Extra-corporeal blood purification for critically ill patients with septic acute kidney injury

Abstract

Septic acute kidney injury (AKI) is a leading cause of renal impairment in the critical care setting and is independently associated with increased mortality and morbidities. As the knowledge on pathophysiological mechanisms of AKI increases, its clinical management is evolving. The published literature on critically ill septic AKI patients has predominantly come from Caucasian patients. There is little data on the clinical features, management and outcome of critically ill septic AKI in Chinese patients. Results from my single-centred cross-sectional survey (n=3687) showed that septic AKI affected 27% of critically ill Chinese patients. Among those with documented sepsis upon ICU admission or during ICU stay, 71.6% developed AKI. Compared with non-septic AKI patients, septic AKI patients were older, had higher disease severity scores and required more intensive/invasive organ support. Renal replacement therapy (RRT) was used more often in septic AKI (23.3% vs. 12.6% for non-septic AKI, p<0.001), but full or partial renal recovery was also more common (97.5% vs. 93.6%, p<0.001) compared with non-septic AKI. However, the optimal timing for starting RRT among critically ill septic AKI patients remained controversial. My study (n=120) found no significant difference in organ function, defined as Sequential Organ Failure Assessment (SOFA) score changes within 48 hours after the initiation of RRT (improvement by 1.5 points for “early” vs. 2 points for “late”, p=0.523), and mortality (at 28-day 48.4% for “early” vs. 48.3% for “late”, p=0.994) when the initiation of RRT was classified using renal function-based criteria. APACHE score was the only independent predictor for organ function improvement. The application of global assessment tools as RRT initiation criteria warrant further investigation. Blood purification has emerged as an adjunctive therapy in critically ill septic AKI patients as they are effective in clearing endotoxin or inflammatory mediators. Four different techniques were assessed. Firstly, among those septic AKI patients due to gram-negative sepsis (n=30), SOFA score was improved by 37% at 48 hours post initiation of endotoxin/ cytokine adsorptive continuous venovenous haemofiltration (CVVH) compared to a deterioration of 3% among the control group (p=0.013). The treatment was well tolerated. Secondly, among those septic AKI patients with shock due to intra-abdominal sepsis (n=15), Alteco endotoxin haemoadsorption offered no extra benefit over the control group in terms of SOFA score changes at 48 and 72 hours. Thirdly, polymethylmethacrylate (PMMA) based CVVH (n=11) may delay organ function recovery, as assessed by SOFA score, when compared with septic AKI patients with shock who received polysulfone (PS) based CVVH (n=14). The 28-day mortality (55% vs. 21%, p=0.115) showed a trend in favour of the PS-CVVH groups. Finally, among septic AKI patients with shock (n=7), high cut-off CVVH achieved good cytokine modulation. Clinical improvement, in terms of SOFA changes and vasopressor usage, was noted after 24-36 hours of treatment. Albumin loss was limited. Since multiple factors including co-morbidities, causal microorganisms, and life-support measures impact on the outcome of septic AKI patients, whether the addition of blood purification procedures could benefit (or harm) these patients can only be determined through large-scale prospective randomised controlled studies.