A Trial To Assess Risk of Delirium in Older Adults Undergoing Hip Fracture Surgery With Spinal or General Anesthesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Trial To Assess Risk of Delirium in Older Adults Undergoing Hip Fracture Surgery With Spinal or General Anesthesia (NCT02190903), a randomized na study. The primary outcome is Number of Participants With Postoperative Delirium After Hip Fracture Surgery.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. Participants were assigned to standard care general endotracheal anesthesia or standard care spinal anesthesia. The listed phase is NA. The sponsor is the University of Pennsylvania. The record gives a start date of 2013-10, primary completion in 2015-04, and a completed status.

The brief summary characterizes the project as a pilot and describes an aim to address uncertainty about anesthetic technique and delirium through standardized treatment regimens and outcome assessment. It states a hypothesis that spinal rather than general anesthesia decreases delirium risk after hip fracture surgery. These are statements of the study's aims, not evidence that the planned comparison was successfully estimated or that the hypothesis was supported.

Registry enrollment is 15. For the primary outcome, the arm-level records each list 6 participants: 2 with postoperative delirium in the general endotracheal anesthesia arm and 0 in the regional spinal anesthesia arm. The registry record does not explain why the enrollment figure and the arm-level outcome counts do not match, nor does it report participant flow, exclusions, or the analysis population. The randomization method and allocation concealment procedures are not reported in the registry record. Although the study summary refers to standardized regimens, further protocol details 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.

Before assignment: A total of 15 patients provided informed consent for participation; 3 were withdrawn from the study prior to randomization. 2 of these patients were withdrawn due to ineligibility; 1 was withdrawn due to other reasons.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Postoperative Delirium After Hip Fracture Surgery, measured over Up to 5 days post hip fracture surgery.

The primary endpoint is the number of participants with postoperative delirium after hip fracture surgery. Its timeframe is up to 5 days after surgery. The registry describes assessment with the Confusion Assessment Method Instrument (CAM), a validated method based on acute onset of signs and symptoms with a fluctuating course and inattention, together with disorganized thinking or an altered level of consciousness.

This is a binary participant-level outcome: each participant is classified according to whether delirium was identified during the stated assessment period. Counting participants with an event gives a direct description of how many in each arm met the endpoint. A comparison between randomized groups could address whether observed delirium occurrence differed between the assigned anesthesia strategies, subject to the design and completeness of the data.

The endpoint is clinically relevant to the trial's stated question because postoperative delirium is the outcome the study set out to assess. The registry does not report further details about the timing or frequency of individual CAM assessments, how repeated assessments were combined, or how missing assessments were handled. The posted result therefore describes the recorded endpoint counts, not the full measurement process.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary: participants either met the registry's definition of postoperative delirium during the stated period or did not. For each arm, the posted result gives the number of participants with the event and the number listed for that outcome. This is a straightforward descriptive form of reporting. It allows readers to see the observed event counts, but it is not, on its own, a complete statistical comparison.

A comparative analysis would ordinarily express how the outcome differs between randomized groups and quantify uncertainty around that estimate. A confidence interval is a range of estimates compatible with the data under the method used; it helps communicate precision rather than merely whether a result passes a significance threshold. The registry record does not report a confidence interval or an estimable two-arm comparison for the primary binary endpoint. It is therefore not possible to interpret the counts as a precise estimate of the underlying effect.

General statistical principle: binary outcomes with few events can yield unstable estimates. When event counts are sparse, conventional approximations may perform poorly, and methods designed for sparse data may be considered. The registry does not report which inferential method, if any, was planned or used. The posted record lists no analyses. Consequently, no method-specific assumptions or test results can be attributed to this trial.

Randomization is intended to create comparable groups on average, but it does not guarantee that every feature is balanced in a small trial. Nor does randomization remove the need to understand who was included in the analysis and whether outcome measurements were available. The record identifies the trial as randomized and parallel, but details of the randomization procedure, allocation concealment, participant flow, and analysis population are not reported in the registry record. Those omissions limit assessment of how the assigned groups were formed and how completely the primary outcome was observed.

The sample-size assumptions described for planning illustrations are a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the target effect expressed as a stated fraction of the observed effect. Such planning calculations are hypothetical illustrations of the sample size that might be needed under stated assumptions; they are not observed power and do not represent an analysis of the participants in this trial. The record's binary-endpoint comparison is marked as having values missing or not estimable, and no planning sample-size figures are reported in the registry record. No sample-size requirement can therefore be inferred from the posted outcome counts.

