Acute kidney injury in elderly persons

Acute kidney injury induced by antimicrobial agents in the elderly: awareness and mitigation strategies

The use of antimicrobial agents has increased in recent years as treatments have diversified and resistant bacteria have appeared. With increased use of antimicrobial agents, elderly patients are prone to adverse drug reactions (ADRs) as a result of factors such as drug-drug interactions, polypharmacy, long-term use, and over- or under-dosage. In particular, elderly patients using antimicrobials are at increased risk to develop drug-induced acute kidney injury (AKI), which is the most common severe ADR in such patients. AKI is a serious problem that is associated with mortality amongst hospitalized patients. Antimicrobial-induced AKI can be classified into three different types: acute tubular necrosis (ATN), acute interstitial nephritis (AIN), and renal tubule lumen obstruction. AKI can generally be prevented by proper maintenance of fluid balance. To design dosage regimens that ensure efficient drug excretion via the kidney, it is necessary to accurately estimate renal function; however, the kidney undergoes age-dependent structural and functional alterations over time. Therefore, proper management of antimicrobial agents by an antimicrobial stewardship team may lead to decreased incidence of AKI. This article reviews antimicrobial-induced AKI and discusses potential strategies for increasing awareness of AKI and mitigating its clinical effects.

Effects of acute kidney injury on clinical outcomes in patients with upper gastrointestinal bleeding

AIM

Upper gastrointestinal bleeding (UGIB) is a very frequently encountered condition that has a high morbidity and which increases treatment costs. Duration of hospital stay and mortality increases in patients with UGIB complicated by acute kidney injury (AKI). The aim of this study was to reveal risk factors in patients with UGIB developing AKI and to compare clinical outcomes and hospital costs between patients with UGIB developing AKI and those with UGIB not developing AKI.

MATERIAL AND METHODS

This retrospective study included 245 patients admitted to the emergency unit and the intensive care unit for internal diseases at Ankara Numune Education and Research Hospital, Turkey.

RESULTS

The difference in mortality rates between the patients with AKI and those without AKI was significant (p < 0.001). The mean duration of intensive care unit stay was 0.2 ± 1.1 days in the patients without AKI (n = 143) and 2.5 ± 5.6 days in the patients with AKI. It was significantly higher in the patients with AKI (p < 0.001). Hospital stay was significantly longer in the patients with AKI than those without AKI, and as severity of AKI increased, hospital stay became considerably longer (p < 0.001). Hospital costs were significantly higher in the patients with AKI than those without AKI, and as severity of AKI increased, hospital costs considerably rose (p < 0.001).

CONCLUSION

AKI is a condition that lengthens hospital stay, increases hospital costs and creates a burden on health care systems. Detect kidney injury earlier and administering an appropriate treatment can improve clinical outcomes in patients with UGIB developing AKI.

The severity of initial acute kidney injury at admission of geriatric patients significantly correlates with subsequent in-hospital complications

Acute kidney injury (AKI) is associated with higher hospital mortality. However, the relationship between geriatric AKI and in-hospital complications is unclear. We prospectively enrolled elderly patients (≥65 years) from general medical wards of National Taiwan University Hospital, part of whom presented AKI at admission. We recorded subsequent in-hospital complications, including catastrophic events, incident gastrointestinal bleeding, hospital-associated infections, and new-onset electrolyte imbalances. Regression analyses were utilized to assess the associations between in-hospital complications and the initial AKI severity. A total of 163 elderly were recruited, with 39% presenting AKI (stage 1: 52%, stage 2: 23%, stage 3: 25%). The incidence of any in-hospital complication was significantly higher in the AKI group than in the non-AKI group (91% vs. 68%, p < 0.01). Multiple regression analyses indicated that elderly patients presenting with AKI had significantly higher risk of developing any complication (Odds ratio [OR] = 3.51, p = 0.01) and new-onset electrolyte imbalance (OR = 7.1, p < 0.01), and a trend toward more hospital-associated infections (OR = 1.99, p = 0.08). The risk of developing complications increased with higher AKI stage. In summary, our results indicate that initial AKI at admission in geriatric patients significantly increased the risk of in-hospital complications.

RIFLE classification in geriatric patients with acute kidney injury in the intensive care unit

BACKGROUND

The RIFLE classification is widely used to assess the severity of acute kidney injury (AKI), but its application to geriatric AKI patients complicated by medical problems has not been reported.

