Postoperative saline administration following cardiac surgery: impact of high versus low-volume administration on acute kidney injury

Predictive value of perioperative NT-proBNP levels for acute kidney injury in patients with compromised renal function undergoing cardiac surgery: a case control study

BACKGROUND

Acute kidney injury (AKI) significantly increases morbidity and mortality following cardiac surgery, especially in patients with pre-existing renal impairments. N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a marker of cardiac stress and dysfunction, conditions often exacerbated during cardiac surgery and prevalent in chronic kidney disease (CKD) patients. Elevated NT-proBNP levels can indicate underlying cardiac strain, hemodynamic instability and volume overload. This study evaluated the association between perioperative changes in NT-proBNP levels and the incidence of AKI in this particular patient group.

METHODS

This retrospective study involved patients with impaired renal function (eGFR 15-60 ml/min/1.73 m²) who underwent cardiac surgery from July to December 2022. It analyzed the association between the ratio of preoperative and ICU admittance post-surgery NT-proBNP levels and the development of AKI and AKI stage 2-3, based on KDIGO criteria, using multivariate logistic regression models. Restricted cubic spline analysis assessed non-linear associations between NT-proBNP and endpoints. Subgroup analysis was performed to assess the heterogeneity of the association between NT-proBNP and endpoints in subgroups.

RESULTS

Among the 199 participants, 116 developed postoperative AKI and 16 required renal replacement therapy. Patients with AKI showed significantly higher postoperative NT-proBNP levels compared to those without AKI. Decreased baseline eGFR and increased post/preoperative NT-proBNP ratios were associated with higher AKI risk. Specifically, the highest quantile post/preoperative NT-proBNP ratio indicated an approximately seven-fold increase in AKI risk and a ninefold increase in AKI stage 2-3 risk compared to the lowest quantile. The area under the receiver operating characteristic curve for predicting AKI and AKI stage 2-3 using NT-proBNP were 0.63 and 0.71, respectively, demonstrating moderate accuracy. Subgroup analysis demonstrated that the positive association between endpoints and logarithmic transformed post/preoperative NT-proBNP levels was consistently robust in subgroup analyses stratified by age, sex, surgery, CPB application, hypertension, diabetes status and fluid balance.

CONCLUSION

Perioperative NT-proBNP level changes are predictive of postoperative AKI in patients with pre-existing renal deficiencies undergoing cardiac surgery, aiding in risk assessment and patient management.

Postoperative Fluid Therapy in Adult Cardiac Surgical Patients and Acute Kidney Injury: A Prospective Observational Study

Background Normal saline (0.9% NS) is a common intravenous fluid used worldwide. Recent studies have shown that NS use is associated with increased incidence of acute kidney injury (AKI) and a need for renal replacement therapy (RRT). The practice is changing toward using balanced solutions to prevent AKI. Postcardiac surgery patients are more prone to develop AKI after cardiopulmonary bypass (CPB). We aim to study the type of fluid administrated, incidence of AKI, need for RRT, and overall outcome of these patients.

Methods This prospective observational study was conducted in the cardiothoracic intensive care unit (cardiothoracic and vascular surgery intensive care unit) in a cohort of 197 adult patients who underwent on pump cardiac surgery in our hospital from July 2021 to October 2021 as a pilot study. Data was analyzed using SPSS 20.0 (IBM, Chicago, Illinois, United States). A p-value < 0.05 was considered significant.

Results In our study, 58 (29.34%) patients developed AKI in the first three postoperative days and 16 (8.12%) patients required RRT. Incidence of AKI was found to be higher in patients who received NS only, as fluid of choice was 34.48% compared with other intravenous fluids. Patients with AKI had higher positive fluid balance (p < 0.001), longer CPB (p < 0.001), and aortic cross clamp (p = 0.006) times. Intensive care unit and hospital stay and mortality rates were higher in AKI patients than those without AKI (p < 0.001).

Conclusion Our study demonstrated that NS was the commonly used crystalloid in our patients and was associated with increased incidence of AKI and RRT when compared with other balanced salts solutions.