Can dialyzer membrane selection affect outcomes in patients with acute kidney injury requiring dialysis?

The choice of dialyzer membrane may potentially affect not only solute clearances but also blood-dialyzer interactions. Although on one hand alteration of the dialyzer surface or pore size to increase inflammatory mediator loss may potentially be beneficial for patients with acute kidney injury (AKI), dialyzer membrane interactions, which precipitate intradialytic hypotension, may worsen AKI. Several years ago cellulosic membrane dialyzers were shown to reduce both patient survival and renal recovery in patients with AKI. This review looks at the earlier studies of dialyzer membrane choice and outcomes in AKI, besides discussing the newer developments in membrane technology for patients with AKI.     

Comparison of risk factors for contrast‐induced acute kidney injury between patients with and without diabetes

Although it is well known that diabetics are at a higher risk of contrast‐induced acute kidney injury (CI‐AKI) than nondiabetic patients, the reason for this discrepancy is not well known. Thus, in this study, we compared the predisposing factors for CI‐AKI between patients with and without diabetes. We prospectively studied 290 consecutive in‐hospital patients including 88 diabetics undergoing coronary angiography or a percutaneous coronary intervention in Kowsar hospital, and we compared risk factors for CI‐AKI between diabetic and nondiabetic patients. CI‐AKI was defined as RIFLE criteria within 48 hours after contrast exposure. The incidence of CR‐AKI was significantly higher in diabetic patients compared with nondiabetics (P<0.05). The incidence of CI‐AKI was significantly higher in patients with diabetes and left‐ventricular ejection fraction ≤40%, hypercholesterolemia, serum creatinine ≥1.1 mg/dL, estimated glomerular filtration rate (eGFR) <90 mL/min, Contrast volume ≥80 (mL), maximum safe contrast volume factor of 1.5, and dehydration, while in nondiabetics, a significantly higher incidence of CR‐AKI was observed in those with serum creatinine ≥1.1 mg/dL (P=0.02) and/or eGFR<60 mL/min (P=0.01). Multiple logistic regression analysis showed hyperchlosteremia to be the strongest predictor of AKI (P=0.01, B:14.5) in diabetics, followed by eGFR<90 (P=0.05, B:12.4) but, in nondiabetics, only eGFR<60 predicted the occurrence of CI‐AKI (P=0.04, B:2.3). It seems that the predisposing factors to CI‐AKI differ in diabetics and nondiabetics. In patients with diabetes, hypercholesterolemia is the strongest predictor of CI‐AKI, followed by eGFR and diabetics are at risk for CI‐AKI in the early stage of chronic kidney disease (stage 2), accounting for the higher incidence of CI‐AKI in them.     

Management of acute kidney injury in neurotrauma

Fortunately, the incidence of acute kidney injury (AKI) in neurotrauma is low and decreasing. Whereas the majority of AKI occurs in older patients with pre-existing chronic kidney disease, neurotrauma typically occurs in children and young adults with normal renal function. The development of outreach trauma teams has improved initial resuscitation, reducing both volume responsive and volume unresponsive cases of AKI. Most cases occur in the setting of multiple organ trauma with muscle injury, or patients who subsequently develop multiple organ failure. Once AKI has developed and renal replacement therapy is required, continuous modalities of renal replacement therapy offer an advantage to the patient with compromised cerebral perfusion and intracranial hypertension, by reducing the rate of change in serum urea, compared with standard intermittent therapies of hemodialysis and hemofiltration, thus minimizing abrupt changes in serum osmolality. Continuous hemodialysis and hemofiltration are better suited to maintain a normal or high serum sodium and thermal losses through the extracorporeal circuit, than peritoneal dialysis. Dialyzers should preferably be minimally bioincompatible and of a small surface area. In patients at risk of intracranial hemorrhage and those with invasive intracranial monitoring, systemic anticoagulants should either be avoided or regional anticoagulants should be used.     

