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 Isoflurane Preconditioning for Liver Resections (NCT01031550), a randomized na study. The primary outcome is Post Operative Complications Grade IIIb or Greater According to Clavien's Classification Which is a Classification System Used to Grade Surgical Complications.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01031550 |
| Phase | NA |
| Condition | Liver Disease |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 8 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Rutgers, The State University of New Jersey |
| Results posted | Yes |
2. Clinical Question
Population
Patients with liver disease undergoing elective hepatic surgery. The registry lists 8 participants enrolled. Eligibility criteria beyond the description of elective surgery are not reported in the registry record.
Intervention
An isoflurane preconditioning approach. The arm description says anesthesia was maintained with 1MAC isoflurane after induction, with the concentration gradually increased 30 minutes before anticipated inflow occlusion and commencement of liver transaction. The full target concentration and complete protocol are not reported in the registry record.
Comparator
Standard anesthetic management with propofol 100-150mcg/kg/min. Further details about anesthetic management in this arm are not reported in the registry record.
Primary question
Whether the groups differed in postoperative complications graded IIIb or greater according to Clavien's classification during the first 7 post operative days. The registry states that no data analysis was performed because the study was terminated.
The study objective was to examine whether isoflurane could induce clinically effective preconditioning in patients undergoing elective hepatic surgery. In general, preconditioning refers to an intervention intended to prepare tissue for a subsequent stress; that general description does not establish that this intervention changed outcomes in this trial.
The registry describes a comparison between an isoflurane strategy and propofol-based standard management, but it does not report analyzed outcome data for the primary question. It therefore does not establish whether the strategies differed in serious postoperative complications. Nor does it provide a quantified estimate of the size or precision of any difference. The listed secondary outcomes concern postoperative AST, ALT and total bilirubin, length of ICU and hospital stay, and liver lipid peroxidation and apoptosis; results for those outcomes are not reported in the registry record.
3. Trial Design
The registry classifies the study as randomized, double masked, and parallel, with a phase entry of NA. A parallel design assigns participants to a treatment group and follows each group under its assigned approach; that is a general description of the design type, not a report of how assignments were generated or concealed. The particular randomization procedure and the identities of the people masked are not reported in the registry record.
The listed arms are standard anesthetic management with propofol 100-150mcg/kg/min and preconditioning with 2 MAC isoflurane. The isoflurane arm description states that anesthesia was maintained with 1MAC after induction and that the concentration would be gradually increased 30 minutes before anticipated inflow occlusion and commencement of liver transaction. The description does not give a complete account of the concentration increase or all treatment procedures. Further protocol details are not reported in the registry record.
The registry lists 8 participants enrolled. The record gives a study start of 2010-01 and primary completion of 2012-01, and reports the study status as terminated. The reason for termination and the timing of the decision are not reported in the registry record. The sponsor is Rutgers, The State University of New Jersey.
There are 4 outcome measures listed, including the primary complication outcome and secondary outcomes concerning liver enzymes, bilirubin, length of stay, lipid peroxidation, and apoptosis. The registry reports 0 analyses and explicitly states that no data analysis was performed because of termination. Thus, randomized allocation and the planned comparison are described, but comparative outcome estimates are not available. The planned enrollment rationale, intended allocation ratio, and procedures for following participants 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.
Before assignment: Subjects may withdraw consent
Overall Study
| Stage | Standard Anesthetic Management | Preconditioning With 2 MAC Isoflurane Group |
|---|---|---|
| STARTED | 5 | 3 |
| COMPLETED | 5 | 3 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Due to termination of the study no data analysis was performed.
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 | Standard Anesthetic Management | Preconditioning With 2 MAC Isoflurane Group | Total |
|---|---|---|---|---|
| Participants analysed | 5 | 3 | 8 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 4 | 3 | 7 |
| Age, Categorical: >=65 years | Participants | 1 | 0 | 1 |
| Age, Continuous | years | 40 (SD 10) | 38 (SD 8) | 39 (SD 9) |
| Sex: Female, Male: Female | Participants | 2 | 1 | 3 |
| Sex: Female, Male: Male | Participants | 3 | 2 | 5 |
| Region of Enrollment: United States | participants | 5 | 3 | 8 |
6. Primary Endpoint
The registry lists the primary outcome as Post Operative Complications Grade IIIb or Greater According to Clavien's Classification Which is a Classification System Used to Grade Surgical Complications, measured over first 7 post operative days.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint concerns postoperative complications graded IIIb or greater according to Clavien's classification, with assessment during the first 7 post operative days. The registry's description defines Grade IIIb as a complication requiring an intervention under general anesthesia. Grade IV refers to life-threatening complications requiring ICU management, with IV a denoting single organ dysfunction and IVb denoting multi-organ dysfunction. Grade V is death. The suffix d indicates that a patient has a complication at discharge and needs follow-up for its full evaluation.
