This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for High Dose IV Lidocaine vs Hydromorphone for Abdominal Pain in the Emergency Department (NCT04398316), a randomized phase 4 study. The primary outcome is Mean Improvement in Pain at 90 Minutes.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04398316 |
| Phase | Phase 4 |
| Condition | Abdominal Pain, Renal Colic |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 4 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Hennepin Healthcare Research Institute |
| Results posted | Yes |
2. Clinical Question
Population
Patients in the emergency department with acute abdominal pain were the intended population. The registry also lists abdominal pain and renal colic as conditions. The posted record does not give further eligibility details or describe the characteristics of participants who enrolled. Enrollment was 4.
Intervention
The intervention was intravenous lidocaine, administered at 2 mg/kg over 5 minutes. The registry’s brief summary describes the intended comparison as lidocaine for patients diagnosed with acute abdominal pain.
Comparator
The comparator was intravenous hydromorphone, administered at a dose of 1 mg over 5 minutes. The record does not give additional details about other care participants may have received alongside the study medication.
Primary question
The primary question was how mean improvement in pain at 90 minutes compared between the medication groups. Pain was recorded on a scale from 0 (no pain) to 10 (maximum pain), and improvement was described as the difference between the score at time 0 and the score at 90 minutes. The subtraction order is not specified in the registry description.
The intended comparison is therefore between two medication strategies, with pain-score change at a specified follow-up time as the primary outcome. The record identifies a phase 4, randomized, parallel trial with quadruple masking. Those design labels describe the planned study structure, but they do not establish that the intended comparison can be estimated from the posted results. The registry reports only four enrolled participants, distributed unevenly between the groups: three assigned to intravenous lidocaine and one to intravenous hydromorphone.
The clinical question also included several secondary outcomes, including pain relief, pain-score improvement at other follow-up times, and patient preference. These outcomes give the study a broader intended scope than its primary endpoint alone. However, secondary outcome results are not reported in the registry record. The record also does not provide enough detail to assess how the intended population was selected, how participants were assigned, or what analysis populations were planned.
3. Trial Design
The registry identifies this as a phase 4, randomized, parallel-group trial with quadruple masking. The two groups received intravenous lidocaine or intravenous hydromorphone. Lidocaine was administered at 2 mg/kg over 5 minutes, and hydromorphone at 1 mg over 5 minutes. The trial was sponsored by Hennepin Healthcare Research Institute.
The recorded start date is 2021-02-18 and the primary completion date is 2021-06-30. The study status is terminated. The record does not state why the trial was terminated, so the reason should not be inferred from the enrollment or the posted outcome figures. It also does not report a detailed randomization procedure, the specific masking arrangements, or the planned sample size.
Although the planned design was a two-group comparison, the posted enrollment was 4: three participants in the lidocaine group and one in the hydromorphone group. This is a very limited basis for estimating a difference between groups, especially for a continuous outcome whose variability is also estimated from the enrolled participants. The unequal group sizes further limit the information available for a direct comparison. No inferential analysis of the primary outcome is posted.
The primary endpoint was mean improvement in pain at 90 minutes. The record lists 15 outcome measures in total, including secondary outcomes for pain relief, pain-score improvement at multiple follow-up times, and medication preference. It does not report results for those secondary outcomes. Details about the protocol, sample-size justification, interim analyses, deviations from the planned design, and procedures for handling incomplete observations are not reported in the registry record.
The design labels should be read as descriptions of the registered study, not as evidence that the planned trial was completed as intended. In particular, randomized allocation and quadruple masking do not resolve the limits imposed by the small enrollment, nor do they substitute for a posted analysis. The registry information supports a description of the trial’s intended comparison and its limited posted results, but not a definitive estimate of comparative efficacy.
