Fluid Chloride and AKI in Cardiopulmonary Bypass: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fluid Chloride and AKI in Cardiopulmonary Bypass (NCT02668952), a randomized phase 2 study. The primary outcome is Change in [TIMP2]*[IGFBP7] Biomarker.

2. Clinical Question

The clinical question is framed around a biomarker associated with acute kidney injury (AKI), rather than a direct comparison of a clinical AKI diagnosis as the primary endpoint. The registry lists AKI as the condition and describes renal outcomes as the study’s broader focus. Secondary outcomes include serum creatinine, serum chloride, postoperative arterial pH, and need for dialysis. The record describes random assignment to two fluid groups but does not report further details about eligibility criteria or the surgical population. Findings therefore describe the posted results for this small group of cardiac surgery patients, not necessarily other patient groups or fluid-use settings.

3. Trial Design

This was a completed phase 2, randomized, parallel-group trial sponsored by the University of New Mexico. The study began in 2016-01, had primary completion on 2017-02-04, and recorded enrollment of 30. Masking was listed as none. The registry summary says investigators proposed randomizing 30 trial-completing cardiac surgery patients, with up to 40 enrolled; the primary outcome summaries include 16 participants assigned to Normal Saline and 14 assigned to Isolyte.

Both fluids were given intravenously as needed during the care of cardiac surgery patients. For each arm, dosage, frequency, and duration were left to the attending physicians’ clinical judgment and usual patterns of use. Thus, the comparison concerns assignment to a fluid group within usual clinical practice as described in the record, rather than a fixed dose or duration reported for every participant. The registry does not report the amounts of fluid each participant received.

The study compared the change in urinary [TIMP2]*[IGFBP7] from the preoperative value to the postoperative measurement at 24 hours. The registry describes positive changes as increases and negative changes as decreases. Six secondary outcomes are listed, covering serum creatinine and chloride at 24 and 48 hours, need for dialysis, and postoperative arterial pH. The posted numeric summaries include 24-hour creatinine, 24-hour chloride, and postoperative pH.

The registry records no masking and a parallel design, but further details about sequence generation, allocation concealment, and trial conduct are not reported in the registry record. The original statistical analysis plan, planned sample-size justification, analysis populations, and interim analyses are also not reported in the registry record. The available record supports a description of the assigned groups and posted outcomes, but it does not permit a detailed reconstruction of every design or analysis decision.

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 Change in [TIMP2]*[IGFBP7] Biomarker, measured over Baseline and postoperatively at 24 hours.

The primary endpoint was change in urinary [TIMP2]*[IGFBP7] between the preoperative measurement and a repeated measurement at 24 hours after surgery. The unit was (ng/mL)^2/1000. A positive change represents an increase, while a negative change represents a decrease. The registry reports the mean and standard deviation for each group.

This biomarker is used as a measure related to kidney stress or injury in the study’s stated question. A biomarker can provide a measured biological signal without being identical to a clinical diagnosis or an outcome such as dialysis. The primary result should therefore be read as a comparison of average biomarker change, not as a direct estimate of the rate of diagnosed AKI. The record does not report a threshold for interpreting an individual participant’s biomarker value or a clinically important difference for the change.

In the Normal Saline group, the mean change was 0.015 with a standard deviation of 0.125 among 16 participants. In the Isolyte group, the mean change was 0.009 with a standard deviation of 0.148 among 14 participants. The estimated mean difference, calculated as Isolyte minus Normal Saline, was -0.006. Its 95% confidence interval ranged from -0.105 to 0.093. That interval describes uncertainty around the estimated difference in group means; it does not establish what happened to every participant.

7. Results Posted in the Registry

• Isolyte Group: mean 0.01 versus 0.01 on control; difference -0.01 (95% CI -0.10 to 0.09), standardized effect d = -0.04; z-test p = 0.905.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Serum Creatinine Level at 24 Hours

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Isolyte Group: mean 0.80 versus 0.85 on control; difference -0.05 (95% CI -0.19 to 0.09), standardized effect d = -0.24; z-test p = 0.497.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Isolyte Group and the control. The interval gives the range of effects that remain compatible with the data.

