Midodrine for the Treatment of Refractory Hypotension: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Midodrine for the Treatment of Refractory Hypotension (NCT01531959), a randomized phase 3 study. The primary outcome is Time Until Discontinuation of IV Vasopressors.

2. Clinical Question

3. Trial Design

This is a phase III, randomized, quadruple-masked, parallel-group trial comparing midodrine with placebo. The registry names Massachusetts General Hospital as sponsor and records the trial as completed. The recorded start is 2012-04, and primary completion is 2019-06. Enrollment is 139.

The clinical setting is patients with refractory hypotension who were otherwise ready for discharge from the ICU. The registry’s stated hypothesis links midodrine to shorter IV vasopressor duration and SICU length of stay, while also naming MGH length of stay and ICU readmission as outcomes the investigators did not want to increase. This is a statement of the trial’s hypothesis, not evidence that any of those outcomes changed.

The study includes Midodrine and Placebo groups. The primary outcome records 66 participants in each group. The registry does not explain the relationship between these group counts and total enrollment, including whether some enrolled participants were excluded from the posted outcome data or had missing outcome information. Allocation ratio, study-drug dose and schedule, eligibility details beyond the population description, and the precise randomization procedure are not reported in the registry record.

The masking field is recorded as quadruple. Which parties were masked and how masking was maintained are not reported in the registry record. The registry lists five outcome measures: the primary time until discontinuation of IV vasopressors and four secondary outcomes. Numerical secondary results are posted for ICU readmission and a combined measure covering hypertension, bradycardia, and hemodynamically significant tachyarrhythmias. Numerical results for ICU length of stay and hospital length of stay are not reported in the registry record. A detailed statistical analysis plan and reported analyses are also not available 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: 139 participants provided informed consent and were enrolled. 3 participants subsequently did no loner meet eligibility criteria and were therefore not randomized, resulting in a total number of started/randomized participants of 136.

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 Time Until Discontinuation of IV Vasopressors, measured over From initiation of the study drug until discontinuation of IV vasopressors, assessed up to 400 hours.

The primary endpoint is time from initiation of the study drug until discontinuation of IV vasopressors, measured in hours and assessed up to 400 hours. It focuses on the duration of ongoing vasopressor treatment in the trial’s target population. The registry describes it as the number of hours from initiation of midodrine until IV vasopressors were discontinued; the comparator group is reported as placebo.

The endpoint is summarized by the median and inter-quartile range. In general, the median is the midpoint of the observed times when ordered, while the inter-quartile range describes the spread between the lower and upper quartiles. These summaries can describe a time outcome without assuming that its distribution is symmetric. The reported median was 23.5 hours for midodrine and 22.5 hours for placebo. The inter-quartile ranges were 10.0 to 54.0 hours and 10.4 to 40.0 hours, respectively.

Time to vasopressor discontinuation is relevant to the stated hypothesis about duration of IV vasopressor use. It is not equivalent to ICU or hospital length of stay, nor does it establish whether discontinuation was sustained or whether patients experienced later complications. The registry does not report the method used to handle participants whose vasopressors were not discontinued within the assessment window, or a statistical comparison with an uncertainty interval for this primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the trial as randomized, quadruple-masked, and parallel-group, but does not report a detailed statistical analysis plan. The distinction matters: design labels describe broad features of the trial, whereas an analysis plan would specify how outcomes, missing observations, and comparisons were to be handled. Because that plan and reported analyses are absent, the statistical interpretation must stay close to the posted summaries and clearly distinguish descriptive observations from inferential claims.

Why report a median and inter-quartile range?

Time outcomes can be unevenly distributed, with many observations concentrated in one range and a smaller number taking much longer. In general, the median describes the midpoint of ordered observations and is less affected by extreme values than the mean. The inter-quartile range describes the central spread, from the lower quartile to the upper quartile. Neither summary alone gives the full distribution or an uncertainty interval for the difference between groups.

The registry reports medians and inter-quartile ranges for time until discontinuation of IV vasopressors. It does not report a primary between-group estimate with a confidence interval or a p-value. A confidence interval, in general, expresses the range of effect values reasonably compatible with the data under the method used; it does not guarantee that the true value lies in that interval. Without such an interval or a reported primary test, the precision of the contrast between the posted medians is not established.

What is special about a time-to-event outcome?

In general, a time-to-event outcome records the time until a defined event occurs. Some participants may not experience the event during the observation period, or their follow-up may end before the event is observed. Appropriate methods can account for such incomplete observation, often through censoring. The registry gives an assessment window of up to 400 hours, but does not report how observations without a recorded discontinuation within that window were handled. It also does not state whether the comparison used a time-to-event model, a rank-based method, or another approach. The posted median summaries should not be taken as proof that any particular method was used.

How should the secondary comparisons be read?

