Fluoroscopy-guided Versus Traditional Placement of Epidural Catheters: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fluoroscopy-guided Versus Traditional Placement of Epidural Catheters (NCT02678039), a randomized na study. The primary outcome is Intravenous Pain Medication.

2. Clinical Question

The trial compared the placement strategies within a randomized, parallel-group design. Both groups received a standardized epidural infusion according to the brief summary, with additional pain medications as needed. The registry lists postoperative pain assessment and pulmonary function among the evaluations performed, but details of the instruments and results beyond the posted outcomes are not reported in the registry record.

3. Trial Design

The registry describes a prospective, randomized, controlled, single-blinded, parallel-group study conducted at Dartmouth-Hitchcock Medical Center. Its listed enrollment is 100, and its status is completed. The record gives a start date of 2012-08 and a primary completion date of 2014-01. The trial is categorized as not applicable for phase.

Participants scheduled for thoracotomy were assigned to fluoroscopy-guided or traditional epidural catheter placement. Fluoroscopy used real-time X-ray guidance to confirm catheter location. The traditional approach relied on palpation of spinal landmarks and loss of resistance. The brief summary says both groups received a standardized epidural infusion with local anesthetic and additional pain medications as needed. The Fluoroscopy arm description specifies 1/8% bupivacaine at 4ml/hr during and after surgery. The Traditional arm description is incomplete in the registry record, so further details about that arm’s infusion are not reported in the registry record.

The brief summary describes blinding of the anesthesia team caring for the patient in the operating room and of one acute pain team member who followed patients after surgery and assessed pain control and pulmonary function. The record labels the trial single-blinded, but does not specify further details about the masking arrangement or which participants, if any, were masked. The method used to generate the random allocation sequence, conceal allocation, or maintain masking is not reported in the registry record.

The primary endpoint was intravenous pain medication use in the first 24 hours after surgery, converted to milligrams of morphine equivalent. A numeric pain intensity measure at 24 hours is also posted as a secondary outcome. The registry lists other secondary outcome titles, but a complete set of outcome definitions, assessment schedules, protocol deviations, and analysis populations is not reported in the registry record. The original statistical plan and the trial’s own sample-size assumptions are 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 Intravenous Pain Medication, measured over 24 hours after surgery.

The primary outcome is intravenous pain medication used during the first 24 hours after surgery, expressed as milligrams of morphine equivalent. Different medications can be converted to a common morphine-equivalent scale, allowing medication use to be summarized as a continuous amount rather than as separate medication categories. The registry describes this outcome as an indirect measure of postoperative pain.

As a general statistical point, an indirect measure can reflect more than the underlying experience it is intended to represent. Medication use may depend on pain, but it can also be affected by medication prescribing, administration, patient preference, clinical practice, and the availability or use of other pain-control approaches. The registry does not provide further details about how these factors were handled or how medication records were converted.

The endpoint is summarized by a mean and standard deviation for each arm. The Fluoroscopy arm’s mean was 63.0 milligrams, with a standard deviation of 33.0; the Traditional arm’s mean was 66.0 milligrams, with a standard deviation of 27.0. These summaries describe average medication use and the spread of individual values within each group. They do not show the distribution of every participant’s outcome or establish how much difference would matter clinically. A threshold for clinical importance is not reported in the registry record.

Using the first 24 postoperative hours gives the outcome a defined time window, but does not describe medication use after that period. The registry does not report a broader cumulative pain-medication endpoint or the details needed to assess medication use over other time intervals.

7. Results Posted in the Registry

• Traditional: mean 66.00 versus 63.00 on control; difference 3.00 (95% CI -8.91 to 14.91), standardized effect d = 0.10; z-test p = 0.622.

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.

Postoperative Pain Intensity Measured by Numeric Scale

• 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:
  • Traditional: mean 6.60 versus 6.30 on control; difference 0.30 (95% CI -0.97 to 1.57), standardized effect d = 0.09; z-test p = 0.644.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Traditional and the control. The interval gives the range of effects that remain compatible with the data.

