This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Infrared Pupillometry During General Anesthesia to Predict Pain (NCT02058511), a na na study. The primary outcome is Pain in Recovery Room.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02058511 |
| Phase | NA |
| Condition | Postoperative Pain, Objective Assessment of Sedation |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 24 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of California, San Francisco |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients undergoing arthroscopic knee surgery of any type under general anesthesia. The registry lists an enrollment of 24. It does not report further participant characteristics or describe a separate population used for the primary pain outcome.
Intervention
Patients underwent anesthesia premedication, induction and maintenance, with infrared pupillometry after administration of anesthetic drugs. The study description also refers to measurements of pupillary reflex dilation and spontaneous pupil-size oscillations, called hippus, during anesthesia and recovery.
Comparator
The study is recorded as a single-group study, with no allocation to a comparison group. The intervention-group description says all enrolled patients undergo the same protocol. Consequently, the record does not define a like-for-like control group for estimating a treatment contrast.
Primary question
The primary endpoint is pain measured by visual analogue score at arrival in the recovery room. The study’s broader aims were to assess whether regional anesthesia techniques block pupillary reflex dilation and whether pupillary responses or hippus relate to early postoperative pain and later analgesia requirements. The registry does not report results establishing whether those relationships were observed.
3. Trial Design
The registry describes a single-group study of infrared pupillometry during general anesthesia in patients undergoing arthroscopic knee surgery. Enrollment is listed as 24. The intervention-group description states that all enrolled patients undergo the same anesthesia and pupillometry protocol. Allocation is recorded as not applicable, and masking is recorded as none. This is not a randomized comparison, and the record does not identify a control arm receiving a different protocol.
The intervention entries cover anesthesia premedication, induction and maintenance, and pupillometry after administration of anesthetic drugs. The study description discusses measuring pupillary reflex dilation in response to painful stimuli, along with spontaneous pupil-size oscillations before and after induction and during recovery. It proposes examining whether femoral and sciatic nerve blocks block pupillary reflex dilation, and whether pupil measurements during or at the end of surgery relate to early recovery-room pain and subsequent analgesia requirements.
The primary outcome is titled “Pain in Recovery Room” and is described as a visual analogue score taken at arrival in the recovery room. The registry also lists a secondary outcome concerning the number of patients in whom a pupillary light reflex could be elicited under stable experimental conditions. It indicates three outcome measures, but the full details of all measures are not reported in the registry record.
The study status is terminated. The record lists a start date of 2012-11 and a primary completion date of 2016-11, but does not report why the study was terminated. Its phase is recorded as not applicable. The registry record does not describe a planned sample-size justification, an analysis plan, or interim analyses.
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
| Stage | Intervention Group |
|---|---|
| STARTED | 24 |
| COMPLETED | 24 |
| NOT COMPLETED | 0 |
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.
| Characteristic | Unit | Intervention Group |
|---|---|---|
| Participants analysed | 24 | |
| Age, Continuous | years | 43 (SD 13) |
| Sex: Female, Male: Female | Participants | 15 |
| Sex: Female, Male: Male | Participants | 9 |
| Region of Enrollment: United States | participants | 24 |
6. Primary Endpoint
The registry lists the primary outcome as Pain in Recovery Room, measured over at arrival in recovery room.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is pain assessed by visual analogue score when the patient arrives in the recovery room. The score is described as running from 0-10, with 10 indicating the worst pain possible. The registry identifies the outcome as a continuous measure summarized by a mean and standard deviation, with the measurement time specified as arrival in the recovery room.
A pain score at this time is relevant to the study’s stated aim of relating measurements taken under anesthesia to discomfort after emergence. Pupillary reflex dilation and hippus are proposed as physiological measurements that might be associated with subsequent pain scores. The endpoint therefore represents a patient-reported recovery-room measure, rather than a direct measure of pupillary activity or block success.
