Technology Insight: treatment of renal failure in the intensive care unit with extended dialysis

Acute kidney injury in the intensive care unit

Acute kidney injury (AKI) is common among critically ill patients and results in increased mortality in this population. This review focuses on the diagnosis and management of AKI. The authors first explore new aspects of diagnosis, including new criteria that take into account even modest changes in renal function, and the development of novel biomarkers to allow earlier identification and better differential diagnosis of AKI. The authors also explore the available data on choice of dialysis modality and dialysis dose for the treatment of AKI, as well as the breakthrough development of the bioartificial kidney. Last, the authors review co-interventions that may have relevance to prognosis of AKI, such as intensive insulin therapy and the use of erythropoietin.

Sustained low-efficiency dialysis versus continuous veno-venous hemofiltration for postsurgical acute renal failure

BACKGROUND

In postsurgical acute renal failure patients with moderate unstable hemodynamics or fluid overload, the choice of dialysis modality is difficult. This study was performed to compare the outcomes between the sustained low-efficiency dialysis (SLED) and continuous veno-venous hemofiltration (CVVH) in these patients.

METHODS

Sequential postsurgical acute renal failure patients undergoing acute dialysis with CVVH (2002-2003), or SLED (2004-2005) as a result of severe fluid overload or moderately unstable hemodynamics were analyzed. Multivariate analyses of comorbidity, disease severity before initiating dialysis, biochemical measurements, and hemodynamic parameters for 3 days after the first dialysis session were performed by fitting multiple logistic regression models to predict patient's 30-day after hospital discharge (AHD) mortality.

RESULTS

Among the 101 recruited patients, 38 received SLED and the rest received CVVH. The 30-day AHD mortality was 62.4%. The independent risk factors of 30-day AHD mortality included older age (P = .008), lower first postdialysis mean arterial pressure (MAP) (P = .021), higher first postdialysis blood urea nitrogen level (P = .009), and absence of a history of hypertension (P = .002). A further linear regression analysis found that dialysis using SLED was associated with higher first postdialysis MAP (P = .003).

CONCLUSIONS

Among the postsurgical patients requiring acute dialysis with severe fluid overload or moderately unstable hemodynamics, the patients treated with SLED had a higher first postdialysis MAP than those treated with CVVH, which led to lower mortality. Further multicenter randomized clinical trials of larger sample size are needed to compare the effects of SLED and CVVH on the outcomes of postsurgical acute dialysis patients.

Risk of underdosing of ampicillin/sulbactam in patients with acute kidney injury undergoing extended daily dialysis--a single case

The fixed antibacterial combination of ampicillin and sulbactam is frequently used for various infections. The normal kidneys eliminate approximately 60% of ampicillin (371.39 Da) and sulbactam (255.22 Da). Concomitant with the decline in renal function, the terminal elimination half-life increases from 1 up to 24 h in patients with ESRD. Patients on three times weekly low flux haemodialysis exhibit a half-life of 2.3 h on and 17.4 h off dialysis. In contrast, in the present observation the elimination half-life in a single patient with acute kidney injury undergoing extended daily dialysis (EDD) with a polysulphone membrane was 1.5 h, indicating that the current dosing regimen for haemodialysis outpatients (ampicillin/sulbactam 2.0/1.0 g/day) would result in a significant underdosing for patients undergoing EDD.

The Hannover Dialysis Outcome study: comparison of standard versus intensified extended dialysis for treatment of patients with acute kidney injury in the intensive care unit

BACKGROUND

Increasing the dose of renal replacement therapy has been shown to improve survival in critically ill patients with acute kidney injury (AKI) in several smaller European trials. However, a very recent large multicentre trial in the USA could not detect an effect of dose of renal replacement therapy on mortality. Based on those studies, it is not known whether a further increase in dialysis dose above and beyond the currently employed doses would improve survival in patients with AKI. We therefore aimed to assess mortality and renal recovery of patients with AKI receiving either standard (SED) or intensified extended dialysis (IED) therapy in the intensive care unit.

METHODS

A prospective randomized parallel group study was conducted in seven intensive care units of a tertiary university hospital. Pre-existing chronic kidney disease was an exclusion criterion. A total of 156 patients (570 screened) with AKI requiring renal replacement therapy were randomly assigned to receive standard dialysis [dosed to maintain plasma urea levels between 120 and 150 mg/dL (20-25 mmol/L)] or intensified dialysis [dosed to maintain plasma urea levels <90 mg/dL (<15 mmol/L)]. Outcome measures were survival at Day 14 (primary) and survival and renal recovery at Day 28 (secondary) after initiation of renal replacement therapy.

RESULTS

Treatment intensity differed significantly (P < 0.01 for plasma urea and administered dose). No differences between intensified and standard treatment were seen for survival by Day 14 (70.4% versus 70.7%) or Day 28 (55.6% versus 61.3%), or for renal recovery amongst the survivors by Day 28 (60.0% versus 63.0%).

CONCLUSIONS

Although this study cannot deliver a definitive answer, it suggests that increasing the dose of extended dialysis above the currently recommended dose might neither reduce mortality nor improve renal recovery in critically ill patients, mainly septic patients, with AKI.