METHODS

We investigated 256 geriatric patients (≥65 years old; mean age, 74.4 ± 6.3 years) who developed AKI in the intensive care unit (ICU) according to the RIFLE classification. Etiologic, clinical, and prognostic variables were analyzed.

RESULTS

They were categorized into RIFLE-R (n = 53), RIFLE-I (n = 102), and RIFLE-F (n = 101) groups. The overall in-hospital mortality was 39.8 %. There were no significant differences in RIFLE category between survivors and non-survivors. Survivors had significantly less needs for a ventilator and vasopressor, and lower number of failing organs. Survivors had higher systolic blood pressure, hemoglobin level, and serum albumin levels. We performed a logistic regression analysis to identify the independent predictors of in-hospital mortality. In a univariate analysis, hypertension, chronic kidney disease, RIFLE classification, number of failing organs, need for a ventilator and vasopressor, systolic blood pressure, hemoglobin level, and serum albumin levels were identified as prognostic factors of in-hospital mortality. However, in a multivariate analysis, hypertension, chronic kidney disease, number of failing organs, and serum albumin levels were independent risk factors, with no significant difference for in-hospital mortality with the RIFLE classification.

CONCLUSION

The RIFLE classification might not be associated with mortality in geriatric AKI patients in the ICU. In geriatric patients with AKI, various factors besides severity of AKI should be considered to predict mortality.

Role of NLRP3 Inflammasomes for Rhabdomyolysis-induced Acute Kidney Injury

Rhabdomyolysis is one of the main causes of community-acquired acute kidney injury (AKI). Although inflammation is involved in the pathogenesis of rhabdomyolysis-induced AKI (RIAKI), little is known about the mechanism that triggers inflammation during RIAKI. Recent evidence has indicated that sterile inflammation triggered by tissue injury can be mediated through multiprotein complexes called the inflammasomes. Therefore, we investigated the role of NLRP3 inflammasomes in the pathogenesis of RIAKI using a glycerol-induced murine rhabdomyolysis model. Inflammasome-related molecules were upregulated in the kidney of RIAKI. Renal tubular injury and dysfunction preceded leukocyte infiltration into the kidney during the early phase of RIAKI, and they were markedly attenuated in mice deficient in NLRP3, ASC, caspase-1, and interleukin (IL)-1β compared with those in wild-type mice. No difference in leukocyte infiltration was observed between wild-type and NLRP3-deficient mice. Furthermore, NLRP3 deficiency strikingly suppressed the expression of renal injury markers and inflammatory cytokines and apoptosis of renal tubular cells. These results demonstrated that NLRP3 inflammasomes contribute to inflammation, apoptosis, and tissue injury during the early phase of RIAKI and provide new insights into the mechanism underlying the pathogenesis of RIAKI.

Early mortality in dialysis and adequacy of predialysis renal care: the picture is more complex than we thought

Two new studies examine clinical events during early dialysis. Foley et al. underline a probable ascertainment bias affecting the mortality rate during the first 6 weeks and find that age is the major risk factor for very early mortality, which can be amplified by short time of predialysis nephrology care. Singhal et al. show that adequacy of predialysis renal care is determined not only by the timing of the nephrology referral but also by the number and timing of visits.

Role of COX-2/mPGES-1/prostaglandin E2 cascade in kidney injury

COX-2/mPGES-1/PGE2 cascade plays critical roles in modulating many physiological and pathological actions in different organs. In the kidney, this cascade is of high importance in regulating fluid metabolism, blood pressure, and renal hemodynamics. Under some disease conditions, this cascade displays various actions in response to the different pathological insults. In the present review, the roles of this cascade in the pathogenesis of kidney injuries including diabetic and nondiabetic kidney diseases and acute kidney injuries were introduced and discussed. The new insights from this review not only increase the understanding of the pathological role of the COX-2/mPGES-1/PGE2 pathway in kidney injuries, but also shed new light on the innovation of the strategies for the treatment of kidney diseases.

