Acute renal failure in the ICU in the 1990s--"anything goes"?

Epidemiología del fracaso renal agudo en las UCI españolas. Estudio prospectivo multicéntrico FRAMI

OBJECTIVE

Multicenter study oriented at establishing the incidence and prognosis of acute kidney failure (AKF) in the ICU of our country.

MATERIAL AND METHODS

Prospective study of adult patients admitted over 8 months in 43 Spanish ICUs to detect AKF defined as creatinine>or=2 mg/dl or diuresis<400 ml/24 hours (in chronic patients 100% increase of creatinine, excluding those with baseline creatinine>or=4 mg/dl).

RESULTS

901 episodes of AKF (AKF episodes (incidence 5.7%), 55% of which occurred on admission. A total of 38.4% of the episodes were due to acute tubular necrosis (ATN), 36.6% to prerenal, and 21.2% to mixed. Renal depuration (RC) was required in 38%. Mortality was 42.3% during the AKF episode (34.1% in those who were admitted with AKF versus 50.9% in those who developed it after admission), 80% in patients with Hepatorenal Syndrome, 51.6% in ATN and 29.9% in prerenal. We detect an independent relationship with mortality for age (OR 1.03), background of diabetes (OR 2.06), development of AKF in the ICU (OR 2.51), oliguria (OR 5.76) and RC (OR 2.32). Recovery of the kidney function occurred in 85.6% of the survivors and RC was maintained in only 1.1% on discharge from the ICU. We calculated the area under the curve of APACHE II on admission (0.62), SOFA on onset of AKF (0.68), Liaño index (0.7) and maximum SOFA (0.79).

CONCLUSIONS

AKF in ICU patients does not show an elevated incidence but does have high mortality, presenting greater seriousness when it appears after admission. However, recovery is elevated in patients who survive. The usual prognostic indexes are not exact in this patient group, the ISA and maximum SOFA being those which shows a closer relationship with mortality.

Prognosis of acute renal failure: an evaluation of proposed consensus criteria

OBJECTIVES

To validate the recently proposed criteria for acute renal injury (ARI), acute renal failure syndrome (ARFS) and severe acute renal failure syndrome (SARFS) and to evaluate the significance of other prognostic factors.

DESIGN AND SETTING

Retrospective analysis of the Riyadh ICU Program database of patients admitted to 22 ICUs in UK and Germany between 1989 and 1998.

PATIENTS

Included in the study were 41,972 patients, of whom 7,522 (17.9%) had ARI, 2,641 (6.3%) had ARFS and 1,747 (4.2%) had SARFS.

RESULTS

Patients with ARI, ARFS or SARFS had a hospital mortality of 29.5%, 49.2% or 63.0%, respectively, compared to 10.3% among patients without acute renal failure. In the presence of contemporaneous failure of any other organs on the day of acute renal failure, hospital mortality increased to 73.3%, 76.2%, 72.1% and 18%, respectively. Multivariate analysis showed that non-surgical admission, need for emergency surgery, development of acute renal failure during stay in ICU, need for mechanical ventilation and the number of other failed organ systems had a greater impact on prognosis than the need for renal replacement therapy.

CONCLUSIONS

The proposed criteria for ARI, ARFS and SARFS correlated with mortality, but other factors had a greater impact on prognosis. Renal replacement therapy did not increase the risk of hospital mortality among patients with acute renal failure.

Acute renal failure needing dialysis in the intensive care unit and prognostic scores

BACKGROUND

Generic prognostic scores used in acute renal failure (ARF) give imprecise results; disease-specific indices applied to distinct populations or intensive care practices becomes inaccurate. The current study evaluates the adequacy of prognostic scores, in patients with severe ARF needing dialysis.

METHODS

Known generic (APACHE II) and disease-specific (ATN-ISS) indices were applied to a cohort (n = 280) with ARF needing dialysis, under intensive care. Possible risk factors as causal factors, organ dysfunctions and clinical variables were examined, and a local index assembled by multivariate logistic regression analysis. Area under the receiver operating characteristics (ROC) curves evaluated the indices discriminating capacity. Goodness-of-fit testing and linear regression analysis appraised calibration. Validation was accomplished by the bootstrapping technique. The end-point was hospital mortality.

RESULTS

Overall mortality was 85%. Female gender < 44 years (OR: 0.29; 95% CI: 0.10-0.84), liver/obstructive biliary disease (OR: 6.03; 95% CI: 1.65-22.08), being conscious (OR: 0.49; 95% CI: 0.21-1.14), use of vasoactive drug (OR: 3.13; 95% CI: 1.25-7.83), respiratory dysfunction (OR: 5.20; 95% CI: 1.25-7.83) or sepsis (OR: 2.62; 95% CI: 1.14-6.02) were associated with outcome. Areas under the ROC curve of 0.815, 0.652 and 0.814; Goodness-of-fit test P = 0.593, P < 0.001 and P = 0.002; and linear regression R2 = 0.973, R2 = 0.526 and R2 = 0.919 for the local index, APACHE II and ATN-ISS, respectively, indicate better performance by the local index. The local index median area under the ROC curve, by bootstrapping, was 0.820 (95% CI: 0.741-0.907).

CONCLUSIONS

APACHE II score was inaccurate, and ATN-ISS poorly calibrated. When mortality or intensive care practices significantly deviate, local scores may better evaluate prognosis in severe ARF.

