Acute kidney injury (AKI) complicates pediatric cardiac surgery, particularly in single-ventricle palliation. While retrograde lower body perfusion (LBP) has been associated with a renal-protective signal during aortic arch reconstruction, its efficacy has not been evaluated in homogeneous cohorts undergoing comprehensive stage II palliation for hypoplastic left heart syndrome (HLHS).

Single-center retrospective cohort study over a seven-year period (January 2017–July 2024) comparing consecutive patients receiving retrograde LBP versus historical controls at a tertiary pediatric cardiac center. Sixty-four infants with HLHS undergoing comprehensive stage II palliation following hybrid stage I (bilateral pulmonary artery banding and ductal stenting): 21 with LBP, 43 without LBP. The LBP group received retrograde perfusion via weight- and vessel-diameter-adapted femoral artery catheter integrated into the arterial line of the cardiopulmonary bypass circuit. Perfusion was delivered through a three-way stopcock under continuous flow monitoring. All other aspects of perfusion, surgical, and anesthesiologic management were standardized between groups.

Unadjusted AKI incidence showed a protective trend of LBP (4.8% vs 23.3%, OR 0.17, p = 0.085). LBP significantly reduced cumulative AKI burden (0.05 vs 1.26 AKI time-point burden units/patient, p < 0.001). The LBP group showed higher postoperative urine output (p < 0.03) and lower urea levels at multiple postoperative time points (p < 0.05) and a trend toward lower creatinine levels (6h p = 0.062; 12h p = 0.064, p = 0.019 at day 2). Intraoperative lactate levels showed transient differences at select time points (p < 0.05) with postoperative convergence between groups. No predefined femoral catheter-related vascular complications were identified through hospital discharge.

While the primary outcome of AKI incidence did not reach statistical significance, retrograde LBP via femoral cannulation was feasible and safe and was associated with consistent trends toward renal protection across cumulative AKI burden, urine output, and renal function biomarkers. These preliminary, hypothesis-generating findings necessitate confirmation in a prospective, adequately powered trial to establish causality and clinical relevance.