Blood HCO3 - concentration predicts the long-term prognosis of acute kidney injury patients

Aim: To evaluate the value of HCO3 - concentrations in long-term prognosis after acute kidney injury. Patients & methods: A total of 169 AKI patients were included in this study. At the 12‐month follow-up, the patients were divided into recovered and unrecovered groups. Results: The blood HCO3 - concentrations were significantly correlated with poor prognosis. The area under the curve for renal prognosis of 6 months later blood HCO3 - concentrations was 0.798. Combined HCO3 - and Scr level area under the curve was 0.952. Conclusion: The blood HCO3 - level was useful in evaluating renal prognosis of acute kidney injury patients. The combination of blood HCO3 - concentration and Scr level increased the accuracy of prediction.

Effect of aging on renal function plus monitoring and support

Several anatomic changes and physiologic alterations occur in the aging kidney, awareness of which is essential for the early recognition of acute kidney injury (AKI) to improve outcomes in hospitalized geriatric patients. There are no unique diagnostic methods or treatment modalities in the care of the geriatric patient with AKI. Therapy is mainly supportive, and the full spectrum of treatment options, including renal replacement therapy (RRT), should not be withheld from a patient based on age. More studies need to be performed to determine the optimal timing, intensity, and modality of RRT in the geriatric population.

The aging kidney: increased susceptibility to nephrotoxicity

Three decades have passed since a series of studies indicated that the aging kidney was characterized by increased susceptibility to nephrotoxic injury. Data from these experimental models is strengthened by clinical data demonstrating that the aging population has an increased incidence and severity of acute kidney injury (AKI). Since then a number of studies have focused on age-dependent alterations in pathways that predispose the kidney to acute insult. This review will focus on the mechanisms that are altered by aging in the kidney that may increase susceptibility to injury, including hemodynamics, oxidative stress, apoptosis, autophagy, inflammation and decreased repair.

Increased risk of acute kidney injury associated with higher infusion rate of mannitol in patients with intracranial hemorrhage

Object

Mannitol, an osmotic agent used to decrease intracranial pressure, can cause acute kidney injury (AKI). The objectives of this study were to assess the impact of mannitol on the incidence and severity of AKI and to identify risk factors and outcome for AKI in patients with intracranial hemorrhage (ICH).

Methods

The authors retrospectively evaluated 153 adult patients who received mannitol infusion after ICH between January 2005 and December 2009 in the neurosurgical intensive care unit. Multivariate analysis was used to evaluate the risk factors for AKI after ICH. Based on the odds ratio, weighted scores were assigned to predictors of AKI.

Results

The overall incidence of AKI among study participants was 10.5% (n = 16). Acute kidney injury occurred more frequently in patients who received mannitol infusion at a rate ≥ 1.34 g/kg/day than it did in patients who received mannitol infusion at a rate < 1.34 g/kg/day. A higher mannitol infusion rate was associated with more severe AKI. Independent risk factors for AKI were mannitol infusion rate ≥ 1.34 g/kg/day, age ≥ 70 years, diastolic blood pressure (DBP) ≥ 110 mm Hg, and glomerular filtration rate < 60 ml/min/1.73 m2. The authors developed a risk model for AKI, wherein patients with a higher risk score showed a graded association with a higher incidence of AKI.

Conclusions

The incidence of AKI following mannitol infusion in patients with ICH was 10.5%. A higher mannitol infusion rate was associated with more frequent and more severe AKI. Additionally, age ≥ 70 years, DBP ≥ 110 mm Hg, and established renal dysfunction before starting mannitol therapy were associated with development of AKI.

Epidemiology and outcomes in community-acquired versus hospital-acquired AKI

BACKGROUND AND OBJECTIVE

Compared with AKI in hospitalized patients, little is known about patients sustaining AKI in the community and how this differs from AKI in hospital. This study compared epidemiology, risk factors, and short- and long-term outcomes for patients with community-acquired (CA) and hospital-acquired (HA) AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 15,976 patients admitted to two district general hospitals between July 11, 2011, and January 15, 2012 were studied. Through use of an electronic database and the AKI Network classification, 686 patients with CA-AKI and 334 patients with HA-AKI were identified. Patients were followed up for 14 months, and data were collated on short-term and long-term renal and patient outcomes.

