Inflammation and Postoperative Tramadol Analgesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Inflammation and Postoperative Tramadol Analgesia (NCT04330157), a registered phase not stated study. The primary outcome is Analgesic Affect of Tramadol After Major Abdominal Surgery.

2. Clinical Question

The clinical question therefore has two parts: whether pain scores change after tramadol administration, and whether that change differs according to systemic inflammation. The described before-and-after assessments can characterize pain around dosing, but without a randomized comparator they cannot by themselves separate a drug-related change from other influences over time. The record identifies the population and dosing schedule, but does not provide an analyzed estimate for either part of the question.

3. Trial Design

The registry record describes a completed study sponsored by Osijek University Hospital, with an enrollment of 50 and a study classification of “other.” The recorded start date is 2019-01-01 and the primary completion date is 2020-01-01. The brief summary states that patients admitted to intensive care after major abdominal surgery would receive intravenous tramadol, 100 mg every 6 hours, and that pain would be assessed before and half an hour after administration.

This is not described as a randomized comparison. Allocation is not stated, and the registry record specifically indicates that the arms are not a like-for-like control comparison. It therefore would be inappropriate to describe the study as establishing a randomized treatment contrast. The registry entries also do not identify a separate control regimen or explain how any groups were formed.

The primary outcome description specifies verbal Numeric Rating Scale assessments before and 30 minutes after each dose during the first 24 postoperative hours. It defines a scale from 0 to 10, where 0 means no pain and 10 means maximum pain. Scores were determined only in awake patients. The registry record does not state how many assessments each person contributed, whether all scheduled assessments were completed, or how repeated measurements were handled in analysis.

The registry record lists two outcome measures, but it does not include posted analysis results. It also does not report detailed eligibility criteria, the method for assessing systemic inflammation, a statistical analysis plan, or a sample-size justification. The enrollment figure describes the recorded study size; it is not evidence that a specified statistical precision or power was achieved.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: NRS score was determinated only in awake patients

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 Analgesic Affect of Tramadol After Major Abdominal Surgery, measured over NRS was assessed before and 30 minutes after each tramadol dose during first 24 postoperative hours.

The primary endpoint is the verbal Numeric Rating Scale pain score, recorded before and 30 minutes after each tramadol dose during the first 24 postoperative hours. The scale runs from 0, meaning no pain, to 10, meaning maximum pain. Only awake patients contributed a score according to the outcome description.

Pain scores are used to represent a patient’s reported pain at a particular assessment. Measuring before and after a dose can describe how scores change over that interval. Repeating the assessments across the postoperative period can also show how reported pain varies over time. The registry specifies the median and inter-quartile range as the summary format. In general, the median describes the middle of the observed scores, while the inter-quartile range describes the spread of the central half of those scores. These summaries can be useful when a distribution is skewed or when extreme values make a mean less representative.

The endpoint does not, by itself, measure systemic inflammation. The title raises inflammation as a possible influence on analgesia, but the registry entries do not describe an inflammation measure or an analysis relating it to pain-score changes. Nor are endpoint values or comparisons posted. Thus, the defined outcome indicates what was intended to be assessed, not what change was observed or how precisely any association was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is summarized using the median and inter-quartile range. These are descriptive statistics: they characterize the center and spread of recorded pain scores without requiring the mean to represent the typical observation. In general, the median is the middle value after scores are ordered. The inter-quartile range describes the span from the lower quarter of observations to the upper quarter. This approach can be informative when scores are unevenly distributed or clustered near parts of the scale. The registry specifies these summaries, but no resulting median or inter-quartile range is posted.

What does a confidence interval express?

In general, a confidence interval expresses the uncertainty around an estimate under the assumptions of the statistical method used. A narrow interval indicates greater precision than a wide interval, while an interval spanning a broad range of plausible values indicates less precision. An interval does not repair weaknesses in study design, remove bias, or establish causation. The registry record does not report a confidence interval for the primary outcome, and the analysis method used to produce one is not reported in the registry record.

Why do repeated observations matter?

The outcome description calls for assessments before and after each dose during the first 24 postoperative hours. If a patient contributes multiple scores, those scores are repeated observations from the same person rather than independent observations. In general, measurements from one person can be related to one another because they share the person’s characteristics and clinical course. Analyses that treat correlated observations as independent can misstate uncertainty. Methods for repeated data can account for that dependence, but the registry record does not report which method, if any, was used.

