Phenylephrine vs. Norepinephrine Infusion After Spinal Anesthesia for Cesarean Delivery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Phenylephrine vs. Norepinephrine Infusion After Spinal Anesthesia for Cesarean Delivery (NCT02354833), a randomized phase 4 study. The primary outcome is Number of Rescue Boluses to Maintain SBP.

2. Clinical Question

The study’s stated purpose was to compare the infusions in maintaining blood pressure during spinal anesthesia for cesarean delivery. The registry describes blood pressure control as relevant to nausea and vomiting during and after cesarean delivery, but the primary outcome reported is rescue-bolus use, not nausea or vomiting. The listed secondary outcome is the percentage of participants experiencing both nausea and emesis.

The primary outcome is a measure of how often additional rescue medication was used to keep systolic blood pressure within the stated target range. It therefore captures a treatment-management measure over the surgical period, rather than a direct measure of blood pressure values over time. The registry reports the primary outcome values and a between-group test, but does not report a confidence interval or a measure of dispersion for those values. Those omissions limit how precisely the size of the between-group difference can be assessed.

3. Trial Design

The registry identifies this as a Phase 4, randomized, parallel-group trial with no masking. It lists West Virginia University as the sponsor and the status as completed. The recorded start was 2014-08, and the primary completion was 2015-08. Enrollment is listed as 85. The brief summary states that the study planned to enroll 80 pregnant research subjects aged 18 years and above; the registry record does not explain the relationship between that planned number and the recorded enrollment.

Participants were assigned to one of two infusion groups according to a computer-generated system, as described in the brief summary. The phenylephrine group received a continuous infusion at 0.1 mcg/kg/min, while the norepinephrine group received a continuous infusion at 0.05 mcg/kg/min. The brief summary says participants would receive spinal anesthesia with a local anesthetic and morphine. The record identifies the trial as unmasked; it does not report who knew each participant’s assignment or whether outcome assessment was masked.

The primary outcome was the number of rescue boluses to maintain systolic blood pressure within 100-120% of baseline, measured at the time of surgery, up to 2 hours. The record lists one secondary outcome: the percentage of participants experiencing both nausea and emesis. It also records 4 outcome measures and 5 analyses, but the full descriptions and results for all of them are not available in the trial details. The registry record does not report the randomization procedure beyond the computer-generated assignment described in the summary, allocation concealment, or a detailed statistical analysis plan.

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.

Population: We conducted a prospective, observational, randomized, open labeled trial on parturient scheduled for elective cesarean delivery under spinal anesthesia.

6. Primary Endpoint

The registry lists the primary outcome as Number of Rescue Boluses to Maintain SBP, measured over At time of surgery, up to 2 hours.

The primary endpoint counts rescue boluses used to maintain systolic blood pressure within 100-120% of baseline. It applies during surgery, up to 2 hours. In this trial, a rescue bolus is an additional intervention used when the ongoing infusion is not sufficient to keep blood pressure in the target range. The endpoint therefore reflects the need for additional intervention during the period being studied.

This measure is useful as a treatment-management outcome because it represents how often clinicians had to supplement the assigned continuous infusion to meet the stated blood-pressure target. It is not itself a continuous record of blood pressure, nor does it directly quantify the duration or severity of any blood-pressure excursion. The registry does not report those additional measures as part of the primary endpoint description.

The posted results give a value of 25 for phenylephrine and 21 for norepinephrine. The record does not identify whether these values are group means, totals, or another summary of the endpoint, and it reports no measure of spread. The reported analysis is a two-sided t-test. Without a clearer summary definition and information about variation among participants, readers cannot judge the distribution of rescue-bolus counts or the precision of the group comparison from the endpoint values alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports a two-sided t-test for the primary endpoint, the number of rescue boluses used to maintain systolic blood pressure within 100-120% of baseline. It gives p = 0.12 and endpoint values of 25 for phenylephrine and 21 for norepinephrine. It does not report the test statistic, degrees of freedom, confidence interval, or a measure of dispersion. The record therefore permits a description of the reported test, but not an independent reconstruction of its uncertainty.

