Field Trial of Hypotensive Versus Standard Resuscitation for Hemorrhagic Shock After Trauma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Field Trial of Hypotensive Versus Standard Resuscitation for Hemorrhagic Shock After Trauma (NCT01411852), a randomized phase 2 study. The primary outcome is Total Volume of All Crystalloid Given for Early Resuscitation (Feasibility).

2. Clinical Question

3. Trial Design

This was a randomized, single-masked, parallel-group phase 2 pilot trial sponsored by the University of Washington. The registry lists an enrollment of 192 and a completed status. The recorded start was 2012-03, and primary completion was 2013-04. The registry describes the study as a comparison of controlled resuscitation and standard resuscitation for patients with hemorrhagic shock after trauma.

The treatment groups differed in their assigned saline resuscitation approach. The standard resuscitation arm is described as early aggressive fluid resuscitation, while the controlled resuscitation arm used a smaller bag intended to limit fluid administered in the field. The registry record does not specify who was masked, how masking was maintained, or whether masking was assessed. It also does not report the randomization sequence method, allocation concealment procedures, or the protocol for deviations from assigned treatment.

The primary feasibility outcome was total volume of crystalloid given for early resuscitation, measured in liters. The record defines the endpoint period from emergency medical services arrival at the scene until the end of the study period, and separately describes the period as running from first intravenous or intraosseous insertion through two hours after hospital arrival or hemorrhage control, whichever occurred first. The registry wording therefore supplies both a scene-based endpoint description and a timeframe with hospital-based stopping conditions; additional operational clarification is not reported in the registry record.

The study was designated a pilot trial, and its stated primary aim was to assess feasibility and safety. A formal sample-size justification, planned interim analyses, and a detailed statistical analysis plan are not reported in the registry record. The enrollment figure describes the trial, while the number contributing to the primary endpoint differs by arm in the posted outcome data. Reasons for any difference between enrollment and outcome counts are not reported 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.

Prehospital Intervention Phase

Reasons for not completing this period:

Hospital Intervention Phase

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Patients with traumatic shock due to blunt or penetrating mechanisms

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: Demographic, Injury, and Out-of-Hospital Care Characteristics

6. Primary Endpoint

The registry lists the primary outcome as Total Volume of All Crystalloid Given for Early Resuscitation (Feasibility), measured over From time of first intravenous or intraosseous insertion through the first 2 hours after hospital arrival or hemorrhage control, which ever occurs first.

The primary endpoint measures the volume of crystalloid fluid administered during early resuscitation. It is reported as a mean in liters, with a 95% confidence interval for each arm. The endpoint is called early crystalloid volume in the registry description. The study rationale frames this measure as a feasibility outcome: the stated null hypothesis was that controlled resuscitation would result in the same volume of early crystalloid as standard crystalloid resuscitation.

As a feasibility measure, fluid volume addresses whether the assigned approaches produced different amounts of early crystalloid administration in the trial setting. It does not by itself establish whether one approach improves survival, prevents complications, or changes other patient outcomes. Those questions require their own outcome definitions and analyses. Although the brief summary identifies survival to 24 hours as a safety hypothesis, survival findings are not reported in the registry record.

The endpoint description uses a scene-to-study-period definition, while the stated timeframe refers to first intravenous or intraosseous insertion through the first two hours after hospital arrival or hemorrhage control, whichever occurred first. These descriptions may reflect different aspects of the endpoint definition, but the registry record does not explain their relationship. The volume measure is therefore best interpreted within the definitions as posted, without assuming additional timing or measurement rules.

A mean summarizes the average recorded volume in each group. The confidence interval communicates uncertainty around that estimated mean; it is not a range containing every participant's fluid volume. The interval for the between-group difference is especially relevant to the feasibility comparison because it expresses uncertainty about the contrast between assigned approaches.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical explanation: a randomized comparison estimates how an outcome differs between assigned groups, while random allocation is intended to reduce systematic differences in treatment assignment. The registry identifies this study as randomized, single-masked and parallel-group. It does not report the sequence-generation method, allocation concealment, the identity of the masked people, or details of the analysis population. Those omissions limit what can be said about the trial's implementation and analysis beyond its recorded design labels.

