Compare Pharmaceutical Economics and Efficacy of Sevoflurane With Low Fresh Gas Flow Balanced Anesthesia, Propofol Target Controlled Infusion Anesthesia and Propofol Induction Sevoflurane Maintenance Anesthesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Compare Pharmaceutical Economics and Efficacy of Sevoflurane With Low Fresh Gas Flow Balanced Anesthesia, Propofol Target Controlled Infusion Anesthesia and Propofol Induction Sevoflurane Maintenance Anesthesia (NCT01191476), a randomized phase 4 study. The primary outcome is Cost of Volatile Induction and Maintenance Anesthesia (VIMA) With Sevoflurane, Total Intravenous Anesthesia (TIVA) With Propofol, or Intravenous Induction With Propofol and Inhalational Maintenance With Sevoflurane.

2. Clinical Question

The clinical question is therefore chiefly economic: it concerns the cost definition used for the anesthetic drugs, not a broad assessment of the total cost of surgery or care. Recovery measures were also recorded, including times to loss of consciousness, eye opening, extubation, and orientation. These outcomes describe aspects of anesthetic induction and recovery, but they are secondary to the registered cost endpoint. The registry does not report a direct randomized comparison between the two propofol-containing strategies, so the posted pairwise estimates against sevoflurane should not be read as a formal comparison between those strategies.

3. Trial Design

The registry describes a prospective, randomized, open-label, multicenter, parallel-group phase 4 study. It was conducted in laparoscopic surgery in China and focused on elective procedures where predicted anesthetic use was between 1 and 3 hours. The registry lists enrollment as 336 and the study status as completed. The start and primary completion dates are recorded as 2010-11 and 2011-05.

Participants were assigned to one of three anesthetic strategies. The sevoflurane group received inhalational induction and maintenance; the arm description specifies vital capacity induction at 8% and maintenance at 0.8-1.5 minimum alveolar concentration. The propofol group received propofol by target controlled infusion for both induction and maintenance. In the combined strategy, participants received a propofol bolus for intravenous induction followed by sevoflurane maintenance. The arm description gives the propofol induction dose as 1.5 mg/kg and sevoflurane maintenance at 0.8-1.5 MAC.

Masking is listed as none, so this was an open-label comparison. The reported arm counts for the primary cost outcome are 112 for sevoflurane, 111 for propofol, and 111 for propofol induction with sevoflurane maintenance. Random allocation can help balance groups on average, but open-label conduct means that assignment was not concealed from participants or clinical staff after allocation. The record does not report the randomization method, allocation concealment, participating-center count, or how any departures from assigned anesthesia were handled.

The registry states that a full analysis set was used for the primary cost determination. A fuller definition of that population, including the handling of exclusions or missing cost records, is not reported in the registry record. The original design assumptions, including the intended statistical model and sample-size justification, 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.

Before assignment: The study was a prospective, randomized (1:1:1), open-label, multi-center study comparing the cost of inhalational anesthesia with sevoflurane to intravenous (IV) anesthesia with propofol, or propofol for induction and sevoflurane for maintenance of anesthesia. The full analysis set was used for determination of all primary and secondary endpoints.

Overall Study

Analysis population for the primary outcome, as defined in the registry: The full analysis set was used for the determination of cost of anesthesia.

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 Cost of Volatile Induction and Maintenance Anesthesia (VIMA) With Sevoflurane, Total Intravenous Anesthesia (TIVA) With Propofol, or Intravenous Induction With Propofol and Inhalational Maintenance With Sevoflurane, measured over Anesthetic Duration between 1 to 3 Hours.

The primary endpoint is the mean cost of anesthetic drugs, measured in Yuan, for an anesthetic duration between 1 and 3 hours. The registry defines the sevoflurane cost as its unit price multiplied by the volume used. For propofol target controlled infusion, cost is the unit price multiplied by the total volume of propofol in the syringe. For the combined propofol-induction and sevoflurane-maintenance strategy, the two drug costs are added according to the corresponding unit prices and volumes.