RESULTS

The incidence of CA-AKI among all hospital admissions was 4.3% compared with an incidence of 2.1% of HA-AKI, giving an overall AKI incidence of 6.4%. Patients with CA-AKI were younger than patients with HA-AKI. Risks for developing HA and CA-AKI were similar and included preexisting CKD, cardiac failure, ischemic heart disease, hypertension, diabetes, dementia, and cancer. Patients with CA-AKI were more likely to have stage 3 AKI and had shorter lengths of hospital stay than patients with HA-AKI. Those with CA-AKI had better (multivariate-adjusted) survival than patients with HA-AKI (hazard ratio, 1.8 [95% CI, 1.44-2.13; P<0.001] for HA-AKI group). Mortality for the CA-AKI group was 45%; 43.7% of these deaths were acute in-hospital deaths. Mortality for the HA-AKI group was 62.9%, with 68.1% of these deaths being acute in-hospital deaths. Renal referral rates were low across the cohorts (8.3%). Renal outcomes were similar in both CA-AKI and HA-AKI groups, with 39.4% and 33.6% of patients in both groups developing de novo CKD or progression of preexisting CKD within 14 months, respectively.

CONCLUSION

Patients with CA-AKI sustain more severe AKI than patients with HA-AKI. Despite having risk factors similar to those of patients with HA-AKI, patients with CA AKI have better short- and long-term outcomes.

Hemojuvelin modulates iron stress during acute kidney injury: improved by furin inhibitor

AIMS

Free iron plays an important role in the pathogenesis of acute kidney injury (AKI) via the formation of hydroxyl radicals. Systemic iron homeostasis is controlled by the hemojuvelin-hepcidin-ferroportin axis in the liver, but less is known about this role in AKI.

RESULTS

By proteomics, we identified a 42 kDa soluble hemojuvelin (sHJV), processed by furin protease from membrane-bound hemojuvelin (mHJV), in the urine during AKI after cardiac surgery. Biopsies from human and mouse specimens with AKI confirm that HJV is extensively increased in renal tubules. Iron overload enhanced the expression of hemojuvelin-hepcidin signaling pathway. The furin inhibitor (FI) decreases furin-mediated proteolytic cleavage of mHJV into sHJV and augments the mHJV/sHJV ratio after iron overload with hypoxia condition. The FI could reduce renal tubule apoptosis, stabilize hypoxic induced factor-1, prevent the accumulation of iron in the kidney, and further ameliorate ischemic-reperfusion injury. mHJV is associated with decreasing total kidney iron, secreting hepcidin, and promoting the degradation of ferroportin at AKI, whereas sHJV does the opposite.

INNOVATION

This study suggests the ratio of mHJV/sHJV affects the iron deposition during acute kidney injury and sHJV could be an early biomarker of AKI.

CONCLUSION

Our findings link endogenous HJV inextricably with renal iron homeostasis for the first time, add new significance to early predict AKI, and identify novel therapeutic targets to reduce the severity of AKI using the FI.

How good are we at managing acute kidney injury in hospital?

Introduction

Acute kidney injury (AKI) is a common clinical problem associated with adverse outcomes. This study identifies the incidence of AKI in two UK district general hospitals' without on-site renal services and assesses AKI management and level of nephrologist input.

Methods

The AKIN classification was used to identify 1020 AKI patients over 6 months. Data were collated on patient demographics, AKI management and referral to nephrology and intensive care services. Short/long-term renal outcomes were investigated. Patients were followed up for 14 months post-discharge.

Results

Incidence of hospital-based AKI was 6.4%. Mean patient age was 73 years. There was 28.1% acute in-hospital mortality with a further 21.6% 14-month mortality. Only 8.3% of patients were referred to nephrology services for in-hospital review, and only 8.1% had outpatient nephrology follow-up. Compliance with the AKI National Confidential Enquiry into Patient Outcomes and Deaths (NCEPOD) recommendations was poor with 32.8% of patients having renal imaging and 15% of patients having acid–base status assessed. NCEPOD compliance improved with nephrology input. Patients referred to nephrology were likely to be younger with pre-existing CKD and severe AKI. 10.5% of AKI episodes were unrecognized. Forty percent of those with unrecognized AKI, (compared with 15% of recognized AKI) developed de novo or progression of pre-existing CKD.

Conclusion

AKI in DGHs is mostly managed without nephrology input. There are significant shortcomings in AKI recognition and management in this setting. This is associated with poor mortality and long-term CKD. This study supports a need to improve the teaching and training of front-line medical staff in identifying AKI. Additionally, implementation of AKI e-alert systems may encourage early recognition and provide a prompt for renal referral.