In general, grading complications provides a structured way to distinguish events by their severity and the care they require. An endpoint focused on more severe grades can therefore address complications that involve substantial intervention or critical illness, rather than treating every postoperative event as equivalent. That is the rationale for using a severity classification; it does not show that the endpoint was observed or analyzed in this study.
The registry's primary outcome population text says that no data analysis was performed due to termination. It does not report counts by grade, the number of participants with a qualifying complication, or a comparative estimate. The registry also marks the primary outcome as not reduced to one comparison because it has several categories or time points. The exact method for combining qualifying grades or handling multiple events is not reported in the registry record. Consequently, the record does not permit an estimate of how often the endpoint occurred in either group or how precisely any group difference was measured.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The main interpretive point is that this is a randomized trial record without an analyzed primary outcome. Although the registry describes the treatment groups and defines the complication endpoint, it states that the study was terminated and that no data analysis was performed. It gives no comparative estimate, confidence interval, or p-value for postoperative complications. No treatment effect, in either direction, can be quantified from the primary outcome information recorded.
The registry lists 8 enrolled participants, with 5 in the standard anesthetic management safety group and 3 in the isoflurane preconditioning safety group. Those group counts describe the safety denominators in the record; they do not substitute for an analyzed efficacy comparison. A small enrollment also means that even if outcome counts had been posted, estimates could have been imprecise. In this record, outcome counts for the primary endpoint are not reported, so neither the direction nor the precision of a comparative effect can be assessed.
The registry's entry for the primary outcome says no data analysis was performed due to termination. The study is also marked as having 0 analyses, and the outcome is not reduced to a single comparison because it has several categories or time points. These statements explain why the registry does not offer a single summary estimate. They do not establish whether any qualifying complication occurred; the primary endpoint results are not reported in the registry record.
Safety entries list 0 serious adverse events and 0 other adverse events among participants at risk in each group: 5 in standard management and 3 in isoflurane preconditioning. These entries should be read as counts recorded in the safety fields, not as a formal demonstration that risks were equivalent. Death counts are not reported in the registry record. The record does not provide event definitions, surveillance details, or a narrative describing how adverse events were collected.
The sample-size assumptions describe planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such illustrations are planning calculations, not observed power. Since the primary outcome was not analyzed and no observed effect or resulting planning counts are reported in the registry record, those assumptions cannot supply evidence about efficacy or precision in this trial. They also should not be treated as the trial's original design justification.
Overall, the registry supports a description of the trial question, design labels, enrollment, termination, and limited adverse-event counts. It does not support a conclusion about whether isoflurane preconditioning changed postoperative complications, liver measures, or length of stay. The absence of an analysis is not evidence of no effect; it leaves the comparative question unanswered in the posted results.
9. Statistical Methods Explained
Randomization is a method for assigning participants to groups by chance. In general, it is intended to reduce systematic differences between groups at the start of a study, so that a later comparison can be interpreted more fairly. The registry classifies this trial as randomized, but the method used to generate assignments, conceal assignments before enrollment, and maintain balance is not reported in the registry record. The record's randomized label should therefore be understood as a design classification rather than a complete account of implementation.
A parallel design means the groups receive different assigned approaches over the study rather than crossing from one approach to another. In general, a parallel-group analysis compares outcomes across the assigned groups. The trial is listed as double masked, but the registry does not identify which people were masked, how masking was maintained, or whether it was assessed. Those details are not reported in the registry record. Masking is generally intended to reduce the influence of expectations on care, outcome assessment, or reporting; the registry label alone does not show how well it worked.
The primary outcome is a graded complication measure. In general, a categorical endpoint can be described with counts in each category, or it can be reduced to a defined comparison such as whether a participant experienced an event meeting a threshold. Which summary is appropriate depends on the prespecified question and endpoint rules. The registry describes grades IIIb or greater and lists multiple grades, but does not report a single analysis or the detailed rule for combining events. It explicitly indicates that the primary outcome was not reduced to one comparison because of multiple categories or time points. No outcome counts or category-specific analyses are reported in the registry record.
A treatment-effect estimate would express the observed contrast between groups using a defined scale, such as a difference in event proportions or a relative measure. A confidence interval generally describes the range of effect values compatible with the data and method, reflecting statistical uncertainty. A p-value, when reported, summarizes how incompatible the observed data are with a specified null model under the assumptions of a test; it is not the probability that a treatment works. These are general explanations. The registry contains no primary outcome estimate, confidence interval, or p-value, so none can be interpreted for this comparison.
For a binary complication endpoint, an analysis would ordinarily need a clear participant-level definition, group-specific event counts, and a specified comparative method. If the endpoint is retained as ordered severity categories, the analysis would need to address the ordering and category structure. If multiple events or time points are included, a plan is needed to define which observations contribute and how repeated or multiple events are handled. These are general statistical considerations; the registry does not report the detailed endpoint coding, statistical test, model, or approach to multiple complications.
