Dialysis modalities in the intensive care unit

Predicting Outcomes in Critically ill Patients with Acute Kidney Injury Undergoing Intermittent Hemodialysis - A Retrospective Cohort Analysis

Purpose

Despite advances in the management of critically ill patients with acute kidney injury (AKI), the prognosis is poor. The evidence base on risk factors for poor outcomes in these patients is scarce. Our aim was to identify predictors of outcome in AKI patients undergoing intermittent hemodialysis (IHD).

Methods

We retrospectively analyzed patient records from consecutive, critically ill patients with AKI treated with IHD in one teaching secondary care hospital from 2002 to 2006. We used multivariate Cox proportional hazard regression analysis to identify predictors of mortality, hemodynamical instability during hemodialysis and failing renal recovery.

Results

Totally, we included 39 patients with a mean APACHE II score of 20.1 (SD 7.5) who had an average of 5.1 ± 4.8 hemodialysis sessions. All-cause mortality was 35.9% (14/39 patients). In multivariate analysis, pre-existing cardiac co-morbidity (HR 1.92 [0.58–6.47]), metabolic acidosis (2.40 [0-74-7.74]) and presence of ARDS (1.83 [0.52–6.46]) were the strongest predictors. 7 patients (18%) sustained new hemodynamic instability during hemodialysis, for which ARDS (6.42 [0.64–64.03]) was a strong predictor. Among survivors, 20 patients (80%) had partial or complete renal recovery. Preexisting renal insufficiency (3.13 [0.34–29.13]) and high net ultrafiltration quantities (3.30 [0.40–26.90]) were the strongest predictors for failing renal recovery. As a consequence of the small samples size none of the associations was statistically significant.

Conclusions

Presence of ARDS and high net ultrafiltration rates seem to represent key factors affecting prognosis in patients with AKI undergoing IHD. Targeting these risk factors may improve the poor prognosis of these patients.

Promoting Kidney Function Recovery in Patients with AKI Requiring RRT

AKI requiring RRT is associated with high mortality, morbidity, and long-term consequences, including CKD and ESRD. Many patients never recover kidney function; in others, kidney function improves over a period of many weeks or months. Methodologic constraints of the available literature limit our understanding of the recovery process and hamper adequate intervention. Current management strategies have focused on acute care and short-term mortality, but new data indicate that long-term consequences of AKI requiring RRT are substantial. Promotion of kidney function recovery is a neglected focus of research and intervention. This lack of emphasis on recovery is illustrated by the relative paucity of research in this area and by the lack of demonstrated effective management strategies. In this article the epidemiologic implications of kidney recovery after AKI requiring RRT are discussed, the available literature and its methodologic constraints are reviewed, and strategies to improve the understanding of factors that affect kidney function recovery are proposed. Measures to promote kidney function recovery are a serious unmet need, with a great potential to improve short- and long-term patient outcomes.

THE INFLUENCE OF USING THE NEEDLE ADAPTER TO REDUCE THE BIOMECHANICAL RISK FACTORS WITHIN HEMODIALYSIS ARTERIOVENOUS GRAFTS

Hemodialysis vascular access failure is related to increased morbidity and mortality in hemodialysis patients, representing a challenging clinical problem which results in a high percentage of hospital entrance and an important economic burden on government's disbursement. In this paper, the feasibility of using the needle adapter to reduce the biomechanical risk factors within arteriovenous grafts is considered. The three-dimensional (3D) tapered 6 to 8 mm loop graft in the presence of venous and arterial needles with and without adapter was numerically simulated. Navier–Stokes equations for incompressible Newtonian fluid are the governing equation of this problem. k – ω two equations turbulence modeling were applied to capture flow features of low Reynolds turbulent flow regions in this simulation. The physiological velocity waveform was used as an arterial inlet boundary condition. The venose outlet boundary condition was a time dependent physiological pressure waveform. The results for the dialysis without the adapter demonstrated that the graft wall experiences increased hemodynamic stresses as a result of the hitting needle jet flow. The dialysis with the adapter demonstrated that the venous anastomosis experiences lower biomechanical risk factors in comparison to the dialysis without the adapter and it reduced the vascular access failure. Using adapter caused less damage to endothelial cells during hemodialysis.

