Acute renal failure in the intensive care unit. Therapy overview, patient risk stratification, complications of renal replacement, and special circumstances

Renal replacement therapy III: IHD, CRRT, SLED

Acute renal failure in critically ill patients is a growing clinical problem. Options for renal replacement therapy in these patients use convective and diffusive clearance and may be intermittent, as in classic hemodialysis, or continuous. New ways of delivering dialysis in the intensive care unit, such as sustained low-efficiency dialysis, are also under development. It may be that renal replacement therapy needs to be tailored to the needs of each individual patient. Current and future research studies should provide the answers to many of these questions.

Relationship of urine output to dialysis initiation and mortality in acute renal failure

BACKGROUND

A non-oliguric state is considered a good prognostic indicator in acute renal failure (ARF), and may lead to withholding renal replacement therapy in anticipation of recovery. The present study explores the relationship between urine volume and the start of dialysis and hospital mortality in patients with ARF.

METHODS

In a non-concurrent cohort of patients with ARF treated exclusively with intermittent hemodialysis (IHD), demographic, clinical and laboratory characteristics were collected at the time of the first nephrology consultation and at the start of dialysis. Multiple linear and logistic regression analyses were used to identify factors associated with the time to initiation of dialysis and hospital mortality, respectively.

RESULTS

Urine volume correlated with the time from admission to start of dialysis (r = 0.60; p < 0.001). Higher urine volume, lower serum creatinine and lower APACHE II score were independently associated with increased time from admission to start of dialysis. Hospital mortality was independently associated with a higher urine volume (odds ratio, OR 3.8, 95% confidence interval, CI, 1.1-12.8, p = 0.03), a higher MOF score (OR 4.9, 95% CI 1.1-21.6, p = 0.03) and a higher number of dialysis treatments performed in the 1st week (OR 3.7, 95% CI 1.2-11.3, p = 0.03).

CONCLUSIONS

Among patients with ARF requiring IHD, increased urine output is associated with higher mortality. This observation may reflect physician bias toward later initiation of dialysis in non-oliguric ARF. Further research is needed to help identify patients with non-oliguric ARF who require early dialytic support.

Heat loss and continuous renal replacement therapy

Because of the devastating consequences of thermal imbalance, it is imperative that nurses understand these concepts and apply them to the daily care of their patients. Heat loss, heat conservation, and heat generation interplay to maintain the narrow range that is considered optimal for human cellular function. These concepts factor into patients who are critically ill but are especially important for patients undergoing continuous renal replacement therapy. Many of these types of dialysis expose the individual patient's blood to room temperature dialysate via an extracorporeal circuit 24-hours a day, sometimes for several weeks at a time. Critical care and advanced practice nurses must understand the interplay of the processes of heat loss, conservation, and heat generation to ensure patients undergoing this therapy achieve maximum benefit with the fewest complications possible.

The change in renal replacement therapy on acute renal failure in a general intensive care unit in a university hospital and its clinical efficacy: a Japanese experience

The aim of our study was to examine renal replacement therapies (RRT) that have been used for acute renal failure (ARF) in our intensive care unit (ICU) patients and to compare their outcomes. Sixteen patients who underwent intermittent hemodialysis (IHD), 14 patients who underwent continuous hemofiltration (CHF) in combination with IHD (CHF + IHD), and 38 patients who underwent continuous hemodiafiltration (CHDF) were evaluated. Regarding the effects of blood purification on hemodynamics and renal function, the percentage increase in blood pressure and percent rapid increase in urinary output were the greatest in the CHDF group. The hourly urinary output after the start of initial blood purification increased only in the CHDF group. The survival rate was significantly higher in the CHDF group. These results suggest that CHDF should be the first-line therapy for patients with ARF and that we are moving in the right direction regarding the application of RRT to treat ARF in ICU patients.

Cost of acute renal failure requiring dialysis in the intensive care unit: clinical and resource implications of renal recovery

OBJECTIVE

Acute renal failure can be treated with continuous renal replacement therapy (CRRT) or intermittent hemodialysis. There is no difference in mortality, although patients treated with CRRT may have a higher rate of renal recovery. Given these considerations, an estimate of the costs by modality may help in choosing the method of dialysis. As such, the objective of this study was to estimate the cost of CRRT and intermittent hemodialysis in the intensive care unit and to explore the impact of renal recovery on subsequent clinical outcomes and costs among survivors.

DESIGN

Retrospective cohort study of all patients who developed acute renal failure and required dialysis between April 1, 1996, and March 31, 1999.

SETTING

Two tertiary care intensive care units in Calgary, Canada.

PATIENTS

A total of 261 critically ill patients.

INTERVENTIONS

None.

MEASUREMENTS

All patients were followed to determine in-hospital and subsequent clinical outcomes (survival and frequency of renal recovery). The immediate and potential long-term costs of CRRT and intermittent hemodialysis were measured.

MAIN RESULTS

The cost of performing CRRT ranged from Can 3,486 dollars to Can 5,117 dollars per week, depending on the modality and the anticoagulant used, and it was significantly more expensive than intermittent hemodialysis (Can 1,342 dollars per week). Survivors with renal recovery spent significantly fewer days in hospital (11.3 vs. 22.5 days, p<.001) and incurred less healthcare costs (11,192 dollars vs. 73,273 dollars, p<.001) over the year after hospital discharge compared with survivors who remained on dialysis.

