Ninvasive Cardiac Output Measurements During Cesarean Delivery Under Spinal Anesthesia.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ninvasive Cardiac Output Measurements During Cesarean Delivery Under Spinal Anesthesia. (NCT01928797), a randomized na study. The primary outcome is Percentage of Participants With a Cardiac Output Within and Outside 20% of Baseline Values.

2. Clinical Question

The clinical rationale described in the registry is that cardiac output and blood pressure can decrease after spinal anesthesia for cesarean delivery. The investigators aimed to assess whether additional cardiac output measurements could inform blood pressure management and possibly reduce nausea and vomiting. The record describes the primary outcome in terms of the percentage of participants with cardiac output within and outside 20% of baseline values. Its narrative also refers to differences in mean cardiac output and to maintaining blood pressure and cardiac output within 20% of baseline. These descriptions do not establish a single numerical result or a single comparison that can be interpreted from the registry record.

3. Trial Design

This was a randomized, parallel-group study with no masking. The registry records an enrollment of 60 and a completed status. The study began on 2013-11-01, and primary completion is recorded as 2014-12-31. The phase is listed as not applicable. Brigham and Women's Hospital is the named sponsor.

The comparison was between care guided by blood pressure and heart rate alone and care that additionally used cardiac output monitor data to guide vasopressors. In the control group, cardiac output was measured but was not used by anesthesiologists to guide blood pressure treatment. In the study group, the monitor data were used alongside blood pressure and heart rate. Both descriptions refer to phenylephrine and ephedrine; the study-group description also refers to a standardized protocol.

Random allocation is intended to make treatment groups comparable on average, but the record does not describe the allocation procedure, such as how the sequence was generated or concealed. Masking is listed as none, so the trial should be understood as unmasked; further details about who knew the assigned group are not reported in the registry record. The record does not report more detailed eligibility criteria, the study setting, or the planned number of participants beyond the enrollment figure. It also does not report how participants were assigned to groups in practice or whether all enrolled participants contributed data to each outcome.

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 Percentage of Participants With a Cardiac Output Within and Outside 20% of Baseline Values, measured over intraoperatively during surgery.

The primary outcome is titled as the percentage of participants with cardiac output within and outside 20% of baseline values, measured intraoperatively during surgery. The accompanying description frames the clinical aim more broadly: assessing cardiac output differences between groups and maintaining cardiac output and blood pressure within 20% of baseline after spinal anesthesia. Blood pressure and cardiac output are related but distinct measurements, so the registry's title and narrative do not specify a single, unambiguous summary measure. The record does not report category-specific counts, group estimates, or a numerical comparison for this outcome.

A threshold relative to baseline can describe whether measurements stayed near a participant's starting value, while a mean difference can describe the average separation between groups. These are different summaries and answer different statistical questions. A percentage within a threshold describes the proportion meeting a defined condition; it does not, by itself, show how far measurements outside the threshold were from baseline. The registry record does not specify the precise calculation, aggregation over intraoperative measurements, or handling of repeated measurements used for the primary outcome.

The outcome is relevant to the study's stated question because the investigators wanted to know whether cardiac output information could affect hemodynamic management and vasopressor selection. However, the outcome title alone does not establish that such a change occurred. Numerical results and the analysis connecting the endpoint to vasopressor choices are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how observations are turned into estimates and how much uncertainty should accompany those estimates. The registry record identifies randomization and a parallel-group comparison, but it does not report the statistical analysis plan, the estimator for the primary outcome, or a method for quantifying uncertainty. The concepts below are general explanations, not claims about analyses performed in this trial.

What does randomization contribute?

In a randomized study, assignment is intended to reduce systematic differences between groups at the start of the comparison. It does not guarantee that the groups will be identical, especially in a study of limited size. Statistical analysis then compares outcomes between assigned groups, with the precise method depending on the endpoint and the prespecified analysis plan. The registry record does not report the randomization sequence method, allocation concealment, or whether analyses followed assigned groups.

Why does the endpoint definition matter?

A percentage meeting a threshold and a mean measurement are different outcome summaries. A threshold-based endpoint needs a clearly defined rule for classifying each participant, including how multiple measurements during surgery are combined. A mean-based endpoint needs a defined measurement time or summary across measurements. These decisions affect what the estimate means and which statistical model is suitable. The registry record's primary-outcome title and narrative refer to both a within-or-outside threshold and mean cardiac output differences, but the exact operational definition is not reported in the registry record.

