informative than a binary statement about statistical significance. The posted evidence supports caution: it does not establish a precise effect, and it does not rule out differences in either direction.

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 expressed as participants per arm, not total events. They use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning row targets a stated fraction of the observed effect, and the calculations are based on the observed effect rather than the trial’s original design. The trial’s original sample-size assumptions and justification are not reported in the registry record.

The 80% power column gives the number of participants per arm associated with an 80% chance of detecting the specified effect under the planning assumptions, if that effect and those assumptions hold. The 90% power column gives the corresponding per-arm figure for a 90% chance. These are prospective planning quantities; they are not outcomes measured in the trial. This is not observed power.

The rows for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect show how the planning requirement changes when the target effect is smaller than the observed estimate. A smaller effect is harder to distinguish from random variation, so it requires more participants under the same assumptions. The accompanying curve represents this relationship visually; it should be read as a planning aid, not as a record of the trial’s actual design or a guarantee of future results.

The figures are specific to the relevant comparison and its observed effect, so they should not be treated as a universal sample-size recommendation. They also rely on equal allocation and the normal approximation stated in the planning assumptions. The registry record does not report whether the actual trial used these assumptions, whether it planned for a different target effect, or whether it incorporated any allowance for missing data or multiple outcomes.

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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.100; pooled standard deviation σ = 0.951.
2. n = 2 × (1.96 + 0.842)² × 0.951² / 0.100² = 1,418.9, rounded up to 1,419 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
delta <- 0.1                      # observed difference in means
sigma <- 0.950727275795313                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2249585)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 1,419 (80% power), 1,900 (90% power)
 75% of observed effect: n per arm = 2,523 (80% power), 3,377 (90% power)
 50% of observed effect: n per arm = 5,676 (80% power), 7,598 (90% power)
power.t.test: 1419.9 
Simulated power at n = 1,419 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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 lists a primary endpoint of cardiac index and five secondary outcomes. It does not report how the trial’s original analysis addressed the possibility of multiple statistical tests. Testing multiple outcomes or comparisons can increase the chance of at least one apparently unusual result even when no underlying effects are present. In general, multiplicity procedures may adjust thresholds or otherwise account for a family of tests, but no such procedure is reported in the registry record. The comparison p-values described for cardiac index are explicitly unadjusted recalculations.

The record’s analysis count is 0. It does not provide a detailed statistical analysis plan, identify a prespecified model, or explain whether any outcomes or comparisons were selected after examining the data. It also does not report an adjustment strategy for baseline variables, repeated measurements, or other covariates. These omissions make the displayed summary comparisons useful as descriptive, unadjusted contrasts, but they do not establish how the investigators’ full analysis was conducted.

Information about missing data is also not reported in the registry record. The arm-level counts attached to the cardiac-index summaries do not establish whether all randomized participants had an outcome measurement, whether any values were excluded, or how missing measurements were handled. The record does not state whether participants were analyzed according to randomized assignment, treatment received, or another analysis population. It therefore does not support labeling the posted summaries as intention-to-treat, per-protocol, or another formal population.

These gaps matter because missingness and analysis-population choices can affect estimates and uncertainty. In general, excluding participants with unavailable measurements may lead to a different result from an analysis that uses all randomized participants, depending on why measurements are missing and how they are handled. No such mechanism or method can be inferred from the registry record. The appropriate reading is limited to the outcome summaries and unadjusted comparisons that are posted, with no claim about unreported analyses or corrections.

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 adverse-event record reports zero serious adverse events among 43 participants in the conventional-block, standard-pressure group, among 44 participants in the deep-block, standard-pressure group, and among 44 participants in the deep-block, low-pressure group. It also reports zero other adverse events among the listed at-risk participants in each of those groups. These are the registry’s recorded counts for the categories it labels serious and other adverse events.

The deaths fields are empty in the record, so deaths are not reported in the registry record. An empty value should not be interpreted as a reported zero. The record also does not provide event terms, definitions, observation duration, or additional detail about how adverse events were collected.

These figures describe what is recorded, not proof that no adverse events occurred outside the recorded categories or observation process. They do not establish that a treatment is safe or unsafe, and they should not be generalized beyond the listed groups and record. The listed counts should be read with the limitations in reporting and follow-up information in mind.

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

The posted cardiac-index summaries show group means of 2.6 for conventional blockade with standard pressure and 2.7 for each of the two listed deep-block groups. The unadjusted recalculated mean differences against the reference are 0.1 in both comparisons. The confidence intervals cross zero, and the unadjusted p-values are 0.624 and 0.59. Taken together, these summaries do not establish a clear direction or a precise size for either average contrast.

That interpretation is limited to cardiac index at 30 min after onset of laparoscopy. It is not a conclusion about all points during surgery, all cardiopulmonary outcomes, surgical conditions, or patient outcomes. The registry lists secondary measures, but their numerical results are not reported in the registry record in the registry record. A conclusion about those measures cannot be drawn from the primary endpoint summaries.

