The Effects of Modified Ultrafiltration on Vancomycin Levels During Cardiopulmonary Bypass in Cardiac Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effects of Modified Ultrafiltration on Vancomycin Levels During Cardiopulmonary Bypass in Cardiac Surgery (NCT02051595), a na early/phase 1 study. The primary outcome is Circulating Vancomycin Concentration.

2. Clinical Question

3. Trial Design

The registry lists NCT02051595 as a completed early-phase 1 study sponsored by the University of Florida. It records enrollment of 25 and a start date of 2014-04, with primary completion in 2015-04. These details describe the registered study, but do not establish how many participants contributed usable outcome measurements.

The design is single-group, allocation is marked NA, and masking is listed as none. There is no separate untreated, alternative-treatment, or randomized control group described. The study is therefore structured around measuring concentrations over time in the surgical setting, rather than estimating a contrast between assigned groups. The registry describes subjects receiving vancomycin prophylaxis before cardiac surgery with CPB and MUF.

The planned outcome collection includes up to ten blood samples. The registry lists a pre-CPB measurement; measurements after CPB begins at 5, 30, 60, 108, and 240 minutes; a measurement prior to ultrafiltration; a measurement at the end of ultrafiltration; and samples of ultrafiltrate and cell-saver effluent. The record does not explain whether every participant was expected to contribute at every listed time point, or how incomplete sampling would be handled.

The stated aim is to quantify concentration changes associated with CPB and MUF. With no separate comparator group, the design can describe observed concentrations and their timing, if numerical results are available. It cannot by itself isolate the effects of CPB or MUF from other changes occurring during surgery. The registry record does not report the protocol rationale, a sample-size justification for the study, or a detailed statistical analysis plan.

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

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 Circulating Vancomycin Concentration, measured over Time points: pre CPB (t=1), post CPB at 5 (t=2), 30 (t=3), 60 (t=4), 108 (t=5), 240 (t=6) minutes, prior to ultrafiltration (t=7), end of ultrafiltration (t=8), ultrafiltrate (t=9) ,effluent of cell saver (t=10).

The primary outcome is circulating vancomycin concentration, a continuous measure reported in µg/mL. The registry identifies the mean as the summary measure and the standard deviation as its dispersion measure. Concentrations are scheduled for assessment at several points around CPB and MUF, as well as in ultrafiltrate and cell-saver effluent.

Measuring concentrations over time is relevant to the stated study question because it describes how the measured level varies across the surgical process. The blood measurements address circulating concentration at particular times; the fluid samples provide measurements from the ultrafiltrate and cell-saver effluent. These are distinct sampling contexts, and their values should not be treated as interchangeable without further information.

In general, a mean describes the average measurement within a group at a specified time, while a standard deviation describes variation among measurements around that mean. The registry record gives the outcome definition and measurement schedule, but numerical means and standard deviations are not reported in the registry record. It also does not report a numerical estimate of change, a confidence interval, or a test of change over time. Thus, the endpoint is defined, but its observed magnitude and precision cannot be evaluated from the recorded outcome information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is a continuous concentration, with the mean and standard deviation identified as its summary statistics. The design involves repeated measurements from a single group across perioperative time points. The registry defines those measurements, but does not report the numerical results or the methods used to analyze them. The explanations below describe general statistical concepts relevant to this type of measurement; they should not be read as a claim that a particular method was used in this study.

What does the mean describe?

In general, a mean is the arithmetic average of measurements in a defined group. For concentration data, a mean at a given time point would describe the group’s average measured concentration at that time. A mean alone does not show whether individual measurements clustered closely or varied widely, which is why the registry also identifies the standard deviation as a dispersion measure.

In general, the standard deviation describes the spread of individual observations around their mean. A larger spread indicates more variability in the measurements, while a smaller spread indicates that observations are more closely grouped. It is not the same as the uncertainty of the mean: that uncertainty also depends on the number of observations and the analysis. The registry record does not report time-specific means, standard deviations, or the number of measurements used to calculate them.

Why do repeated measurements need care?