Serum Chloride Level at 24 Hours

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Isolyte Group: mean 106.00 versus 110.00 on control; difference -4.00 (95% CI -6.19 to -1.81), standardized effect d = -1.31; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Isolyte Group than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Postoperative Arterial pH

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Isolyte Group: mean 7.41 versus 7.38 on control; difference 0.03 (95% CI -0.00 to 0.06), standardized effect d = 0.74; z-test p = 0.050.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Isolyte Group and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes provide several different views of postoperative laboratory values and clinical care. The listed measures include serum creatinine and chloride at 24 and 48 hours, need for dialysis, and postoperative arterial pH. They are related to the study’s kidney and fluid-composition question, but they do not measure the same thing as the primary change in urinary [TIMP2]*[IGFBP7]. A difference in one secondary measure cannot be assumed to imply a corresponding difference in the primary biomarker or in a clinical diagnosis.

The available secondary comparisons show a clearer separation in serum chloride than in the primary biomarker. The 24-hour chloride comparison has an unadjusted p-value of <0.001 and a confidence interval that excludes zero. In contrast, the posted 24-hour creatinine comparison has an interval including zero, and the pH interval extends to -0.0. These patterns do not resolve the primary endpoint’s uncertainty. They indicate that the observed chloride values differed more distinctly between groups in this trial, while the other posted comparisons are less conclusive about group differences.

Secondary results generally carry less weight when they are unadjusted and multiple outcomes are examined. Unless outcomes and analysis priorities are specified in advance, selecting an apparently notable result from a set of tests can overstate the evidence. The registry record does not report a multiplicity adjustment, a formal hierarchy of confirmatory outcomes, or a prespecified interpretation threshold for these secondary measures. Their p-values should therefore be understood as unadjusted evidence across a set of outcomes, not as standalone proof.

Numerical findings for secondary outcomes should be interpreted with the endpoint and its measurement time in mind. A laboratory value at 24 hours is not interchangeable with a value at 48 hours, and a measure of chloride concentration is not itself a measure of kidney injury. The registry record does not report all details needed to judge how missing measurements or the analysis population may affect the secondary comparisons. Overall, the secondary pattern adds context about measured postoperative values but does not replace or settle the primary comparison.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Serum Creatinine Level at 24 Hours
• Serum Chloride Level at 24 Hours
• Proportion of Patients With Need for Dialysis
• Postoperative Arterial pH
• Serum Creatinine Level at 48 Hours
• Serum Chloride at 48 Hours

9. Statistical Interpretation

10. Statistical Methods Explained

These results compare continuous measurements between two randomized groups. A continuous outcome can take a range of values, such as a biomarker concentration or a laboratory measurement. The registry reports group means and standard deviations, then gives a mean difference for each posted comparison. For the primary outcome, the contrast is expressed as Isolyte minus Normal Saline. A negative estimate means the Isolyte group’s mean was lower on the reported scale; it does not indicate that every participant in that group had a lower value.

What does a mean describe?

The mean is the arithmetic average of the observed values in a group. It is useful for describing the center of a distribution, but it does not show the full pattern of individual outcomes. For the primary endpoint, the group means were 0.015 and 0.009, while the standard deviations were 0.125 and 0.148. The standard deviation describes how dispersed individual observations are around their group mean. In this comparison, the spread of observations is important context for understanding why the estimated difference is uncertain.

A mean difference compares the two group averages on the outcome’s original measurement scale. The primary estimate of -0.006 is the reported difference between the Isolyte and Normal Saline means. It is not an adjusted estimate from a model described in the registry record. The posted comparison is an unadjusted recalculation from the group summary statistics. The registry record does not report a different sponsor analysis for this outcome, and the discrepancy indicator is false.

What does a confidence interval communicate?

A confidence interval gives a range of values compatible with the observed data under the calculation’s assumptions. It expresses estimation uncertainty, not the range of individual participants’ measurements and not a guarantee that the true value lies inside the particular interval. The primary 95% confidence interval extends from -0.105 to 0.093. Its width is substantial relative to the point estimate, so the data do not pin down the size or direction of the group difference precisely. Since the interval includes zero, it is compatible with no mean difference as well as with differences in either direction.

The interval and p-value answer related but different questions. The p-value of 0.905 is an unadjusted measure of how compatible the data are with a null hypothesis of no mean difference, under the calculation’s assumptions. It is not the probability that the null hypothesis is true, and it does not measure the probability that the result will replicate. A p-value does not tell whether a difference is clinically important. The confidence interval is more useful for seeing the range of differences that remain compatible with the data.

Why can group variation matter?

Greater variability makes it harder to distinguish a group difference from ordinary variation in measurements. In general, when observations are highly dispersed, a mean estimate tends to be less precise unless there is more information from participants. This is why both group means and standard deviations matter. The primary result’s standard deviations are large relative to the estimated mean difference, contributing to a wide interval. That description is statistical, not a judgment about the clinical importance of the biomarker.