The secondary outcome comparisons include recalculated, unadjusted summaries based on posted counts. A risk difference is, in general, a difference between the proportions experiencing an outcome in two groups. Its confidence interval describes uncertainty around that estimated difference under the calculation method. A p-value assesses compatibility of the observed data with a specified null hypothesis, given the assumptions of the test; it is not the probability that the null hypothesis is true and does not measure clinical importance.

The p-values for the secondary comparisons are reported as unadjusted. The registry does not report an adjustment for testing multiple outcomes, nor does it report which outcome comparisons were prespecified in a formal analysis plan. When several outcomes are examined, the chance of at least one apparently unusual result can increase. General statistical practice therefore treats unadjusted secondary results as more exploratory than a prespecified primary analysis, particularly when event counts are small. No multiplicity correction should be inferred from the posted record.

The recalculated comparisons use the posted arm counts and are not a substitute for a full trial analysis. The registry does not report covariate adjustment, stratification, or a model for the secondary outcomes. The confidence intervals and p-values should therefore be understood as unadjusted comparisons, not as estimates controlling for baseline characteristics or other design features. The record does not indicate that these recalculations were the investigators’ planned analyses.

What do the planning illustrations mean?

General power calculations estimate how much information a future study would need, under stated assumptions, to detect a chosen effect with a specified probability. The planning illustrations in the posted material use the observed effect as a starting point and consider smaller fractions of it. The stated assumptions include a two-sided significance level of 0.05, equal allocation, and a normal approximation. They are illustrations based on the observed result, not the original trial’s design justification, and not observed power.

Observed power is not a useful retrospective measure of whether a study succeeded; once the data are observed, the effect estimate and its uncertainty are more informative. Planning calculations based on an observed effect can also be unstable when the underlying result is imprecise, especially for outcomes with few events. The registry does not report the original sample-size justification, the assumptions used to design this trial, or whether any planned sample-size target was revised.

What can be inferred from the registry record?

The posted outcome summaries support direct description of the reported medians, ranges, and event counts. They do not support reconstruction of unreported analyses. The analysis population, handling of missing observations, treatment of participants with incomplete follow-up, and rules for deviations from assigned treatment are not reported in the registry record. Nor is there a reported protocol-level account of interim analyses or stopping rules. These omissions limit how completely the posted results can be assessed, but they do not change the values that are reported.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report whether the trial’s statistical plan used a hierarchy of outcomes, adjusted significance thresholds, or another method to account for multiple comparisons. The listed outcomes include a primary endpoint and four secondary outcomes. Without a reported plan, it is not possible to determine which secondary comparisons were prespecified for formal testing or how their results were intended to be interpreted together. The posted secondary p-values are unadjusted.

Missing-data methods are not reported in the registry record. This includes the number of participants with missing primary or secondary outcomes, reasons for missingness, and any method used to handle incomplete observations. The relationship between enrollment of 139 and the 66 participants recorded in each primary outcome group is also not explained. It should not be assumed that all enrolled participants contributed to every analysis, or that any particular exclusion or imputation method was used.

The record does not identify the analysis population, such as whether participants were analyzed according to randomized assignment or according to treatment received. It does not report how treatment discontinuation, protocol deviations, or incomplete follow-up were handled. For a time-to-event outcome assessed up to 400 hours, the approach to participants without a recorded event during that period is not stated.

Interim analyses, stopping rules, and the original sample-size justification are not reported in the registry record. These omissions do not show that such procedures were or were not used; they mean the posted record does not document them. In general, multiplicity, missing-data handling, and analysis-population definitions affect how uncertainty and potential bias should be assessed. Their absence from the record limits the ability to reproduce or fully evaluate the trial’s intended inferential analysis.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: death (1.5%).

The registry records serious adverse events in 0 of 66 participants in the midodrine group and 1 of 66 in the placebo group. It records deaths in 0 participants in the midodrine group and 1 in the placebo group; the listed serious adverse event term is Death, at 1.5%. These are small counts and should be read as counts observed in the registry record, not as a reliable estimate of comparative risk.

Zero reported events in a group does not establish that an event cannot occur, and a single event in the other group does not establish a causal relationship with treatment. The record does not provide a detailed narrative of the event, its timing, or an assessment of relatedness. It also does not report a formal safety comparison or uncertainty interval for serious adverse events.

The registry separately records other adverse events affecting 20 participants in the midodrine group and 17 in the placebo group. The broader event details and participant-level patterns are not available in the summary. Safety counts should therefore be considered descriptive and interpreted alongside the limited follow-up and reporting details documented in the registry, rather than as a definitive comparison of safety between groups.

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

The primary result describes time until IV vasopressors were discontinued in the two randomized groups. The reported medians are 23.5 hours for midodrine and 22.5 hours for placebo, with inter-quartile ranges of 10.0 to 54.0 hours and 10.4 to 40.0 hours. These summaries show the distributional summaries reported in the registry; they do not establish the size or precision of a treatment effect. No inferential comparison for the primary endpoint is reported in the registry record.