Even when a planning calculation is available, basing the target on an observed effect can be uncertain, particularly when the underlying trial is small. The observed effect may not be a reliable estimate of the effect expected in future research. General statistical principle: planning results depend on the chosen target effect, significance level, allocation, and statistical approximation; changing these assumptions can change the resulting sample size. The record does not give a design justification or explain how the enrollment target was determined. The brief summary's description of an adequately-powered trial is an aim in the summary, not a reported statistical justification.

The registry reports a participant count endpoint, not a time-to-event endpoint. The record does not provide time-to-event analyses, adjusted models, or covariate-specific results. It also does not report a protocol-defined primary analysis method, a handling rule for incomplete assessments, or an interim-analysis plan. None should be inferred from the randomized design or from the outcome counts.

For this result, the appropriate statistical reading is to separate the observed data from an estimate of an effect. The event counts are the descriptive observations. A formal estimate would require a reported comparison and a measure of its uncertainty, neither of which is available in the registry record. In general, a missing inferential result is not evidence of no difference; it means the registry record does not supply a basis for quantifying the comparison.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("General Endotracheal Anesthesia", "Regional (Spinal) Anesthesia")
n      <- c(6, 6)
events <- c(2, 0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  General Endotracheal Anesthesia  6  2  33.3  4.3  77.7  9.7  70.0  9.9  71.0
ARM  Regional (Spinal) Anesthesia  6  0  0.0  0.0  45.9  0.0  39.0  0.4  41.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and reports no secondary outcomes. It lists no analyses. This means the record does not provide a set of multiple outcome-specific results from which to assess how multiplicity was handled. Whether additional outcomes or analyses were prespecified in a protocol is not reported in the registry record.

Multiplicity concerns arise when several outcomes, time points, subgroups, or statistical tests are examined. Repeated opportunities to find an apparently notable result can affect the interpretation of statistical evidence. General statistical principle: a prespecified analysis plan can clarify which comparisons are primary and how additional analyses are to be interpreted. The registry record does not report a multiplicity strategy, so no adjustment or hierarchy should be assumed.

Missing-data handling is also not reported in the registry record. The posted primary outcome counts list 6 participants in each arm, while the enrollment figure is 15. The record does not explain this difference, describe exclusions or withdrawals, or state whether outcome assessments were missing. It is not possible to determine from the registry record whether the posted counts represent all randomized participants, an evaluable subset, or another analysis population.

The record does not state whether analysis followed randomized assignment, whether participants were analyzed according to treatment received, or how any deviations from assignment were addressed. It does not report imputation, sensitivity analyses, or an approach to incomplete CAM assessments. These details matter because an analysis restricted to participants with observed outcomes can be affected if missingness is related to group assignment or delirium status. That is a general concern, not a claim that missing outcomes occurred in this trial.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: myocardial infarction (16.7%).

The registry's serious adverse event entries list 1 affected participant in the general endotracheal anesthesia group and 0 in the regional spinal anesthesia group. Each group has 6 participants listed as at risk for serious adverse events. The serious-event term listed is Myocardial Infarction, with 16.7% shown for that term. The record also lists 0 deaths in each group.

The other adverse event counts are 0 in both groups, with 6 participants at risk in each. These are descriptive safety entries, not a comparative safety analysis. The registry does not report an inferential comparison, event timing, details for individual cases, or a method for attributing events to an anesthesia strategy. The listed term and group counts should therefore be read as registry reports, not as proof of a causal relationship.

Safety counts and the primary delirium endpoint address different outcomes. A count of serious events does not establish whether the groups differ in overall safety, particularly when the numbers are small and no statistical comparison is posted. The record's serious-event entries do not change the interpretation of the primary delirium result.

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

The result shows that the registry recorded 2 participants with postoperative delirium in the general endotracheal anesthesia arm and 0 in the regional spinal anesthesia arm, with 6 participants listed for the primary outcome in each arm. It also shows that the registry does not provide an estimable two-arm comparison for this binary endpoint. Those details describe what was posted; they do not establish the size or precision of an anesthesia effect.

The result does not demonstrate that spinal anesthesia prevents delirium, nor does it show that the two approaches have equivalent delirium outcomes. A zero event count in one arm is not proof that the underlying risk is zero. With sparse event counts, the data may be compatible with a range of underlying possibilities, and the absent comparative estimate and confidence interval prevent a more quantified interpretation.