A particular feature of the definition is that the total propofol volume prepared in the syringe is counted even when some anesthetic remains unused, because the registry says it could not be reused. Thus, the endpoint reflects a specified drug-use and accounting rule, not simply the quantity ultimately administered. This matters when interpreting the group means: the cost values answer the question under the registered costing convention, and other costing rules might represent a different economic question.

Mean and standard deviation are the reported summary measures. A mean describes the group’s average cost, while the standard deviation describes variation among individual observations around that average. The endpoint can compare the average drug costs recorded under the three strategies, but does not by itself measure total hospital expenditure, staff time, equipment costs, other resource use, or broader economic consequences. Those components are not reported in the registry record.

7. Results Posted in the Registry

• Propofol: mean 548.52 versus 380.78 on control; difference 167.74 (95% CI 126.24 to 209.24), standardized effect d = 1.06; z-test p = <0.001.
• Propofol Induction Sevoflurane Maintenance: mean 269.40 versus 380.78 on control; difference -111.38 (95% CI -135.75 to -87.01), standardized effect d = -1.20; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Time to Loss of Consciousness

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Propofol: mean 100.32 versus 48.54 on control; difference 51.78 (95% CI 40.69 to 62.87), standardized effect d = 1.23; z-test p = <0.001.
  • Propofol Induction Sevoflurane Maintenance: mean 68.76 versus 48.54 on control; difference 20.22 (95% CI 12.47 to 27.97), standardized effect d = 0.69; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Propofol than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Propofol Induction Sevoflurane Maintenance than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Time to Eye Opening

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Propofol: mean 9.79 versus 8.38 on control; difference 1.41 (95% CI -0.04 to 2.86), standardized effect d = 0.26; z-test p = 0.057.
  • Propofol Induction Sevoflurane Maintenance: mean 8.69 versus 8.38 on control; difference 0.31 (95% CI -0.63 to 1.25), standardized effect d = 0.09; z-test p = 0.518.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Propofol and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Propofol Induction Sevoflurane Maintenance and the control. The interval gives the range of effects that remain compatible with the data.

Time to Extubation

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Propofol: mean 11.32 versus 9.69 on control; difference 1.63 (95% CI 0.16 to 3.10), standardized effect d = 0.29; z-test p = 0.030.
  • Propofol Induction and Sevoflurane Maintenance: mean 9.79 versus 9.69 on control; difference 0.10 (95% CI -0.87 to 1.07), standardized effect d = 0.03; z-test p = 0.839.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Propofol than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Propofol Induction and Sevoflurane Maintenance and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes cover induction and recovery timing: time to loss of consciousness, time to eye opening, time to extubation, and time to orientation. Posted numeric summaries are available for the first three, but a result for orientation is not reported in the registry record. Taken together, the available means suggest that recovery and induction timing did not follow exactly the same pattern as the primary cost result. They address different clinical processes and should not be treated as direct measures of drug expenditure.

The secondary comparisons are reported against the sevoflurane group, so the estimates do not provide a formal head-to-head analysis between the two propofol-containing strategies. Some of the posted comparisons have small unadjusted p-values and others do not; such results are not conclusive evidence about the full pattern of secondary outcomes. Their interpretation depends on estimate size, uncertainty, measurement procedures, and the fact that several outcomes and comparisons were considered.

In general, testing multiple outcomes creates more opportunities for apparently noteworthy results to arise by chance if no adjustment or hierarchy is used. The registry record does not report a multiplicity procedure, a prespecified hierarchy, or a statistical analysis plan for the secondary outcomes. As a result, unadjusted secondary findings carry less weight than a single prespecified primary comparison. They are best understood as supporting descriptive context for the trial rather than as independently definitive conclusions.