What the mean represents

The primary endpoint is a continuous measure, expressed as a volume in liters. A group mean is the arithmetic average of the recorded values for participants contributing to that endpoint. Means are useful for summarizing a distribution in a compact form, but they can be affected by unusually high or low observations. The registry does not post a measure of dispersion for the primary endpoint, such as a standard deviation, so the amount of participant-to-participant variation cannot be read directly from the posted primary results.

The endpoint results include confidence intervals around each group mean and around the between-group difference. General statistical explanation: a confidence interval describes the uncertainty of an estimate under a specified statistical procedure and its assumptions. A narrower interval indicates greater precision than a wider interval on the same scale. The interval is not a prediction range for individual outcomes and should not be interpreted as showing where most participants' values fall. The registry does not identify the method used to calculate the primary confidence intervals.

Why the difference and its direction matter

The posted primary contrast is defined as standard resuscitation minus controlled resuscitation. This direction determines how to read the sign: a positive difference indicates a higher estimated mean in the standard group. When comparing results across outcomes, the contrast definition matters because a difference calculated in the reverse order has the same magnitude but the opposite sign. The registry does not report a primary p-value, so the primary interpretation rests on the posted estimates and confidence intervals rather than a reported significance test.

General statistical explanation: an estimate is a point summary, while its interval conveys uncertainty around that summary. A result's practical importance cannot be determined from the point estimate alone; it depends on the outcome's meaning, the plausible range of effects, and the clinical context. The registry does not state a threshold for a clinically important difference in early crystalloid volume. Consequently, the posted difference should not be labelled clinically important or unimportant on the basis of the record alone.

Reading the secondary comparisons

The posted secondary outcomes include binary and continuous measures. For binary measures, a risk difference expresses the difference between group proportions on the probability scale. For continuous measures, a mean difference expresses the difference between group averages in the measure's units. These statistics answer different questions and are not interchangeable. The registry includes an unadjusted recalculation for certain secondary comparisons, alongside registry-reported analyses. Such a recalculation is a simple comparison from posted summary statistics and is not a substitute for a sponsor's own analysis when the two differ. The record does not identify methods for several reported analyses.

General statistical explanation: an unadjusted comparison does not account for other variables that might be related to the outcome. It can be informative as a transparent summary, but it may not match an analysis that uses covariate adjustment, a different population, or a different statistical model. Where a registry-reported analysis and a recalculation differ, the sponsor's own analysis takes precedence. The record does not provide enough detail to reconstruct all reported analyses or determine why different methods might yield different estimates.

Interpreting planning illustrations

The sample-size planning illustrations are based on observed effects and assume a two-sided significance level of 0.05, equal allocation, and a normal approximation. They consider detecting specified fractions of the observed effect and report participants per arm for 80% power and participants per arm for 90% power for non-time-to-event outcomes. These are planning illustrations, not observed power and not a retrospective measure of whether the trial was adequate. The record does not say that these assumptions were used to design the trial, and the illustrations should not be mistaken for the trial's original sample-size calculation.

General statistical explanation: planning calculations ask how many participants might be needed under chosen assumptions to detect a target effect with a stated probability, if the assumptions hold. Their results depend on the target effect, variability, allocation, significance level and analysis method. Using an effect estimated from the same trial can make a planning exercise especially dependent on the uncertainty of that estimate. The registry does not report a protocol-based sample-size justification, so the illustrations cannot fill that gap.

Variation and distributional assumptions

General statistical explanation: continuous outcomes may have distributions with unequal variability, skewness, or extreme values. Such features can affect how well methods based on normal approximations describe uncertainty. When data are over-dispersed relative to a model's assumptions, standard errors can be too small if the extra variability is ignored, making intervals too narrow and tests too optimistic. This general concern does not establish that the trial's primary data were over-dispersed. The registry does not provide the primary outcome's standard deviation, participant-level distribution, diagnostic checks, or analysis model, so those features cannot be assessed from the posted record.

For the secondary continuous outcomes, standard deviations are posted for the group summaries, and unadjusted recalculations are available for selected comparisons. A standard deviation describes spread among observed values, while a confidence interval around a mean difference describes uncertainty about the estimated contrast. The two quantities answer different questions. Neither should be used to infer the distribution's shape when no distributional details or diagnostics are reported.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a multiplicity adjustment or a hierarchy specifying which secondary outcomes were intended to support confirmatory conclusions. This matters because the record lists numerous secondary outcome measures, and examining many outcomes increases the chance of finding an apparently notable result even if no corresponding underlying effect exists. A p-value from an individual secondary comparison does not account for the full set of comparisons unless an appropriate strategy is used. The record does not say whether such a strategy was planned or applied.

