Acute kidney injury (AKI) is a common postoperative complication that occurs in 20 to 30% of cardiac surgical patients (Sreekanth 2023). Postoperative AKI is associated with mortality after surgery, which increases to 50-60% when renal replacement therapy is required ( Lee 2021 and Sreekanth). While AKI may occur after various surgical procedures, it is more prevalent and often more severe in the context of cardiac surgeries.
Cardiac surgery-associated AKI is influenced by a combination of factors inherent to both the surgical procedure and the underlying cardiac condition. Cardiac surgeries include complex procedures such as coronary artery bypass grafting (CABG), valve replacements, and congenital defect corrections, to name a few. These surgeries often require the use of cardiopulmonary bypass machines, which can inadvertently affect kidney function. Maintaining appropriate perfusion pressure and cardiac output during procedures utilizing cardiopulmonary bypass machines is critical for prevention of AKI.
The causes of AKI after cardiac surgery are complex and multifactorial. Many of the factors involved with an increased AKI risk are not modifiable, such as advanced age, diabetes, hypertension, hyperlipidemia, peripheral vascular disease, and preexisting chronic kidney disease . The effects of other risk factors can be mitigated, such as those related to the surgical and anesthetic management. Examples include: use and management of cardiopulmonary bypass machines, aortic cross-clamping, blood transfusion, vasopressors, nephrotoxic drugs, and finally, prevention and appropriate correction of ischemia-reperfusion injury. These risk factors potentially alter the renal perfusion, inducing oxidative stress and inflammation, damaging the renal tubules and glomeruli, and activating the coagulation and complement systems; all mechanisms that can lead to development of AKI .
Early detection of AKI is paramount to improving patient outcomes. Real-time and continuous urine output monitoring, in addition to advancements in electronic health records and machine learning algorithms, have enabled healthcare professionals to better predict AKI risk by considering various patient-specific factors.
In conclusion, while various biomarkers and diagnostic methods contribute to the understanding of cardiac surgery-associated AKI, the most accessible and reliable tool for the detection of AKI is consistent and accurate urine output monitoring. As medical technology continues to advance, incorporating this fundamental, yet effective approach into routine clinical practice can make a significant difference in the lives of patients undergoing cardiac surgery, ensuring that AKI is promptly detected and managed to enhance recovery prospects and reduce mortality rates.
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