The findings do not establish that the groups are equivalent, that any difference is absent, or that the primary endpoint changed by a particular amount. The registry also does not provide numerical results for ICU and hospital length of stay. Therefore, the stated hypothesis about length of stay cannot be evaluated from the posted numerical results. The available secondary counts concern readmission and a combined cardiovascular event measure, which are distinct from the primary endpoint and have their own uncertainty.

In general, randomized comparisons can support causal interpretation when the trial design and analysis are carried out as planned and relevant sources of bias are addressed. The registry identifies randomization and quadruple masking, but does not report enough detail to assess the procedures or the analysis population. The absence of a documented primary inferential analysis, detailed missing-data handling, and multiplicity plan limits the strength of conclusions that can be drawn from the record alone.

These results do not offer medical advice and do not determine what care is appropriate for an individual. They describe the outcomes posted for this trial. Further interpretation would require fuller information about the protocol, participant flow, outcome completeness, and the planned analysis, none of which is reported in the registry record.

13. Why This Trial Matters Statistically

This trial illustrates why an outcome’s summary measure and its uncertainty need to be considered together. A median and inter-quartile range can describe a time outcome clearly, but group medians alone do not show how precisely the groups differ. Here, the registry posts descriptive primary summaries without a confidence interval or p-value for the primary comparison. That makes it possible to state what was observed, but not to assess the precision of a between-group effect from the primary result alone.

The record also demonstrates how different endpoints answer different statistical questions. Vasopressor discontinuation time, ICU readmission, cardiovascular events, and length of stay are not interchangeable. Secondary counts can add context, but unadjusted findings across multiple outcomes carry greater risk of chance patterns, particularly when event counts are limited. A complete interpretation depends on knowing which outcomes were prespecified and how the analyses were planned.

Sample-size planning also requires careful interpretation. The planning illustrations are based on observed effects and stated assumptions, rather than the original trial design. Such illustrations can help convey how the amount of information needed changes under different assumed effect sizes, but they are not evidence of the trial’s observed power and do not recover the original design rationale. The registry does not report that rationale.

Finally, the record’s missing details matter statistically. The enrollment figure and posted outcome group sizes are not reconciled, and the analysis population, missing-data handling, and full analysis plan are not documented. This case therefore distinguishes a completed trial record from a fully reported statistical analysis: completion status and posted numerical summaries do not, on their own, resolve uncertainty about how results were generated or how much weight they can support.

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 most important limitation in interpreting this trial record is that the primary endpoint has descriptive summaries but no reported inferential comparison. Without an uncertainty interval or reported primary test, the precision of the difference between groups cannot be evaluated from the registry record. The median and inter-quartile range do not provide a complete account of the time-to-event distribution.

The registry does not report how observations were handled when IV vasopressors were not discontinued within the assessment window, or how incomplete follow-up was treated. This is particularly relevant to a time-to-event outcome. It also does not report the analysis population or reconcile total enrollment of 139 with the 66 participants recorded in each primary group. These are reporting gaps; the record does not establish their cause.

Two of the four listed secondary outcomes have numerical results posted, while numerical results for ICU and hospital length of stay are not reported in the registry record. The available secondary p-values are unadjusted, and no multiplicity plan is reported. Counts for adverse events and readmissions are limited, so estimates based on these data may be uncertain. The record does not give enough detail to determine the full event ascertainment process or the relatedness assessment for the serious event.

Other trial-specific details are also absent, including drug dose and schedule, the allocation procedure, the parties covered by masking, the original sample-size justification, and any interim analysis or stopping rules. The registry does record randomization and quadruple masking, but the operational details are not reported. These limitations constrain assessment of the trial’s design and analyses; they do not justify assumptions about unreported procedures or results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Midodrine for the Treatment of Refractory Hypotension — NCT01531959.
• Registry record last updated 2020-10-28; status last verified 2020-10.
• Results first posted 2019-09-06.
• 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 phase III, randomized, quadruple-masked, parallel-group trial sponsored by Massachusetts General Hospital. It records enrollment of 139, a start date of 2012-04, and primary completion in 2019-06. The population was patients with refractory hypotension who were otherwise ready for discharge from the ICU; the study compared midodrine with placebo.

The primary outcome was time until discontinuation of IV vasopressors, measured in hours and assessed up to 400 hours. The posted medians were 23.5 hours for midodrine and 22.5 hours for placebo. No inferential comparison for that primary result is reported in the registry record. Numerical secondary results are posted for ICU readmission and a combined cardiovascular event measure; numerical results for ICU and hospital length of stay are not reported.

The record does not report a detailed statistical analysis plan, analysis population, missing-data methods, multiplicity procedure, or original sample-size justification. The posted results support descriptive interpretation, with caution about uncertainty and incomplete reporting.