Biocompatible hemodialysis membranes for acute renal failure

An Official ATS/ERS/ESICM/SCCM/SRLF Statement: Prevention and Management of Acute Renal Failure in the ICU Patient: an international consensus conference in intensive care medicine

OBJECTIVES

To address the issues of Prevention and Management of Acute Renal Failure in the ICU Patient, using the format of an International Consensus Conference.

METHODS AND QUESTIONS

Five main questions formulated by scientific advisors were addressed by experts during a 2-day symposium and a Jury summarized the available evidence: (1) Identification and definition of acute kidney insufficiency (AKI), this terminology being selected by the Jury; (2) Prevention of AKI during routine ICU Care; (3) Prevention in specific diseases, including liver failure, lung Injury, cardiac surgery, tumor lysis syndrome, rhabdomyolysis and elevated intraabdominal pressure; (4) Management of AKI, including nutrition, anticoagulation, and dialysate composition; (5) Impact of renal replacement therapy on mortality and recovery.

RESULTS AND CONCLUSIONS

The Jury recommended the use of newly described definitions. AKI significantly contributes to the morbidity and mortality of critically ill patients, and adequate volume repletion is of major importance for its prevention, though correction of fluid deficit will not always prevent renal failure. Fluid resuscitation with crystalloids is effective and safe, and hyperoncotic solutions are not recommended because of their renal risk. Renal replacement therapy is a life-sustaining intervention that can provide a bridge to renal recovery; no method has proven to be superior, but careful management is essential for improving outcome.

Dialysis and pediatric acute kidney injury: choice of renal support modality

Dialytic intervention for infants and children with acute kidney injury (AKI) can take many forms. Whether patients are treated by intermittent hemodialysis, peritoneal dialysis or continuous renal replacement therapy depends on specific patient characteristics. Modality choice is also determined by a variety of factors, including provider preference, available institutional resources, dialytic goals and the specific advantages or disadvantages of each modality. Our approach to AKI has benefited from the derivation and generally accepted defining criteria put forth by the Acute Dialysis Quality Initiative (ADQI) group. These are known as the risk, injury, failure, loss, and end-stage renal disease (RIFLE) criteria. A modified pediatrics RIFLE (pRIFLE) criteria has recently been validated. Common defining criteria will allow comparative investigation into therapeutic benefits of different dialytic interventions. While this is an extremely important development in our approach to AKI, several fundamental questions remain. Of these, arguably, the most important are "When and what type of dialytic modality should be used in the treatment of pediatric AKI?" This review will provide an overview of the limited data with the aim of providing objective guidelines regarding modality choice for pediatric AKI. Comparisons in terms of cost, availability, safety and target group will be reviewed.

Need for quality improvement in renal systematic reviews

BACKGROUND AND OBJECTIVES

Systematic reviews of clinical studies aim to compile best available evidence for various diagnosis and treatment options. This study assessed the methodologic quality of all systematic reviews relevant to the practice of nephrology published in 2005.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We searched electronic databases (Medline, Embase, American College of Physicians Journal Club, Cochrane) and hand searched Cochrane renal group records. Clinical practice guidelines, case reports, narrative reviews, and pooled individual patient data meta-analyses were excluded. Methodologic quality was measured using a validated questionnaire (Overview Quality Assessment Questionnaire). For reviews of randomized trials, we also evaluated adherence to recommended reporting guidelines (Quality of Reporting of Meta-Analyses).

RESULTS

Ninety renal systematic reviews were published in year 2005, 60 of which focused on therapy. Many systematic reviews (54%) had major methodologic flaws. The most common review flaws were failure to assess the methodologic quality of included primary studies and failure to minimize bias in study inclusion. Only 2% of reviews of randomized trials fully adhered to reporting guidelines. A minority of journals (four of 48) endorsed adherence to consensus guidelines for review reporting, and these journals published systematic reviews of higher methodologic quality (P < 0.001).

CONCLUSIONS

The majority of systematic reviews had major methodologic flaws. The majority of journals do not endorse consensus guidelines for review reporting in their instructions to authors; however, journals that recommended such adherence published systemic reviews of higher methodologic quality.