Choice of renal replacement therapy modality and dialysis dependence after acute kidney injury: a systematic review and meta-analysis

PURPOSE

Choice of renal replacement therapy (RRT) modality may affect renal recovery after acute kidney injury (AKI). We sought to compare the rate of dialysis dependence among severe AKI survivors according to the choice of initial renal replacement therapy (RRT) modality applied [continuous (CRRT) or intermittent (IRRT)].

METHODS

Systematic searches of peer-reviewed publications in MEDLINE and EMBASE were performed (last update July 2012). All studies published after 2000 reporting dialysis dependence among survivors from severe AKI requiring RRT were included. Data on follow-up duration, sex, age, chronic kidney disease, illness severity score, vasopressors, and mechanical ventilation were extracted when available. Results were pooled using a random-effects model.

RESULTS

We identified 23 studies: seven randomized controlled trials (RCTs) and 16 observational studies involving 472 and 3,499 survivors, respectively. Pooled analyses of RCTs showed no difference in the rate of dialysis dependence among survivors (relative risk, RR 1.15 [95 % confidence interval (CI) 0.78-1.68], I(2) = 0 %). However, pooled analyses of observational studies suggested a higher rate of dialysis dependence among survivors who initially received IRRT as compared with CRRT (RR 1.99 [95 % CI 1.53-2.59], I (2) = 42 %). These findings were consistent with adjusted analyses (performed in 7/16 studies), which found a higher rate of dialysis dependence in IRRT-treated patients [odds ratio (OR) 2.2-25 (5 studies)] or no difference (2 studies).

CONCLUSIONS

Among AKI survivors, initial treatment with IRRT might be associated with higher rates of dialysis dependence than CRRT. However, this finding largely relies on data from observational trials, potentially subject to allocation bias, hence further high-quality studies are necessary.

Sustained Low-Efficiency Daily Dialysis as Renal Replacement Therapy for the Critically Ill

Understanding proper management of acute kidney injury (AKI) is important given that studies consistently demonstrate an increasing incidence rate of AKI in the critically ill. AKI carries a significant risk for mortality, which only increases if dialysis becomes a necessary treatment. It is not clear whether modalities other than conventional intermittent hemodialysis improve outcomes in AKI. Sustained low-efficiency daily dialysis (SLEDD) is a more recent extracorporeal treatment whose distinguishing characteristic is its hybrid integration of both continuous and intermittent hemodialysis modalities. Besides providing comparable hemodynamic stability through its decreased blood flow rate and extended hours of use, SLEDD is less complicated, is less expensive, and is convenient for staff and patient. As a result, its use in critical care is on the rise.

The 90-day mortality and the subsequent renal recovery in critically ill surgical patients requiring acute renal replacement therapy

BACKGROUND

Particular attention should be paid to postoperative patients that suffer from severe acute kidney injury (AKI) requiring renal replacement therapy (RRT).

METHODS

This multicenter prospective observational study included 342 patients with postoperative AKI requiring RRT from January 2002 to December 2006.

RESULTS

There were 137 (40%) survivors at 90 days after the commencement of RRT. Independent predictors of 90-day mortality were older age, presence of sepsis, status post-cardiopulmonary resuscitation, necessity of continuous renal replacement therapy (CRRT), requirement of total parenteral nutrition, lower body mass index, higher Sequential Organ Failure Assessment score, and higher serum lactate level at the commencement of RRT. Further analysis among the survivors showed that lower serum creatinine at intensive care unit admission, lower Simplified Acute Physiology Score II and inotropic equivalent score at the commencement of RRT, and using CRRT were independent predictors for subsequent renal recovery.