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
| Stage | Intravenous Lidocaine | Intravenous Hydromorphone |
|---|---|---|
| STARTED | 3 | 1 |
| COMPLETED | 3 | 1 |
| NOT COMPLETED | 0 | 0 |
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.
| Characteristic | Unit | Intravenous Lidocaine | Intravenous Hydromorphone | Total |
|---|---|---|---|---|
| Participants analysed | 3 | 1 | 4 | |
| Age, Continuous | years | 37.33 (SD 13.58) | 61 (SD 0) | 43.25 (SD 16.21) |
| Sex: Female, Male: Female | Participants | 2 | 0 | 2 |
| Sex: Female, Male: Male | Participants | 1 | 1 | 2 |
| Race/Ethnicity, Customized: Race – White (Caucasian, Non-Hispanic) | Participants | 1 | 1 | 2 |
| Race/Ethnicity, Customized: Race – Black (African American or African) | Participants | 1 | 0 | 1 |
| Race/Ethnicity, Customized: Race – American Indian (Native American) or Alaskan Native | Participants | 1 | 0 | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Mean Improvement in Pain at 90 Minutes, measured over 90 minutes.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was mean improvement in pain at 90 minutes. The registry defines the pain measure as a score from 0 (no pain) to 10 (maximum pain) and describes improvement using the difference between the score at time 0 and the score at 90 minutes. The record does not specify the subtraction order, so the sign of a value cannot be interpreted with certainty as improvement or worsening from the wording alone.
A change score is used to express how a participant’s recorded pain differs between an initial assessment and a later assessment. Taking the mean across participants can summarize the group’s average change. It is a clinically interpretable kind of measure because it relates to a patient-reported symptom at a defined follow-up time. In general, selecting a fixed time point also makes the intended comparison explicit: the endpoint concerns the 90-minute assessment, not pain at every point during the emergency department visit.
The usefulness of a group mean depends on the amount and quality of the underlying observations. With only three participants in one group and one in the other, the posted group summaries cannot support a reliable estimate of the difference between treatment groups. The registry does not report a confidence interval or a test for the primary comparison. It also does not describe how missing pain scores, if any, were handled. Therefore, the endpoint definition is clear enough to identify the intended outcome, but the posted record does not establish a precise comparative result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary-outcome summaries are a mean improvement of 3.67 with a standard deviation of 3.51 among 3 participants receiving intravenous lidocaine, and a mean of -1.0 with a standard deviation of 0.0 among 1 participant receiving intravenous hydromorphone. These are separate group summaries, not an estimated treatment contrast. The registry does not report an inferential comparison for the primary endpoint.
The size of each group is central to interpretation. The hydromorphone summary is based on one participant, so it cannot show how much outcomes might vary among other participants receiving that medication. A standard deviation of 0.0 in a group of one should not be read as evidence that responses are generally uniform; with only one observation, between-participant variability cannot be characterized. In the lidocaine group, the reported standard deviation describes the observed spread among a small number of participants, but it remains an imprecise estimate of variability in a broader population.
The sign of the reported means also requires care. The endpoint description says the measure is the difference between pain at time 0 and 90 minutes, but it does not state which score is subtracted from which. Without that convention, the direction represented by a positive or negative value is not fully defined by the registry text. The figures can be quoted as posted, but they should not be converted into a claim that one group experienced greater improvement.
A comparison between group means would ordinarily require an estimate of the difference and a measure of its uncertainty. Neither is reported as an analysis in the registry. No confidence interval or p-value is posted, and the registry indicates that a two-arm continuous-endpoint comparison was not estimable from the posted values. A numerical contrast should not be created from these summaries, particularly because the comparison involves very small and unequal groups.
The record also lists secondary outcomes, but their results are not reported in the registry record. Accordingly, the primary summaries do not establish a broad pattern across outcomes or follow-up times. The record’s terminated status adds context, but the reason for termination is not reported and should not be guessed. Overall, the posted results describe a handful of observations. They do not provide a precise or inferential estimate of the relative effects of the two medications.
9. Statistical Methods Explained
What do the group summaries describe?