What does a two-sided t-test assess?

In general, a t-test compares group summaries while accounting for the estimated variability in the data. A two-sided test considers departures in either direction rather than testing only whether one group has a larger value. The p-value depends on the data, the test’s assumptions, and the null hypothesis used. The registry record does not state further details about the implementation of this t-test, such as whether a pooled-variance or unequal-variance version was used.

A test result and an effect estimate answer different questions. The test result addresses compatibility with a null hypothesis under the test’s assumptions. An effect estimate describes the magnitude and direction of the group contrast. For a fuller interpretation, estimates are commonly paired with confidence intervals, which express uncertainty in the estimated effect under the analysis method. The registry record does not report a confidence interval for the primary endpoint, so the precision of the comparison cannot be read directly from the reported p-value.

Why does the count outcome matter?

In general, count outcomes take nonnegative integer values and can have many observations at zero or a small number of common values. Their variability may increase with their average, and their distributions may be asymmetric. These features can make the assumptions behind a conventional t-test less suitable in some settings. Over-dispersion is a general concern when count data vary more than a model assumes; accounting for it can affect standard errors and confidence intervals. The registry record does not report the distribution of rescue-bolus counts, a check of test assumptions, or a count-specific model. Without those details, the appropriateness and sensitivity of the selected analysis cannot be assessed from the record alone.

The endpoint’s summary is also not clearly identified. The record gives the group values but does not say whether they are means, totals, or another summary. It lists the outcome parameter as a number and reports a t-test, but no dispersion measure or confidence interval accompanies the values. These gaps matter because the same group values can have different interpretations depending on how they were calculated and how observations are distributed.

What can be inferred from the p-value?

In general, a p-value is not a measure of clinical importance, and it is not a substitute for an effect estimate with an interval. The reported p = 0.12 should be read as the result of the registry’s stated two-sided t-test, not as a probability that the infusions are the same or different. It does not establish equivalence. The registry record does not report an equivalence or noninferiority framework, a margin, or a confidence interval to assess such a question.

The record also does not report whether the primary analysis followed an intention-to-treat, per-protocol, or other analysis population. It does not describe missing-outcome handling, adherence to assigned infusion, or exclusions from the analysis. Those details can influence the interpretation of a randomized comparison, but cannot be reconstructed from the group values and p-value alone.

What do the planning assumptions mean?

In general, sample-size calculations describe planning under stated assumptions; they are not observed power for a completed trial. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of the observed effect. The record does not report the trial’s own sample-size justification or the specific resulting planning estimates in the registry record. These planning assumptions should not be confused with the observed enrollment or with evidence about the precision of the reported primary-outcome result.

Overall, the registry states the test used and its p-value, but leaves several components needed for a fuller statistical appraisal unreported: an unambiguous endpoint summary, variability, interval estimates, test details, distributional checks, analysis population, and missing-data methods. Those omissions do not change the reported result, but they constrain independent evaluation of its robustness and precision.

10. Analyses Reported by the Sponsor

The registry reports the comparison as a two-sided t-test with p = 0.12. The primary outcome values are 25 for phenylephrine and 21 for norepinephrine. No confidence interval or dispersion measure accompanies those values, and the registry does not provide a test statistic or enough summary detail to independently reconstruct the comparison.

No simple unadjusted recalculation is available for this count-other endpoint in the record. In particular, the posted summary does not identify the type of group summary represented by the values or provide the variability needed for a new comparison. There is therefore no recalculated estimate or p-value to set against the registry’s reported analysis. The registry record does not indicate a discrepancy between a recalculation and the reported analysis; rather, a recalculation cannot be made from the available summary information.