In general, measurements taken from the same participant are related. A participant’s concentration at one time may be more similar to that participant’s concentration at another time than to a different participant’s measurement. An analysis that treats all repeated observations as independent can misrepresent the amount of information in the data and produce uncertainty estimates that are too narrow or otherwise inappropriate.

Methods for repeated measurements can account for this within-participant relationship. The suitable approach depends on the study question, the measurement schedule, the data structure, and assumptions about missing observations and variability. The registry record does not report a repeated-measures model, covariance structure, or other method for accounting for within-participant dependence. It is therefore not possible to determine from the record how the dependence among measurements was handled.

What does a confidence interval add?

In general, a confidence interval gives a range of values compatible with an estimate under the assumptions of the statistical method. A narrow interval indicates greater statistical precision than a wide interval, all else equal. It does not guarantee that the estimate is free from bias, and it does not address limitations such as the lack of a comparator group. No confidence interval for the primary concentration outcome is reported in the registry record.

A p value, when used, addresses how compatible data are with a specified statistical null hypothesis under the model’s assumptions. It does not measure the size or practical importance of an effect. The registry record does not report a p value or identify a hypothesis test for the primary outcome. No conclusion about statistical significance can be drawn from the outcome information recorded.

How should the planning assumptions be read?

The registry’s planning assumptions describe an illustrative calculation based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They also describe examining a stated fraction of the observed effect. Such assumptions describe a hypothetical planning exercise; they do not establish that the trial itself used those design choices. In particular, this study is registered as single-group, not as a two-arm equal-allocation trial.

In general, sample-size calculations estimate how many observations a planned study might need under specified assumptions. Their outputs are planning illustrations, not observed power and not evidence that a study had a particular probability of detecting an effect after the data were collected. The registry record does not report a trial-specific sample-size justification. Nor does the planning framework substitute for the missing numerical outcome results. Any hypothetical calculation based on an observed effect should be interpreted cautiously when the effect estimate and its uncertainty are not reported in the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Vancomycin Concentrations")
n   <- c(25)
m   <- c(15.6)
sp  <- c(4.4)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Vancomycin Concentrations  25  15.600  4.400  13.784  17.416

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies one primary outcome measure: circulating vancomycin concentration. That outcome is scheduled across multiple time points and sample types. Repeated assessment creates several possible summaries or comparisons, but the record does not specify which time-point contrasts, if any, were designated for formal testing.

Multiplicity refers, in general, to the increased chance of a false-positive finding when many hypotheses are tested. Statistical plans may address this by identifying a primary contrast in advance or by adjusting inference across multiple tests. The registry record does not report a multiplicity strategy, a hierarchy of time-point comparisons, or a prespecified contrast. It is not possible to determine whether multiplicity was addressed in an analysis outside the information recorded.

The record also does not report how missing measurements were handled, how many participants contributed data at each time point, or whether any analysis population was defined beyond the enrolled group. The description of up to ten samples does not establish that all samples were collected or analyzed. Methods such as complete-case analysis, imputation, or model-based handling of incomplete repeated measurements are not reported in the registry record.

These omissions affect interpretation of both the estimates and their uncertainty. The analysis population, missing-data approach, and multiplicity plan are not reported in the registry record. No claim about the presence or absence of missing measurements, or about the actual handling of multiple comparisons, can be made from the available record.

12. 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 0% reporting threshold.

The adverse-event record lists 25 at risk for serious adverse events and 0 affected. It also lists 25 at risk for other adverse events and 0 affected. These are the counts recorded for the Vancomycin Concentrations group. The death count is not reported in the registry record, and no serious adverse-event terms are listed.

These figures describe what is entered in the registry; they do not provide event details, timing, severity grades, or a narrative assessment of events. The record does not explain the adverse-event collection period or provide information about completeness of reporting. A recorded count of 0 affected should therefore be read as the registry’s reported count, not as proof that no event occurred outside the recorded information.

Safety counts also do not answer the primary concentration question. They are separate from the continuous vancomycin measurements, and they do not establish a comparison with another group. The registry record does not report a comparator group for safety outcomes.

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

The record defines a study that sought to measure circulating vancomycin concentrations during cardiac surgery with CPB and MUF. Its single-group design and repeated sampling schedule are suited to describing measurements over the course of the procedure, if those measurements and their analysis are reported. The registry provides the outcome definition and planned time points, but not numerical primary outcome results.

