Cerebral Blood Flow During Propofol Anaesthesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cerebral Blood Flow During Propofol Anaesthesia (NCT02951273), a registered phase not stated study. The primary outcome is Changes in Internal Carotid Artery Blood Flow by Treatment of Anaesthesia-induced Hypotension.

2. Clinical Question

3. Trial Design

The registry record describes a completed study titled “Cerebral Blood Flow During Propofol Anaesthesia,” sponsored by Copenhagen University Hospital, Rigshospitalet. The listed enrolment is 30. The study dates are 2016-12-08 for start and 2017-07-06 for primary completion. Gastrointestinal neoplasms are listed as the condition, and the arm description refers to patients undergoing oesophageal- or ventricular resection.

The study has one listed arm, “Study of cerebral blood flow.” Its primary endpoint is structured around measurements during anaesthesia-induced hypotension before phenylephrine and 3-5 min after phenylephrine. That timing describes a within-study, across-time question rather than a randomized comparison between treatment groups. Allocation is not stated in the registry record, and the record explicitly cautions that the arms are not a like-for-like control comparison.

The registry summary describes several related questions: cerebral blood flow during anaesthesia and standard treatment of possible reductions in blood pressure; blood flow in relation to mesenteric traction syndrome (MTS); and blood flow during short-term ventilation changes. Listed secondary outcomes include internal carotid artery blood flow, frontal lobe oxygenation, forehead skin blood flow and oxygenation, carbon-dioxide reactivity, heart rate, and relationships involving mean arterial pressure and cardiac output. The record lists 12 outcome measures and 12 analyses.

Details needed to reconstruct the conduct of the study are not reported in the registry record. These include the recruitment method, eligibility criteria, detailed measurement schedule beyond the primary endpoint, and how participants were handled if a measurement was unavailable. The registry does not describe a randomized allocation procedure or a separate control group.

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 Changes in Internal Carotid Artery Blood Flow by Treatment of Anaesthesia-induced Hypotension, measured over Two measurements; one measurement during anaesthesia-induced hypotension (mean arterial pressure < 65 mmHg) before administration of phenylephrine and one measurement 3-5 min after administration of phenylephrine..

The primary endpoint is change in unilateral internal carotid artery blood flow, measured in ml/min with duplex ultrasound. The specified measurements are taken during anaesthesia-induced hypotension, before administration of phenylephrine, and 3-5 min after administration. The endpoint therefore focuses on blood flow around the treatment of low blood pressure under anaesthesia, rather than on a long-term clinical outcome.

Blood flow in the internal carotid artery is used as a measure relevant to cerebral circulation. The registry’s study rationale notes that anaesthesia may reduce blood pressure and raises the question of whether blood flow to the brain could become insufficient. It also identifies blood pressure treatment as an important part of the clinical context. These points explain why a blood-flow measure is of interest, but they do not establish what the measured change was or what it means for patient outcomes.

The endpoint is defined as a mean with a 95% confidence interval. A mean describes the central value of a continuous measurement, while a confidence interval conveys uncertainty around an estimated mean. The registry record does not report the observed endpoint mean, the estimate of change, or its 95% confidence interval. It also does not report a result that would allow the size or direction of the blood-flow change to be described.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of outcome is this?

The primary measure is continuous: internal carotid artery blood flow is recorded in ml/min. The registry specifies the mean as the summary parameter and a 95% confidence interval as the measure of uncertainty. General: a mean summarizes the central level of a continuous measurement. A confidence interval describes uncertainty in an estimated quantity, conditional on the analysis assumptions. Neither quantity says, by itself, whether a change matters clinically.

What comparison is defined?

The primary endpoint is set at two time points: during anaesthesia-induced hypotension before phenylephrine, and 3-5 min after its administration. The hypotension threshold is mean arterial pressure < 65 mmHg. This is a before-and-after measurement schedule, not a stated randomized assignment to phenylephrine or a control treatment. The record does not report whether the analysis used a paired method, how repeated measurements were modelled, or whether covariates were included. It is therefore appropriate to describe the stated timing without attributing an unreported statistical procedure to the investigators.

General: measurements from the same participant at different times are often statistically related. Analyses that account for such within-participant dependence can differ from analyses that treat all readings as independent. The registry record does not specify how that dependence was handled, so the exact analysis cannot be reconstructed from the record.

How should uncertainty be read?

The registry names a 95% confidence interval for the mean. General: a confidence interval gives a range of estimates compatible with the observed data and the method’s assumptions. It helps readers judge how precisely an effect has been estimated. A confidence interval is not a guarantee that the true value lies within the particular interval, nor does it identify the probability that a treatment works. The actual endpoint estimate and interval are not reported in the registry record, so their width and location cannot be evaluated.