The registry identifies catheter failure and postoperative pain intensity measured by a numeric scale among the secondary outcome titles. The detailed secondary results include a 24-hour pain-intensity comparison. The posted means are close, and the uncertainty interval for the contrast includes zero. Broadly, that result does not point to a sharply separated pattern between the two randomized groups.

The available secondary pain result is directionally consistent with the primary comparison in the limited sense that neither posted mean contrast is large relative to its uncertainty. It does not independently confirm the primary result, because the outcomes measure different aspects of postoperative experience: one is medication use and the other is reported pain intensity. The registry does not report a clinical-importance threshold for either contrast.

Other listed secondary outcome results are not reported in the registry record. Although the record lists repeated numeric-scale outcome titles, the timing and full results for all listed outcomes are not available in the posted details. The incidence of catheter failure is named, but its results are not reported in the registry record.

The secondary comparisons are unadjusted. As a general statistical point, testing multiple outcomes can increase the chance of finding an apparently notable result even when there is no underlying difference, unless the analysis plan addresses multiplicity. The record does not report a multiplicity correction, a hierarchy of outcomes, or a prespecified strategy for interpreting secondary findings. That uncertainty makes the secondary results less decisive than a single prespecified primary comparison and argues against treating them as independent confirmation.

The registry does not report a complete statistical analysis plan or all analyses performed. The secondary findings should therefore be treated as descriptive evidence about the outcomes that are actually posted, rather than as a complete account of all potential benefits or harms measured by the study.

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

• Incidence of Epidural Catheter Failure
• Postoperative Pain Intensity Measured by Numeric Scale
• Postoperative Pain Intensity Measured by Numeric Scale
• Postoperative Pain Intensity Measured by Numeric Scale

9. Statistical Interpretation

10. Statistical Methods Explained

The registry posts a continuous primary outcome summarized by a mean and standard deviation in each randomized arm. A mean describes the arithmetic average of the recorded medication amounts. A standard deviation describes how dispersed individual measurements are around that mean; it is not a measure of uncertainty in the estimated mean itself. The reported arm sizes are 47 and 53.

What does the mean difference represent?

The comparison is expressed as Traditional minus Fluoroscopy. The reported means are 66.0 and 63.0 milligrams, respectively, and the estimated difference is 3.0 milligrams. A positive value on this scale means that the Traditional arm’s observed mean is higher; a negative value would mean it is lower. This direction describes the contrast, not a judgment about which approach is preferable. The registry’s outcome description frames medication use as an indirect measure of postoperative pain.

How should the confidence interval be read?

As a general explanation, a confidence interval gives a range of values reasonably compatible with the observed data under the assumptions of the analysis. The posted interval for the primary mean difference is -8.91 to 14.91 milligrams. Because this range includes zero and extends in both directions, it does not pin down whether the population mean is higher in one arm or the other. An interval is not a guarantee that the true value lies within its endpoints, and its interpretation depends on the statistical model and study conduct.

What does the p-value add?

The posted unadjusted p-value is 0.622. As a general explanation, a p-value measures how compatible the observed data are with a specified null hypothesis, under the assumptions of the test. It does not measure the probability that the null hypothesis is true, the probability that the result occurred by chance, or the size or importance of an effect. The p-value and confidence interval address related evidence about the difference, but the interval also displays a range of effect sizes compatible with the data.

The registry does not report the test used to produce the sponsor’s comparison, whether covariates were included, or how the analysis addressed any departures from model assumptions. The posted comparison is therefore best read as the registry’s reported group contrast, without attributing an unreported model or adjustment to it.

Why do sample summaries not give the whole distribution?

As a general point, means and standard deviations condense a group’s observations into a small set of descriptive statistics. They do not show whether values are symmetric, skewed, clustered, or affected by unusually high measurements. Medication amounts may have a distribution that is not well described by a mean and standard deviation alone, but the distributional shape is not reported in the registry record. No individual-level data are posted in the record.

For a continuous outcome, an analysis of means commonly relies on assumptions about the sampling distribution of the estimated contrast. General statistical practice considers independence of observations, the adequacy of the chosen model, and whether the uncertainty estimate is appropriate for the outcome distribution. The registry record does not report diagnostic checks, transformations, robust methods, or sensitivity analyses. It is not possible to determine from the posted summary whether these issues were assessed.