For a continuous outcome, a mean describes the average score in the analyzed group, while a standard deviation describes variation among individual scores around that average. Those summaries would help readers understand both the typical score and how much scores vary. However, the registry record does not report the primary endpoint’s mean, standard deviation, analyzed population, or a relationship between pain scores and pupillary measurements. The endpoint definition alone cannot establish whether pupillometry predicted pain.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a planned investigation of pupil responses under anesthesia and their possible relationship to pain after surgery. Its primary endpoint is a recovery-room visual analogue pain score. The study description also proposes assessing whether regional anesthesia blocks pupillary reflex dilation and whether pupil measurements relate to later analgesia requirements. These are research questions, not reported findings.
The primary endpoint’s result is not reported in the registry record. No group mean or standard deviation for recovery-room pain is listed, and no association estimate linking pupillary measurements with pain is reported. The record also lists no statistical analyses. As a result, the posted registry information does not permit an assessment of the size or precision of any observed relationship, nor whether any proposed prediction was supported by the collected data.
The single-group design matters when interpreting the study. All enrolled patients are described as undergoing the same protocol, and no like-for-like control group is identified. The record therefore does not provide a randomized contrast between different study protocols. Any interpretation would need to distinguish a descriptive pattern within the observed group from evidence that a particular intervention caused a change.
The stated enrollment is 24, but enrollment alone does not show how many participants contributed usable primary-outcome data or pupillometry measurements. The analysis population and any exclusions or missing observations are not reported in the registry record. The enrollment figure should not be treated as the denominator for every outcome without that information.
The study status is terminated, but the reason is not reported in the registry record. Termination by itself does not explain whether data were collected, whether the planned measurements were feasible, or why no analysis is listed. Those details should not be inferred. In particular, absence of posted results does not establish that the study found no relationship or that the methods failed.
The record’s sample-size assumptions describe planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those assumptions are not a description of the actual single-group study design. Any such sample-size figures are planning illustrations rather than observed power, and the registry record does not give the observed effect or the computed illustrations’ values. The sponsor’s own analysis would take precedence if a discrepancy were identified, but no sponsor analysis is reported.
9. Statistical Methods Explained
What does the primary summary measure?
General: A mean is a measure of the center of a continuous outcome. A standard deviation describes how dispersed individual observations are around that mean. Neither summary alone describes every feature of the outcome distribution, and neither indicates how precisely the mean has been estimated. The primary endpoint is specified as a mean with standard deviation, but the registry record does not report either value for recovery-room pain.
General: A confidence interval, when reported, gives a range of values compatible with the data and the method used to calculate it. Its width reflects statistical precision under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but the interval does not by itself establish causation or clinical importance. The registry record does not report a confidence interval for the primary endpoint or for any relationship involving pupillary measurements.
What would an association analysis address?
General: An association analysis asks whether measurements vary together in the observed data. For this study, that could concern pupil reflex dilation or hippus in relation to recovery-room pain or later analgesia requirements, as described in the study aims. An association would not by itself show that a pupil measurement causes pain, or that changing the measurement would change pain. Interpretation would depend on how measurements were defined, when they were taken, which participants had usable observations, and what covariates or repeated measurements were handled.
The registry record does not report an association estimate, a model specification, an adjustment set, or a statistical test for these aims. It also does not report the extent of pupillary reflex dilation, hippus measurements, or analgesia requirements. Thus, no direction, magnitude, or precision of a relationship can be evaluated from the posted registry information.
Why does the design affect interpretation?
General: A single-group study can describe outcomes and patterns among participants who received the same protocol. Without a comparison group, it cannot directly estimate a between-group contrast under that protocol. Other factors may account for patterns observed within the group, and a descriptive association should not be read as a causal effect.
Here, the record identifies a single-group model, allocation as not applicable, and no masking. It describes all enrolled patients as undergoing the same protocol. There is no randomized comparator identified in the registry record. The study’s question about whether regional anesthesia blocks pupillary reflex dilation may involve measurements or procedures within the clinical protocol, but the record does not describe a controlled group comparison or provide results for that question.
How should the planning assumptions be read?