Over-dispersion is a general concern when outcome variation exceeds what a statistical model assumes. If a model assumes less variability than is actually present, its uncertainty estimates may be too small and inferences too confident. The registry does not report a model-based assessment of over-dispersion for the primary endpoint. Here, the posted summaries include standard deviations, and the recalculated comparison uses those summary statistics rather than a reported adjusted model.

What does unadjusted mean in these results?

An unadjusted comparison is a direct comparison that does not account for other participant characteristics or covariates in a statistical model. Randomization is intended to make assigned groups comparable on average, but in a small trial, chance differences in participant characteristics can still occur. The registry record does not report covariate-adjusted estimates or the variables that might have been included in such an analysis. The recalculated summaries should therefore be read as simple group comparisons.

Multiplicity is the issue that arises when several outcomes or comparisons are examined. With more opportunities to find a small p-value, chance findings become more plausible across the set of tests. The registry lists six secondary outcomes and does not report an adjustment for multiple comparisons or a hierarchy specifying which secondary tests were confirmatory. Secondary p-values are unadjusted and should be treated as exploratory evidence rather than as a set of independently definitive findings.

What can the posted statistics establish?

The statistics describe the observed group summaries and quantify uncertainty in the estimated differences. They do not establish why a difference occurred, identify an individual participant’s outcome from a group average, or show whether a biomarker difference corresponds to a clinical benefit or harm. The registry does not report a clinical interpretation threshold for the primary biomarker. Accordingly, statistical significance and clinical importance should not be treated as interchangeable concepts.

All interpretations also depend on the quality and completeness of the measurements and the analysis population. The registry record does not report how missing measurements were handled, whether all randomized participants were included in each outcome analysis, or whether the planned analysis followed an intention-to-treat principle. Those details matter because exclusions or incomplete outcome collection can affect how well a group comparison reflects the randomized assignment.

11. Confidence Intervals and Precision

The primary mean difference was -0.006, with a 95% confidence interval from -0.105 to 0.093. The estimate is close to zero on the reported scale, but the interval extends appreciably in both directions. The data are therefore compatible with an average change that is lower in the Isolyte group, close to no mean difference, or higher in the Isolyte group. The interval does not establish equivalence, because the registry record does not report an equivalence margin or a design for testing equivalence.

Precision concerns how narrowly the data locate the underlying group difference. A narrow interval would indicate greater precision; a wide interval leaves more possible values compatible with the observations. The primary interval is wide in relation to the point estimate, and the group standard deviations are 0.125 and 0.148. The trial’s primary outcome summaries include 16 participants in one group and 14 in the other. These features help explain why a point estimate alone would be an incomplete account of the result.

The interval reflects uncertainty in the estimated mean difference under the calculation’s assumptions. It is not an interval containing most individual measurements, and it does not show the range of possible outcomes for a particular patient. Nor does it account for every uncertainty about trial conduct, missing data, measurement quality, or the choice of analysis. Those elements are not fully described in the registry record.

The unadjusted p-value of 0.905 is consistent with the interval’s inclusion of zero, but the interval conveys more information about direction and plausible magnitude. The result should not be reduced to a binary significant or not-significant label. Its main statistical message is that the observed estimate is small while uncertainty remains broad enough that a range of mean differences cannot be ruled out by these data.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total participants, for these continuous-outcome comparisons. They are illustrations calculated from the observed effect under the stated assumptions: a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The trial’s original sample-size justification and design assumptions are not reported in the registry record.

The 80% power column describes the number of participants per arm that the planning calculation estimates would be needed for an 80% chance of detecting the specified effect if that effect were the true one and the assumptions held. The 90% power column uses a higher target chance of detection, which generally requires more participants. These are design-planning quantities, not observed outcomes of the completed trial.

For the primary endpoint, planning for 100% of the observed effect gives 8,085 participants per arm for 80% power and 10,823 participants per arm for 90% power. Planning for 75% of the observed effect gives 14,373 participants per arm for 80% power and 19,241 participants per arm for 90% power. Planning for 50% of the observed effect gives 32,338 participants per arm for 80% power and 43,292 participants per arm for 90% power. The general pattern is that a smaller effect is harder to distinguish from variability, so detecting it requires more participants under the same planning assumptions.