What do the standardized effects mean?

The comparison also reports a standardized effect, d = 0.100. As a general explanation, standardizing expresses a mean difference relative to a measure of variability, making effects from different scales easier to compare in principle. The standardized value is not in milligrams and does not replace the original-scale estimate. Its practical meaning depends on the outcome and context; a threshold for clinical importance is not reported in the registry record.

The record also includes planning illustrations based on fractions of the observed effect. These are prospective calculations using stated assumptions, not evidence about what the completed trial was originally designed to detect. The original sample-size justification and analysis plan are not reported in the registry record. No observed-power interpretation should be attached to the posted post hoc planning figures.

Finally, the registry reports no analyses in its analysis listings. This limits what can be established about the statistical methods actually used, including handling of missing data, protocol deviations, covariate adjustment, and multiplicity. The posted summaries and comparison remain interpretable as reported statistics, but they do not supply a complete account of the analysis process.

11. Confidence Intervals and Precision

The primary mean difference is 3.0 milligrams, with a 95% confidence interval from -8.91 to 14.91 milligrams. This interval is wide enough to include differences in both directions as well as zero. The estimate therefore has limited precision for distinguishing a small difference from no difference or from a difference in the opposite direction.

As a general explanation, precision concerns the range of values compatible with the data and the analysis assumptions. A confidence interval communicates this uncertainty more directly than a point estimate alone. It does not identify which value in the range is most likely, and it does not show whether any particular value would be clinically important. The registry does not report a clinical-importance threshold for morphine-equivalent medication use.

The arm standard deviations are 33.0 and 27.0 milligrams, indicating substantial variation in the observed medication amounts relative to the group means. The reported standard errors for the two arm means are 4.814 and 3.709. Standard deviations describe variation among participant outcomes, whereas standard errors describe uncertainty in estimated means; the two quantities answer different questions.

The confidence interval’s width is also shaped by the sample size and the variability of the outcome. As a general principle, more observations or less variability can improve precision, if other design and analysis features are comparable. The registry does not report the original precision target or the minimum difference the investigators intended to distinguish. It also does not report missing-data details or sensitivity analyses that might affect uncertainty.

The interval should not be read as proof of equivalence. Equivalence requires a prespecified margin and an analysis designed to assess whether the plausible differences fall within that margin. Such a margin and an equivalence analysis are not reported in the registry record. The posted interval instead conveys uncertainty about the mean difference under the reported comparison.

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 planning figures are illustrative calculations based on the observed effect, not the trial’s original design assumptions. They use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The calculation considers detecting the stated fraction of the observed effect. The trial’s own sample-size assumptions and justification are not reported in the registry record.

For these continuous outcomes, the figures are participants per arm, not the combined total across both arms. The 80% power column describes the number of participants per arm estimated to give an 80% chance of detecting the specified effect under the calculation’s assumptions, if that effect is truly present. The 90% power column gives the corresponding number for a 90% chance. These are planning probabilities tied to a stated model and effect size, not guarantees about a future study.

Each planning row uses a different fraction of the observed effect: 100%, 75%, or 50%. Smaller target effects require more participants per arm to achieve the same stated power under the same assumptions. The figures can therefore help illustrate how sample-size requirements depend on the size of the effect a study aims to detect. They should not be interpreted as a reconstruction of the investigators’ original planning.

These calculations are not observed power. Observed power is not a useful substitute for examining the estimate and its confidence interval after a trial is complete. The primary confidence interval directly describes the uncertainty in the posted mean difference, while the planning figures address hypothetical study designs under specified assumptions.

The calculations use equal allocation even though the posted arm sizes are 47 and 53. They also use a normal approximation. Whether those assumptions would be appropriate for a future study depends on its design, outcome distribution, recruitment, analysis plan, and other features. Those details are not established by the illustrations.