New tides: using zebrafish to study renal regeneration

Over the past several decades, the zebrafish has become one of the major vertebrate model organisms used in biomedical research. In this arena, the zebrafish has emerged as an applicable system for the study of kidney diseases and renal regeneration. The relevance of the zebrafish model for nephrology research has been increasingly appreciated as the understanding of zebrafish kidney structure, ontogeny, and the response to damage has steadily expanded. Recent studies have documented the amazing regenerative characteristics of the zebrafish kidney, which include the ability to replace epithelial populations after acute injury and to grow new renal functional units, termed nephrons. Here we discuss how nephron composition is conserved between zebrafish and mammals, and highlight how recent findings from zebrafish studies utilizing transgenic technologies and chemical genetics can complement traditional murine approaches in the effort to dissect how the kidney responds to acute damage and identify therapeutics that enhance human renal regeneration.

Acute kidney injury, sodium disorders, and hypercalcemia in the aging kidney: diagnostic and therapeutic management strategies in emergency medicine

This article summarizes the current literature regarding the structural and functional changes of the aging kidney and describes how these changes make the older patient more susceptible to acute kidney injury and fluid and electrolyte disorders. It discusses the clinical manifestations, evaluation, and management of hyponatremia and shows how the management of hypernatremia in geriatric patients involves addressing the underlying cause and safely correcting the hypernatremia. The current literature regarding evaluation and management of hypercalcemia in older patients is summarized. The management of severe hypercalcemia is discussed in detail. The evaluation and management of acute kidney injury is described.

The clinical features and outcome of crush patients with acute kidney injury after the Wenchuan earthquake: differences between elderly and younger adults

BACKGROUND

On May 12, 2008, a devastating earthquake hit Wenchuan county of China's Sichuan province. Acute kidney injury (AKI) is one of the most lethal but reversible complications of crush syndrome after an earthquake. However, little is known about the epidemiological features of elderly crush patients with AKI. The aim of the present study is to compare clinical features and outcome of crush related AKI between elderly and younger adults in the Wenchuan earthquake.

MATERIALS AND METHODS

A questionnaire was sent to 17 reference hospitals that treated the victims after the earthquake. Clinical and laboratory characteristics of crush patients with AKI were retrospectively analysed.

RESULTS

228 victims experienced crush related AKI, of which 211 were adults, including 45 elderly (age ≥ 65 years) and 166 younger adults (age, 15-64 years). Compared with the resident population, the percentage of patients was higher amongst elderly (19.7% versus 7.6%, P<0.001). The distribution of gender was similar in elderly and younger adults. Mean systolic blood pressure was higher in elderly groups. Although no statistical differences in number of injury and injury severity score were observed between elderly and younger adults, elderly victims had lower frequency of extremities crush injury; higher incidences of thoracic traumas, limb, rib, and vertebral fractures; lower serum creatinine, potassium and creatinine kinase levels; lower incidence of oliguria or anuria; lower dialysis requirement; underwent less fasciotomies and amputations, received less blood and plasma transfusions. Mortality were 17.8% and 10.2% in elderly and younger adults, respectively (P=0.165). Stratified analysis demonstrated the elderly receiving dialysis had higher mortality rate compared with younger patients (62.5% versus 10.5%, P<0.001). Multivariate logistic regression analysis indicated that need for dialysis and sepsis were independent risk factors for death in the elderly patients.

CONCLUSIONS

Elderly crush victims more frequently developed AKI in the Wenchuan earthquake, and they differ from younger adults in injury patterns and treatment modalities. The elderly patients with AKI requiring dialysis were at a relatively high risk of mortality.

Epidemiology of postoperative acute kidney injury in Hungarian intensive care units: an exploratory analysis

BACKGROUND

The aim of this study was to evaluate the incidence and outcome of postoperative acute kidney injury (AKI) after major noncardiac surgery in Hungarian intensive care units (ICUs).

METHODS

We conducted an analysis of a multicenter survey on the epidemiology of AKI in Hungarian ICUs in respect of surgical interventions. The cohort study consisted of all patients (n = 295) over the age of 18 years who were admitted to ICUs after surgery between 1 October 2009 and 30 November 2009. AKI was defined and classified by the acute kidney injury network (AKIN) criteria.