Timing of renal replacement therapy initiation in acute renal failure: a meta-analysis

BACKGROUND

Some studies have suggested that early institution of renal replacement therapy (RRT) might be associated with improved outcomes in patients with acute renal failure (ARF).

STUDY DESIGN

A systematic review and meta-analysis of randomized controlled trials and cohort comparative studies to assess the effect of early RRT on mortality in patients with ARF.

SETTING & POPULATION

Hospitalized adult patients with ARF.

SELECTION CRITERIA FOR STUDIES

We searched several databases for studies that compared the effect of "early" and "late" RRT initiation on mortality in patients with ARF. We included studies of various designs.

INTERVENTION

Early RRT as defined in the individual studies.

OUTCOMES

The primary outcome measure was the effect of early RRT on mortality stratified by study design. The pooled risk ratio (RR) for mortality was compiled using a random-effects model. Heterogeneity was evaluated by means of subgroup analysis and meta-regression.

RESULTS

We identified 23 studies (5 randomized or quasi-randomized controlled trials, 1 prospective and 16 retrospective comparative cohort studies, and 1 single-arm study with a historic control group). By using meta-analysis of randomized trials, early RRT was associated with a nonsignificant 36% mortality risk reduction (RR, 0.64; 95% confidence interval, 0.40 to 1.05; P = 0.08). Conversely, in cohort studies, early RRT was associated with a statistically significant 28% mortality risk reduction (RR, 0.72; 95% confidence interval, 0.64 to 0.82; P < 0.001). The overall test for heterogeneity among cohort studies was significant (P = 0.005). Meta-regression yielded no significant associations; however, early dialysis therapy was associated more strongly with lower mortality in smaller studies (n < 100) by means of subgroup analysis.

LIMITATIONS

Paucity of randomized controlled trials, use of variable definitions of early RRT, and publication bias preclude definitive conclusions.

CONCLUSION

This hypothesis-generating meta-analysis suggests that early initiation of RRT in patients with ARF might be associated with improved survival, calling for an adequately powered randomized controlled trial to address this question.

Delivery of renal replacement therapy in acute kidney injury: what are the key issues?

BACKGROUND AND OBJECTIVES

The prescription and delivery of renal replacement therapy for acute kidney injury is subject to a wide variation and is conditioned by a multiplicity of factors. A variety of renal replacement therapy modalities are now available to treat acute kidney injury; however, there are no standards for the dosage, choice of modality, and intensity and duration of these therapies. Although several observational and interventional studies have addressed these topics, there are no consensus recommendations in this field.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The available literature on this topic and draft consensus recommendations for research studies in this area were developed using a modified Delphi approach and an international multidisciplinary network.

RESULTS

The following questions were most important: What is the "dosage" of renal replacement therapy delivered to patients with stage 3 acute kidney injury? What is the optimal "dosage" of renal replacement therapy to maximize patient and renal survival? Is there a minimal "dosage" of renal replacement therapy required in patients with single-organ failure? Does modality of renal replacement therapy selected have an effect on patient and/or renal survival? In cases of continuous renal replacement therapy, does citrate anticoagulation confer a benefit?

CONCLUSIONS

This report summarizes the available evidence and elaborates on the key questions and the methods that should be used so that the goal of standardizing the care of patients with acute kidney injury and improving outcomes can be achieved.

Biocompatible hemodialysis membranes for acute renal failure

BACKGROUND

Acute renal failure (ARF) is associated with substantial morbidity and mortality. Some studies have reported a survival advantage among patients dialyzed with biocompatible membranes (BCM) compared to bioincompatible membranes (BICM). These findings were not consistently observed in subsequent studies.