Special issues in the patient with renal failure

Renal failure commonly occurs in an ICU as part of the evolution of an underlying disease process. Appropriate and rapid resuscitation and treatment prevents or reverses prerenal insults. Patients usually make a complete recovery if the disease process is reversible and the renal injury mild or moderate. More severe degrees of renal injury initially require conservative management with attention to maintaining a diuresis, preventing fluid, electrolyte, and acid-base imbalances, and ensuring adequate nutrition. Renal replacement therapy is required for the more severe forms of renal failure. Continuous forms of RRT are gaining favor as they are associated with less hemodynamic instability, though current evidence does not demonstrate any clear outcome benefit. Mortality is high when the severe form of ARF is established. ARF may have some attributable mortality, but the poor outcome is usually related more to the underlying medical problems and concurrent multisystem derangements.

Refining predictive models in critically ill patients with acute renal failure

Mortality rates in acute renal failure remain extremely high, and risk-adjustment tools are needed for quality improvement initiatives and design (stratification) and analysis of clinical trials. A total of 605 patients with acute renal failure in the intensive care unit during 1989-1995 were evaluated, and demographic, historical, laboratory, and physiologic variables were linked with in-hospital death rates using multivariable logistic regression. Three hundred and fourteen (51.9%) patients died in-hospital. The following variables were significantly associated with in-hospital death: age (odds ratio [OR], 1.02 per yr), male gender (OR, 2.36), respiratory (OR, 2.62), liver (OR, 3.06), and hematologic failure (OR, 3.40), creatinine (OR, 0.71 per mg/dl), blood urea nitrogen (OR, 1.02 per mg/dl), log urine output (OR, 0.64 per log ml/d), and heart rate (OR, 1.01 per beat/min). The area under the receiver operating characteristic curve was 0.83, indicating good model discrimination. The model was superior in all performance metrics to six generic and four acute renal failure-specific predictive models. A disease-specific severity of illness equation was developed using routinely available and specific clinical variables. Cross-validation of the model and additional bedside experience will be needed before it can be effectively applied across centers, particularly in the context of clinical trials.

Epidemiology, management, and outcome of severe acute renal failure of critical illness in Australia

OBJECTIVE

To study the epidemiology, style of management, and outcome of intensive care patients with acute renal failure requiring replacement therapy in Australia.

DESIGN

Prospective epidemiologic study.

SETTING

Australian adult intensive care units providing acute renal replacement therapy.

PATIENTS

Adult intensive care patients with acute renal failure treated with renal replacement therapy.

INTERVENTIONS

Demographic and clinical data collection for 3 months.

MEASUREMENTS AND MAIN RESULTS

A standardized data collection form for each case of severe acute renal failure was used to collect demographic, biochemical, clinical, and outcome data. Severe acute renal failure affected 299 patients (approximately eight cases per 100,000 adults per year). Among these patients, 99 (33.1%) had impaired baseline renal function, 238 (79.6%) needed mechanical ventilation, and 232 (77.6%) needed continuous vasoactive drug administration. Critical care physicians controlled patient care and renal replacement therapy in 289 cases (96.7%). Critical care nurses performed such therapy alone in 288 (96.3%) cases. Continuous renal replacement therapy was used in 292 (97.7%) patients. There was no nephrological input in 173 (57.8%) cases. Predicted mortality rates were 52.1% by Simplified Acute Physiology Score II, 49.5% by Acute Physiology and Chronic Health Evaluation II score, and 51.9% by an acute renal failure-specific score. Actual mortality rate was 46.8%. Only 25 (15.7%) patients were dialysis-dependent at hospital discharge. Of these patients, 20 (80%) had premorbid chronic impairment of renal function.

CONCLUSION

In Australia, critical care physicians and nurses manage severe acute renal failure with limited consultative nephrological input. Renal replacement therapy is continuous and outcomes are satisfactory. Our findings support the view that this approach to management of severe acute renal failure is safe.

A prospective, multicenter study of the epidemiology, management, and outcome of severe acute renal failure in a "closed" ICU system

The safety and effectiveness of "closed" intensive care units (ICUs) are highly controversial. The epidemiology and outcome of acute renal failure (ARF) requiring replacement therapy (severe ARF) within a "closed" ICU system are unknown. Accordingly, we performed a prospective 3-mo multicenter observational study of all Nephrology Units and ICUs in the State of Victoria (all "closed" ICUs), Australia, and focused on the epidemiology, treatment, and outcome of patients with severe ARF. We collected demographic, clinical, and outcome data using standardized case report forms. Nineteen ward patients and 116 adult ICU patients had severe ARF (13.4 cases/100, 000 adults/yr). Among the ICU patients with severe ARF, 37 had impaired baseline renal function, 91 needed ventilation, and 95 needed vasoactive drugs. Intensivists controlled patient care in all cases. Continuous renal replacement therapy (CRRT) was used in 111 of the ICU patients. Nephrological opinion was sought in only 30 cases. Predicted mortality was 59.6%. Actual mortality was 49.2%. Only 11 ICU survivors were dialysis dependent at hospital discharge. In the state of Victoria, Australia, intensivists manage severe ARF within a "closed" ICU system. Renal replacement is typically continuous and outcomes compare favorably with those predicted by illness severity scores. Our findings support the safety and efficacy of a "closed" ICU model of care.