These figures are not observed power and do not show the probability that the completed trial’s result is correct. Because the calculations use an effect estimated from a small trial, they are sensitive to that estimate; the primary observed mean difference is -0.006 and its confidence interval is broad. The planning figures are best read as illustrations of how sample size changes with the target effect, not as a claim about the trial’s original design or a recommendation for a future study.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -0.006; pooled standard deviation σ = 0.136.
2. n = 2 × (1.96 + 0.842)² × 0.136² / -0.006² = 8,084.5, rounded up to 8,085 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -0.006                      # observed difference in means
sigma <- 0.13616258663818                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2668952)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 8,085 (80% power), 10,823 (90% power)
 75% of observed effect: n per arm = 14,373 (80% power), 19,241 (90% power)
 50% of observed effect: n per arm = 32,338 (80% power), 43,292 (90% power)
power.t.test: 8085.4 
Simulated power at n = 8,085 per arm: 0.796 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists six secondary outcomes in addition to the primary endpoint. Examining multiple outcomes can increase the chance that at least one result appears statistically notable by chance, even when there is no corresponding underlying effect. The record does not report a multiplicity adjustment, a hierarchy of testing, or which secondary outcomes were intended to be confirmatory. The secondary p-values are therefore unadjusted, and their interpretation should account for the fact that several outcomes were considered.

The registry record does not report how missing outcome data were handled. It does not specify whether any participants lacked the preoperative or 24-hour biomarker measurement, whether analysis was restricted to participants with complete measurements, or whether a method was used to account for missing values. The posted primary summaries include 16 participants in the Normal Saline group and 14 in the Isolyte group, but those group counts alone do not describe the completeness of every measurement or the handling of all randomized participants.

The analysis population is also not reported in enough detail to determine whether the primary comparison included everyone as randomized, only participants who completed the study, or another defined group. The registry summary describes an aim of 30 trial-completing patients, with up to 40 enrolled, while the posted primary summaries total 30 participants. The record does not explain whether the summaries follow an intention-to-treat, per-protocol, or other analysis principle.

Details about interim analyses, the original statistical analysis plan, and the trial’s sample-size justification are not reported in the registry record. Without those details, it is not possible to assess whether the posted comparisons follow a prespecified plan or whether analysis decisions were made after reviewing the data. This does not invalidate the descriptive results, but it limits how confidently they can be interpreted as confirmatory evidence. Clear reporting of outcome completeness, analysis populations, and multiplicity handling would help readers evaluate the strength and scope of the statistical conclusions.

15. 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 0% reporting threshold.

The posted adverse-event figures show zero serious adverse events in the Normal Saline group, with 16 participants at risk, and zero in the Isolyte group, with 14 participants at risk. The registry also reports zero other adverse events in each group and zero deaths in each group. These are event counts in the groups as recorded, not proof that no adverse effects occurred or that the fluids have identical safety profiles.

Safety interpretation depends on how events were defined, collected, and attributed, as well as the duration and completeness of follow-up. The registry record does not report further details about those procedures or provide serious adverse-event terms. With relatively few participants, the absence of recorded events provides limited information about uncommon outcomes. The figures describe what was reported for this trial and should not be generalized beyond the study population and follow-up information recorded.

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

The primary result is an estimate of the difference in mean change in urinary [TIMP2]*[IGFBP7] between two randomized fluid groups. The observed means were 0.015 for Normal Saline and 0.009 for Isolyte, and the estimated difference was -0.006. The 95% confidence interval, from -0.105 to 0.093, includes zero and is wide enough to leave uncertainty about both the direction and size of a possible difference. The result does not establish a clear separation in average biomarker change.

That finding should not be translated into a claim that the fluids are equivalent or that neither is associated with a difference. The trial does not report an equivalence margin or a non-inferiority framework. Failure to obtain a clearly separated estimate is not the same as demonstrating that any possible difference is small enough to be clinically unimportant. Conversely, a statistical difference in a secondary laboratory measure does not establish a clinical benefit or harm.

The primary endpoint is a biomarker change, not a direct count of participants with diagnosed AKI. The registry lists AKI as a condition and includes secondary measures relevant to kidney function and postoperative care, but the primary comparison does not directly answer how often clinical AKI occurred. No threshold for a clinically important biomarker change is reported in the registry record. Consequently, the clinical meaning of a difference of the estimated size cannot be determined from the posted statistics alone.