CONCLUSIONS

The development of AKI requiring RRT in postoperative critical patients represents a substantial risk for mortality and morbidity.

Intermittent versus continuous renal replacement therapy: a matter of controversy

BACKGROUND

Acute Renal Failure (ARF) requiring some form of replacement therapy is a frequent complication in the critically ill patient. Despite potential therapeutic advantages the expectation of an improvement in patient outcomes using Continuous Renal Replacement Therapy (CRRT) compared to conventional Intermittent Haemodialysis (IHD) remains controversial.

AIMS AND METHOD

This article will review the literature on the issues surrounding the use of IHD versus CRRT in the management of the critically ill patient. Articles were selected according to level of evidence with priority given to meta-analyses and randomised controlled trials.

DISCUSSION

Several operational features of CRRT allow this technique to be tolerated more easily in critical illness than IHD. The gradual removal of fluid reduces the incidence of hypotension and the risk of volume overload. Decreased variability in the concentration of solutes enables greater azotemia control. However, CRRT is required to operate uninterrupted to achieve a treatment dose that is equivalent to a conventional IHD treatment schedule. In the absence of definitive evidence to validate superior patient survival and return of renal function there is disagreement as to the most appropriate form of Renal Replacement Therapy (RRT) for the critically ill patient. The introduction of 'hybrid' therapies offers a further alternative treatment strategy, which combine favourable aspects of IHD and CRRT.

CONCLUSION

The decision to use IHD or CRRT should be guided by the therapeutic needs of the patient rather than the operational differences between the two techniques. The resources and expertise available at the organisation are also important in determining the mode best able to manage the critically ill patient at any stage and may change according to the severity of illness. The emergence of hybrid therapies provides a compromise option which encompasses many of the features of both systems, but does not embrace all options of either approach.

Early renal replacement therapy in patients with postoperative acute liver failure associated with acute renal failure: effect on postoperative outcomes

BACKGROUND

Acute liver failure after major surgical procedures is associated with a high risk of multiple organ failure, including acute renal failure. The optimal time to initiate renal replacement therapy for acute renal failure is controversial because of the poor overall clinical outcomes.

STUDY DESIGN

From July 2002 to January 2005, all patients who had no history of liver disease, but developed acute liver failure and subsequent renal failure requiring renal replacement therapy after major surgery, at a surgical intensive care unit, were retrospectively analyzed. Patients were divided into early or late dialysis groups based on an arbitrary blood urea nitrogen cut-off level of 80 mg/dL before renal replacement therapy.

RESULTS

Eighty consecutive patients (21 women), with a mean age of 57.8+/-17.0 (SD) years, comprised the study group. The late dialysis group (n=26) had a higher ICU mortality rate (p=0.02) and a lower renal function recovery rate (p=0.02) than the early dialysis group (n=54). Fifty-three (66.3%) patients died during their ICU stay. Independent risk factors for ICU mortality were renal replacement therapy modality (intermittent hemodialysis versus continuous venous-venous hemofiltration; odds ratio [OR]=4.32, 95% CI 1.26 to 14.79; p=0.02), predialysis APACHE II score> 20 (OR=6.52, 95% CI 1.61 to 26.36; p < 0.01), and late dialysis (OR=4.01, 95% CI 1.05 to 15.27; p=0.04).

CONCLUSIONS

The mortality rate in postoperative patients with acute liver failure-associated acute renal failure was very high. Earlier initiation of renal replacement therapy, based on the predialysis blood urea nitrogen level, with continuous venous-venous hemofiltration might provide a better ICU survival rate.

Continuous renal replacement therapy is associated with less chronic renal failure than intermittent haemodialysis after acute renal failure

OBJECTIVE

Acute renal failure can be treated with continuous renal replacement therapy (CRRT) or intermittent haemodialysis (IHD). Whether this choice affects renal recovery has been debated, since it has implications on quality of life and costs. Our objective was to determine the impact of CRRT and IHD on renal recovery.