Circulating angiopoietin-1 and angiopoietin-2 in critically ill patients: development and clinical application of two new immunoassays

Introduction

In critically ill patients, the massive release of angiopoietin-2 (Ang-2) from endothelial Weibel–Palade bodies interferes with constitutive angiopoietin-1 (Ang-1)/Tie2 signaling in endothelial cells, thus leading to vascular barrier breakdown followed by leukocyte transmigration and capillary leakage. The use of circulating Ang-1 and Ang-2 as novel biomarkers of endothelial integrity has therefore gained much attention. The preclinical characteristics and clinical applicability of angiopoietin immunoassays, however, remain elusive.

Methods

We developed sandwich immunoassays for human Ang-1 (immunoradiometric sandwich assay/immunoluminometric sandwich assay) and Ang-2 (ELISA), assessed preanalytic characteristics, and determined circulating Ang-1 and Ang-2 concentrations in 30 healthy control individuals and in 94 critically ill patients. In addition, Ang-1 and Ang-2 concentrations were measured in 10 patients during a 24-hour time course with respect to interference by intravenous antibiotic treatment and by extended daily dialysis.

Results

The assays had detection limits of 0.12 ng/ml (Ang-1) and 0.2 ng/ml (Ang-2). Inter-assay and intra-assay imprecision was ≤8.8% and 3.7% for Ang-1 and was ≤4.6% and 5.2% for Ang-2, respectively. Angiopoietins were stable for 24 hours and were resistant to four freeze–thaw cycles. Angiopoietin concentrations were not associated with age, body mass index or renal function in healthy individuals. Ang-1 and Ang-2 concentrations correlated with severity of illness in critically ill patients. Angiopoietin concentrations were not influenced by antibiotic treatment or by extended daily dialysis.

Conclusion

Ang-1 and Ang-2 might serve as a novel class of biomarker in critically ill patients. According to preclinical and clinical validation, circulating Ang-1 and Ang-2 can be reliably assessed by novel immunoassays in the intensive care unit setting.

Sustained low-efficiency dialysis (SLED) for acute lithium intoxication

Acute lithium intoxication may cause serious neurologic and cardiac manifestations, up to the patient's death. Owing to its low molecular weight, relatively small volume of distribution close to that of total body water, and its negligible protein binding, lithium can be efficiently removed by any extracorporeal modality of renal replacement therapy (RRT). However, the shift from the intracellular to the extracellular compartment, with the inherent rebound phenomenon after the end of RRT, might limit the efficacy of the conventional, short-lasting haemodialysis. There have been no published studies up to now concerning the use of sustained low-efficiency dialysis (SLED) in lithium intoxication. This report describes a woman with a voluntary acute lithium ingestion of 40 tablets of lithium carbonate (8.12 mEq lithium each). The lithium concentration increased up to 4.18 mEq/l about 24 h after admission, notwithstanding treatment with intravenous crystalloids and gastric lavage. She developed mental status changes, oliguria, hypotension and bradycardia. We started SLED (8 h) with a blood flow of 200 ml/min and countercurrent dialysate flow of 300 ml/min. Lithium serum levels decreased by 86% during treatment, and the patient fully awoke recovering a normal mental status within the first 4 h of treatment. SLED was completed safely within the prescribed time. After the end of treatment, the rebound of lithium concentration was unremarkable. Renal function fully recovered, and the patient was transferred into a psychiatric facility 3 days after admission.

[Acute renal failure. Extracorporeal therapy]

Acute renal failure is increasingly found in critically ill patients as part of the multiple organ dysfunction syndrome. Intermittent hemodialysis and continuous renal replacement therapy are standard extracorporeal replacement therapies. Continuous therapies are thought to be especially useful in cardiovascularly instable patients in the intensive care unit. Recently, slow, extended daily dialysis was introduced as a hybrid method, combining the advantages of intermittent and continuous renal replacement therapy. While controlled studies have uniformly shown that a high dose of such replacement therapy increases survival, studies have failed to support a definitive advantage for any method in terms of patient survival. Therefore, the choice of renal replacement therapy should be based on personal experience, the available resources/infrastructure as well as the needs of the individual patient.

[Extracorporeal blood purification in the intensive care units]

Mortality remains high in intensive care patients with renal failure requiring extra corporeal blood purification. This article reviews the recent data that have led to the improvement of the care for such patients. We will discuss the criteria to determine the choice of the technique (intermittent or continuous), of the membrane, of the prescribing dose, and the type of anticoagulation and when to initiate such a treatment.

[Mobile single-pass batch hemodialysis system in intensive care medicine. Reduction of costs and workload in renal replacement therapy]

This paper describes the introduction of a single-pass batch hemodialysis system for renal replacement therapy in a 14 bed intensive care unit. The goals were to reduce the workload of intensive care unit physicians using an alternative and simpler method compared to continuous veno-venous hemodiafiltration (CVVHDF) and to reduce the costs of hemofiltrate solutions (80,650 EUR per year in our clinic in 2005). We describe and evaluate the process of implementation of the system as well as the achieved and prospective savings. We conclude that a close cooperation of all participants (physicians, nurses, economists, technicians) of a hospital can achieve substantial benefits for patients and employees as well as reduce the economic burden of a hospital.