Present status and future perspectives on the development of bioartificial kidneys for the treatment of acute and chronic renal failure patients

A bioartificial renal tubule device (BTD) consisting of a hollow-fiber module and human proximal tubular epithelial cells has been completed technically by Humes and colleagues and a few other groups. Humes and colleagues developed BTD, treated acute kidney injury patients with multiorgan failure by continuous hemofiltration (CHF) in conjunction with BTD, and reported a significantly higher survival rate than that by CHF with BTD without cells in the Food and Drug Administration phase IIa trial. However, BTD has never been approved by the US Government, as the CHF+BTD treatment did not show a significant difference from the control group in the phase IIb trial. Human proximal tubular epithelial cells were confirmed to be overgrown on artificial membrane, which resulted in the inhibition of active transports and the metabolism of essential substances. Function of the BTD could be maintained in a U0126-contained medium, even if the BTD had to have been waited by a new acute kidney injury patient for several weeks. For wearable kidneys, heparin-covalently bound membrane or methacryloyloxyethyl phosphorylcholine (MPC) polymer-coated membranes are candidates for antithrombogenic hemofilters, while endothelial progenitor cells from a cord blood, CD133(+) cells-attached hemofilter in which the permeability of the cells was enhanced by the enlarged diameter of fenestrae by treating with cytochalasin B are another candidate. The MPC blend membrane containing 1% of the MPC polymer in polysulfone was developed as a BTD module. MPC was 7 times larger at the sponge layer than at the skin layer of the membrane, resulting in hemocompatibility at the sponge layer and cytocompatibility at the skin layer.     

Who may not benefit from continuous renal replacement therapy in acute kidney injury?

This study aimed to identify factors that may predict early kidney recovery (less than 48 hours) or early death (within 48 hours) after initiating continuous renal replacement therapy (CRRT) in acute kidney injury (AKI) patients. This is a multicenter retrospective observational study of 14 Japanese Intensive care units (ICUs) in 12 tertiary hospitals. Consecutive adult patients with severe AKI requiring CRRT admitted to the participating ICUs in 2010 (n = 343) were included. Patient characteristics, variables at CRRT initiation, settings, and outcomes were collected. Patients were grouped into early kidney recovery group (CRRT discontinuation within 48 hours after initiation, n = 52), early death group (death within 48 hours after CRRT initiation, n = 52), and the rest as the control group (n = 239). The mean duration of CRRT in the early kidney recovery group and early death group was 1.3 and 0.9 days, respectively. In multivariable regression analysis, in comparison with the control group, urine output (mL/h) (odds ratio [OR]: 1.02, 95% confidence interval [CI]: 1.01–1.03), duration between ICU admission to CRRT initiation (days) (OR: 0.65, 95% CI: 0.43–0.87), and the sepsis‐related organ failure assessment score (OR: 0.87, 95% CI; 0.78–0.96) were related to early kidney recovery. Serum lactate (mmol/L) (OR: 1.19, 95% CI: 1.11–1.28), albumin (g/dL) (OR: 0.52, 95% CI: 0.28–0.92), vasopressor use (OR: 3.68, 95% CI: 1.37–12.16), and neurological disease (OR: 9.64, 96% CI: 1.22–92.95) were related to early death. Identifying AKI patients who do not benefit from CRRT and differentiating such patients from the study cohort may allow previous and future studies to effectively evaluate the indication and role of CRRT.     

Renal replacement therapy in the critically ill patient with acute kidney injury

The mortality of patients with acute renal failure (ARF) has remained unacceptably high for many years, with renal replacement therapy (RRT) remaining the mainstay of treatment. Clinical research has hitherto been hindered by a lack of a universal definition. However, changes are upon us in the shape of a new term, acute kidney injury (AKI), proposed to encompass the spectrum of ARF, along with a new definition and staging system. There is a renewed optimism that the establishment of clinical databases and the utilization of new clinical biomarkers will catalyze the development of new therapeutic strategies. In the interim, we must optimize the delivery of RRT to patients with AKI. It is remarkable how few studies are currently available in the literature to guide medical practitioners on the key issues of initiation, modality, type of buffer, dose of RRT, vascular access, and anticoagulation. On the horizon, the outcomes of two major clinical trials comparing doses and modalities of RRT in AKI are eagerly awaited.