The primary outcome concerns mean anesthetic cost under a defined pricing and volume rule, while the secondary measures concern elapsed time at different stages. These endpoints answer related but distinct questions. A difference in a recovery-time measure would not itself establish a difference in cost, and the cost comparison does not explain the observed recovery-time pattern. The registry does not report an analysis connecting the secondary measures to the primary cost outcome.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Time to Loss of Consciousness
• Time to Eye Opening
• Time to Extubation
• Time to Orientation

9. Statistical Interpretation

10. Statistical Methods Explained

The primary endpoint is continuous: it is a measured cost in Yuan, summarized by a mean and standard deviation. A mean is the arithmetic average of the observations in a group. The standard deviation describes how dispersed those observations are around the mean. A larger standard deviation indicates greater spread in the recorded values, but it does not describe the shape of the distribution or identify the experiences of individual participants.

The pairwise estimates compare each non-reference group with sevoflurane. For the propofol comparison, the posted mean difference is 167.7 Yuan; for propofol induction with sevoflurane maintenance, it is -111.4 Yuan. The sign depends on the order of subtraction. Positive values indicate a higher mean in the comparison arm than in the sevoflurane reference; negative values indicate a lower mean. The estimates are unadjusted comparisons based on the posted group summaries. The registry does not report an adjusted model for these outcomes.

A p-value describes how compatible the observed data are with a specified null model, under the assumptions used for the calculation. It is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of a difference. The primary comparisons have p < 0.001. Their interpretation should be considered with the estimated mean differences and intervals, rather than by treating a threshold alone as a complete summary. The registry record does not report the statistical analysis plan or a multiplicity adjustment.

For the secondary continuous outcomes, the posted comparisons are likewise mean differences against sevoflurane. Their units differ by outcome: time to loss of consciousness is in seconds, while eye opening and extubation are in minutes. The interpretation of an estimate therefore depends on both its direction and its unit. A one-unit difference in seconds is not the same scale as a one-unit difference in minutes. The record names time to orientation but does not report its results.

What a standard deviation contributes

In general, the standard deviation describes variation among observations, whereas the standard error describes the estimated uncertainty in a group mean. They answer different questions: the first concerns how variable participant-level measurements are; the second concerns how precisely the group mean is estimated. The registry reports standard deviations for the outcomes. The posted comparison calculations also use standard errors, but the registry record does not give a detailed account of the underlying analysis model or assumptions.

In general, cost observations can be unevenly distributed, for example if some observations are much larger than most others. In such settings, the mean and standard deviation may not fully describe the distribution, and methods that account for skewness or over-dispersion can be useful. Whether the cost observations in this trial had those features, and whether any such methods were used, is not reported in the registry record. It would be inappropriate to infer a distribution or model solely from group summary statistics.

How to read the interval estimates

In general, a confidence interval expresses uncertainty around an estimate under a specified statistical method. A wider interval indicates less precision than a narrower interval on the same scale. For the primary comparisons, the posted intervals do not cross zero: 126.2 to 209.2 Yuan for propofol versus sevoflurane, and -135.7 to -87.01 Yuan for the combined strategy versus sevoflurane. This gives a range of values compatible with the respective comparison under the method used to produce the interval. The confidence level and exact method for the posted intervals are not reported in the registry record, so they should not be assigned a level that is not documented.

General statistical interpretation also distinguishes statistical evidence from the size and relevance of an estimate. A small p-value does not show whether a difference matters for a particular decision, and an interval does not account for limitations in the measurement definition, generalizability, or analysis reporting. In this study, the endpoint specifically counts the full propofol syringe volume even when some remains unused. The numerical estimates therefore address that accounting definition and should not be treated as a complete economic evaluation.

What the reported analysis leaves unclear

The registry identifies the full analysis set for the primary cost determination, but does not define inclusion and exclusion rules in detail. It does not report how missing observations were handled, whether any outcome transformations were used, or whether the model included center effects or other covariates. It also does not describe a formal analysis of the secondary outcomes. These are methodological details that can affect the interpretation of estimates and their uncertainty; their absence should be treated as uncertainty about reporting, not as evidence that a particular method was or was not used.