RESULTS

Forty-eight (18.1%) patients had AKI during their ICU stay. By AKIN criteria, 27 (10.2%) patients were in stage 1, 11 (4.2%) patients in stage 2, and 10 (3.8%) patients in stage 3. The overall mortality rate of AKI was 39.6% (AKI 1: 25.9%, AKI 2: 40%, and AKI 3: 54.5%; p < 0.001) and the ICU mortality rate was 33.3% (AKI 1: 18.5%, AKI 2: 10%, and AKI 3: 54.5%; p < 0.001). According to logistic regression analysis, age (OR: 1.048; CI: 1.014-1.082; p = 0.005), vasopressor treatment (OR: 9.751; CI: 8.579-10.923; p < 0.001), sepsis (OR: 10.791; CI: 9.353-12.233; p = 0.001), serum-creatinine peak-concentration (OR: 1.035; CI: 1.021-1.047; p < 0.001), and intra-abdominal surgery (OR: 2.558; CI: 1.75-3.366; p = 0.020) were independent predictors for AKI.

CONCLUSIONS

The results of this study confirm that there is a high incidence of AKI following major noncardiac surgery, which is associated with higher ICU and in-hospital mortality.

Recent advances in acute kidney injury epidemiology

PURPOSE OF REVIEW

Expanding rates of acute kidney injury (AKI) coupled with increasing awareness of its short-term and long-term sequelae have focused efforts to identify patients at risk for this disease and its complications. This review details the recent attempts to identify novel risk factors for AKI, describes further refinements in the diagnostic and prognostic approach using biological markers of injury, and highlights the features of AKI that independently predict poor long-term outcomes.

RECENT FINDINGS

The presence of proteinuria predicts the development of AKI independently of estimated glomerular filtration rate. Initial results from a large prospective study of AKI biomarkers in cardiac surgery indicate lower agreement with serum creatinine as an AKI standard than observed in early studies. AKI severity and duration are important predictors of chronic kidney disease and long-term mortality. A minority of patients surviving AKI with decreased kidney function is seen by a nephrologist.

SUMMARY

Although the pathophysiologic link is unclear, proteinuria is an easily measurable risk factor for AKI worth considering before anticipated procedures or medication exposures carrying nephrologic risk. Investigation extending beyond agreement with serum creatinine is needed to fully understand the diagnostic and prognostic value of AKI biomarkers. Severity and duration are components of AKI that can help risk-stratify survivors in need of monitoring or nephrology referral.

Loss of calpain 10 causes mitochondrial dysfunction during chronic hyperglycemia

We showed that renal calpain 10, a mitochondrial and cytosolic Ca(2+)-regulated cysteine protease, is specifically decreased in kidneys of diabetic rats and mice, and is associated with diabetic nephropathy. The goals of this study were to examine renal calpain 10 and mitochondrial dysfunction in streptozotocin-induced hyperglycemic rats and determine the effects of siRNA-mediated knock down of renal calpain 10 on mitochondrial function. Four weeks after streptozotocin injection, calpain 10 protein and mRNA were decreased and calpain 10 substrates accumulated. We detected increased state 2 respiration in isolated renal mitochondria and increased markers of mitochondrial fission and mitophagy. All changes were prevented by daily insulin injection. Compared to scrambled siRNA, calpain 10 siRNA resulted in a marked decrease in renal calpain 10 at 2, 5 and 7 days. In concert with the loss of renal calpain 10, calpain 10 substrates accumulated, mitochondrial fusion decreased, mitochondrial fission and mitophagy increased. In summary, insulin-sensitive hyperglycemia induced loss of renal calpain 10 is correlated with renal mitochondrial dysfunction, fission and mitophagy, and specific depletion of renal calpain 10 produces similar mitochondrial defects. These results provide evidence that diabetes-induced renal mitochondrial dysfunction and renal injury may directly result from the loss of renal calpain 10.

Advanced age affects the outcome-predictive power of RIFLE classification in geriatric patients with acute kidney injury

The RIFLE (risk, injury, failure, loss, and end-stage) classification is widely used to gauge the severity of acute kidney injury, but its efficacy has not been formally tested in geriatric patients. To correct this we conducted a prospective observational study in a multicenter cohort of 3931 elderly patients (65 years of age or older) who developed acute kidney injury in accordance with the RIFLE creatinine criteria after major surgery. We studied the predictive power of the RIFLE classification for in-hospital mortality and investigated the potential interaction between age and RIFLE classification. In general, the survivors were significantly younger than the nonsurvivors and more likely to have hypertension. In patients 76 years of age and younger, RIFLE-R, -I, or -F classifications were significantly associated with increased hospital mortality in a stepwise manner. There was no significant difference, however, in hospital mortality in those over 76 years of age between patients with RIFLE-R and RIFLE-I, although RIFLE-F patients had significantly higher mortality than both groups. Thus, the less severe categorizations of acute kidney injury per RIFLE classification may not truly reflect the adverse impact on elderly patients.