Sample-size planning uses assumptions about the effect to be detected, variability or event frequency, significance threshold, power target, and allocation. General planning estimates depend on those assumptions and do not describe what happened in the enrolled participants. The registry's planning description specifies a two-sided significance level of 0.05, equal allocation, and a normal approximation, with target effects expressed as fractions of the observed effect. It also distinguishes participants per arm for 80% power from total events for time-to-event calculations. These are planning conventions, not evidence of achieved power or a rationale for the study's actual enrollment. The underlying observed effect and planning counts are not reported in the registry record, and the registry does not provide the original sample-size justification.
The absence of posted analysis matters for every inferential method. No method can recover the missing endpoint outcomes or establish an effect without the data and specified analysis. The registry reports 0 analyses and says no primary outcome analysis was performed because of termination. The statistical test or model intended for the primary comparison, any covariate adjustment, handling of incomplete observations, and rules for analysis populations are not reported in the registry record. It is therefore not appropriate to infer an analysis plan from the design labels or outcome description.
Over-dispersion is a general issue that arises when observed variation in count data exceeds what a chosen model assumes; ignoring it can make uncertainty estimates too narrow. It is relevant only if a suitable count outcome and model are being analyzed. The registry does not report a count-data analysis for this trial, so there is no basis to assess whether over-dispersion arose or how it was handled. More broadly, model diagnostics, assumptions, and sensitivity analyses are not reported in the registry record.
Finally, numerical sample-size illustrations based on an observed effect should not be read as evidence that the trial had adequate power or that a null finding was established. The primary outcome was not analyzed, and no observed effect is available in the registry record. Without an estimate and its uncertainty, conclusions about the magnitude or statistical precision of a treatment contrast are not possible.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 4 outcome measures. The primary outcome is postoperative complications graded IIIb or greater; the secondary outcomes concern peak postoperative AST, ALT and total bilirubin, ICU and hospital stay, and liver lipid peroxidation and apoptosis. Considering several outcomes can raise a multiplicity issue: in general, repeated testing can increase the chance of finding an apparently notable result by chance. A prespecified strategy might identify a primary outcome, adjust for multiple comparisons, or treat secondary analyses as exploratory. The multiplicity strategy is not reported in the registry record.
The registry states that no data analysis was performed because the study was terminated and lists 0 analyses. It therefore reports no primary or secondary outcome estimates and no analysis-specific p-values. Whether interim analyses were planned or performed is not reported in the registry record. The reason for termination is also not reported in the registry record, so it cannot be characterized as related to efficacy, safety, recruitment, or another cause.
Missing-data procedures are not reported in the registry record. There is no account of participants with incomplete follow-up, how missing outcome assessments were handled, or whether any sensitivity analyses were planned. Analysis populations, such as an intention-to-treat or per-protocol population, are not reported in the registry record. The registry's enrollment and safety-group counts do not establish which participants would have been included in an efficacy analysis.
These omissions are consequential because analysis choices can affect interpretation, especially when the endpoint includes grades or multiple time points. With no reported analysis and no stated missing-data or population rules, the posted record cannot establish whether all randomized participants were analyzed or how incomplete information would have been addressed.
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 |
|---|---|---|---|
| Standard Anesthetic Management | 0 | 5 | 0.0% |
| Preconditioning With 2 MAC Isoflurane Group | 0 | 3 | 0.0% |
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 |
|---|---|
| Standard Anesthetic Management | 0 of 5 |
| Preconditioning With 2 MAC Isoflurane Group | 0 of 3 |
The adverse-event entries list 5 participants at risk in the standard anesthetic management group and 3 at risk in the preconditioning with 2 MAC isoflurane group. In the serious adverse-event fields, the affected count is 0 for each group. In the other adverse-event fields, the affected count is also 0 for each group. These are the recorded counts; they are not a comparison adjusted for differences between groups.
A count of 0 recorded events does not establish that the treatments have equivalent safety. With a small enrolled study, the record may offer limited information about uncommon events, and the registry does not provide a detailed account of event ascertainment or follow-up. The safety entries do not give event rates or uncertainty estimates. Death counts are not reported in the registry record; a blank death entry should not be interpreted as a reported count of 0.
The registry provides no serious adverse event terms. It also does not report event narratives, timing, severity details beyond the serious/other categories, or whether any events led to changes in treatment. The listed zero counts should therefore be read narrowly as registry entries, not as comprehensive proof that no safety events occurred or as a finding that one anesthetic approach is safer.