A before-and-after comparison also has a paired structure when both scores come from the same patient around a dose. In general, a paired analysis focuses on within-person changes and accounts for the fact that the measurements belong together. That differs from comparing scores from unrelated groups. The record specifies the timing of assessments but does not report whether the analysis used paired changes, a repeated-measures model, or another approach.

What does over-dispersion mean in general?

Over-dispersion arises when observed variation is greater than a statistical model expects. If a model assumes less variability than is present, its uncertainty estimates can be too small. This concept is especially relevant for some count outcomes; it is not a reported finding for this pain-score endpoint. The registry record gives no model diagnostics or results that would establish over-dispersion.

What can planning illustrations show?

Sample-size planning is generally a forward-looking exercise: it asks how many participants might be needed to detect an assumed effect under stated statistical assumptions. The planning illustrations associated with the study are described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is expressed as a stated fraction of the observed effect. These are planning illustrations, not the study’s own design justification and not observed power. They do not show that the study had a particular probability of detecting an effect after the data were collected. The registry record does not report a sample-size justification for the trial itself.

The described planning setup assumes two arms and equal allocation, but that does not make the study a randomized two-arm trial. The record says allocation is not stated and that the arms are not a like-for-like control comparison. Any planning calculation should therefore be read as an illustration tied to its assumptions, not as a description of how participants were assigned or as a substitute for an analysis of the actual data.

Finally, statistical significance and clinical meaning are distinct general concepts. A p-value, when reported, addresses how compatible data are with a specified statistical model and null hypothesis; it does not directly measure the magnitude or importance of an effect. An effect estimate and its uncertainty are needed to judge the range of differences consistent with the data. No p-value, estimate, or confidence interval for the primary outcome is reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures, but it does not report a detailed statistical analysis plan, a hierarchy among all outcomes, or a procedure for addressing multiple comparisons. The primary outcome is identified, yet the record does not explain whether additional assessments, time points, or subgroup analyses were prespecified or how their results would be interpreted together.

In general, testing many outcomes or contrasts can increase the chance of finding an apparently notable result by chance. A multiplicity plan can define which question is primary and how other tests are handled. Without a reported plan, it is not possible to determine whether any planned adjustment was used or whether the presented results, if later reported elsewhere, reflect a prespecified analysis. No analysis results are posted in the registry record.

The outcome is restricted to awake patients, but the record does not report the number of scheduled scores that were missing, the reasons for missingness, or a method for handling missing observations. In general, missing data can affect both the estimate and its uncertainty, especially when the likelihood of a missing score is related to pain or clinical status. The registry record also does not report an analysis population definition, such as which enrolled patients or assessments were included in each analysis.

These are unreported features, not evidence that a particular procedure was or was not carried out. The record does not report interim analyses, stopping rules, or a statistical plan for repeated measurements. Those details cannot be inferred from the study’s completed status or its enrollment figure.

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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry record lists 43 participants at risk in the serious adverse-effect category, with 0 affected, and 43 at risk in the other adverse-effect category, with 16 affected. It also lists 0 deaths. These are the posted figures; the record does not include serious adverse-effect terms in its listed leading terms.

A count of 0 serious events means that none were recorded in that category among the listed participants at risk. It does not establish that the risk is absent, nor does it determine how often an event might occur in a larger or different population. A zero count can be compatible with uncertainty about uncommon events. Likewise, the count in the other adverse-effect category does not show whether events were mild or severe, whether they occurred after a particular dose, or whether tramadol caused them.

The adverse-effect figures should be read separately from the pain endpoint. They do not provide an efficacy estimate, and the outcome record does not report an analysis connecting adverse effects with pain scores or systemic inflammation. The registry entries do not describe event definitions, collection procedures, timing, or the detail behind the category count. The counts are a limited description of recorded safety information, not a comprehensive characterization of risk.

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

The record describes a completed study in patients after major abdominal surgery, with intravenous tramadol dosing and pain assessments scheduled around doses. It identifies the verbal Numeric Rating Scale as the primary outcome and specifies that only awake patients contributed scores. This establishes what the study set out to measure, but not what the measurements showed.

The posted record contains no outcome analysis results. It therefore does not establish the direction or size of any change in pain scores, the precision of an estimate, or whether score changes varied with systemic inflammation. The title alone cannot answer those questions. The record does not describe an inflammation measure or an analysis of its relationship to analgesia.