CONCLUSIONS

Immediate cost savings could be achieved by increasing the use of intermittent hemodialysis rather than CRRT for patients with acute renal failure in the intensive care unit. Because of the high cost of ongoing dialysis, CRRT may still be an economically efficient treatment if it improves renal recovery among survivors; further study in this area is required.

Hepatorenal syndrome. Definition, pathophysiology, and intervention

Hepatorenal syndrome is a well characterized entity in which vasodilation of splanchnic vessels and intense constriction of the renal cortical vasculature occur in concert. The condition is often fatal unless orthotopic liver transplantation (OLT) is performed. Many extracorporeal blood purification techniques exist which can be offered to patients awaiting OLT. Continuous hemofiltration, with or without other modalities such as therapeutic plasma exchange and hemoperfusion, may be helpful in improving the level of consciousness of these patients. Unfortunately, mortality and hepatic regeneration do not appear to be affected by such interventions. The development of a hybrid bioartifical liver support system and pharmacologic manipulation of the hemodynamic perturbations that occur in HRS provide particularly appealing prospects as a means of providing a bridge to liver transplantation in the future.

Use of a low-molecular-weight heparinoid (danaparoid sodium) for continuous renal replacement therapy in intensive care patients

The purpose of this study was to evaluate the efficacy and safety of danaparoid in the treatment of critically ill patients with acute renal failure and suspected heparin-induced thrombocytopenia (HIT) needing renal replacement therapy (RRT). We conducted a retrospective analysis of 13 consecutive intensive care patients with acute renal failure and suspected HIT who were treated with danaparoid for at least 3 days during RRT. In eight patients, continuous venovenous hemofiltration was performed. The mean infusion rate of danaparoid was 140 +/- 86 U/hour. Filter exchange was necessary every 37.5 hours. In five patients, continuous venovenous hemodialysis was used. A bolus injection of 750 U danaparoid was followed by a mean infusion rate of 138 +/- 122 U/hour. Filters were exchanged every 24 hours. In 7 of 13 patients, even a low mean infusion rate of 88 +/- 35 U/hour was efficient. Mean anti-Xa (aXa) levels were approximately 0.4 +/- 0.2 aXa U/mL. Persistent thrombocytopenia despite discontinuation of heparin treatment was observed in 9 of 13 patients, owing to disseminated intravascular coagulation (DIC). HIT was confirmed by an increase in platelet count and positive heparin-induced antibodies in 2 of 13 patients. No thromboembolic complications occurred, but major bleeding was observed in 6 of 13 patients, which could be explained by consumption of coagulation factors and platelets due to DIC in 5 of 6 patients. Nine of 13 patients died of multiorgan failure or sepsis, or both. In none of these patients was the fatal outcome related to danaparoid treatment. In critically ill patients with renal impairment and suspected HIT, a bolus injection of 750 U danaparoid followed by a mean infusion rate of 50 to 150 U/hour appears to be a safe and efficient treatment option when alternative anticoagulation is necessary.

Effects of different doses in continuous veno-venous haemofiltration on outcomes of acute renal failure: a prospective randomised trial

BACKGROUND

Continuous veno-venous haemofiltration is increasingly used to treat acute renal failure in critically ill patients, but a clear definition of an adequate treatment dose has not been established. We undertook a prospective randomised study of the impact different ultrafiltration doses in continuous renal replacement therapy on survival.

METHODS

We enrolled 425 patients, with a mean age of 61 years, in intensive care who had acute renal failure. Patients were randomly assigned ultrafiltration at 20 mL h(-1) kg(-1) (group 1, n=146), 35 mL h(-1) kg(-1) (group 2, n=139), or 45 mL h(-1) kg(-1) (group 3, n=140). The primary endpoint was survival at 15 days after stopping haemofiltration. We also assessed recovery of renal function and frequency of complications during treatment. Analysis was by intention to treat.

RESULTS

Survival in group 1 was significantly lower than in groups 2 (p=0.0007) and 3 (p=0.0013). Survival in groups 2 and 3 did not differ significantly (p=0.87). Adjustment for possible confounding factors did not change the pattern of differences among the groups. Survivors in all groups had lower concentrations of blood urea nitrogen before continuous haemofiltration was started than non-survivors. 95%, 92%, and 90% of survivors in groups 1, 2, and 3, respectively, had full recovery of renal function. The frequency of complications was similarly low in all groups.

INTERPRETATION

Mortality among these critically ill patients was high, but increase in the rate of ultrafiltration improved survival significantly. We recommend that ultrafiltration should be prescribed according to patient's bodyweight and should reach at least 35 mL h(-1) kg(-1).

New perspectives for prevention/treatment of acute renal failure

Acute renal failure continues to be a difficult clinical problem in critically ill patients, despite advances in critical care and dialysis. This review focuses on some of the current issues in the nondialytic and dialytic management of these patients. Critical analysis of some still frequently used drugs in these patients such as diuretics and dopamine in so-called 'renal doses' has revealed little beneficial effect. Recent data are in conflict with previous suggestions that biocompatible membranes have a positive effect on the recovery of renal function and on patient mortality. The choice between intermittent haemodialysis and continuous renal replacement therapy should be made on an individual basis and not on the basis of 'dogmatic' opinion.