Cardiopulmonary bypass (CPB) makes complex cardiac surgery possible, but prolonged exposure to extracorporeal circulation may contribute to postoperative renal dysfunction. Maruf and colleagues examined the relationship between bypass duration and early acute kidney injury (AKI) in a prospective observational study of 100 adults. Their findings associate longer bypass time with more frequent AKI, higher postoperative serum creatinine, reduced urine output, and slower clinical recovery.
The study was conducted at the National Institute of Cardiovascular Diseases in Dhaka, Bangladesh, between July 2022 and June 2024. Participants were aged 18–65 years and underwent cardiac surgery using CPB. Patients were selected by convenience sampling and divided after surgery into two groups based on their recorded bypass duration: 50 patients had CPB times of 120 minutes or less, and 50 had CPB times exceeding 120 minutes. This was an observational comparison, not a randomized trial.
Patients with pre-existing chronic kidney disease, previous kidney transplantation, emergency surgery, an ejection fraction below 30%, previous cardiac surgery, or surgery without CPB were excluded. These exclusions are important when considering applicability: the results do not directly describe several high-risk populations commonly encountered in cardiac surgical practice.
The groups were broadly comparable in reported baseline characteristics. Mean age was 37.8 years in the shorter-duration group and 38.46 years in the longer-duration group. Sex distribution, comorbidities, body mass index, and underlying cardiac disease patterns did not differ significantly. Isolated valvular heart disease was the most common diagnosis. Mean CPB duration was 93.00 ± 11.42 minutes versus 137.10 ± 12.08 minutes, respectively (p < 0.001).
The principal finding was a substantial difference in early postoperative AKI. Seven patients in the shorter-duration group developed AKI, compared with 23 in the longer-duration group: 14% versus 46% (p < 0.001). This corresponds to an absolute difference of 32 percentage points and an approximately 3.3-fold difference in observed occurrence. These comparisons are unadjusted and should not be interpreted as an independent causal effect of bypass duration.
Renal measurements also differed during the first three postoperative days. Baseline serum creatinine was similar at 0.83 ± 0.11 versus 0.86 ± 0.13 mg/dL (p = 0.108). At 24, 48, and 72 hours after surgery, serum creatinine was significantly higher in the longer-duration group, while urine output was significantly lower at each time point. All reported postoperative comparisons reached p < 0.001. The full-text article defines AKI using KDIGO criteria: a serum creatinine rise of at least 0.3 mg/dL within 48 hours, an increase to at least 1.5 times baseline during the early postoperative period, or urine output below 0.5 mL/kg/hour for at least six hours.
Renal replacement therapy was required in four patients in the longer-duration group (8%) and none in the shorter-duration group. Three in-hospital deaths occurred in the longer-duration group (6%), compared with none in the shorter-duration group. Neither comparison was statistically significant. The small number of events limits conclusions about dialysis or mortality, and the study does not establish a reliable treatment-independent difference in either outcome.
Recovery was slower among patients with CPB durations exceeding 120 minutes. Mean mechanical ventilation duration was 8.90 ± 3.84 hours versus 6.98 ± 2.69 hours. Mean intensive care unit stay was 10.15 ± 4.68 days versus 4.87 ± 1.58 days, and mean postoperative hospital stay was 14.36 ± 5.55 days versus 10.11 ± 3.05 days. Each comparison was statistically significant (p < 0.001).
For perfusionists, the study reinforces the relevance of bypass duration when assessing postoperative renal risk. However, 120 minutes was the grouping threshold chosen for this analysis; the findings do not establish a universal safe limit or demonstrate a sudden change in risk at that point. Longer bypass time can also reflect more complex surgery or perioperative difficulties, which may themselves influence renal outcomes.
The authors identify important limitations, including a single-center design, convenience sampling, short follow-up, and unadjusted perioperative factors. Baseline similarity does not remove the possibility of confounding. The study therefore supports attention to early renal surveillance following prolonged CPB, while leaving unresolved how much of the observed risk is attributable to bypass exposure itself versus other clinical factors.
Overall, this prospective study found that CPB durations exceeding 120 minutes were associated with more frequent early postoperative AKI and longer recovery in a selected adult cardiac surgical population. Larger studies with adjustment for surgical complexity and perioperative factors are needed to clarify the independent contribution of bypass duration and the longer-term implications of these early renal findings.
From an evidence-appraisal perspective, the prospective design and repeated early postoperative measurements provide useful information about the temporal relationship between CPB exposure and renal recovery. Nevertheless, separating patients by the duration recorded after surgery does not ensure that the groups experienced equivalent procedures, hemodynamic conditions, or other perioperative exposures. Those differences would need to be measured and addressed before interpreting bypass time as an independent predictor. The reported p-values indicate that the observed group differences were unlikely under the statistical comparisons used; they do not resolve confounding or establish causation.
The practical value of this report is therefore its description of an early postoperative risk pattern, rather than a new intervention or mandatory time target. Perfusion and cardiac surgical teams can use the findings as a basis for discussion about renal outcomes and the information needed for more rigorous local analysis. The abstract does not test a particular renal-protection protocol, compare perfusion devices, or establish that shortening CPB alone would prevent AKI. Any such conclusion would go beyond the evidence presented.
Source: Maruf TH, et al. Cureus. 2026;18(9):e115589. DOI: 10.7759/cureus.115589.