The primary outcome is continuous: each participant contributes a pain-improvement score, and the group result is expressed as a mean with a standard deviation. The mean is the arithmetic average of the observed scores in that group. The standard deviation describes how dispersed those observed scores are around their mean. In general, the mean describes the location of the observations, while the standard deviation describes their spread; neither alone describes the uncertainty in a comparison between groups.
For intravenous lidocaine, the registry reports a mean of 3.67 and a standard deviation of 3.51 among 3 participants. For intravenous hydromorphone, it reports a mean of -1.0 and a standard deviation of 0.0 among 1 participant. The latter group’s single observation cannot provide a meaningful estimate of between-participant spread. The reported standard deviation of 0.0 is a feature of the posted summary and sample size, not evidence that the underlying response has no variability.
Why is a group comparison different from two means?
A treatment comparison asks how outcomes differ between groups, not merely what each group’s mean is. An analysis would generally estimate a contrast and quantify its uncertainty. The registry does not post such an estimate for this endpoint and indicates that the continuous two-arm comparison was not estimable from the available values. Since the sample is small and the groups are unequal, the summaries do not support a stable estimate of the difference. No contrast should be calculated from them for this interpretation.
In general, a confidence interval gives a range of values compatible with the data and the assumptions of a statistical method. A wider interval indicates less precision; an interval is not a guarantee about the true value. No confidence interval for the group comparison is reported in the registry record. A p-value, which in general measures how incompatible the observed data are with a specified null hypothesis under a statistical model, is also not reported. The absence of these quantities means there is no posted inferential result to interpret.
What can randomization and masking contribute?
Randomization is intended, in general, to reduce systematic differences between treatment groups at allocation. Masking is intended to reduce the influence of treatment knowledge on care, assessment, or reporting. The registry labels the trial randomized and quadruple-masked, but does not describe the randomization method or the operational details of masking. Even when these design features are implemented as intended, they cannot make a very small sample informative about outcome variability or overcome an analysis that is not estimable.
The parallel model indicates that the intended groups were followed as separate treatment arms. The record does not provide enough information to assess allocation concealment, adherence, crossovers, or how the analysis accounted for any departures from assigned treatment. These details are not reported in the registry record and should not be assumed.
How should planning illustrations be read?
The sample-size illustrations use a two-sided significance level of 0.05, equal allocation between the two groups, and a normal approximation. The stated effect to detect is a fraction of the observed effect. These are planning assumptions for illustrative calculations, not evidence about the trial’s original design or a report of observed power. The registry does not report the trial’s own sample-size justification.
In general, a sample-size calculation asks how many participants would be needed under specified assumptions to target a chosen level of power for a chosen effect. It is sensitive to assumptions about the effect size, variability, allocation, and analysis. An illustration based on an observed effect can be especially unstable when the observed estimate comes from a small sample; a single participant can have substantial influence on a group summary. Such an illustration should not be treated as a design justification, a forecast, or proof that the study could detect or exclude a meaningful effect.
The stated assumptions include equal allocation, whereas the posted enrollment was not equal between the groups. The illustrations should therefore be understood as hypothetical planning exercises rather than descriptions of the enrolled sample. The calculations do not supply an inferential analysis of the trial results and do not change the fact that the primary two-arm comparison is not reported as estimable.
Why does dispersion matter?
In general, dispersion matters because outcomes that vary widely among participants make a group mean less precise than outcomes that cluster closely, all else being equal. Small samples make estimates of dispersion uncertain. In this trial, the lidocaine group has a reported standard deviation, but it is based on only 3 participants; the hydromorphone group has only one participant, so its observed standard deviation cannot characterize population variability. These features limit any attempt to quantify uncertainty in a comparative effect.
Some outcome data can also be more variable than a simple statistical model assumes. Over-dispersion, in general, means that the observed variability exceeds what a model expects. When present, it can make uncertainty estimates too optimistic if the analysis does not accommodate it. The registry does not report a model assessment or an analysis method for this endpoint, so no conclusion about over-dispersion or model fit is possible.