It is also not reported whether the posted analyses followed a prespecified statistical analysis plan, which outcomes were designated in advance for particular analyses, or whether any analyses were exploratory. The primary feasibility aim is described, as is a safety hypothesis involving survival to 24 hours after the dispatch call. However, the registry record does not provide a complete analysis plan for these aims, and it does not post the survival results associated with that safety hypothesis.

Missing-data methods and analysis populations are not reported in the registry record. The primary endpoint group counts are 95 and 96, while the registry enrollment is 192; the record does not explain the relationship between enrollment and the endpoint counts or give reasons for any missing outcome data. This description does not establish that data were missing, or why counts differ. It identifies information needed to evaluate completeness and the handling of participants without an endpoint measurement.

The registry does not report whether the primary analysis followed intention-to-treat principles, used a per-protocol population, or applied another population definition. Nor does it describe imputation, sensitivity analyses, exclusions after randomization, or adjustment for baseline characteristics. These details can affect interpretation of estimates and their uncertainty. Without them, readers can describe the posted results but cannot assess the impact of unreported analytic choices. The absence of this information in the registry should not be taken as proof that the investigators did not consider these issues; it means that the relevant details are not reported in the registry record.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: renal impairment (7.3%), pneumonia (6.2%), wound infection (5.2%), urinary tract infection (3.2%), deep vein thrombosis (dvt) (2.1%).

The registry reports serious adverse events for 8 of 95 participants in the standard resuscitation group and 18 of 96 participants in the controlled resuscitation group. It reports zero other adverse events in each group. These counts describe the posted safety data; they do not establish that an event was caused by the assigned treatment. The registry lists serious adverse event terms including renal impairment, pneumonia, wound infection, urinary tract infection, deep vein thrombosis and sepsis, with percentages attached to those terms. The record does not clarify the denominator or group attribution for those term-specific percentages, so they should be read as registry-listed figures without assigning them to a particular arm.

The registry does not report death counts in the adverse-event data, and results for the stated survival-to-24-hours safety hypothesis are not reported in the registry record. A difference in serious adverse event counts is descriptive and does not by itself determine whether the groups differ statistically or whether events are attributable to treatment. The record does not provide an adverse-event comparison estimate, confidence interval, significance test, or detailed event definitions. These omissions limit the safety interpretation; the counts should not be converted into a claim about relative safety.

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

The primary result describes a difference in early crystalloid volume between the randomized groups in this pilot trial. The estimated mean was higher in the standard resuscitation group, and the confidence interval for the posted standard-minus-controlled difference was above zero. This supports a descriptive conclusion that the assigned approaches were associated with different early crystalloid volumes in the posted endpoint data. It does not establish that the volume difference caused a change in survival, complications, or recovery.

The trial's stated aims included feasibility and safety. The primary endpoint speaks directly to feasibility as defined by fluid volume, but the safety hypothesis was framed around survival to 24 hours after the 911 call was received at dispatch. Those survival findings are not reported in the registry record. Serious adverse-event counts are available, but the record does not provide enough analysis detail to turn those counts into a definitive comparative safety conclusion.

The result also does not show that one resuscitation approach is appropriate for every patient with traumatic shock. The registry describes a specific pilot trial, its assigned saline interventions, and a population with traumatic shock due to blunt or penetrating mechanisms. It does not report enough information to establish generalizability to other populations, treatment settings, protocols, or clinical circumstances. The registry entry is not a substitute for a full report with detailed eligibility criteria, protocol procedures, participant flow, and analysis methods.

Confidence intervals communicate uncertainty about the estimated effects, but they do not eliminate uncertainty about study design, measurement, missing data, or applicability. A favorable-looking point estimate on one outcome cannot resolve questions not measured or not reported. Similarly, the absence of a posted result for an outcome should not be treated as evidence that no effect occurred. The appropriate conclusion is limited to the endpoint values and safety counts recorded, with the important unreported elements kept explicit.

