Acute kidney injury (AKI) is a frequent complication after cardiac surgery performed
under cardiopulmonary bypass (CPB) and represents a major determinant of short- and
long-term adverse outcomes. The pathophysiology of postoperative AKI is multifactorial
and involves hemodilution, non-pulsatile flow, ischemia-reperfusion injury, systemic
inflammatory response, and alterations in renal perfusion during CPB. Despite similar
surgical and anesthetic management, not all patients develop AKI, suggesting that
preoperative patient-related factors and intraoperative perfusion stress play a critical
role.
In recent years, easily accessible inflammatory indices derived from routine
hematological and biochemical parameters, such as the neutrophil-to-lymphocyte ratio,
systemic immune-inflammation index, and C-reactive protein to albumin ratio, have been
proposed as potential predictors of postoperative complications, including AKI. In
addition, intraoperative parameters reflecting perfusion stress, such as cardiopulmonary
bypass duration, arterial lactate levels, and acid-base disturbances, may further
contribute to renal injury. However, studies evaluating these factors together in the
setting of cardiac surgery with CPB are limited.
This single-center, retrospective observational cohort study will include adult patients
who underwent cardiac surgery under cardiopulmonary bypass. Demographic data,
comorbidities, preoperative laboratory parameters, echocardiographic findings, and
intraoperative CPB-related variables will be collected retrospectively from institutional
medical records. Acute kidney injury will be defined and staged according to the KDIGO
serum creatinine criteria within 48-72 hours after surgery. Urine output criteria will
not be evaluated due to limitations inherent to retrospective data collection.
The primary objective of the study is to identify independent predictors of postoperative
AKI by assessing the combined effects of preoperative renal function, inflammatory
markers, and intraoperative perfusion stress parameters. Secondary objectives include
evaluation of AKI severity and in-hospital mortality. Multivariable logistic regression
and receiver operating characteristic analyses will be used to determine the predictive
value of selected parameters.
By improving understanding of the factors associated with postoperative AKI, this study
aims to support better perioperative risk stratification and inform future prospective
investigations in patients undergoing cardiac surgery with cardiopulmonary bypass.