Elderly patients with acute kidney injury (AKI): clinical features and risk factors for mortality

PURPOSE

Elderly patients with AKI are associated with considerable mortality. The clinical features and risk factors predicting poor outcomes of these patients are not known. The aim of this study is to investigate the clinical features and risk factors affecting mortality in elderly patients with AKI.

METHODS

A prospective study on the elderly patients with AKI (age ≥65 years old) was conducted. A consecutive sample of 99 elderly patients with AKI was evaluated. These patients were divided into survivor group and non-survivor group according their outcomes. Factors including clinical characteristics and laboratory features were compared between these two groups. Analysis of correlations between death and categorized risk factors was done by means of Pearson's chi-squared test (or Fisher's exact test). Multivariate logistic regression was performed to analyze the possible risk factors for death.

RESULTS

The main causes of the elderly patients with AKI were ischemia (53.34%), surgery (33.33%), sepsis/infection (10.10%), nephrotoxic drug (3.03%). The mortality rate of the elderly patients with AKI was 42%. Significant differences were found between the survival group and non-survival group of the elderly patients in concomitant disease, complicated with multiple organ dysfunction syndrome (MODS), albumin, etc. Concomitant disease and MODS were found to be the independent risk factors for death of the elderly patients with AKI after adjusting for age, sex, pre-albumin, sepsis/infection, and serum creatinine (SCr).

CONCLUSION

This study found that concomitant disease and MODS were the independent risk factors for the death of elderly patients with AKI.

Calpains, mitochondria, and apoptosis

Mitochondrial activity is critical for efficient function of the cardiovascular system. In response to cardiovascular injury, mitochondrial dysfunction occurs and can lead to apoptosis and necrosis. Calpains are a 15-member family of Ca(2+)-activated cysteine proteases localized to the cytosol and mitochondria, and several have been shown to regulate apoptosis and necrosis. For example, in endothelial cells, Ca(2+) overload causes mitochondrial calpain 1 cleavage of the Na(+)/Ca(2+) exchanger leading to mitochondrial Ca(2+) accumulation. Also, activated calpain 1 cleaves Bid, inducing cytochrome c release and apoptosis. In renal cells, calpains 1 and 2 promote apoptosis and necrosis by cleaving cytoskeletal proteins, which increases plasma membrane permeability and cleavage of caspases. Calpain 10 cleaves electron transport chain proteins, causing decreased mitochondrial respiration and excessive activation, or inhibition of calpain 10 activity induces mitochondrial dysfunction and apoptosis. In cardiomyocytes, calpain 1 activates caspase 3 and poly-ADP ribose polymerase during tumour necrosis factor-α-induced apoptosis, and calpain 1 cleaves apoptosis-inducing factor after Ca(2+) overload. Many of these observations have been elucidated with calpain inhibitors, but most calpain inhibitors are not specific for calpains or a specific calpain family member, creating more questions. The following review will discuss how calpains affect mitochondrial function and apoptosis within the cardiovascular system.

[Acute kidney injury]

Acute kidney injury plays a pivotal role in intensive care medicine and exerts crucial adverse effects on the course of the disease and overall prognosis of the critically ill patient. Intensive renal support, including initiation of earlier dialysis or maximal uremic toxin removal by higher dosage and frequency of renal replacement therapy, and individualized selection of modality were not able to decrease excessive mortality in this population. Systemic acute inflammation, mediated, at least in part, by cytokines, and not secondary uremic side effects, seems to have a major impact on nonrenal organ damage. Assessment of short-term outcome in critically ill patients who develop acute kidney injury may underestimate the true burden of disease. The overall survival at 5 years in patients discharged alive after severe acute kidney injury necessitating renal replacement therapy is only 20-30%, comparable to cancer patients. In addition, acute renal damage was identified as an independent risk factor for progression of chronic renal insufficiency. Current research focuses on strategies for the prevention of acute kidney injury and on the establishment of effective biomarkers for the early recognition and accurate diagnosis of subclinical renal damage.

