Acute kidney injury in the intensive care unit

Acute kidney injury in intensive care units according to RIFLE classification: a population-based study

INTRODUCTION

Recent studies of the incidence of acute kidney injury (AKI) are largely based on estimated baseline serum creatinine values. The aim of this study was to more accurately determine the incidence of AKI using the RIFLE criteria for intensive care unit (ICU) patients of a whole population.

MATERIALS AND METHODS

All adult patients admitted to the ICUs of Landspitali - The National University Hospital of Iceland in 2007 (n = 1026) were studied with meticulous search for baseline creatinine. The underlying risk factors and contributing causes for AKI were defined, and survival and ratio of end-stage renal failure evaluated.

RESULTS

A measured baseline creatinine value was found for all but two patients with AKI. The incidence of AKI according to RIFLE criteria was 21.7% [95% confidence interval (CI): 19.0-24.1%], with 7.1% (95 CI: 5.6-8.9%), 6.8% (95 CI: 5.3-8.5%) and 7.8% (95 CI: 6.2-9.6%) in the risk, injury and failure subgroups. Using estimated baseline creatinine overestimated the incidence of AKI by 3.5%. The sensitivity and specificity of the RIFLE criteria using estimated baseline creatinine were 76% and 95%. Renal replacement therapy was required for 17% of the AKI patients. One year survival of AKI patients was 51%, but only 2.5% of patients surviving 90 days required chronic renal replacement therapy.

CONCLUSIONS

The incidence of AKI in the ICU was lower than previously published, perhaps due to overestimation of AKI using estimated baseline creatinine or bias from tertiary referrals. AKI patients have high mortality, but the survivors have a low incidence of end-stage renal failure.

Renal management in the critically ill patient

Acute kidney injury is common in the hospital setting and morbidity and mortality outcomes depend on early recognition and early intervention. Identifying patients at risk of acute kidney injury is critical in prevention, early identification, and appropriate treatment.

Is contrast exposure safe among the highest risk trauma patients?

BACKGROUND

Despite improvements in the diagnosis and management of acute kidney injury (AKI), posttraumatic renal dysfunction continues to be associated with increased morbidity and mortality. Intravenous (IV) contrast is known to induce AKI in high-risk groups including the elderly and critically ill. We sought to determine whether IV contrast exposure among high-risk trauma patients resulted in renal dysfunction as defined by the Acute Kidney Injury Network criteria.

METHODS

We performed a 3-year retrospective analysis of all patients admitted to our Level I trauma center surgical intensive care unit for >48 hours. Patients with preexisting chronic renal dysfunction were excluded. We performed univariate and bivariate analyses to identify risk factors for AKI. Multivariable logistic regression analysis identified independent predictors for AKI. Subgroup analysis was undertaken among high-risk groups to include elderly patients (aged ≥65 years) with admission hypotension (systolic blood pressure <90 mm Hg) and an Injury Severity Score (ISS) ≥25.

RESULTS

Of the 6,317 patients, 571 (9.0%) patients met the inclusion criteria; 170 (29.8%) patients developed AKI. Age ≥65 years (odds ratio [OR] 2.26, 95% confidence interval [CI] = 1.06-4.80, p <0.034) and ISS ≥25 (OR 1.86, 95% CI = 1.12-3.07, p <0.015) were determined to be independent predictors of AKI. IV contrast was not identified to be a predictor of AKI. Upon subgroup analysis, IV contrast exposure was not a predictor of AKI among the elderly, hypotensive, or severely injured patients (ISS ≥25).

CONCLUSION

A complete trauma workup including studies requiring IV contrast exposure should be considered safe even among high-risk trauma patients.

Acute kidney insufficiency in the critically ill

Acute kidney insufficiency (AKI), or injury, is common in the critically ill patient. Minimal increases in serum creatinine (Scr) have been associated with greater morbidity, mortality, and hospital cost. In 2002, the Acute Dialysis Quality Initiative (ADQI) proposed a consensus definition (the RIFLE classification) which was modified after continuing evidence suggested that small changes in Scr (≥0.3 mg/dL) led to worsening outcomes. This group, known as the Acute Kidney Injury Network (AKIN), suggests 3 stages of worsening kidney function. Such definitions may aid in identifying patients at greatest risk and further the development of preventive strategies. This review will focus on the epidemiology and etiology of AKI as well as provide a mechanistic description of drug-induced AKI. In addition, a brief review of continuous renal replacement therapies is provided.

Improvement of cytokine response and survival time by bioartificial kidney therapy in acute uremic pigs with multi-organ dysfunction

OBJECTIVE

To explore whether bioartificial kidney (BAK) ameliorates cytokine response and biochemical indices, and prolongs the survival time in acute uremic pigs with multiple organ dysfunction syndrome (MODS).