The absence of a randomized, like-for-like control comparison matters for interpretation. In general, change over time can reflect influences other than the treatment being studied. A before-and-after pattern, even if an estimate were posted, would not automatically show that tramadol caused the change. The registry entries do not identify a comparison group or state how allocation occurred.

The record’s adverse-effect counts describe recorded categories among participants listed as at risk, including 0 serious events and 0 deaths. Those counts do not establish that serious harms cannot occur, and the other adverse-effect count does not demonstrate causation. Safety and pain outcomes answer different questions and should not be conflated.

Overall, the registry information supports a description of the planned clinical measurements and the limited posted safety counts. It does not support a conclusion that tramadol did or did not reduce pain, or that inflammation did or did not influence analgesia. It also does not show how precisely either question was examined. Those conclusions require outcome estimates, an analysis method, and enough information about the comparison and missing observations to assess the result.

13. Why This Trial Matters Statistically

This study raises a useful statistical question: how should pain be analyzed when measurements are made repeatedly around treatment doses, and when the scientific interest concerns whether systemic inflammation modifies the observed pattern? The registry specifies repeated before-and-after pain assessments and identifies a median with inter-quartile range as the outcome summary. These features make timing, within-person dependence, and the definition of the analysis population important considerations.

The record also illustrates the difference between a research question and a result. A study title can state a scientific aim, while the available registry information may describe only the planned measurement. Without estimates and uncertainty, readers cannot assess the strength or precision of the evidence. A completed status and an enrollment count do not replace those results.

Design is equally important. Since the record does not describe a randomized, like-for-like control comparison, any analysis of changes around dosing would need cautious interpretation. Statistical adjustment can address some measured differences, but it cannot by itself guarantee that all alternative explanations have been removed. The record does not provide enough detail to assess such an approach.

The endpoint’s restriction to awake patients highlights another important issue: the analyzed observations may represent only the times when patients could report a score. Clear reporting of missing assessments and analysis populations would help readers understand the scope of the results. Those details are not reported in the registry record.

Thus, the study is statistically noteworthy as an example of how measurement timing, repeated observations, missing scores, and comparison structure shape an analysis. The posted information identifies these questions but does not provide enough outcome or methods detail to resolve them.

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 registry record does not report pain-score results, estimates of change, uncertainty intervals, or p-values. This prevents assessment of the magnitude, direction, and precision of the primary outcome. It also does not report an analysis linking systemic inflammation to analgesia, despite that relationship being the stated focus in the study title.

The record does not describe how systemic inflammation was measured, when it was assessed, or how any inflammation groups or values were incorporated into an analysis. It also does not specify how the study arms were formed. Allocation is not stated, and the record indicates that the arms are not a like-for-like control comparison. A causal treatment contrast cannot be inferred from the study description alone.

The outcome was determined only in awake patients. The registry does not report how many assessments were unavailable, why they were unavailable, or how missing measurements were handled. This leaves uncertainty about which patients and time points contribute to any eventual summary. It also does not detail how repeated scores from the same patient were analyzed.

Further design and analysis information is not reported in the registry record, including eligibility details, the statistical analysis plan, a trial-specific sample-size justification, interim analyses, or rules for stopping. The record lists two outcomes but does not describe a multiplicity strategy. The adverse-effect information is also limited: event definitions, timing, ascertainment, and detailed event terms are not described in the listed details. These omissions constrain interpretation; they do not establish that the study lacked procedures, only that those procedures are not described in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Inflammation and Postoperative Tramadol Analgesia — NCT04330157.
• Registry record last updated 2021-07-30; status last verified 2021-07.
• Results first posted 2021-07-30.
• 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 study sponsored by Osijek University Hospital, with enrollment of 50 and a study classification of “other.” The recorded start date is 2019-01-01, and the primary completion date is 2020-01-01. Patients after major abdominal surgery were described as receiving intravenous tramadol, 100 mg every 6 hours.

The primary outcome is a verbal Numeric Rating Scale pain score, assessed before and 30 minutes after each dose during the first 24 postoperative hours. The scale runs from 0, no pain, to 10, maximum pain; only awake patients contributed scores. The specified summary is the median with inter-quartile range.

The registry record lists two outcome measures and no posted analysis results. It does not describe an inflammation measure or a statistical analysis relating inflammation to analgesia. Safety figures list 0 serious adverse effects among 43 at risk, 16 affected in the other adverse-effect category among 43 at risk, and 0 deaths. These descriptive details do not supply an efficacy estimate or establish causation.