12. What the Result Does, and Does Not, Mean
The record establishes that investigators planned a randomized, double-masked, parallel comparison of isoflurane preconditioning with propofol-based standard anesthetic management for elective hepatic surgery. It also establishes that the study enrolled 8 participants and was terminated. The primary endpoint was defined around postoperative complications graded IIIb or greater during the first 7 post operative days.
What the registry does not establish is whether either group had fewer qualifying complications, whether the groups differed in liver enzyme or bilirubin measures, or whether length of stay differed. No data analysis was performed, and no comparative estimates are reported. Without outcome counts and an analysis, there is no basis to describe the size, direction, or precision of a treatment effect. The record cannot establish efficacy, lack of efficacy, or equivalence.
The safety fields list 0 serious and 0 other adverse events affected in each arm, with 5 and 3 participants at risk, respectively. Those entries provide a limited descriptive snapshot, but no uncertainty estimates or detailed event ascertainment are reported. Death counts are not reported in the registry record. These safety entries should not be treated as a definitive comparison of risk.
In general, a terminated study without outcome analysis leaves its planned clinical question unanswered, rather than resolving it in favor of either intervention. The registry does not state why the study ended, whether follow-up was complete, or what information was available when the termination decision was made. No inference about those matters is warranted. The appropriate interpretation is limited: the record describes the design and planned outcomes, while the comparative clinical findings are unavailable.
13. Why This Trial Matters Statistically
This trial matters statistically because its design labels and stated question are not accompanied by analyzed outcome data. Randomization and masking are important features of a clinical comparison in general, but they do not themselves demonstrate a treatment effect. Valid interpretation also depends on outcome ascertainment, analysis rules, and the data obtained. In this record, no primary analysis was performed.
The endpoint also illustrates a common challenge in clinical research: a severity-graded outcome may contain several categories and may require a clear rule for forming a comparison. The registry identifies postoperative complications graded IIIb or greater and notes that the outcome was not reduced to one comparison because of multiple categories or time points. Without event counts or a defined analytic summary, readers cannot tell how the endpoint would have been represented in an estimate.
The small enrollment and early termination further limit what can be learned from the posted record. The 8 enrolled participants are not a basis for declaring a treatment difference or absence of difference, particularly when outcome results are not reported. The registry's planning assumptions cannot remedy this limitation: planning illustrations are not observed power and do not replace an estimate based on participant outcomes.
More broadly, the record shows why a completed or terminated trial should be interpreted through its reported results, not solely through its intended design. Here, the posted information supports a careful description of the question, groups, endpoint, enrollment, and limited safety counts. It does not supply the evidence needed to quantify comparative effects. Keeping that distinction clear prevents design features or empty outcome fields from being mistaken for statistical findings.
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 principal trial-specific limitation is that the registry says the study was terminated and no data analysis was performed. The reason for termination is not reported in the registry record. The primary endpoint has no reported participant counts, grade distribution, effect estimate, or measure of uncertainty. Thus, the planned comparison cannot be evaluated from the posted outcomes.
Enrollment was 8 participants. The registry lists 5 participants at risk in the standard anesthetic management group and 3 in the isoflurane preconditioning group for adverse-event reporting. The registry does not give the efficacy analysis population or state whether all enrolled participants completed follow-up. Group-specific outcome follow-up and missingness are not reported in the registry record.
Important design and analysis details are also absent. The randomization method, allocation concealment, identities of masked parties, complete intervention protocol, original sample-size justification, statistical model, and approach to multiple outcomes are not reported in the registry record. Neither are interim analysis plans, missing-data methods, or analysis-population definitions. The registry does not explain how multiple complication grades, categories, or time points would have been combined in a single analysis.
The safety entries show no affected participants in the serious or other adverse-event categories, but event collection procedures and death counts are not fully reported. These limitations mean the entries cannot support a comprehensive safety assessment. Taken together, the record is informative about the trial's intended comparison and status but does not contain the outcome data needed for a clinical effect estimate.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Isoflurane Preconditioning for Liver Resections — NCT01031550.
- Registry record last updated 2017-03-20; status last verified 2017-02.
- Results first posted 2013-12-12.
- 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
NCT01031550, titled “Isoflurane Preconditioning for Liver Resections,” is a randomized, double-masked, parallel trial sponsored by Rutgers, The State University of New Jersey. It enrolled 8 participants and is listed as terminated. The registry describes propofol-based standard anesthetic management and an isoflurane preconditioning group for elective hepatic surgery.
The primary outcome was postoperative complications graded IIIb or greater during the first 7 post operative days. Secondary outcomes include postoperative AST, ALT and total bilirubin, ICU and hospital stay, and liver lipid peroxidation and apoptosis. The registry states that no data analysis was performed because the study was terminated and lists 0 analyses. It reports 0 serious and 0 other adverse events affected in each safety group; death counts are not reported in the registry record. No comparative efficacy estimate or conclusion can be drawn from the posted results.