Random assignment makes the two groups suitable for a comparative question, but this was a small trial with 30 participants represented in the primary summaries. The results describe these study groups and the reported measurements; they do not establish what would happen in all cardiac surgery patients or under other fluid administration practices. The registry record also lacks details about missing data, analysis populations, and the original statistical plan, which limits assessment of the robustness of the comparison.

The 24-hour chloride result shows a difference in the measured serum chloride values between groups, while the primary biomarker result remains imprecise. These outcomes are distinct. A chloride difference does not prove a corresponding change in kidney injury, and the primary biomarker comparison does not explain why chloride values differed. The posted statistics support a careful description of measurements and uncertainty, not a treatment recommendation or a conclusion about mechanism.

17. Why This Trial Matters Statistically

This trial is statistically informative because it places a biologically motivated fluid comparison alongside a measured kidney-related biomarker and postoperative laboratory outcomes. Its randomized, parallel-group design provides a direct framework for comparing assigned fluid groups. The primary result also illustrates why both an estimated difference and its uncertainty matter: the mean difference is -0.006, but its confidence interval extends from -0.105 to 0.093.

The contrast between the primary biomarker result and the secondary chloride result is useful for statistical interpretation. A measurable difference in one outcome does not guarantee a detectable difference in another outcome that reflects a different biological process or measurement. The outcomes should be evaluated on their own scales and with attention to their uncertainty, rather than treated as interchangeable indicators.

The study also shows the limitations of relying on a small randomized comparison to estimate an effect precisely. The sample-size illustrations based on the observed primary effect are large, reflecting how difficult it would be to detect that small estimated difference under the stated planning assumptions. Those calculations are not the trial’s original sample-size rationale, which is not reported, and they are not evidence that the completed study had a particular probability of success.

For biostatisticians and clinical researchers, the record highlights important reporting needs: a clear analysis plan, explanation of the analysis population, completeness of outcome measurements, and a strategy for interpreting multiple secondary endpoints. Without those details, the posted results remain useful descriptive estimates but have limits as confirmatory evidence. The study’s central statistical lesson is to avoid interpreting an isolated p-value or a point estimate without its interval, endpoint definition, and design context.

18. 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 is the small number of participants represented in the primary outcome summaries: 16 in the Normal Saline group and 14 in the Isolyte group. The primary confidence interval is broad, so the estimated difference is imprecise. A small trial may also be vulnerable to chance imbalances between groups despite random assignment; baseline balance information is not reported in the registry record.

Fluid administration was left to attending physicians’ judgment and usual patterns of use. The registry record does not report the actual amount, frequency, or duration of fluid received by participants, so the exposure contrast cannot be described in detail. Masking was listed as none, and the record does not report whether outcome measurement or data analysis was blinded.

The primary endpoint is a biomarker change measured at baseline and 24 hours, rather than a reported clinical AKI event rate. The registry does not report a threshold for a clinically meaningful biomarker change. It also does not report detailed eligibility criteria, all participant flow information, measurement completeness, missing-data methods, or the analysis population. These omissions limit assessment of generalizability and potential bias.

Several secondary outcomes are listed, and the registry does not report a multiplicity strategy or a hierarchy of analyses. The original statistical plan, sample-size justification, and interim analyses are not reported in the registry record. The secondary findings should therefore be interpreted cautiously, particularly when considered alongside a primary comparison with substantial uncertainty. These limitations do not erase the observed data, but they constrain how strongly the results can support broader conclusions.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Fluid Chloride and AKI in Cardiopulmonary Bypass — NCT02668952.
• Registry record last updated 2018-05-14; status last verified 2018-04.
• Results first posted 2018-03-19.
• 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.

22. Record Summary

This completed phase 2 randomized, parallel-group trial compared intravenous Normal Saline with Isolyte in cardiac surgery patients undergoing cardiopulmonary bypass. The registry records enrollment of 30, no masking, and primary completion on 2017-02-04. The primary endpoint was change in urinary [TIMP2]*[IGFBP7] from before surgery to 24 hours postoperatively.

The mean changes were 0.015 (SD 0.125) for 16 Normal Saline participants and 0.009 (SD 0.148) for 14 Isolyte participants. The estimated mean difference was -0.006, with a 95% confidence interval from -0.105 to 0.093 and an unadjusted p-value of 0.905. The interval leaves substantial uncertainty about the direction and size of a possible mean difference.

The posted secondary results include serum creatinine, serum chloride, and postoperative arterial pH comparisons. The registry lists six secondary outcomes overall. Details about the original analysis plan, sample-size justification, missing data, and analysis populations are not reported in the registry record.