For a binary outcome, such as whether a participant meets a specified criterion, an analysis may compare the proportion meeting that criterion between groups. For a continuous measurement, an analysis may compare group means or another summary. These approaches are not interchangeable. The registry record does not report whether the primary endpoint was analyzed as binary, continuous, or in another form, nor does it report the corresponding effect measure.

What does uncertainty describe?

A confidence interval is a statistical range around an estimate that reflects sampling uncertainty under the assumptions of the method. A narrow interval indicates greater precision than a wide interval, although either interval must be interpreted in context. A p value addresses how compatible observed data are with a specified statistical null model; it does not measure clinical importance or the probability that a treatment hypothesis is true. Neither confidence intervals nor p values for the primary comparison are reported in the registry record.

Why can repeated measurements matter?

Cardiac output and blood pressure may be observed during the operation, and repeated observations from the same participant are generally correlated rather than independent. Treating each observation as unrelated can misstate uncertainty. A suitable analysis may need to account for the within-participant structure, or it may use a prespecified participant-level summary. The registry record does not report how repeated intraoperative measurements were handled, how baseline was defined, or which time points contributed to the endpoint.

When outcomes are summarized as the percentage within a target range, interpretation also depends on the threshold and on how missing measurements are treated. A participant with incomplete monitoring data might be excluded, classified under a specified rule, or addressed using another method. Each choice can affect the estimate. No such rule is reported in the registry record.

What is over-dispersion?

Over-dispersion is a general feature of count or binary data in which observed variability exceeds what a chosen model assumes. If present and ignored, standard errors can be too small, making intervals appear more precise than warranted. Model choice should reflect the outcome structure and observed variability. The registry record does not report a model for the primary endpoint or whether over-dispersion was assessed; this general concept should not be taken to mean it occurred in this trial.

For all these reasons, an endpoint label and trial design are not enough to reconstruct an analysis. The registry record does not report a prespecified statistical plan, effect estimate, uncertainty interval, or test for the primary comparison. No analysis method should be attributed to the investigators without that information.

10. Multiplicity, Missing Data and Analysis Populations

A trial can assess multiple outcomes, outcome categories, or measurement times. If many comparisons are tested, the chance of obtaining at least one apparently notable result by chance can increase. Statistical plans sometimes address this through a hierarchy of outcomes, adjusted significance thresholds, or other procedures. Such methods are general options; the registry record does not report a multiplicity strategy for this study.

The record identifies a primary outcome about cardiac output within and outside 20% of baseline values, and lists nausea and vomiting and umbilical cord pH as secondary outcomes. The primary-outcome description also refers to mean cardiac output differences and blood pressure management. The record does not specify which outcome categories or time points were tested, how the primary endpoint was summarized, or whether secondary analyses were adjusted for multiple comparisons. Numerical outcome results and p values are not reported in the registry record.

Missing-data handling is also not reported in the registry record. There is no account of missing measurements, participant withdrawals, exclusions from outcome analyses, or methods used to address incomplete observations. That information matters because missingness can affect both the number of observations analyzed and the interpretation of a group comparison.

The analysis populations are not defined in the registry record. It does not state whether the primary analysis included participants according to randomized assignment, only those who received the assigned care, or another population. The enrollment figure alone does not establish the number analyzed for each endpoint. These omissions limit assessment of the analysis and make it inappropriate to infer how missing data, multiple outcomes, or group assignment were handled.

11. 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 3% reporting threshold.

Most frequent non-serious adverse event terms

The adverse-event record lists 30 participants at risk in each group. It records 0 serious adverse events in the control group and 0 in the study group. For other adverse events, it records 1 in the control group and 0 in the study group. These are recorded counts, not estimates of comparative risk, and the record does not provide a statistical comparison or uncertainty interval for them.

The registry record does not list any serious adverse-event terms. Death counts are not reported in the registry record. The meaning and scope of the “other” event category, including event definitions, collection procedures, and the time period covered, are not described in the adverse-event information. These counts therefore should not be interpreted as a complete account of all possible safety outcomes or as evidence of a difference between groups.

Zero recorded events in a group do not establish that the underlying event risk is zero. Safety counts are most informative when read alongside definitions, follow-up duration, completeness of collection, and uncertainty estimates; these details are not reported in the registry record. The figures describe what is recorded, but they do not establish a causal safety conclusion.

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

The trial addresses a practical statistical question: whether adding cardiac output monitor data to blood pressure and heart rate information changes vasopressor-guided care and the maintenance of hemodynamic measurements during cesarean delivery under spinal anesthesia. Randomization and a parallel-group design are appropriate features for comparing care strategies, but those design features alone do not answer the question.