10. Multiplicity, Missing Data and Analysis Populations
The record lists a primary outcome and multiple secondary outcomes, including pain relief, pain-score improvement at other follow-up times, and patient preference. Testing or interpreting many outcomes can raise a multiplicity issue: in general, the more comparisons considered, the greater the chance that some results may appear notable by chance alone. A prespecified approach can clarify which outcome is primary and whether or how secondary analyses are adjusted. The registry record does not report a multiplicity strategy, so it is not possible to determine how multiple outcomes were intended to be handled.
Although the outcomes are listed, secondary outcome results are not reported in the registry record. The record also does not report an analysis population, such as whether the primary analysis was intended to include everyone randomized, everyone treated, or a different defined group. Those distinctions matter because different analysis populations can answer different questions and can be affected differently by missing observations or treatment deviations.
Missing-data procedures are not reported in the registry record. The record does not say whether any pain assessments were missing, how incomplete follow-up was handled, or whether any imputation or sensitivity analysis was planned. No conclusions about the presence or absence of missing outcome data should be drawn from silence on these details. The small enrollment and lack of a posted two-arm analysis already limit interpretation; unreported analysis-population and missing-data details add uncertainty about how the available summaries were assembled.
The registry does not report interim analyses or stopping rules. It identifies the study as terminated but does not state why. Neither a multiplicity adjustment nor a missing-data method should be inferred from the design labels or outcome listings.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Intravenous Lidocaine | 0 | 3 | 0.0% |
| Intravenous Hydromorphone | 0 | 1 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Intravenous Lidocaine | 0 of 3 |
| Intravenous Hydromorphone | 0 of 1 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Intravenous Lidocaine | 3 of 3 |
| Intravenous Hydromorphone | 0 of 1 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Intravenous Lidocaine | Intravenous Hydromorphone |
|---|---|---|---|
| Headache | Nervous system disorders | 1 of 3 | 0 of 1 |
| Feeling tired | General disorders | 1 of 3 | 0 of 1 |
| Paresthesia | Nervous system disorders | 1 of 3 | 0 of 1 |
The serious adverse event summaries report 0 affected among 3 participants at risk in the intravenous lidocaine group and 0 affected among 1 participant at risk in the intravenous hydromorphone group. Deaths are reported as 0 in both groups. These are counts in a very small enrolled sample, not precise estimates of the likelihood of a serious adverse event.
For other adverse events, the record reports 3 affected among 3 at risk in the lidocaine group and 0 affected among 1 at risk in the hydromorphone group. These descriptive counts do not establish that one medication causes more or fewer events. The group sizes are too small for a stable comparative safety estimate, and the registry does not post an inferential safety analysis.
Adverse-event counts should be interpreted in relation to the number at risk, the event definitions, follow-up, and the completeness of reporting. The registry record does not provide further detail on event terms for serious events, and no top serious-event terms are listed. The counts describe what was posted for this study; they should not be generalized as a reliable estimate of safety in a broader population.
12. What the Result Does, and Does Not, Mean
The registry record documents a randomized, quadruple-masked trial intended to compare intravenous lidocaine with intravenous hydromorphone for acute abdominal pain in the emergency department. It identifies mean improvement in pain at 90 minutes as the primary endpoint and reports group summaries for four participants. The numerical summaries are observations from this small enrolled sample, not a precise estimate of the relative effect of the medications.
The record does not report an estimable two-arm analysis of the primary outcome, a confidence interval, or a p-value. It also does not report secondary outcome results. The group means therefore do not establish that either medication produced greater improvement, and they do not quantify how certain a comparative estimate would be. The endpoint’s subtraction order is not specified, which further limits interpretation of the signs of the reported values.