A p-value, if reported, would address compatibility between the observed data and a specified null hypothesis under an analysis model. It would not express the probability that the null hypothesis is true or measure clinical importance. The registry record does not report a primary endpoint p-value. No interpretation of statistical significance can therefore be made from the registry entry.

What does the design allow?

The record lists one arm and does not state allocation. It also cautions that the arms are not a like-for-like control comparison. General: in a nonrandomized before-and-after setting, a change between readings may reflect the measured intervention, time, concurrent clinical management, or other factors. A control group or an adequately justified analysis may help address some alternative explanations, but details of such methods are not reported. The temporal sequence alone does not establish a causal treatment effect.

The study rationale discusses possible influences on cerebral blood flow, including blood pressure, MTS, and ventilation. The secondary outcomes include a multiple-regression relationship involving changes in internal carotid artery blood flow, mean arterial pressure, and cardiac output during treatment of anaesthesia-induced hypotension. The registry lists that analysis but does not report its model specification, estimates, uncertainty, or assumptions. General: regression can describe associations while accounting for selected variables, but it does not automatically remove confounding or establish causality.

What about distributional assumptions?

The record labels the outcome type as continuous and the summary as a mean. It does not report the observed distribution, a measure of dispersion beyond the confidence-interval designation, or diagnostic checks. General: a mean can be sensitive to extreme observations. If measurements are highly skewed or unusually variable, the mean and a model that assumes a particular distribution may provide an incomplete description. Over-dispersion means that variability is greater than a model expects; accounting for it can affect estimated uncertainty. The registry record does not state whether distributional assumptions or over-dispersion were assessed.

No statistical analysis plan, interim-analysis details, or sample-size justification is reported in the registry record. The enrolled sample size is 30, but that fact alone does not show how the study was planned or whether it had adequate precision for a particular effect. Sample-size calculations, when used as planning illustrations, are not observed power and do not substitute for the observed estimate and its uncertainty.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures and 12 analyses. These include outcomes related to internal carotid artery blood flow, frontal lobe oxygenation, forehead skin blood flow and oxygenation, carbon-dioxide reactivity, heart rate, mean arterial pressure, and cardiac output. The existence of multiple listed outcomes raises a general multiplicity question: examining several outcomes or analyses can increase the chance of finding an apparently unusual result by chance, depending on the procedures and hypotheses involved.

The registry record does not report whether the investigators adjusted for multiple comparisons, designated a hierarchy among secondary outcomes, or specified a strategy for controlling an overall error rate. The presence of a stated primary endpoint does not reveal how the other analyses were prioritized or interpreted. No numerical findings for the secondary outcomes are reported in the registry record.

Missing-data handling is not reported in the registry record. The entry does not state whether all enrolled participants contributed primary measurements, how unavailable readings were treated, or whether any imputation or sensitivity analysis was used. It also does not report analysis populations, such as which participants were included in each endpoint analysis. Therefore, the enrolment figure should not be taken as confirmation that every participant contributed complete outcome data.

The statistical analysis plan, interim analyses, and sample-size justification are not reported in the registry record. These omissions prevent assessment of whether the analyses followed a prespecified strategy, how missing observations affected the results, or how the investigators addressed the range of outcomes.

11. 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.

The registry’s serious adverse event summary lists 30 participants at risk and 0 affected in the “Study of Cerebral Blood Flow” group. Deaths are listed as 0. Other adverse events are also listed for 30 participants at risk, with 0 affected. No serious adverse event terms are listed.

These figures describe what the registry record reports for this study. They do not establish that no events occurred outside the recorded categories or reporting period, and they do not describe event severity beyond the serious-event classification. The record does not provide further detail about event collection, surveillance procedures, or the period used for safety assessment.

Because the study lists one arm and no randomized control comparison, the adverse-event figures cannot be used to compare safety between treatments. The zero counts are descriptive registry entries, not evidence of a causal safety difference or a guarantee that an event could not occur. They should be read alongside the limited information about how adverse events were collected and reported.

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

The registry record establishes that this completed study enrolled 30 participants and focused on cerebral blood flow during propofol anaesthesia. Its primary endpoint was unilateral internal carotid artery blood flow measured by duplex ultrasound around phenylephrine administration for anaesthesia-induced hypotension. The listed timing and threshold make the clinical measurement question clear: the study was set up to examine blood flow during hypotension and shortly after treatment.