The registry’s reported test should consequently be described as the posted analysis, not as independently confirmed by a separate calculation. Its p-value is evidence about the test result under its assumptions, but the lack of an interval estimate and supporting summaries limits assessment of precision and robustness.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures and 5 analyses, and identifies one secondary outcome: the percentage of participants experiencing both nausea and emesis. The primary outcome is the number of rescue boluses to maintain systolic blood pressure within 100-120% of baseline. The registry entries available for interpretation do not include results for the listed secondary outcome or full results for every outcome measure and analysis.

When a study assesses multiple outcomes or conducts multiple analyses, the chance of at least one apparently notable result can increase. In general, multiplicity methods can address this issue, but they depend on which outcomes and comparisons were planned and how they were prioritized. The registry record does not report a multiplicity adjustment, a hierarchy among outcomes, or a plan for handling multiple analyses. The reported primary-outcome p-value should therefore be interpreted as the result of its stated test, without assuming that it was adjusted for other analyses.

The record does not report the number of participants with missing primary-outcome data, reasons for missingness, or the method used to handle missing data. It also does not identify the analysis population used for the reported test, such as an intention-to-treat or per-protocol population. Random assignment is described, but the record does not explain whether all randomized participants were analyzed in their assigned groups or whether any exclusions occurred. These omissions leave uncertainty about how closely the reported analysis corresponds to the randomized comparison.

The registry does not report interim analyses, stopping rules, or whether the analysis plan was prespecified. These items should not be inferred from the trial’s completed status or from the reported p-value. In the absence of that information, the available result is best read as the reported primary-outcome comparison, with multiplicity and missing-data handling not reported in the registry record.

12. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports no serious adverse events in either group: 0 among 38 participants at risk in the phenylephrine group and 0 among 43 participants at risk in the norepinephrine group. It reports other adverse events in 24 participants in the phenylephrine group and 22 participants in the norepinephrine group, with 38 and 43 participants at risk, respectively. These are the counts recorded in the adverse-event summary; they do not establish that all events were alike in type, severity, or duration.

No serious adverse-event terms are listed. Death counts are not reported in the registry record. The record does not specify the adverse-event observation period, event definitions, severity grading, or how events were collected. The zero serious-event counts therefore describe what was recorded in the registry, but do not by themselves establish the absence of risk. Likewise, the other-adverse-event counts are descriptive and should not be treated as a formal comparison of safety without details about event definitions, follow-up, and analysis.

The adverse-event information is separate from the primary endpoint. Rescue-bolus use measures an aspect of blood-pressure management, whereas adverse-event counts describe reported safety events. Neither outcome should be used as a substitute for the other.

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

The registry record supports a narrow statement: it reports values of 25 for phenylephrine and 21 for norepinephrine for the primary outcome, and reports a two-sided t-test with p = 0.12. The endpoint concerns rescue boluses used to keep systolic blood pressure within 100-120% of baseline during surgery, up to 2 hours. The result is about that measure in the trial setting, not a general comparison across all outcomes or all uses of the infusions.

The result does not establish that the groups are equivalent. A nonsignificant p-value is not proof that there is no difference, and the registry does not report an equivalence margin or an equivalence analysis. Nor does the p-value show how large or clinically important a contrast might be. The absence of a confidence interval and dispersion measure means the precision of the comparison is not reported.

The endpoint values should also be interpreted cautiously because the registry does not state clearly whether they are means, totals, or another summary. The record does not report individual participant data, distributions of counts, or checks of the t-test assumptions. It is therefore not possible to assess the shape or spread of the rescue-bolus counts from the posted summary alone.

The trial’s randomization and parallel-group design are relevant strengths for comparing assigned infusions, but the record does not describe allocation concealment, analysis populations, missing-data handling, or adherence. These unanswered questions limit assessment of how the reported analysis relates to the randomized assignment. The record names nausea and emesis as a secondary outcome but does not include its result in the information, so no conclusion about that outcome follows from the primary-outcome test.