Epidemiology of acute kidney injury in Hungarian intensive care units: a multicenter, prospective, observational study

Background

Despite the substantial progress in the quality of critical care, the incidence and mortality of acute kidney injury (AKI) continues to rise during hospital admissions. We conducted a national, multicenter, prospective, epidemiological survey to evaluate the importance of AKI in intensive care units (ICUs) in Hungary. The objectives of this study were to determine the incidence of AKI in ICU patients; to characterize the differences in aetiology, illness severity and clinical practice; and to determine the influencing factors of the development of AKI and the patients' outcomes.

Methods

We analysed the demographic, morbidity, treatment modality and outcome data of patients (n = 459) admitted to ICUs between October 1^st, 2009 and November 30^th, 2009 using a prospectively filled in electronic survey form in 7 representative ICUs.

Results

The major reason for ICU admission was surgical in 64.3% of patients and medical in the remaining 35.7%. One-hundred-twelve patients (24.4%) had AKI. By AKIN criteria 11.5% had Stage 1, 5.4% had Stage 2 and 7.4% had Stage 3. In 44.0% of patients, AKI was associated with septic shock. Vasopressor treatment, SAPS II score, serum creatinine on ICU admission and sepsis were the independent risk factors for development of any stage of AKI. Among the Stage 3 patients (34) 50% received renal replacement therapy. The overall utilization of intermittent renal replacement therapy was high (64.8%). The overall in-hospital mortality rate of AKI was 49% (55/112). The ICU mortality rate was 39.3% (44/112). The independent risk factors for ICU mortality were age, mechanical ventilation, SOFA score and AKI Stage 3.

Conclusions

For the first time we have established the incidence of AKI using the AKIN criteria in Hungarian ICUs. Results of the present study confirm that AKI has a high incidence and is associated with high ICU and in-hospital mortality.

Pathophysiology of ischemic acute kidney injury

Acute kidney injury (AKI) as a consequence of ischemia is a common clinical event leading to unacceptably high morbidity and mortality, development of chronic kidney disease (CKD), and transition from pre-existing CKD to end-stage renal disease. Data indicate a close interaction between the many cell types involved in the pathophysiology of ischemic AKI, which has critical implications for the treatment of this condition. Inflammation seems to be the common factor that links the various cell types involved in this process. In this Review, we describe the interactions between these cells and their response to injury following ischemia. We relate these events to patients who are at high risk of AKI, and highlight the characteristics that might predispose these patients to injury. We also discuss how therapy targeting specific cell types can minimize the initial and subsequent injury following ischemia, thereby limiting the extent of acute changes and, hopefully, long-term structural and functional alterations to the kidney.

Impaired endothelial proliferation and mesenchymal transition contribute to vascular rarefaction following acute kidney injury

Acute kidney injury induces the loss of renal microvessels, but the fate of endothelial cells and the mechanism of potential vascular endothelial growth factor (VEGF)-mediated protection is unknown. Cumulative cell proliferation was analyzed in the kidney of Sprague-Dawley rats following ischemia-reperfusion (I/R) injury by repetitive administration of BrdU (twice daily) and colocalization in endothelial cells with CD31 or cablin. Proliferating endothelial cells were undetectable for up to 2 days following I/R and accounted for only ∼1% of BrdU-positive cells after 7 days. VEGF-121 preserved vascular loss following I/R but did not affect proliferation of endothelial, perivascular cells or tubular cells. Endothelial mesenchymal transition states were identified by localizing endothelial markers (CD31, cablin, or infused tomato lectin) with the fibroblast marker S100A4. Such structures were prominent within 6 h and sustained for at least 7 days following I/R. A Tie-2-cre transgenic crossed with a yellow fluorescent protein (YFP) reporter mouse was used to trace the fate of endothelial cells and demonstrated interstititial expansion of YFP-positive cells colocalizing with S100A4 and smooth muscle actin following I/R. The interstitial expansion of YFP cells was attenuated by VEGF-121. Multiphoton imaging of transgenic mice revealed the alteration of YFP-positive vascular cells associated with blood vessels characterized by limited perfusion in vivo. Taken together, these data indicate that vascular dropout post-AKI results from endothelial phenotypic transition combined with an impaired regenerative capacity, which may contribute to progressive chronic kidney disease.