Recent studies have highlighted the close relationship between the kidney and the gastrointestinal (GI) tract—frequently referred to as the kidney–gut axis—in patients with chronic kidney disease (CKD). In this regard, two important pathophysiological concepts have evolved: (i) production and accumulation of toxic end-products derived from increased bacterial fermentation of protein and other nitrogen-containing substances in the GI tract, (ii) translocation of endotoxins and live bacteria from gut lumen into the bloodstream, due to damage of the intestinal epithelial barrier and quantitative/qualitative alterations of the intestinal microbiota associated with the uraemic milieu. In both cases, these gut-centred alterations may have relevant systemic consequences in CKD patients, since they are able to trigger chronic inflammation, increase cardiovascular risk and worsen uraemic toxicity. The present review is thus focused on the kidney–gut axis in CKD, with special attention to the alterations of the intestinal barrier and the local microbiota (i.e. the collection of microorganisms living in a symbiotic coexistence with their host in the intestinal lumen) and their relationships to inflammation and uraemic toxicity in CKD. Moreover, we will summarize the most important clinical data suggesting the potential for nutritional modulation of gut-related inflammation and intestinal production of noxious by-products contributing to uraemic toxicity in CKD patients.

Hemorrhagic complications have been reported in up to 30% of critically ill patients with AKI undergoing RRT with systemic anticoagulation. Because bleeding is associated with significantly increased mortality risk, strategies aimed at reducing hemorrhagic complications while maintaining extracorporeal circulation should be implemented. Among the alternatives to systemic anticoagulation, regional citrate anticoagulation has been shown to prolong circuit life while reducing the incidence of hemorrhagic complications and lowering transfusion needs. For these reasons, the recently published Kidney Disease Improving Global Outcomes Clinical Practice Guidelines for Acute Kidney Injury have recommended regional citrate anticoagulation as the preferred anticoagulation modality for continuous RRT in critically ill patients in whom it is not contraindicated. However, the use of regional citrate anticoagulation is still limited because of concerns related to the risk of metabolic complications, the complexity of the proposed protocols, and the need for customized solutions. The introduction of simplified anticoagulation protocols based on citrate and the development of dialysis monitors with integrated infusion systems and dedicated software could lead to the wider use of regional citrate anticoagulation in upcoming years.

Contrast-induced acute kidney injury (CI-AKI) is the third leading cause of hospital-acquired acute kidney injury. It is more commonly observed following intra-arterial administration of iodinated contrast media (CM) for cardiac procedures in patients with pre-existing chronic kidney disease (CKD), and is associated with increased short- and long-term morbidity and mortality. This review investigates the key current evidence on CI-AKI definition, epidemiology and pathogenesis, as a basis for recommending preventive measures that can be implemented in clinical practice.

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs’ pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy.

Introduction: Regional citrate anticoagulation (RCA) is a valid option in patients at high risk of bleeding who are undergoing continuous renal replacement therapy (CRRT). The aim of this study was to evaluate, in critically ill patients with severe acute kidney injury following cardiac surgery, the efficacy and safety of RCA-continuous veno-venous hemofiltration (CVVH) using a low concentration citrate solution. Methods: In high bleeding-risk cardiac surgery patients, we adopted, as an alternative to heparin or no anticoagulation, RCA-CVVH using a 12 mmol/l citrate solution. For RCA-CVVH settings, we developed a mathematical model to roughly estimate citrate load and calcium loss. In order to minimize calcium chloride supplementation, a calcium-containing solution was used as post-dilution replacement fluid. Statistical analysis was performed using the Student t-test or analysis of variance (ANOVA) with post-hoc tests, Wilcoxon or Kruskal-Wallis tests for non-parametric analysis, and Kaplan-Meier survival analysis with Log Rank test. Results: Thirty-three patients (age 70.8 ± 9.5, Sequential Organ Failure Assessment (SOFA) score 13.9 ± 2.5) were switched to RCA-CVVH from no anticoagulation CRRT. Among them, 16 patients had been previously switched from heparin to no anticoagulation because of bleeding or heparin-related complications. RCA-CVVH filter life (49.8 ± 35.4 hours, median 41, 152 circuits) was significantly longer (P < 0.0001) when compared with heparin (30.6 ± 24.3 hours, median 22, 73 circuits) or no anticoagulation (25.7 ± 21.2 hours, median 20, 77 circuits). Target circuit and systemic Ca⁺⁺ were easily maintained (0.37 ± 0.09 and 1.18 ± 0.13 mmol/l), while the persistence of a mild metabolic acidosis required bicarbonate supplementation (5.8 ± 5.9 mmol/hours) in 27 patients. The probability of circuit running at 24, 48, 72 hours was higher during RCA-CVVH (P < 0.0001), with a lower discrepancy between delivered and prescribed CRRT dose (P < 0.0001). RCA was associated with a lower transfusion rate (P < 0.02). Platelet count (P = 0.012) and antithrombin III activity (P = 0.004) increased throughout RCA-CVVH, reducing the need for supplementation. Conclusions: RCA safely prolonged filter life while decreasing CRRT downtime, transfusion rates and supplementation needs for antithrombin III and platelets. In cardiac surgery patients with severe multiple organ dysfunction syndrome, the adoption of a 12 mmol/l citrate solution may provide a suboptimal buffers supply, easily overwhelmed by bicarbonate supplementation.

Background and objectives A simple anticoagulation protocol was developed for sustained low-efficiency dialysis (SLED) in patients with AKI, based on the use of anticoagulant citrate dextrose solution formulation A (ACD-A) and standard dialysis equipment. Patients’ blood recalcification was obtained from calcium backtransport from dialysis fluid. Design, setting, participants, & measurements All patients treated with SLED (8- to 12-hour sessions) for AKI in four intensive care units of a university hospital were studied over a 30-month period, from May 1, 2008 to September 30, 2010. SLED interruptions and their causes, hemorrhagic complications, as well as coagulation parameters, ionized calcium, and blood citrate levels were recorded. Results This study examined 807 SLED sessions in 116 patients (mean age of 69.7 years [SD 12.1]; mean Acute Physiology and Chronic Health Evaluation II score of 23.8 [4.6]). Major bleeding was observed in six patients (5.2% or 0.4 episodes/100 person-days follow-up while patients were on SLED treatment). Citrate accumulation never occurred, even in patients with liver dysfunction. Intravenous calcium for ionized hypocalcemia (< 3.6 mg/dl or < 0.9 mmol/L) was needed in 28 sessions (3.4%); in 8 of these 28 sessions (28.6%), low ionized calcium was already present before SLED start. In 92.6% of treatments, SLED was completed within the scheduled time (median 8 hours). Interruptions of SLED by impending/irreversible clotting were recorded in 19 sessions (2.4%). Blood return was complete in 98% of the cases. In-hospital mortality was 45 of 116 patients (38.8%). Conclusions This study protocol affords efficacious and safe anticoagulation of the SLED circuit, avoiding citrate accumulation and, in most patients, systematic calcium supplementation; it can be implemented with commercial citrate solutions, standard dialysis equipment, on-line produced dialysis fluid, and minimal laboratory monitoring.