The registry record does not report numerical results for the primary endpoint or the listed secondary outcomes. It therefore does not show the size or direction of any difference between groups, or how precisely any difference was estimated. It also does not report a numerical analysis of whether vasopressor choice changed. The descriptions of the intervention and intended outcomes should not be read as findings.

The recorded adverse-event counts are limited: the registry lists 0 serious adverse events in each group and 1 other adverse event in the control group and 0 in the study group. The record does not provide enough detail to interpret those counts as a comparative safety analysis. They do not resolve the unanswered questions about the primary endpoint or secondary outcomes.

More broadly, a study's completed status means the registry marks it completed; it does not establish that every planned analysis was reported. The enrollment of 60 describes the recorded trial enrollment, not the number of participants with complete measurements or the precision of an outcome estimate. Without outcome estimates, uncertainty measures, analysis populations, and missing-data information, the clinical and statistical implications remain undetermined from the registry record.

The trial's stated objective can be described, and its design and recorded adverse-event counts can be read, but the registry record does not establish whether monitor-guided care changed management or outcomes. No conclusion about benefit or lack of benefit follows from the absence of reported outcome estimates.

13. Why This Trial Matters Statistically

This trial is statistically interesting because the intervention adds physiological information to an existing care strategy rather than comparing a device with no monitoring. The control group had cardiac output measured, but the information was not used by anesthesiologists; the study group used it alongside blood pressure and heart rate. That structure focuses the intended contrast on whether making the additional measurement available changes decisions and outcomes.

The question also illustrates the importance of matching an endpoint to the clinical objective. The registry describes a threshold-based percentage, mean cardiac output differences, maintaining blood pressure and cardiac output near baseline, and changes in vasopressor choice. These concepts are related but are not the same statistical outcome. Clear definitions of the participant-level summary, measurement times, threshold classification, and analysis would be needed to determine precisely what comparison the primary result represents.

Repeated intraoperative measurements raise a further general issue: observations from the same participant are related, and their treatment in the analysis can affect precision. A registry description of the clinical aim does not reveal whether measurements were summarized by participant or analyzed longitudinally. That methodological information is not reported in the registry record.

The record also demonstrates why trial design and trial findings must be kept separate. Random allocation, an enrollment of 60, and a completed status are useful design and administrative details, but they cannot replace group estimates or uncertainty intervals. Since numerical results for the primary and secondary outcomes are not reported, the central comparison cannot be evaluated statistically from this record. The distinction between a clearly stated research question and a fully interpretable result is essential when reading clinical trial registries.

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.

Several limitations of interpretation arise from the information recorded for this specific trial. First, the primary outcome is described in more than one way: its title refers to the percentage of participants with cardiac output within and outside 20% of baseline, while the narrative refers to mean cardiac output differences and maintaining blood pressure and cardiac output within the threshold. The exact endpoint definition and the relationship between these descriptions are not reported in the registry record.

Second, numerical primary and secondary outcome results are not reported in the registry record. Group estimates, comparisons, and measures of uncertainty are absent, so the direction, magnitude, and precision of any outcome difference cannot be assessed. The record does not report a numerical analysis of vasopressor choice either.

Third, key analysis details are not reported in the registry record: the statistical plan, analysis population, handling of repeated measurements, missing-data methods, multiplicity approach, and participant flow for each outcome. The record also does not provide detailed eligibility criteria or a full account of masking beyond listing the study as unmasked. These gaps limit assessment of the validity and scope of any potential comparison.

Finally, the adverse-event record gives counts but does not describe event definitions or collection procedures, and it does not report death counts. The recorded counts cannot serve as a substitute for the unreported outcome analyses or a complete safety interpretation.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Ninvasive Cardiac Output Measurements During Cesarean Delivery Under Spinal Anesthesia. — NCT01928797.
• Registry record last updated 2017-11-14; status last verified 2017-10.
• Results first posted 2017-09-26.
• 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

The registry record describes a completed, randomized, unmasked, parallel-group trial sponsored by Brigham and Women's Hospital. It records an enrollment of 60, with a study start date of 2013-11-01 and primary completion date of 2014-12-31.

The comparison was between vasopressor care guided by blood pressure and heart rate, with cardiac output measured but not used in the control group, and care that additionally used cardiac output monitor data in the study group. The primary outcome concerns cardiac output within and outside 20% of baseline values during surgery. Nausea and vomiting and umbilical cord pH are also listed as outcomes.

Numerical results for the primary and secondary outcomes, and the statistical analysis details needed to interpret them, are not reported in the registry record. The adverse-event record lists 0 serious events in each group and other adverse-event counts of 1 in the control group and 0 in the study group.