DESIGN

Nationwide retrospective cohort study between the years 1995 and 2004. Follow-up ranged between 3 months and 10 years.

SETTING

Thirty-two Swedish intensive care units.

PATIENTS AND PARTICIPANTS

Eligible subjects were adults treated in Swedish general intensive care units with RRT. A total of 2,642 patients from 32 ICUs were included. We then excluded patients with end-stage renal disease (252) and patients lacking a diagnosis in the in-patient register (188). Thus, 2,202 patients were studied. Follow-up was complete.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

The primary outcome was renal recovery. Secondarily we studied the mortality of the cohort. There were no differences between IHD and CRRT patients regarding baseline characteristics, such as age, sex and comorbidities. Of the 1,102 patients surviving 90 days after inclusion in the cohort, 944 (85.7%) were treated with CRRT and 158 (14.3%) were treated with IHD. Seventy-eight patients (8.3%; confidence interval, CI, 6.6-10.2), never recovered their renal function in the CRRT group. The proportion was significantly higher among IHD patients, where 26 subjects or 16.5% (CI 11.0-23.2) developed need for chronic dialysis.

CONCLUSIONS

The use of CRRT is associated with better renal recovery than IHD, but mortality does not differ between the groups.

Critical care in the United States of America

There are numerous factors that continue to influence the practice of critical care medicine. This article focuses on issues that have significantly impacted critical care practice during the last decade, such as changing socioeconomic factors, the increasing influence of specialty groups and governmental agencies, and the translation of evidence-based medicine into practice.

Management of acute renal failure

Acute renal failure is a common condition, frequently encountered in both community practice and hospital inpatients. While it remains a heterologous condition, following basic principles makes investigation straightforward, and initial management follows a standard pathway in most patients. This article shows this, advises on therapeutic strategies, including those in special situations, and should help the clinician in deciding when to refer to a nephrologist, and when to consider renal replacement therapy.

Acute renal failure after lung transplantation: incidence, predictors and impact on perioperative morbidity and mortality

The incidence, predictors and clinical significance of acute renal failure (ARF) after lung transplantation are not well described. We retrospectively collected data on 296 patients transplanted at our center between April 1992 and December 2000; follow-up was extended until December 2002. Patients were initially divided into two groups: ARF (doubling of baseline creatinine within 2 weeks after surgery) and NoARF. The ARF group was subdivided into ARFD (dialyzed) and ARFnD (not dialyzed). The incidence of ARF was 56% (166/296), but most cases were ARFnD (n = 143). Independent predictors of ARFD (n = 23) were: baseline GFR (OR 0.98, CI 0.96-0.99, p = 0.012), pulmonary diagnosis other than COPD (OR 6.80, CI 1.5-30.89, p = 0.013), mechanical ventilation > 1 d (OR 6.16, CI 1.70-22.24, p = 0.006) and parenteral amphotericin B use (OR 3.04, CI 1.03-8.98, p = 0.045). Both ARFnD and ARFD were associated with longer duration of mechanical ventilation, increased hospital stay and increased early mortality. One-year patient survival was 92.3%, 81.8% and 21.7% in the NoARF, ARFnD and ARFD groups, respectively (p < 0.0001). After controlling for important covariates, ARFD remained associated with an increased hazard of dying (HR 6.77, CI 4.00-11.44, p < 0.0001). In conclusion, ARF occurs commonly after lung transplantation and affects important clinical outcomes, especially when dialysis is required.

