Kidney Protection During Surgery on the Thoracoabdominal Aorta: A Systematic Review

Background Acute kidney injury (AKI) is a common complication of surgery to repair the thoracoabdominal aorta, and is associated with risks of dialysis and early mortality. Renal ischaemia, initiated by clamping of the suprarenal aorta, is a major cause. Consequently, perfusion techniques are commonly used to sustain renal blood flow or facilitate hypothermic kidney preservation during surgery. This systematic review provides a comprehensive assessment of renal and mortality outcomes by perfusion techniques, to evaluate their ability to provide effective kidney protection. Methods & Results Searches of PubMed, Web of Science, ClinicalTrials.gov and ClinicalTrialsRegister.EU were conducted to identify relevant studies published from 1995 to 2024. Included studies were quality assessed, and data were extracted by perfusion techniques. Outcomes of the highest quality studies were used to synthesise a narrative discussion. Forty-five studies were included in our analysis, featuring three extracorporeal strategies: Left heart bypass (LHB; n=24), cardiopulmonary bypass with deep hypothermic circulatory arrest (DHCA; n=19), and partial cardiopulmonary bypass (pCPB; n=12). Three categories of selective renal perfusion strategy were identified: Warm blood, cold blood and cold crystalloid. Our analysis identified operative mortality as 0-23.4% following LHB, 2.2-12.5% following DHCA and 0-42.1% following pCPB. The incidence of renal replacement therapy was 0-40.0% following LHB, 0-15.0% following DHCA and 0-22.2% following pCPB. Conclusions Strong evidence supports the use of distal aortic perfusion (DAP) with LHB or pCPB, to reduce the risks of dialysis and operative mortality associated with aortic cross clamping. Furthermore, when DAP cannot prevent kidney ischaemia, adjunctive perfusion of the renal arteries with cold histidine-tryptophan-ketoglutarate (HTK) can reduce the risk of AKI. However, no professional guidance on the management of HTK exists, and rates of AKI remain high despite its use. Selective renal perfusion with warm blood is identified as a risk factor for AKI and operative mortality. DHCA is associated with low rates of AKI, warranting further prospective investigation. Finally, intravascular haemolysis and myoglobinaemia are acknowledged as important risk factors that require urgent research to address the problem of AKI.