The registry's sample-size illustrations do not establish that the trial had adequate power for a particular clinical outcome. They are planning exercises based on observed effects under stated assumptions, not observed power and not the original trial design calculation. The registry does not report a protocol-based sample-size justification. Accordingly, the posted results are best read as estimates from a completed pilot trial whose precision and scope are described by the available outcome data, rather than as a final answer to all questions about resuscitation after traumatic hemorrhagic shock.

13. Why This Trial Matters Statistically

This trial is statistically informative because it separates a feasibility question from a clinical safety question. Early crystalloid volume provides a direct measure of whether assigned fluid strategies produced different fluid amounts during the defined early resuscitation period. That outcome can help characterize implementation of the trial contrast. It should not be conflated with survival or other patient outcomes, which require their own estimates and evidence.

The randomized parallel-group design makes the comparison between assigned strategies central to interpretation. The posted primary estimate includes a confidence interval, allowing readers to consider both the estimated difference and its precision rather than relying on a point estimate alone. At the same time, the lack of reported analysis details, including the primary method and missing-data handling, limits evaluation of how the estimate was generated.

The record also illustrates why pilot findings and planning calculations need careful separation. Planning illustrations derived from observed effects can inform future design scenarios under explicit assumptions, but they do not establish the trial's original design rationale or retrospective power. The registry does not report the original sample-size justification, and the illustrations should not be read as proof that the pilot was sized for definitive conclusions.

Finally, the range of secondary endpoints and safety data shows how a trial can generate multiple kinds of evidence while still leaving key questions unanswered in the registry. Without a reported multiplicity strategy, detailed analysis plan, and survival results for the stated safety hypothesis, secondary findings and event counts should be interpreted as context rather than a basis for sweeping claims. The statistical value of the record lies in its clearly reported primary volume estimates and in recognizing the boundaries of what remains unreported.

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 specific to this trial follow from the registry information. The primary endpoint is described using both a scene-to-study-period definition and a timeframe beginning at intravenous or intraosseous insertion and ending after hospital arrival or hemorrhage control. The registry does not explain how those descriptions fit together, so the exact operational measurement window is not fully clear from the record.

The primary endpoint summaries include means and confidence intervals but no standard deviation or participant-level distribution. The registry also does not identify the method used for the primary confidence intervals, report a primary p-value, or provide a detailed analysis model. These omissions make it difficult to evaluate assumptions, the influence of extreme values, or the robustness of the reported estimate.

The record does not report full eligibility criteria, participant flow, the randomization method, allocation concealment, masking details, protocol deviations, or the analysis population. It does not explain why the primary outcome counts differ from the enrollment figure, whether data were missing, or how missing observations were handled. These are limitations of the available registry description and should not be interpreted as proof that the trial procedures were deficient.

The trial is identified as a pilot, but a formal sample-size justification and prespecified statistical analysis plan are not reported. The planning illustrations are based on observed effects and should not be treated as the original design calculation. The registry lists multiple secondary measures without reporting a multiplicity approach, and it does not post survival results for the stated safety hypothesis. These gaps constrain both confirmatory interpretation and conclusions about safety.

Finally, descriptions of the assigned interventions are truncated in the registry record, and the term-specific serious adverse-event percentages are not clearly attributed to a denominator or group. Further protocol and outcome detail is not reported in the registry record. These points limit reproducibility and the interpretation of treatment delivery and safety patterns.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Field Trial of Hypotensive Versus Standard Resuscitation for Hemorrhagic Shock After Trauma — NCT01411852.
• Registry record last updated 2015-01-13; status last verified 2014-12.
• Results first posted 2014-10-20.
• 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 describes a completed, randomized, single-masked, parallel-group phase 2 pilot trial sponsored by the University of Washington, with enrollment of 192. It compared controlled resuscitation, described as a 0.9% sodium chloride 250 mL bolus, with standard resuscitation, described as a 0.9% sodium chloride 2000 mL bolus, in patients with traumatic shock.

The primary feasibility endpoint was early crystalloid volume. The posted mean was 2.04 liters for standard resuscitation and 1.04 liters for controlled resuscitation; the standard-minus-controlled difference was 1.0 liters, with a 95% confidence interval from 0.6 to 1.4 liters. The record also posts selected secondary outcomes and serious adverse event counts. Survival results for the stated safety hypothesis, detailed statistical methods, missing-data handling, and the original sample-size justification are not reported in the registry record.