Accordingly, the record does not establish the amount or direction of any concentration change. It does not report an estimate with which to assess precision, and it does not provide enough information to judge variability across participants or completeness of sampling. The stated purpose is not itself a result.

The design also does not provide a randomized contrast that would separate changes associated with CPB from changes associated with MUF or other aspects of surgery. A pattern over time in a single group, even if documented, would not by itself identify the cause of that pattern. The registry record does not describe a comparison group or an analysis designed to isolate those effects.

The reported safety counts are limited to the registry entries for serious and other adverse events. They should not be interpreted as a complete account of safety without further information about collection and reporting. Overall, the record supports an understanding of the study’s question, structure, and planned measurements, but it does not support a quantitative conclusion about the primary outcome.

14. Why This Trial Matters Statistically

This study raises a statistical question about how a continuous concentration measure behaves over time in a surgical setting. Its schedule includes measurements before and after CPB, around MUF, and in collected fluid samples. Such a design can be informative descriptively, but analysis must respect the fact that repeated observations from one participant are related and that different sample types represent different measurement contexts.

The registry also illustrates why outcome definitions and outcome results are not interchangeable. Naming the measure, units, summary statistics, and time points tells readers what the study intended to observe. Without numerical values, however, readers cannot evaluate the magnitude of the observations, their variability, or the uncertainty around a change.

Its single-group structure is another important statistical feature. It can frame a within-study description, but it does not create a randomized counterfactual comparison. Any causal interpretation would require information and assumptions beyond a sequence of measurements in one group. A clear distinction between temporal association and a treatment contrast is therefore essential.

Finally, reporting the numbers contributing at each time point, the handling of incomplete measurements, and the analysis plan would help readers assess the reliability of any estimates. Those details are not reported in the registry record. The case is a useful reminder that a completed study and a clearly stated objective do not, on their own, provide enough information for statistical interpretation of an unreported outcome.

15. 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 main limitation for interpreting this specific study is that numerical results for the primary concentration outcome are not reported in the registry record. Although the endpoint, units, summary measures, and sampling schedule are specified, there are no reported concentration means or standard deviations from which to assess the observed pattern or its variability.

The single-group design has no separate comparator. It therefore cannot distinguish changes related to CPB or MUF from changes associated with other parts of surgery using a randomized between-group contrast. The registry does not report a design or analysis that separates those influences.

The sampling description allows up to ten samples, but the record does not state the number collected or analyzed at each time point. It does not report whether all participants contributed every measurement, how missing samples were handled, or what population was included in the primary analysis. This prevents assessment of whether the planned repeated schedule was achieved and how incomplete data may have affected estimates.

Further limitations include the absence of a reported statistical analysis plan, confidence intervals, hypothesis tests, and a multiplicity approach for repeated time points. The record also does not provide additional eligibility details or explain the rationale for the enrollment target. These omissions limit assessment of precision, analysis choices, and generalizability. They should be understood as limitations of what is reported in the registry record, not as evidence that particular procedures were or were not carried out.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Effects of Modified Ultrafiltration on Vancomycin Levels During Cardiopulmonary Bypass in Cardiac Surgery — NCT02051595.
• Registry record last updated 2019-08-13; status last verified 2019-08.
• Results first posted 2015-07-21.
• 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.

19. Record Summary

NCT02051595 is listed as a completed early-phase 1, single-group study sponsored by the University of Florida, with enrollment of 25. The registry records a start date of 2014-04 and primary completion in 2015-04. Allocation is marked NA and masking is listed as none.

The study’s stated purpose is to quantify changes in plasma vancomycin concentration associated with CPB and MUF during cardiac surgery. Its primary outcome is circulating vancomycin concentration, measured in µg/mL and summarized by mean and standard deviation. The planned schedule includes pre-CPB and later perioperative measurements, as well as ultrafiltrate and cell-saver effluent samples.

Numerical primary outcome results and detailed analysis methods are not reported in the registry record. The adverse-event record lists 0 affected for serious and other adverse events, with 25 at risk in each category; deaths are not reported in the registry record.