The record does not report the observed primary endpoint values, an estimated change, a confidence interval, or a p-value. As a result, the magnitude and direction of any measured change are not available from the registry entry. The record also does not report results for the listed secondary outcomes. It is not possible to determine from the entry whether blood flow changed, how precisely any change was estimated, or whether the findings support an association with the other physiological measures.

The study’s rationale identifies questions about blood pressure, MTS, and ventilation, but a stated rationale is not a finding. Similarly, listing an outcome or analysis does not show that it was statistically significant or clinically important. The safety summary reports 0 serious adverse events and 0 deaths among 30 at risk, but these registry figures do not establish comparative safety.

The design information also limits causal interpretation. The registry lists one arm, does not state allocation, and notes that the arms are not a like-for-like control comparison. The primary measurement schedule is around an intervention, but without reported outcome estimates and fuller analysis details, the registry entry does not support a conclusion about the effect of phenylephrine on cerebral blood flow. Any interpretation should distinguish the physiological question the study was designed to address from evidence about the result.

13. Why This Trial Matters Statistically

This study raises a clear statistical challenge: a clinically relevant physiological measure is recorded around a short-term change in treatment, while blood pressure and other factors may also change during anaesthesia. The registry’s endpoint definition gives a specific measurement window and method, allowing readers to understand what was intended to be measured. It also makes visible the distinction between a before-and-after physiological assessment and a randomized treatment comparison.

The record lists a range of related outcomes, including blood flow, oxygenation, heart rate, and relationships involving mean arterial pressure and cardiac output. Such breadth can be valuable for describing physiology, but it makes prespecification, multiplicity, and transparent reporting important. The registry does not report the analysis strategy for these issues, so the evidential weight of individual findings cannot be assessed from the entry.

The case also illustrates why effect estimates and uncertainty are essential. Naming a continuous outcome and a 95% confidence interval indicates how results could be summarized, but without the actual estimate and interval there is no way to judge either the size or precision of a change. A sample size of 30 does not by itself reveal precision, and it cannot replace the outcome results.

Finally, the registry’s safety counts need a careful descriptive reading. Zero reported events are informative as a record of the observed counts, but do not establish comparative safety or rule out events beyond the reported scope. Clear reporting of estimates, uncertainty, analysis populations, missing-data handling, and adverse-event methods would be needed for a fuller statistical assessment.

14. 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 limitation of the registry entry for statistical interpretation is that it does not report the primary endpoint results. There is no observed blood-flow mean, estimate of change, 95% confidence interval, or p-value in the record. Without these, the size, direction, and precision of the primary finding cannot be assessed. Numerical results for the listed secondary outcomes are also not reported in the registry record.

The design description is limited. The registry lists one arm and does not state allocation; it also cautions that the arms are not a like-for-like control comparison. The primary endpoint’s before-and-after timing does not independently distinguish a phenylephrine-associated change from other changes occurring during care. The record does not describe the analysis model or adjustment for potential influences on blood flow.

Important analysis details are not reported in the registry record, including how repeated measurements were handled, whether missing observations occurred and how they were addressed, which participants were included in each analysis, and whether any multiplicity procedure was used. The analysis plan, interim analyses, and sample-size justification are also not reported.

The safety record gives counts but does not describe ascertainment methods or the safety observation period. Consequently, the zero counts should be treated as registry-reported descriptive data, not as a complete account of all possible harms. The available record supports an account of the study question and measurement schedule, but not a detailed evaluation of efficacy, precision, or comparative safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Cerebral Blood Flow During Propofol Anaesthesia — NCT02951273.
• Registry record last updated 2018-01-17; status last verified 2017-12.
• Results first posted 2017-11-17.
• 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.

18. Record Summary

NCT02951273 is a completed study titled “Cerebral Blood Flow During Propofol Anaesthesia,” sponsored by Copenhagen University Hospital, Rigshospitalet. The registry lists enrolment of 30 and the condition gastrointestinal neoplasms. The arm description refers to patients undergoing oesophageal- or ventricular resection.

The primary endpoint is unilateral internal carotid artery blood flow in ml/min, assessed by duplex ultrasound. The stated measurements are during anaesthesia-induced hypotension before phenylephrine and 3-5 min after administration; hypotension is defined as mean arterial pressure < 65 mmHg. The endpoint is summarized as a mean with a 95% confidence interval.

The registry lists 12 outcome measures and 12 analyses. It reports 0 serious adverse events and 0 deaths among 30 at risk. Primary and secondary outcome estimates, analysis details, missing-data methods, and multiplicity procedures are not reported in the registry record.