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

Objectives: Post-operative acute kidney injury (AKI) is a common complication of surgery to repair the thoracoabdominal aorta, and is associated with increased risks of dialysis and early mortality. Perfusion techniques are routinely used during surgery to reduce renal injury. We conducted a systematic review of renal and mortality outcomes by perfusion technique, to evaluate their effectiveness in providing kidney protection. Methods: We searched PubMed, Web of Science, ClinicalTrials.gov and ClinicalTrialsRegister.EU to identify relevant studies published from 1995 to 2023. Included studies were quality assessed, and data extracted. Findings of the highest quality studies were used to synthesise a narrative discussion. Results: 44 studies were included in our analysis, featuring three systemic perfusion strategies: Left heart bypass (LHB; n=24), cardiopulmonary bypass with deep hypothermic circulatory arrest (DHCA; n=17), and partial cardiopulmonary bypass (pCPB; n=11). Three categories of selective renal perfusion (SRP) strategy were identified: Warm blood, cold blood and cold crystalloid. Our analysis found that operative mortality was 0-22.0% following LHB, 2.2-12.5% following DHCA and 0-42.1% following pCPB. The incidence of post- operative renal replacement therapy (RRT) was 0-40.0% following LHB, 0-13.8% following DHCA and 0- 31.6% following pCPB. Conclusions: Intra-operative perfusion strategies can facilitate kidney protection through improved oxygenation or hypothermic preservation. Distal aortic perfusion (DAP), with LHB or pCPB, is associated with lower rates of dialysis and operative mortality than simple aortic cross clamping. Whilst DHCA is associated with low rates of AKI, its use has not been evaluated through high-quality research. For extensive aneurysm repairs, adjunctive SRP with cold blood or crystalloid fluids is shown to enhance kidney protection during DAP , whereas warm blood SRP is associated with increased rates of AKI and operative mortality. We identify the optimisation of warm blood SRP and the attenuation of intravascular haemolysis as urgent areas of research to address the problem of AKI. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Protocols [https://www.crd.york.ac.uk/PROSPEROFILES/166428\_PROTOCOL\_20200122.pdf][1] ### Funding Statement This study did not receive any funding. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. [1]: https://www.crd.york.ac.uk/PROSPEROFILES/166428_PROTOCOL_20200122.pdf