This retrospective, single-centre observational study evaluates perioperative determinants and clinical outcomes of postoperative acute kidney injury (AKI) in patients undergoing pulmonary endarterectomy (PEA) between 2018 and 2020. AKI is classified according to KDIGO 2012 criteria using both serum creatinine changes and urine output over 48 hours. Preoperative, intraoperative and postoperative variables are assessed using multivariable logistic regression. Intraoperative time variables - including extracorporeal circulation (ECC) duration, deep hypothermic circulatory arrest (DHCA) duration and aortic cross-clamp time - are entered simultaneously to identify which component independently captures renal risk. The study also evaluates a parsimonious multivariable risk-stratification model based on routinely available perioperative data. Secondary outcomes include 30-day mortality, intensive care unit stay, hospital length of stay and renal replacement therapy requirement. Findings from this study may provide insights into perioperative risk stratification and renal monitoring strategies in patients undergoing pulmonary endarterectomy.

Pulmonary endarterectomy (PEA) is the established curative treatment for chronic thromboembolic pulmonary hypertension (CTEPH). Despite favourable haemodynamic outcomes, postoperative acute kidney injury (AKI) is a frequent and clinically relevant complication, reported in 7.1% to 57.5% of PEA series.

This retrospective observational study was conducted at a tertiary referral centre for PEA. Of 126 consecutive adult patients screened between January 2018 and December 2020, 117 were included in the primary analysis after applying predefined exclusion criteria and excluding one patient with insufficient postoperative renal data for KDIGO staging.

AKI was defined according to KDIGO 2012 criteria using both serum creatinine and urine output assessed over 48 hours. Four separate multivariable logistic regression models were constructed: Model A assessed preoperative variables; Model B assessed intraoperative time variables including ECC duration, DHCA duration and ACC time entered simultaneously; Model C assessed clinical and postoperative variables; and Model D was a parsimonious combined model incorporating variables identified as independent determinants across Models A through C.

Model discrimination was evaluated using receiver operating characteristic analysis with 95% confidence intervals estimated by non-parametric bootstrapping. Model calibration was assessed using the Hosmer-Lemeshow test, and bootstrap internal validation with 1000 resamples was used to estimate optimism-corrected AUC for the combined model. Linearity of the association between ECC duration and AKI was examined using restricted cubic spline modelling.

ECC duration, rather than DHCA or aortic cross-clamp duration, was the intraoperative time variable independently associated with AKI. Age was the principal preoperative determinant, and early postoperative albumin was independently associated with lower AKI odds. Despite comparable haemodynamic improvement in both groups, 30-day mortality was significantly higher in patients who developed AKI.

Inclusion Criteria:

• Patients aged 18-85 years
• Underwent pulmonary endarterectomy between 2018 and 2020

Exclusion Criteria:

• Age below 18 years
• Pregnant women

This study will include adult patients aged 18 to 85 years who underwent pulmonary endarterectomy at the Cardiothoracic Surgery Unit of Kosuyolu Kartal Heart Training and Research Hospital (Kosuyolu KHTRH), a single tertiary referral center in Istanbul, Turkey, between January 1, 2018, and December 31, 2020. Patients meeting the inclusion criteria will have complete perioperative data available, including total circulatory arrest duration and postoperative renal function parameters. Individuals younger than 18 years of age and pregnant women at the time of surgery will be excluded.