General: Sample-size calculations can illustrate the amount of information a future comparison might need under specified assumptions. They depend on assumptions about the effect to detect, variability, significance level, allocation, and statistical model. A planning calculation does not show that a study had a particular probability of detecting an effect after data collection; that would be a claim about observed power and should not be inferred from a planning illustration.
The registry’s stated assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect framed as a fraction of the observed effect. These assumptions do not match the recorded single-group design with no like-for-like control comparison. The record does not report the observed effect or the resulting sample-size illustration values. They therefore cannot be used to infer the study’s actual design, actual power, or the reliability of an unreported result.
General: Over-dispersion occurs when observed variability exceeds what a statistical model assumes. If a model ignores that excess variability, its uncertainty estimates can be too small and its inference too confident. Whether over-dispersion is relevant depends on the outcome and analysis model. The registry record does not specify a model for the pupillometry or pain analyses, so it is not possible to determine whether this issue arose or how it was handled.
What is not available for evaluating the analysis?
The registry record lists no statistical analyses. It does not report a statistical test, model, confidence interval, p-value, missing-data method, or analysis population. No analytic choices should be inferred from the outcome description or the planning assumptions. If analysis results are reported elsewhere in the registry at a later time, they would be needed to assess estimates and their precision.
10. Confidence Intervals for Each Arm
No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.
| Arm | Participants | Mean | Standard deviation | 95% CI for the mean |
|---|---|---|---|---|
| Intervention Group | 24 | 5.000 | 2.000 | 4.155 to 5.845 |
R code and output
arm <- c("Intervention Group")
n <- c(24)
m <- c(5)
sp <- c(2)
sd <- sp # posted standard deviations
for (i in seq_along(n)) {
se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}
CARM Intervention Group 24 5.000 2.000 4.155 5.84511. Multiplicity, Missing Data and Analysis Populations
The registry record identifies “Pain in Recovery Room” as the primary outcome and lists a secondary outcome concerning the number of patients in whom a pupillary light reflex could be elicited under stable experimental conditions. It also indicates three outcome measures, but the details of all measures are not reported in the registry record. The study description includes several aims, including block-related pupillary responses, pain scores, and analgesia requirements.
General: Multiplicity arises when several outcomes, comparisons, time points, or analyses are examined. Considering many results can increase the chance that some appear notable by chance. A prespecified hierarchy, adjustment method, or clear distinction between primary and exploratory analyses can help readers interpret such findings. The registry record does not report a multiplicity plan, adjustment method, or detailed analysis hierarchy. No conclusion about how multiplicity was handled is possible.
The registry record does not describe a missing-data plan, report how many participants contributed to each outcome, or state how incomplete measurements were handled. The enrollment figure of 24 does not establish the number included in the primary endpoint analysis. The analysis population is not reported in the registry record, and no reasons for missing or excluded observations are given. These omissions limit assessment of whether the reported participants, if results are later posted, represent everyone enrolled or only those with available measurements.
12. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Intervention Group | 0 | 24 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Intervention Group | 0 of 24 |
The registry lists an intervention-group population of 24 at risk for serious adverse events and records 0 affected. It also lists 24 at risk for other adverse events and records 0 affected. These are the registry’s reported counts; they do not substitute for a description of the events monitored, the observation period, or the completeness of follow-up.
The deaths entry is null, and the serious adverse-event terms are not listed. A null entry is not the same as a reported count of zero, so deaths are not reported in the registry record. The record also does not provide further event definitions or explain how adverse events were collected. The listed zero affected for the serious and other adverse-event categories should be read as the recorded figures, not as proof that no unrecorded event occurred.
Because this is a single-group study, the safety entries do not provide a comparative estimate against a control group. They also cannot establish that any event was caused or not caused by the protocol. The registry figures describe what is recorded for this group, with the limitations of the accompanying reporting.
13. What the Result Does, and Does Not, Mean
The record establishes that a single-group study of infrared pupillometry during general anesthesia was registered for patients undergoing arthroscopic knee surgery, with enrollment listed as 24 and status listed as terminated. It specifies recovery-room pain measured by visual analogue score as the primary outcome and describes aims involving pupillary reflex dilation, hippus, regional anesthesia, and later analgesia requirements.