The appropriate interpretation is descriptive and bounded: the registry records a primary-outcome comparison and its p-value, while leaving important information about effect precision and analysis details unreported. The result neither establishes a clinically important benefit nor proves that the groups have the same outcome.

14. Why This Trial Matters Statistically

This trial illustrates the distinction between reporting a test result and reporting the information needed to understand an effect. A two-sided t-test p-value is available, but the record does not give a confidence interval, measure of dispersion, or a clear description of the group summary represented by the primary-outcome values. A reader can identify the test and its result, yet cannot fully assess the magnitude or precision of the comparison.

The outcome is a count of rescue boluses. In general, choosing an analysis for count data requires attention to the distribution and variability of the counts, not only to the fact that a group comparison was performed. The registry does not report those details or any assessment of test assumptions. This makes the record useful for illustrating why endpoint type, summary definition, and uncertainty measures belong together in statistical reporting.

The design also provides a reminder that randomization is one part of interpretation rather than a complete description of an analysis. The trial is identified as randomized and parallel, but the record does not report the analysis population, missing-data approach, or multiplicity strategy. Those details are needed to understand how the reported estimate and test relate to all randomized participants and to the other outcomes assessed.

Finally, the registry distinguishes a primary outcome from a secondary outcome involving nausea and emesis, but the available results do not include the secondary outcome’s result. Keeping claims tied to the reported endpoint avoids extending a finding about rescue-bolus use to other outcomes. The central statistical lesson is to read the p-value alongside the endpoint definition, the group summaries, uncertainty, and the limits of what the registry reports.

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.

Several limitations specific to this trial’s registry record affect interpretation. The primary endpoint is described as a number of rescue boluses, but the record does not say whether the values 25 and 21 are means, totals, or another summary. It also gives no measure of dispersion or confidence interval. As a result, the magnitude and precision of the group comparison cannot be fully evaluated from the posted results.

The reported test is a two-sided t-test, but further implementation details and checks of its assumptions are not reported. This is relevant because the endpoint is a count. The record contains no participant-level outcome data or distributional summary with which to assess whether the test’s assumptions fit the observed counts. No alternative count-based analysis is reported in the registry record.

The record does not describe allocation concealment, who was aware of assignment, adherence to the assigned infusion, exclusions, or the analysis population. Masking is listed as none, but the record does not explain who was unmasked or whether outcome assessment could have been masked. Missing-data amounts and handling are also not reported. These gaps limit assessment of potential bias and of how the analysis reflects random assignment.

The brief summary says the study planned to enroll 80 participants aged 18 years and above, while the registry lists enrollment of 85. The record does not explain this difference. It also does not report a sample-size justification, interim-analysis procedures, or a detailed statistical plan. The secondary outcome is named, but its result is not included in the registry record. Safety-event definitions and follow-up duration are not reported. These are limitations of the record’s statistical and outcome detail; they should not be filled in by assumptions about the trial.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Phenylephrine vs. Norepinephrine Infusion After Spinal Anesthesia for Cesarean Delivery — NCT02354833.
• Registry record last updated 2017-01-04; status last verified 2017-01.
• Results first posted 2017-01-04.
• 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

The registry record describes a completed Phase 4, randomized, parallel-group trial with no masking, sponsored by West Virginia University. It compares continuous phenylephrine at 0.1 mcg/kg/min with continuous norepinephrine at 0.05 mcg/kg/min after spinal anesthesia for cesarean delivery. Enrollment is listed as 85.

The primary outcome is the number of rescue boluses used to maintain systolic blood pressure within 100-120% of baseline during surgery, up to 2 hours. The reported values are 25 for phenylephrine and 21 for norepinephrine; the registry reports a two-sided t-test with p = 0.12. It does not report a confidence interval or measure of dispersion, and the type of summary represented by the outcome values is not specified.

The record names one secondary outcome concerning nausea and emesis, but its result is not included in the registry record for interpretation. Analysis populations, missing-data methods, multiplicity handling, and several details needed to evaluate the primary comparison are not reported in the registry record.