These results do not establish that either medication is effective or ineffective. They also do not establish equivalence, non-inferiority, or a lack of difference. Those conclusions require an appropriate analysis and adequate precision; neither is available in the posted record. Similarly, the adverse-event counts describe a small number of participants and cannot support a general comparative safety conclusion.
The record identifies the study as terminated, but its reason for termination is not reported. It does not report the planned sample-size justification, the analysis populations, missing-data handling, multiplicity procedures, or a full statistical plan. Readers should therefore distinguish the registered intention to compare the treatments from the limited descriptive data that were posted. The main statistical message is about the information available: the trial record gives a few group-level observations but no precise comparative result.
13. Why This Trial Matters Statistically
This trial illustrates why registration of a randomized design and masking does not by itself guarantee an interpretable treatment comparison. The study was intended to compare two intravenous medications using a clearly timed primary pain outcome, but the posted enrollment was 4, with 3 participants in one group and 1 in the other. That enrollment leaves very little information for estimating group variability or a comparative effect.
It also shows why sample summaries and treatment contrasts are not interchangeable. Separate means can describe the observed groups, but a comparative conclusion requires an estimate of the difference and its uncertainty. The registry does not report an estimable two-arm analysis. The hydromorphone group’s single participant also means its standard deviation cannot represent the range of responses that might occur among participants more generally.
The record’s terminated status is another reason to separate study intent from evidential strength. The registry does not report the reason for termination, so the status cannot be used to infer the cause or the investigators’ conclusions. Likewise, planning illustrations based on observed effects are not observed power and do not replace a reported sample-size justification or analysis.
For clinical researchers and biostatisticians, the example reinforces the importance of interpreting precision alongside point estimates, of reporting analysis methods and populations, and of distinguishing planned outcomes from results actually reported. A small set of descriptive outcomes can document what was observed, but it cannot answer a comparative efficacy question with precision on its own.
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 direct limitation is the small enrollment: 4 participants in total, with 3 in the lidocaine group and 1 in the hydromorphone group. The small and unequal groups sharply limit the information available for estimating means, variability, and a between-group contrast. In particular, the single-person hydromorphone group cannot provide a meaningful estimate of outcome dispersion.
The registry does not report an estimable primary comparison, a confidence interval, or a p-value. The primary endpoint description does not specify the subtraction order used to define improvement, which makes interpretation of positive and negative values less direct. Secondary outcomes are listed, but their results are not reported in the registry record. The clinical question therefore cannot be assessed across the full set of intended outcomes.
The trial status is terminated, but the reason is not reported. The registry record also does not report the planned sample-size justification, detailed randomization and masking procedures, the statistical analysis plan, analysis populations, missing-data handling, multiplicity procedures, or interim analyses. These omissions limit assessment of how closely the posted summaries reflect the intended analysis.
Finally, adverse-event counts come from the same small enrollment and are descriptive. They do not provide a precise comparison of safety. The posted information is useful for identifying the registered design and the limited observations available, but it does not support broad conclusions about comparative pain outcomes or adverse events.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: High Dose IV Lidocaine vs Hydromorphone for Abdominal Pain in the Emergency Department — NCT04398316.
- Registry record last updated 2024-01-17; status last verified 2023-12.
- Results first posted 2024-01-17.
- 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.
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18. Record Summary
NCT04398316 is a phase 4, randomized, parallel-group trial with quadruple masking, sponsored by Hennepin Healthcare Research Institute. The study compared intravenous lidocaine, administered at 2 mg/kg over 5 minutes, with intravenous hydromorphone, administered at 1 mg over 5 minutes, for acute abdominal pain in the emergency department. The recorded start date is 2021-02-18, the primary completion date is 2021-06-30, and the status is terminated.
The primary endpoint was mean improvement in pain at 90 minutes on a scale from 0 (no pain) to 10 (maximum pain). Enrollment was 4: three participants in the lidocaine group and one in the hydromorphone group. The record posts group summaries but no estimable two-arm primary analysis. Secondary results and the reason for termination are not reported in the registry record.