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 = 3.000; pooled standard deviation σ = 29.966.
2. n = 2 × (1.96 + 0.842)² × 29.966² / 3.000² = 1,566.3, rounded up to 1,567 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 <- 3                      # observed difference in means
sigma <- 29.9663076109943                     # 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(2678039)
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 = 1,567 (80% power), 2,097 (90% power)
 75% of observed effect: n per arm = 2,785 (80% power), 3,728 (90% power)
 50% of observed effect: n per arm = 6,266 (80% power), 8,388 (90% power)
power.t.test: 1567.2 
Simulated power at n = 1,567 per arm: 0.793 (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 registry identifies one primary outcome and lists several secondary outcome titles, including catheter failure and numeric pain-intensity measures. Testing multiple outcomes raises a general statistical concern: the more comparisons examined, the greater the chance that one may appear noteworthy by chance alone. A prespecified testing hierarchy or an adjustment for multiple comparisons can address this concern, depending on the study’s aims.

A multiplicity strategy is not reported in the registry record. The posted p-values are unadjusted, and the record does not state whether other adjustments were planned or performed. The absence of a reported adjustment does not establish that none was used; it means the registry record does not document one. Secondary findings should consequently be interpreted with appropriate caution, particularly when several outcomes or measurement times may have been considered.

Information about missing data is also not reported in the registry record. The arm summaries give sample sizes of 47 and 53, but the record does not say whether these are all randomized participants, all participants with an observed endpoint, or a different analysis population. It does not describe withdrawals, exclusions, missing outcome values, imputation, or sensitivity analyses. The effect of missing data on the comparisons cannot be assessed from the posted summaries alone.

The record does not identify an intention-to-treat analysis, a per-protocol analysis, or another defined analysis population. It also does not report how participants who did not receive their assigned placement strategy, if any, were handled. No assumptions about such events or about adherence can be made from the registry record.

These gaps matter because the interpretation of a randomized comparison depends not only on the group summaries but also on which participants contributed data and how the analysis dealt with incomplete observations and multiple endpoints. The posted primary estimate remains a useful description of the reported comparison, but the analytic population and robustness of the findings are not fully documented.

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.

The registry reports zero serious adverse events among 47 participants at risk in the Fluoroscopy arm and zero among 53 at risk in the Traditional arm. It also reports zero other adverse events among 47 and 53 participants at risk, respectively. Death counts are not reported. No serious adverse event terms are listed.

These figures indicate that no events in the reported categories were recorded in the posted results for the listed participants at risk. They do not establish that no adverse events occurred outside the reporting categories or reporting period, and zero observed events do not prove that the underlying risk is zero. As a general statistical point, rare events can remain uncertain when event counts are absent or small.

The registry record does not provide event definitions, observation periods, severity criteria for non-serious events, or details about how adverse events were collected and attributed. It is therefore not possible to assess the completeness of event ascertainment or compare safety beyond the counts posted. The death fields are not reported, which is distinct from a posted count of zero.

The adverse-event summaries should be read as the registry’s reported counts, not as a complete safety profile for the procedures or the perioperative care used in the study.

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

The trial’s posted primary result is an estimated mean difference of 3.0 milligrams of morphine equivalent, comparing Traditional with Fluoroscopy during the first 24 hours after surgery. The 95% confidence interval ranges from -8.91 to 14.91 milligrams, and the unadjusted p-value is 0.622. These data do not precisely establish the direction or size of a population difference in the primary outcome.

This is not the same as demonstrating that the approaches are equivalent. Equivalence would require a defined margin for an acceptable difference and a suitable analysis. Neither an equivalence margin nor an equivalence analysis is reported in the registry record. Nor does a non-small p-value establish that there is no effect. The observed estimate and its interval are the more informative description of what the posted data can support.

The primary measure is medication use, an indirect indicator of postoperative pain. It is not a direct measurement of pain intensity, function, recovery, or longer-term outcomes. A numeric pain-intensity result at 24 hours is also posted, but the registry does not report a full set of results for all listed secondary outcomes. These findings do not answer questions about outcomes beyond the measures and time windows reported.

The trial record describes randomized assignment, which is intended to support a fair comparison between groups. However, details about sequence generation, allocation concealment, missing data, analysis populations, and the analysis plan are not reported in the registry record. These limitations mean the posted summaries cannot by themselves resolve all concerns about how the comparison was conducted and analyzed.