The result also does not answer broader questions about other patient groups, other procedures, different anesthesia regimens, or outcomes outside the stated postoperative period. The registry's primary endpoint is delirium assessed up to 5 days after hip fracture surgery. The record does not report results for additional outcomes or analyses.

The study was randomized, which is relevant to the design, but the registry record does not report participant flow, allocation details, a statistical analysis, or the relationship between enrollment and the arm-level outcome counts. These gaps constrain what can be concluded from the record. Its appropriate contribution is a limited description of the posted outcome counts and the fact that a formal comparison is not available.

The trial summary's hypothesis provides context for why the comparison was undertaken, but it should not be substituted for the observed evidence. No treatment recommendation follows from these registry results. Further interpretation would require fuller information about the study conduct and a reported analysis with an uncertainty measure.

14. Why This Trial Matters Statistically

This trial raises a practical statistical issue: a randomized design can produce a clear descriptive count pattern while still leaving the comparative question unresolved. The posted delirium counts differ between the arms, but the registry does not provide an estimable two-arm analysis. Without an effect estimate and its uncertainty, the apparent pattern cannot be calibrated as evidence for a particular size of difference.

The small arm-level outcome records also illustrate why sparse binary outcomes need careful interpretation. General statistical principle: when events are uncommon or counts are small, estimates can be sensitive to a single participant, and uncertainty can be wide. Reporting the counts is useful, but readers also need to know the analysis method and see an uncertainty measure to judge what the data can support.

The gap between the enrollment figure and the number listed in each primary outcome arm highlights the importance of transparent participant accounting. A clear flow from enrollment through randomization, follow-up, outcome assessment, and analysis helps readers understand who contributed to the result. That accounting is not reported in the registry record, so the scope of the posted outcome counts remains uncertain.

Finally, the trial summary's stated intention to be adequately powered contrasts with the limited inferential information in the registry result. A design aim does not replace a reported analysis or a rationale for the target enrollment. This record is a useful example of why outcome counts, analysis plans, participant flow, and precision estimates all matter when evaluating randomized trial evidence.

15. Limitations

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

The central limitation for interpreting the primary result is that the registry does not provide an estimable two-arm comparison for the binary endpoint. No inferential test or confidence interval is reported, and the record lists no analyses. The arm-level counts alone cannot quantify the uncertainty around a difference between anesthesia groups.

The enrollment figure is 15, whereas the primary outcome entries list 6 participants in each arm. The registry record does not explain the discrepancy or describe participant flow, exclusions, withdrawals, or outcome availability. This prevents a clear assessment of whether the posted outcome counts represent the intended analysis population.

Further design and analysis details are not reported in the registry record, including the randomization procedure, allocation concealment, the statistical analysis plan, missing-data methods, and any interim analyses. The record does not report whether CAM assessments were incomplete or how multiple assessments during the outcome period were handled. These are unknowns; the registry does not establish that any particular problem occurred.

The no-masking design may be relevant when considering outcome assessment, but the registry does not report procedures to minimize assessment bias or details of assessor masking. The outcome description identifies CAM as the assessment method, but does not supply operational details beyond its stated criteria. The study's small arm-level outcome counts further restrict the precision that could be expected from a comparison.

Finally, the trial summary describes an adequately-powered aim, but a sample-size justification is not reported in the registry record. The record provides no secondary outcome results and no analysis results beyond the primary arm counts. These limitations make the posted evidence insufficient for a firm comparative conclusion.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Trial To Assess Risk of Delirium in Older Adults Undergoing Hip Fracture Surgery With Spinal or General Anesthesia — NCT02190903.
• Registry record last updated 2018-07-30; status last verified 2018-07.
• Results first posted 2018-07-30.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT02190903 is a completed randomized, parallel-group trial with no masking, sponsored by the University of Pennsylvania. It compared standard care general endotracheal anesthesia with standard care regional spinal anesthesia for older adults undergoing hip fracture surgery. The registry lists enrollment of 15 and gives a start date of 2013-10 and primary completion in 2015-04.

The primary outcome was the number of participants with postoperative delirium assessed by CAM up to 5 days after surgery. The posted outcome counts are 2 of 6 in the general anesthesia arm and 0 of 6 in the spinal anesthesia arm. The registry does not provide an estimable two-arm comparison, a confidence interval, or any listed analyses. Participant flow, the relationship between enrollment and outcome counts, and the statistical analysis plan are not reported in the registry record.