OBJECTIVES

To ascertain whether the use of BCM confers an advantage in either survival or recovery of renal function over the use of BICM in adult patients with ARF requiring intermittent hemodialysis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library), MEDLINE (from 1966), EMBASE (from 1980), the Mexican Index of Latin American Biomedical Journals IMBIOMED (from 1990), the Latin American and Caribbean Health Sciences Literature Database LILACS (from 1982), and reference lists of articles. Search date: January 2007

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing the use of a BCM with a BICM in patients > 18 years of age with ARF requiring intermittent hemodialysis.

DATA COLLECTION AND ANALYSIS

Two authors extracted the data independently. Cellulose-derived dialysis membranes were classified as BICM, and synthetic dialyzers were considered as BCM. The main outcomes were all-cause mortality and recovery of renal function by type of dialyzer. We further explored these outcomes according to the flux properties (high-flux or low-flux) of each of these dialyzers. A meta-analysis was conducted by combining data using a random-effects model.

MAIN RESULTS

Ten studies were included in the primary analysis of mortality, with a total of 1100 patients. None of the pooled risk ratios (RRs) reached statistical significance. The pooled RR for mortality was 0.93 (95% confidence interval (CI) 0.81 to 1.07). The overall RR for recovery of renal function, which was inclusive of 1038 patients from nine studies, was 1.09 (95% CI 0.90 to 1.31). The pooled RR for mortality by dialyzer flux property was 1.05 (95% CI 0.81 to 1.37). The pooled RR for recovery of renal function by flux property was 1.30 (95% CI 0.83 to 2.02). A meta-analysis of mortality among kidney transplant recipients was not possible, however the analysis of recovery of renal function in this patient population revealed an RR of 1.05 (95% CI 0.87 to 1.26). Results of sensitivity analyses did not differ significantly from the primary analyses.

AUTHORS' CONCLUSIONS

There is no demonstrable clinical advantage to the use of BCM versus BICM in patients with ARF who require intermittent hemodialysis.

Dialyzer membrane characteristics and outcome of patients with type 2 diabetes on maintenance hemodialysis

BACKGROUND

Effects of dialyzer membrane characteristics on morbidity and mortality are highly controversial.

METHODS

Post hoc, we analyzed data from the German Diabetes and Dialysis Study that evaluated atorvastatin in high-risk patients. Four groups were identified being constantly dialyzed with high-flux synthetic (n = 241), low-flux synthetic (n = 247), low-flux semisynthetic (n = 119), or cellulosic low-flux membranes (n = 41). Two end points were investigated: (1) a cardiovascular end point consisting of cardiac death, nonfatal myocardial infarction, and stroke and (2) death.

RESULTS

After 4 years of follow-up, adjusted multivariate relative risks (RRs) were calculated. The RR to reach a cardiovascular end point was greater for patients dialyzed with cellulosic low-flux (RR, 2.33; 95% confidence interval [CI], 1.38 to 3.94; P = 0.002), low-flux semisynthetic (RR, 1.92; 95% CI, 1.35 to 2.73; P = 0.0003), or low-flux synthetic membranes (RR, 1.35; 95% CI, 0.99 to 1.85; P = 0.06) than for those treated with high-flux synthetic dialyzers. The likelihood to die was greater with cellulosic low-flux (RR, 4.14; 95% CI, 2.79 to 6.15; P < 0.0001), low-flux semisynthetic (RR, 2.24; 95% CI, 1.66 to 3.02; P < 0.0001), and low-flux synthetic membranes (RR, 1.59; 95% CI, 1.22 to 2.07; P = 0.0006) than with high-flux synthetic membranes. With respect to low-flux synthetic membranes, RRs of mortality for patients using cellulosic low-flux and low-flux semisynthetic membranes were 161% (RR, 2.61; 95 % CI, 1.80 to 3.79; P < 0.0001) and 41% (RR, 1.41; 95% CI, 1.07 to 1.86; P = 0.016) greater. Cellulosic low-flux membrane use was associated with an 85% (RR, 1.85; 95% CI, 1.24 to 2.76; P = 0.0025) greater RR of death than low-flux semisynthetic membranes.

CONCLUSION

These data suggest that biocompatibility and permeability may impact on death and cardiovascular events in hemodialysis patients with type 2 diabetes mellitus.