The comparisons also do not isolate every component of the treatment combinations. Deep blockade with standard pressure can be contrasted with conventional blockade at standard pressure. The comparison involving low pressure also changes the blockade condition relative to the reference. Because the listed arm descriptions do not include conventional blockade with low pressure, these comparisons do not separately estimate the pressure contrast under conventional blockade.

In general, a nonsmall p-value does not demonstrate that groups are identical, and an interval crossing zero does not rule out all potentially meaningful differences. It indicates that the data and calculation method leave uncertainty around the effect estimate. The present summaries cannot be used to claim that one treatment works, does not work, or is equivalent to another. No equivalence margin or non-inferiority framework is reported in the registry record.

The registry does not report a detailed analysis plan, missing-data methods, or analysis populations. Accordingly, the most defensible reading is descriptive: the reported means are close, while the recalculated intervals permit differences in either direction. This is a limited statistical account of one endpoint at one recorded time point, not a comprehensive assessment of the trial’s full clinical questions.

16. Why This Trial Matters Statistically

This trial raises a useful statistical issue: the treatment conditions combine neuromuscular blockade level and abdominal pressure, while the posted arm descriptions include only certain combinations. A comparison that changes more than one feature at once cannot identify the separate contribution of each feature. For the contrast involving deep blockade and low pressure, both listed treatment conditions differ from the reference group. This limits what can be attributed specifically to pressure from that comparison.

The endpoint also illustrates the difference between a point estimate and its precision. Both recalculated mean differences are 0.1, but each confidence interval spans zero and values on both sides of it. Reporting only the mean differences would conceal the uncertainty; focusing only on p-values would also omit the range of compatible effects. Interpreting the estimates together with their intervals gives a more complete account of what these summaries support.

The record’s sample-size illustrations provide another teaching point. They are planning calculations based on the observed effects and stated assumptions, not documentation of the original trial design. Smaller targeted effects require larger planned group sizes under those assumptions. Keeping planning calculations distinct from observed results prevents a retrospective calculation from being mistaken for the trial’s original justification or an assessment of achieved power.

Finally, the record lists several secondary outcomes but does not provide their numerical results or a multiplicity plan. This is relevant because a trial can ask several related questions, and interpretation of multiple tests depends on the analysis strategy. In this case, the registry entries support a cautious, endpoint-specific interpretation while leaving important aspects of the complete analysis unreported.

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.

The registry record does not report detailed eligibility criteria or participant characteristics. It also does not describe the randomization procedure, allocation concealment, or which people were masked despite listing the trial as triple-masked. The arm descriptions identify three treatment combinations, but do not include a conventional-block, low-pressure combination. This limits separation of the effects of blockade and pressure across all possible combinations.

The primary endpoint is reported at one specified time, 30 min after onset of laparoscopy. The record does not provide other cardiac-index time points or detailed measurement-quality information beyond the stated arterial waveform analysis system and radial-artery measurement. The five listed secondary outcomes do not have numerical results in the registry record, so the broader stated aims about cardiopulmonary responses and surgical conditions cannot be assessed from the posted primary-endpoint figures.

The cardiac-index comparisons are unadjusted recalculations from group summaries. The registry record does not report an original statistical analysis plan, adjusted analyses, missing-data handling, or the analysis population. It also does not report multiplicity handling, which matters when several outcomes or comparisons are considered. The recorded group counts do not establish how many randomized participants had usable measurements or how participant flow affected the endpoint summaries.

The adverse-event information is limited to the recorded counts by category and group; event details and observation duration are not reported in the registry record. Deaths are not reported in the registry record. Finally, the sample-size illustrations are based on the observed effect and stated planning assumptions, rather than documented original design assumptions. These limitations call for interpreting the posted summaries narrowly, without extending them to unreported outcomes or analyses.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Effects of Neuromuscular Blockade Level and Intra-abdominal Pressure on Surgical Conditions and Cardiopulmonary Responses During Laparoscopic Colon Surgery With the Trendelenburg Position — NCT02249585.
• Registry record last updated 2018-08-06; status last verified 2017-11.
• Results first posted 2018-08-06.
• 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.

21. Record Summary

The registry describes a completed, randomized, triple-masked, parallel trial sponsored by Seoul National University Hospital, with enrollment recorded as 131. The study start is listed as 2014-09 and primary completion as 2016-10. Its stated focus is neuromuscular blockade level and abdominal pressure during laparoscopic colon surgery in the Trendelenburg position.

The primary endpoint is mean cardiac index, measured 30 min after onset of laparoscopy and reported in L/min/m^2. The arm summaries report means of 2.6, 2.7, and 2.7. The two unadjusted recalculated mean differences against the conventional-block, standard-pressure group are 0.1; both confidence intervals span zero.

The registry lists five secondary outcomes, but their numerical results are not reported in the registry record. Detailed analysis methods, missing-data handling, analysis populations, and multiplicity procedures are also not reported in the registry record. The posted cardiac-index results therefore support a limited description of the measured endpoint, not a complete account of every trial question.