In general, randomization is intended to make groups comparable in expectation, while analysis methods quantify the uncertainty in observed group differences. Open-label allocation does not undo randomization, but knowledge of assigned strategy can be relevant to how care is delivered and measurements are recorded. The primary outcome is a drug-cost calculation based on price and recorded volume, and the registry does not report whether outcome assessment or data processing was blinded. The level of protection against measurement or implementation differences therefore cannot be determined from the record.

11. Confidence Intervals and Precision

The primary mean-difference intervals are 126.2 to 209.2 Yuan for propofol compared with sevoflurane, and -135.7 to -87.01 Yuan for propofol induction with sevoflurane maintenance compared with sevoflurane. Both intervals are entirely on one side of zero, consistent with the direction of the corresponding posted mean differences. Their widths also show that the estimates are not single exact values: the data are compatible with a range of differences under the calculation used.

In general, an interval is a way to express precision around an estimate, and its interpretation depends on the method and confidence level. The registry record does not report the confidence level or the precise procedure for these intervals. The intervals should therefore be read as the posted ranges around the mean differences, without assuming an undocumented level. They do not account for uncertainties that are outside the calculation, such as whether the cost definition captures all relevant resources or whether the trial population represents other settings.

The standard deviations also give context for the group means. Cost standard deviations were 108.5 Yuan for sevoflurane, 195.1 Yuan for propofol, and 74.04 Yuan for the combined strategy. The greater spread in a group does not, by itself, establish why costs varied or indicate whether the distribution was symmetric. It does indicate that participants’ recorded costs were not all identical and that averages should be interpreted alongside variability.

The primary estimates are more precise than a point estimate alone, but the registry’s reporting gaps matter. Analysis details, treatment of missing observations, and any center adjustment are not reported in the registry record. Those omissions make it difficult to assess whether the interval calculations fully reflect the study design and analysis choices. Precision of the posted estimate is not the same as certainty that the result generalizes beyond the measured drug costs and trial setting.

12. 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 illustrations are planning calculations based on observed effects, not the trial’s original design calculation. For these continuous outcomes, the figures are participants per arm. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. The original trial’s sample-size assumptions and justification are not reported in the registry record.

The 80% power column describes the planning number of participants per arm that would give an 80% chance of detecting the chosen effect under those assumptions, if the assumed effect and model were correct. The 90% power column uses a higher target chance of detection and therefore generally calls for more participants per arm. For example, planning for 75% of the observed cost difference between propofol and sevoflurane gives 25 participants per arm for 80% power and 34 participants per arm for 90% power. These are hypothetical future-study planning figures, not a reinterpretation of the participants enrolled in the completed trial.

Smaller effects are harder to distinguish from random variation, so planning to detect a smaller fraction of the observed effect requires more participants per arm. The illustrations use the observed result as their starting point, which means their usefulness depends on whether that effect is a reasonable planning assumption for a future study. They are not observed power: they do not measure the probability that this completed trial detected a true effect after the results are known.

13. 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 = 167.740; pooled standard deviation σ = 157.701.
2. n = 2 × (1.96 + 0.842)² × 157.701² / 167.740² = 13.9, rounded up to 14 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 <- 167.74                      # observed difference in means
sigma <- 157.701255685541                     # 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(1191476)
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 = 14 (80% power), 19 (90% power)
 75% of observed effect: n per arm = 25 (80% power), 34 (90% power)
 50% of observed effect: n per arm = 56 (80% power), 75 (90% power)
power.t.test: 14.9 
Simulated power at n = 14 per arm: 0.775 (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.

