Early Initiation Renal Replacement Therapy for Fluid Management to Reduce Central Venous Pressure is More Conducive to Renal Function Recovery in Patients with Acute Kidney Injury

Early Initiation Renal Replacement Therapy for Fluid Management to Reduce Central Venous Pressure is More Conducive to Renal Function Recovery in Patients with Acute Kidney Injury

Acute kidney injury (AKI) is a severe complication in critically ill patients, particularly those with septic shock in the intensive care unit (ICU). It is associated with high mortality and significant economic burdens. Sepsis is the leading cause of AKI in the ICU, accounting for approximately 45% to 70% of all AKI cases. Renal replacement therapy (RRT) is a common treatment for severe AKI, especially when supportive therapy and endogenous renal function are insufficient to meet metabolic demands. However, the optimal timing for initiating RRT and the factors influencing renal function recovery remain unclear. This study aims to explore whether early initiation of RRT for fluid management to reduce central venous pressure (CVP) can enhance renal function recovery in patients with AKI.

The study conducted a retrospective analysis of septic patients who received RRT treatment. Patients were divided into two groups based on the timing of RRT initiation: early initiation (within 12 hours of meeting the diagnostic criteria for renal failure) and delayed initiation (after a delay of 48 hours if renal recovery had not occurred). The study evaluated parameters such as renal function recovery at discharge, fluid balance, and CVP levels.

A total of 141 patients were enrolled, with 40.4% (57 patients) in the early initiation group and 59.6% (84 patients) in the delayed initiation group. Baseline characteristics were similar between the two groups, and there was no significant difference in 28-day mortality. However, a significant difference was observed in the renal function recovery rate at discharge, with the early initiation group showing better outcomes. Specifically, early initiation of RRT and dehydration to reduce CVP were more conducive to renal function recovery in patients with AKI.

The study found that delayed initiation of RRT was associated with longer durations of RRT support and mechanical ventilation. Patients in the delayed initiation group also had inferior renal recovery and a higher rate of dialysis dependence at hospital discharge. The cause of kidney injury is not only the toxic effects of creatinine (Cr) and blood urea nitrogen (BUN) but also the damaging effects of high CVP and fluid overload on the kidneys over time. Early initiation of dialysis in AKI might improve acid-base status control and toxin removal, reducing the burden on the kidneys and preventing further deterioration of renal function.

The study compared patients with different levels of renal function recovery and found that recovery was correlated with the initiation of RRT, CVP levels, fluid balance, and diastolic perfusion pressure (DPP). Regression analysis showed that the main factors affecting renal function recovery were the initiation of RRT and CVP levels. Fluid balance was statistically insignificant in the regression analysis, possibly because fluid overload is not positively correlated with CVP, and systemic circulation backward resistance may be more important than overall fluid balance in patients with AKI.

Previous studies have shown that baseline CVP is higher in patients with AKI than in those without AKI. High CVP affects kidney function not only in patients with heart failure but also in those with normal heart function. The study found that CVP levels were lower in patients with rapid renal function recovery, especially in those who received early-initiation RRT. There were no differences in other factors such as central venous-to-arterial carbon dioxide difference (Pv-aCO2) and central venous oxygen saturation (ScvO2) among patients with different renal function recovery, suggesting that heart function was not a significant factor affecting renal function recovery.

Maintaining optimal blood pressure is crucial for preventing AKI, especially in vasopressor-dependent patients. While mean arterial pressure (MAP) is widely used as an index for optimal blood pressure, recent studies have shown that lower DAP and higher CVP are associated with septic AKI, while MAP is not. The study confirmed that high CVP and low DPP are important factors affecting renal function recovery. High CVP is likely the most critical factor affecting renal perfusion pressure.

The study had several limitations. It was retrospective, and the small number of patients may have introduced bias. Factors such as positive end-expiratory pressure were not investigated. Additionally, the lack of long-term renal function indicators and the speed of renal function recovery may impact long-term renal function and quality of life. Further studies are needed to investigate the effects of different treatment strategies on long-term renal function.

In conclusion, the study confirms that early initiation of RRT for fluid management to reduce CVP levels is more conducive to renal function recovery in patients with septic AKI compared to delayed-initiation RRT. The findings highlight the importance of timely RRT initiation and effective fluid management in improving outcomes for critically ill patients with AKI.

doi.org/10.1097/CM9.0000000000000240

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