No conclusion about clinical importance can be made without an appropriate threshold for meaningful differences, which is not reported. The results also should not be generalized beyond the study population and setting without considering how closely another context matches the patients, care, and procedures described in the record. The statistics summarize the reported comparison; they are not medical advice and do not establish that either method should be selected in practice.

17. Why This Trial Matters Statistically

This trial is statistically informative because it illustrates the difference between a point estimate and the precision of that estimate. The primary mean difference is 3.0 milligrams, but the confidence interval extends from -8.91 to 14.91 milligrams. The point estimate alone might appear to suggest a small separation, while the interval makes clear that the data leave substantial uncertainty about the direction and magnitude of the population difference.

It also demonstrates why a result that does not meet a conventional significance threshold should not automatically be described as proof of no difference. The interval includes zero, but it also includes positive and negative differences. Without a clinical-importance threshold or an equivalence framework, the result cannot establish that all meaningful differences have been ruled out.

The endpoint itself raises a useful measurement question. Medication use is a continuous, clinically interpretable quantity, but it is only an indirect measure of pain. Pairing medication use with a reported pain-intensity outcome can offer different perspectives, though the registry’s limited secondary reporting and undocumented multiplicity plan constrain how much additional weight those results can bear.

The record also illustrates the importance of distinguishing planning calculations from an original trial design. The posted planning figures use the observed effect and stated assumptions; they do not show what effect the investigators intended to detect when planning the trial. The original sample-size justification is not reported in the registry record.

Finally, randomized allocation is an important design feature, but complete interpretation also needs information about the analysis population, missing observations, masking, and statistical methods. Several of these details are not reported. Recognizing those gaps helps keep conclusions proportionate to the evidence that is actually documented.

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.

Several limitations specific to the posted record constrain interpretation. The trial population is described as patients scheduled for thoracotomies at one medical center, but eligibility criteria, baseline characteristics, and details about the representativeness of participants are not reported in the registry record. The findings therefore cannot be assessed across patient subgroups or settings from the posted information.

The primary outcome covers medication use during the first 24 hours after surgery. The registry does not report whether the endpoint was measured consistently across participants, the detailed conversion procedures for morphine equivalents, or how rescue medication and other pain treatments were incorporated. These omissions make it difficult to evaluate measurement variability and the possible influence of care processes on the outcome.

The Traditional arm description is truncated, and the record does not give a complete account of the infusion details for that arm. It also does not report the actual masking procedures beyond the brief summary’s description of the anesthesia team and one acute pain team member. Details of random-sequence generation and allocation concealment are not reported in the registry record.

The posted arm sizes do not establish the analysis population, and missing-data handling, withdrawals, adherence, and protocol deviations are not reported. The registry does not provide a full statistical analysis plan, the original sample-size justification, model diagnostics, or sensitivity analyses. The number and timing of all planned secondary comparisons, and any multiplicity strategy, are also not reported.

Finally, the registry provides limited adverse-event detail. Event definitions and ascertainment periods are not reported, and death counts are not reported. These limitations do not negate the posted estimates, but they restrict assessment of their robustness, clinical meaning, generalizability, and completeness.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Fluoroscopy-guided Versus Traditional Placement of Epidural Catheters — NCT02678039.
• Registry record last updated 2017-09-12; status last verified 2017-08.
• Results first posted 2017-09-12.
• 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

NCT02678039 is a completed, randomized, single-blinded, parallel-group study comparing fluoroscopy-guided with traditional epidural catheter placement for patients scheduled to undergo thoracotomy. The registry lists enrollment of 100 and reports a start date of 2012-08 and primary completion date of 2014-01.

The primary endpoint was intravenous pain medication use, converted to milligrams of morphine equivalent, during the first 24 hours after surgery. The posted arm means were 63.0 milligrams for Fluoroscopy and 66.0 milligrams for Traditional. The mean difference was 3.0 milligrams, with a 95% confidence interval from -8.91 to 14.91 and an unadjusted p-value of 0.622.

A 24-hour numeric pain-intensity result is also posted. Other secondary outcome details, the original design assumptions, analysis populations, missing-data methods, and a complete statistical plan are not reported in the registry record. Adverse-event counts show zero serious and zero other events in both arms; death counts are not reported.