METHODS

Hybridized pigs suffering from MODS and acute renal failure (ARF) were treated with BAK (Group A, n=6) or sham-BAK containing no cells (Group B, n=6), or received no treatment (Group C, n=5). Data on blood pressure, hepatic and renal function, IL-10, TNF-α, arterial blood gas, and survival time of all the pigs was recorded.

RESULTS

Mean arterial pressure (MAP, mmHg) responded more rapidly and reached higher values in Group A (91.82 ± 5.73) compared with Groups B and C at 24 hours (p<0.01). The peak level of serum IL-10 (pg/mL) in Group A (249.57 ± 43.51) was significantly higher than in Groups B and C (132.06 ± 17.53, 104.25 ± 13.42, p<0.01). Serum TNF-α level (pg/mL) in Group A dropped gradually to 402.91 ± 32.47 at 24 hours, and showed a significant discrepancy compared with those before treatment (537.16 ± 38.45) and Group B (512.94 ± 19.5, p<0.05). There was no difference in plasma endotoxin and serum IL-6 between pre-treatment and post-treatment in Groups A and B. BAK treatment, however, resulted in a significant decline in IL-6/IL-10 ratios. The average survival time (hours) in Group A (113.01 ± 14.32) was significantly longer, prolonged by 35.93% and 63.90% compared to Groups B and C (p<0.01), respectively.

CONCLUSIONS

The addition of renal tubule cell therapy to hemofiltration in an acutely uremic animal model with MODS altered systemic cytokine balance, ameliorated MAP, and prolonged survival time.

Paracrine effects of mesenchymal stem cells in cisplatin-induced renal injury require heme oxygenase-1

Multipotent mesenchymal stem cells (MSC) have become a popular and promising therapeutic approach in many clinical conditions. MSC are beneficial in animal models of acute kidney injury (AKI), by mediating differentiation-independent paracrine properties, and have prompted ongoing clinical trials to evaluate the safety and efficacy of MSC. Heme oxygenase-1 (HO-1) is induced in response to stress including AKI and has important anti-apoptotic, anti-inflammatory, and proangiogenic properties in these settings. We therefore examined whether HO-1 plays a role in the beneficial effects of MSC in AKI. We isolated MSC from bone marrow of age-matched HO-1+/+ and HO-1-/- mice. Our studies indicate that while differentiation of MSC into osteo- and adipocytic lineages did not differ between cells isolated from HO-1+/+ and HO-1-/- mice, MSC from HO-1-/- mice had significantly lower angiogenic potential. Moreover, HO-1-/- MSC demonstrated reduced expression and secretion of several important growth and proangiogenic factors (stromal cell-derived factor-1, vascular endothelial growth factor-A, and hepatocyte growth factor) compared with MSC derived from HO-1+/+ mice. In addition, conditioned medium of HO-1+/+ MSC rescued functional and morphological changes associated with cisplatin-induced AKI, while the HO-1-/--conditioned medium was ineffectual. Our studies indicate that HO-1 plays an important role in MSC-mediated protection. The results expand understanding of the renoprotective effects of MSC and may provide novel strategies to better utilize MSC in various disease models.

Acute kidney injury after trauma: Prevalence, clinical characteristics and RIFLE classification

BACKGROUND

Acute kidney injury (AKI) is an uncommon but serious complication after trauma. The objective of this study was to evaluate the prevalence, clinical characteristics and outcome of AKI after trauma.

PATIENTS AND METHODS

This was a retrospective study performed from January 2006 to January 2008 in an emergency specialized hospital in Fortaleza city, northeast of Brazil. All patients with AKI admitted in the study period were included. Prevalence of AKI, clinical characteristics and outcome were investigated.

RESULTS

Of the 129 patients admitted to the intensive care unit (ICU), 52 had AKI. The mean age was 30.1 ± 19.2 years, and 79.8% were males. The main causes of AKI were sepsis in 27 cases (52%) and hypotension in 18 (34%). Oliguria was observed in 33 cases (63%). Dialysis was required for 19 patients (36.5%). Independent risk factors associated with AKI were abdominal trauma [odds ratio (OR) = 3.66, P = 0.027] and use of furosemide (OR = 4.10, P = 0.026). Patients were classified according to RIFLE criteria as Risk in 12 cases (23%), Injury in 13 (25%), Failure in 24 (46%), Loss in 1 (2%) and End-stage in 2 (4%). Overall in-hospital mortality was 95.3%. The main cause of death was sepsis (24%). Mortality was 100% among patients with AKI.

CONCLUSIONS

AKI is a fatal complication after trauma, which presented with a high mortality in the studied population. A better comprehension of factors associated with death in trauma-associated AKI is important, and more effective measures of prevention and treatment of AKI in this population are urgently needed.