A Comparison of Continuous Renal Replacement Therapy to Intermittent Dialysis in the Management of Renal Insufficiency in the Acutely Ill Surgical Patient

Acute renal failure (ARF) occurs in 10 per cent to 23 per cent of intensive care unit patients with mortality ranging from 50 per cent to 90 per cent. ARF is characterized by an acute decline in renal function as measured by urine output (UOP), serum creatinine, and blood urea nitrogen (BUN). Causes may be prerenal, intrarenal, or postrenal. Treatment consists of renal replacement therapy (RRT), either intermittent (ID) or continuous (CRRT). Indications for initiation of dialysis include oliguria, acidemia, azotemia, hyperkalemia, uremic complications, or significant edema. Overall, the literature comparing CRRT to ID is poor. No studies of only surgical/trauma patients have been published. We hypothesize that renal function and hemodynamic stability in trauma/surgical critical care patients are better preserved by CRRT than by ID. We performed a retrospective review of trauma/surgical critical care patients requiring renal supportive therapy. Thirty patients received CRRT and 27 patients received ID. The study was controlled for severity of illness and demographics. Outcomes assessed were survival, renal function, acid-base balance, hemodynamic stability, and oxygenation/ventilation parameters. Populations were similar across demographics and severity of illness. Renal function, measured by creatinine clearance, was statistically greater with CRRT ( P = 0.035). There was better control of azotemia with CRRT: BUN was lower ( P = 0.000) and creatinine was lower ( P = 0.000). Mean arterial blood pressure was greater ( P = 0.021) with CRRT. No difference in oxygenation/ventilation parameters or pH was found between groups. CRRT results in an enhancement of renal function with improved creatinine clearance at the time of dialysis discontinuation. CRRT provides better control of azotemia while preserving hemodynamic stability in patients undergoing renal replacement therapy. Prospective randomized controlled studies and larger sample sizes are needed to further evaluate these modalities.

Dose of Dialysis in Acute Renal Failure

Acute renal failure (ARF) is a cause of significant morbidity and mortality. Despite advances in supportive care, outcomes in ARF have improved little over the past decades. The primary goals in management of patients with ARF are to optimize hemodynamic and volume status, minimize further renal injury, correct metabolic abnormalities, and permit adequate nutrition. Renal replacement therapy (RRT) is often required to achieve these goals while awaiting renal recovery, but the optimal dose of dialysis in patients with ARF is not known. Extrapolation of required dialysis dose from recommendations in chronic dialysis is unlikely to be appropriate because of the lack of a steady state and differences in distribution volume of urea that are intrinsic to ARF. The prescribed dialysis dose in ARF is often low, and actual delivered dose is often even less than prescribed. Delivery of dialysis in ARF is often hampered by the patient's hypercatabolic state, hemodynamic instability, and volume status, as well as suboptimal vascular access with temporary venous catheters. The impact of intermittent hemodialysis (IHD) versus continuous renal replacement therapy (CRRT) on outcomes in ARF is also not clear. Patient disease severity impacts more than dialysis modality in patient outcome, but when patients are stratified for equal disease severity, CRRT may have potential benefits over IHD in terms of patient survival, fluid and metabolic control, and renal recovery. Strategies associated with improved outcomes that have emerged thus far in ARF are to aim for a time-averaged blood urea nitrogen (BUN) of less than 60 mg/dl with IHD, varying IHD frequency as necessary, or to achieve a minimum ultrafiltration rate of 35 ml/kg/hr with CRRT.

Techniques for assessing and achieving fluid balance in acute renal failure

Fluid therapy, together with attention to oxygen supply, is the cornerstone of resuscitation in all critically ill patients. Hypovolemia results in inadequate blood flow to meet the metabolic requirements of the tissues and must be treated urgently to avoid the complication of progressive organ failure, including acute renal failure. The kidney plays a critical role in body fluid homeostasis. Renal dysfunction disturbs this homeostasis and requires special attention to issues of fluid balance and fluid overload. In addition, fluid therapy is the only treatment that has been shown to be effective in the prevention of acute renal failure. Special attention to volume status is therefore required in patients at risk for acute renal failure. Hypovolemia is also a major causal factor of morbidity during hemodialysis and may contribute to further renal insults. Although the importance of fluid management is generally recognized, the choice of fluid, the amount, and assessment of fluid status are controversial. As the choice of fluids becomes wider and monitoring devices become more sophisticated, the controversy increases. This article provides an overview of the concept of fluid management in the critically ill patient with acute renal failure.