14. Multiplicity, Missing Data and Analysis Populations

The trial has a primary cost outcome and multiple secondary outcomes, with pairwise comparisons of the propofol-based strategies against sevoflurane. Considering several comparisons can increase the chance of at least one small p-value even when no underlying differences exist. In general, multiplicity is addressed through methods such as adjusting significance thresholds or defining a prespecified order for testing. Whether either approach was used is not reported in the registry record.

The posted p-values are unadjusted. The registry record does not report a statistical analysis plan, a family of comparisons for multiplicity control, or a hierarchy specifying which secondary results should be treated as confirmatory. The primary cost endpoint is identified, which helps distinguish it from secondary outcomes, but the absence of analysis details limits the interpretation of all reported p-values. Secondary results should not be treated as if they were protected from multiple testing.

Missing-data handling is also not reported in the registry record. Although the primary endpoint is described as using the full analysis set, the record does not define precisely which participants entered that set or explain how missing cost data, missing timing observations, or incomplete measurements were managed. The displayed arm counts for the primary outcome do not establish whether every randomized participant contributed to every outcome. Outcome-specific analysis populations and reasons for any absent data are not reported.

The record does not describe whether analyses followed randomized assignment regardless of treatment received, whether any participants were excluded after allocation, or how protocol deviations were handled. It does not report adjustments for study center or other baseline factors. These omissions do not demonstrate that missingness, multiplicity, or imbalances affected the results; they mean the registry record does not allow those issues to be assessed in detail. Interpretation should remain focused on the posted, unadjusted summaries and comparisons.

15. 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.

Most frequent non-serious adverse event terms

The registry lists serious adverse events as affecting zero participants in each of the three arms. The numbers at risk for this reporting are 112 in the sevoflurane arm, 111 in the propofol arm, and 111 in the propofol-induction and sevoflurane-maintenance arm. These entries describe the registry’s posted serious-event counts; they do not establish that no health events of any kind occurred.

Other adverse events are recorded as affecting 5 participants in the sevoflurane group, 4 in the propofol group, and 5 in the combined-strategy group. The registry record does not provide event terms or further detail in the available safety summary, so the nature, severity, timing, and relationship of these events to anesthesia cannot be assessed from these counts alone. Death counts are not reported in the registry record.

These figures are a limited safety summary, not a complete comparison of safety. A zero count for serious events in the registry does not prove that risk is absent, and small differences in recorded counts should not be interpreted as evidence of a meaningful group difference without fuller definitions, follow-up details, and an appropriate analysis. The record does not report the safety analysis method or a detailed account of event collection.

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

The primary result describes mean anesthetic drug cost under the trial’s registered accounting rules. The posted mean is higher for propofol than for sevoflurane, while the mean for propofol induction with sevoflurane maintenance is lower than the sevoflurane mean. The corresponding unadjusted mean differences and intervals quantify those comparisons within the recorded trial data. They do not, on their own, determine which strategy is preferable for a particular patient or clinical service.

The economic meaning is bounded by the endpoint definition. It accounts for drug unit prices and volumes, including the full propofol syringe volume even when some anesthetic is unused. The cost measure does not include total hospital costs or other resource use in the information reported. It is therefore not a complete cost-effectiveness analysis and does not quantify the value of any outcome relative to expenditure.

The randomized, parallel-group design supports comparisons among assigned strategies, but the open-label conduct and limited reporting of analysis methods should be kept in view. The posted estimates do not establish that the same results would apply to other procedures, anesthetic durations, pricing arrangements, centers, or populations. Generalization beyond elective laparoscopic surgery with predicted anesthetic use between 1 and 3 hours is not established by the registry record.

The recovery-time measures offer additional descriptive information but do not change the definition of the primary economic outcome. Results for time to orientation are not reported in the registry record, and the secondary comparisons are unadjusted. No direct comparison between the two propofol-containing approaches is reported. Taken together, the record supports a reading of the reported group averages and pairwise estimates, while leaving broader clinical, economic, and comparative questions unresolved.

