We thank Drs Gu and Yu for their constructive comments on our study in refining cardiac surgery–specific serum creatinine (SCr) change criteria for cardiac surgery-associated acute kidney injury (CSA-AKI).1 We would like to respond to the four overarching issues raised:
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Criteria/markers to adjudicate CSA-AKI. We agree that urine output is an important criterion component in AKI diagnosis but is highly confounded in perioperative settings, especially with diuretic use and fluid therapy after cardiac surgery, which should be meticulously investigated in separate studies rather than the current one. Emerging biomarkers could help identify CSA-AKI but are not readily incorporated into the current AKI consensus or practice, with unclear practicality and cost-effectiveness.2
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Subgroup/sensitivity analysis. As suggested, we conducted subgroup analyses regarding preoperative renal function, on/off-pump, and fluid balance in Supplements (Supplemental Figures 3 to 6). Although different degrees of threshold variation were observed as expected, the combination and nonexhaustive nature of perioperative factors (including surgical complexity) actually further supports our central argument against a “one-size-fits-all” approach. The main contribution of this study is to challenge the universal definition, rather than to propose a single new threshold. Our subgroup/sensitivity analyses serve to generate hypotheses for future studies.
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Impacts on clinical outcomes. We agree with the need to further assess the new threshold in identifying “real” kidney injury, but this is relatively challenging given the current lack of gold standard approaches to diagnosing it outside of the SCr/urine framework. We reported the new threshold’s impact on dialysis and agree that more granular renal outcomes are warranted. Regarding longer-term prognosis, as with most perioperative studies (eg, surgical risk stratification, perioperative myocardial injury),3,4 the primary focus is on short-term prognosis. Longer-term impact may derive from the short-term and is generally less relevant to downstream management in perioperative settings. Additionally, longer-term prognosis may be influenced by other factors (eg, secondary prevention) during follow-up.
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Transient AKI. We considered this an important and understudied topic, but ultimately did not factor it into the current study, in part because there is no agreed-upon definition for SCr “recovery.” Future analysis is needed.
In conclusion, we believe we share the same view that there are many uncharted territories to be explored for a more cardiac surgery–tailored CSA-AKI system to better inform clinical practice. It is time to call for community-level forces to change this paradigm.
Footnotes
This study was supported by grants from the high-level hospital clinical research of Fuwai Hospital, Chinese Academy of Medical Sciences (2022-GSP-GG-28), the National Natural Science Foundation of China (Key Program; 81830072), and Ministry of Science and Technology of People's Republic of China (2016YFC1302000), all to Dr Zheng. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
References
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