It does not report the primary pain outcome’s mean or standard deviation, or a statistical analysis connecting pupil measurements to pain. Therefore, the registry record cannot establish whether pupil responses predicted recovery-room pain, whether regional anesthesia blocked pupillary reflex dilation, or whether pupil measurements were associated with later analgesia requirements. Nor can it show the magnitude or precision of any such relationship.
The single-group design also limits causal interpretation. The record does not identify a like-for-like control group, so the study description should not be read as evidence from a randomized comparison. The stated planning assumptions involving equal allocation between two arms are not a description of the recorded study design.
These limitations do not mean that the study found no association or that the methods were unsuccessful. The outcome results, analysis details, missing-data information, and reason for termination are not reported in the registry record. Conclusions should remain limited to the registered aims, design, and available outcome and safety entries.
14. Why This Trial Matters Statistically
This study is statistically notable for the gap between a broad set of proposed questions and the limited outcome information reported in the registry. It describes physiological measurements during anesthesia and proposes relating them to patient-reported pain after surgery. To evaluate such a prediction, readers would need the measurement definitions, analyzed population, estimates of association, and uncertainty around those estimates. Those results are not reported in the registry record.
The design also matters. A single-group protocol can support description of measurements and outcomes, but without a like-for-like control group it does not provide a randomized comparison between protocols. This distinction is important when moving from a pattern in observed measurements to a claim about what caused that pattern.
The primary outcome’s specified summary is a mean and standard deviation, which would describe the average recovery-room score and its variability. Yet the absence of those results means readers cannot judge the distribution of pain scores or the precision of the estimate. Enrollment alone cannot replace outcome-specific data, especially when the number contributing to each measure and the missing-data approach are not reported.
Finally, the record’s planning assumptions should be separated from the actual design and from observed evidence. Assumptions based on equal allocation between two arms do not turn a single-group study into a controlled trial, and a sample-size illustration is not observed power. Clear reporting of outcomes and analysis methods would be needed to evaluate the stated prediction aims.
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 main trial-specific limitation for interpretation is that the registry record does not report the primary outcome results or any statistical analyses. The recovery-room pain endpoint is defined, but its mean and standard deviation are absent. Estimates of relationships between pupillometry, pain, block success, or analgesia requirements are also not reported. This prevents evaluation of effect size and precision.
The recorded design is single-group, with no like-for-like control comparison and no masking. Any within-group pattern would need cautious interpretation and could not be treated as a randomized treatment contrast. The registry does not specify whether all planned measurements were collected, how stable experimental conditions were defined, or how measurement quality was assessed beyond the secondary outcome’s title.
The number enrolled is listed as 24, but outcome-specific analysis populations, exclusions, and missing measurements are not reported. The record indicates three outcome measures but does not provide the details of all of them. It also does not describe a multiplicity approach, missing-data methods, statistical models, or an analysis plan. The reason for termination is not reported in the registry record.
These are limits of what can be concluded from the registry record, not evidence that the study necessarily had poor data or no findings. Further results and methods would be needed to assess the study’s execution and the strength of any conclusions.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Infrared Pupillometry During General Anesthesia to Predict Pain — NCT02058511.
- Registry record last updated 2019-02-15; status last verified 2019-02.
- Results first posted 2019-02-15.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
19. Record Summary
The registry describes a terminated, single-group study of infrared pupillometry during general anesthesia for arthroscopic knee surgery. Enrollment is listed as 24; allocation is not applicable, and masking is recorded as none. The primary outcome is a visual analogue pain score at arrival in the recovery room, summarized as a mean and standard deviation. The study aims also concern pupillary reflex dilation, hippus, regional anesthesia, and later analgesia requirements.
The registry record does not report primary endpoint results, statistical analyses, an analysis population, or a reason for termination. It lists 0 affected for serious and other adverse events; deaths are not reported in the registry record. The available information supports describing the registered design and aims, but not evaluating whether pupillary measurements predicted pain or assessing the precision of an observed relationship.