17. Why This Trial Matters Statistically

This trial raises an important statistical distinction between a measurable endpoint and a complete decision outcome. Drug cost can be summarized numerically, but its interpretation depends on what counts as cost. Here, the registry’s rule counts the full propofol syringe volume even when some remains unused. That explicit definition makes the comparison interpretable, while also limiting it to a particular accounting convention.

The three-arm randomized design allows the two alternative strategies to be compared with a shared reference group. The posted estimates show how the mean cost contrasts with sevoflurane, but they do not supply a formal direct comparison between propofol alone and the combined strategy. This is a useful reminder that two significant comparisons against a common reference do not automatically establish a statistically tested difference between the alternatives themselves.

The trial also illustrates why effect estimates, uncertainty, and analysis transparency need to be read together. The primary cost differences have intervals on one side of zero and unadjusted p-values below 0.001, but the registry does not report the confidence level, analysis plan, or multiplicity approach. The numerical results can be described, while some methodological details needed for a fuller assessment remain unavailable in the registry record.

Finally, the secondary outcomes emphasize that a trial can examine several distinct questions at once. Cost and recovery timing have different units and meanings. Without a reported hierarchy or adjustment strategy, secondary comparisons add descriptive context rather than a set of equally strong confirmatory claims. This separation helps readers avoid treating every reported result as the same kind of evidence.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary endpoint is a drug-cost measure rather than a comprehensive economic evaluation. It uses specified unit-price and volume calculations, including the full propofol syringe volume even when not all of it was used. The registry does not report the prices’ source, whether unit prices were consistent across centers, or costs beyond the anesthetic drugs. These omissions limit interpretation outside the stated cost definition.

The trial is open-label, and the registry does not describe blinded measurement or data processing. Its multicenter setting is identified, but the number of centers and any center-specific analyses are not reported in the registry record. The registry also does not explain the allocation procedure or concealment before assignment. These details would help assess implementation and possible variation across sites.

The record does not report the original sample-size justification, statistical analysis plan, missing-data method, or multiplicity procedure. It identifies a full analysis set for the primary cost determination without defining it in detail. The secondary outcome for time to orientation is named but has no posted result. These reporting gaps constrain evaluation of analysis choices and completeness.

Scope is also limited to elective laparoscopic surgery with predicted anesthetic use between 1 and 3 hours. The record does not establish whether the observed cost pattern applies to other types of surgery, different anesthetic durations, other settings, or different prices. The posted comparisons are against sevoflurane, rather than a direct test between the two propofol-containing strategies. Safety counts are brief and lack event-level descriptions in the reported summary.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Compare Pharmaceutical Economics and Efficacy of Sevoflurane With Low Fresh Gas Flow Balanced Anesthesia, Propofol Target Controlled Infusion Anesthesia and Propofol Induction Sevoflurane Maintenance Anesthesia — NCT01191476.
• Registry record last updated 2012-07-03; status last verified 2012-05.
• Results first posted 2012-07-03.
• 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.

22. Record Summary

This completed phase 4 randomized, open-label, multicenter parallel-group study compared three anesthesia strategies in elective laparoscopic surgery in China. The registry lists enrollment as 336 and identifies mean anesthetic cost in Yuan as the primary outcome for anesthetic durations between 1 and 3 hours.

Reported mean costs were 380.8 Yuan with sevoflurane, 548.5 Yuan with propofol, and 269.4 Yuan with propofol induction followed by sevoflurane maintenance. The unadjusted comparisons against sevoflurane were 167.7 Yuan for propofol and -111.4 Yuan for the combined strategy; both had p < 0.001. The cost definition counts the full volume of propofol prepared in a syringe even when some remains unused.

Secondary results include three recovery-time outcomes; time to orientation is named but not reported. The registry does not report the statistical analysis plan, multiplicity procedure, detailed missing-data handling, or original sample-size justification.