Epidemiology and Outcome in Renal Failure

Acute kidney injury is a powerful independent predictor of mortality in critically ill patients: a multicenter prospective cohort study from Kinshasa, the Democratic Republic of Congo

Background

Despite the growing incidence of acute kidney injury (AKI) worldwide, there is little data on the burden and outcomes of AKI in intensive care unit (ICU) in low resource settings. The present study assessed the incidence of AKI and its impact on mortality in ICU in Kinshasa (Democratic Republic of Congo).

Methods

In a prospective cohort study, 476 consecutive critically ill patients (mean age 52 years, 57 % male) were screened for the presence of AKI in seven ICU from January 1st to March 30th, 2015. Serum creatinine was measured by the enzymatic method (Cobas C111 device®). AKI and its stages (no AKI, AKI 1, AKI 2 and AKI 3) were defined according to AKIN recommendations. The primary outcome was 28 days mortality. Survival (time-to death) curves were built using the Kaplan Meier methods. Predictors of mortality were assessed by Cox proportional hazards regression models. p < 0.05 defined the level of statistical significance.

Results

The cumulative incidence of AKI was 52.7 % with AKI stage 1, 2 and 3 in 23.7 %, 16.2 % and 12.8 % of patients, respectively. Among patients who developed AKI, 146 died (58 %) vs 62 patients (28 %) in the group without AKI. Only 6.5 % of the patients with AKI stage 3 benefited from dialysis. Median survival time was 15.0 days in patients without AKI and 3.0 days, 6.0 days and 8.0 days in patients with AKI stage 3, 2 and 1 (p < 0.001), respectively. In addition to respiratory distress-induced polypnea (HRa 1.60; 95 % CI: 1.08–2.37; p = 0.018), oxygen desaturation (HRa 1.53; 95 % CI: 1.13–2.08; p = 0.006) and multi-organic involvement (HRa 1.63; 95 % CI: 1.15–2.30), AKI emerged as an independent predictor of death (HRa 1.82; 95 % CI: 1.34–2.48; p < 0.001).

Conclusion

More than half of critically ill patients in the present cohort developed AKI which contributed substantially to short-term mortality, highlighting the need for its prevention, early detection and management as well as the availability of dialysis in ICU.

Postoperative acute kidney injury in high-risk patients undergoing major abdominal surgery

PURPOSE

Acute kidney injury (AKI) is a frequent complication in high-risk patients undergoing major surgery and is associated with longer hospital stay, increased risk for nosocomial infection and significantly higher costs.

MATERIALS AND METHODS

A prospective observational study exploring the incidence of AKI (AKIN classification at any stage) in high-risk patients within 48 hours after major abdominal surgery was conducted. Patients' preoperative characteristics, intraoperative management, and outcome were evaluated for associations with AKI using a logistic regression model.

RESULTS

Data from 258 patients were analyzed. Thirty-one patients (12%) developed AKI, reaching the AKIN stage 1. No patient reached an AKIN stage higher than 1. AKI patients were older (75.2 vs 70.2 years; P = 0.0113) and had a higher body mass index (26.5 vs 25.1 kg/m(2)). In addition, AKI patients had a significantly longer ICU length of stay (3.4 vs 2.4 days; P= .0017). Creatinine levels of AKI patients increased significantly compared to the preoperative levels at 24 (P= .0486), 48 (P= .0011) and 72 hours (P= .0055), while after 72 hours it showed a downwards trend. At ICU discharge, 28 out of 31 patients (90.3%) recovered preoperative levels. Multivariate analysis identified age (OR 1.088; P= .002) and BMI (OR 1.124; P= .022) as risk factors for AKI development. Moreover, AKI development was an independent risk factor for ICU stays longer than 48 hours (OR 2.561; P= .019).

CONCLUSIONS

Mild AKI is a not rare complication in high-risk patients undergoing major abdominal surgery. Although in almost the totality of cases, the indicators of renal function recovered to preoperative levels, post-operative AKI represents a primary risk factor for a prolonged ICU stay.

Apoptosis and acute kidney injury

Improved mechanistic understanding of renal cell death in acute kidney injury (AKI) has generated new therapeutic targets. Clearly, the classic lesion of acute tubular necrosis is not adequate to describe the consequences of renal ischemia, nephrotoxin exposure, or sepsis on glomerular filtration rate. Experimental evidence supports a pathogenic role for apoptosis in AKI. Interestingly, proximal tubule epithelial cells are highly susceptible to apoptosis, and injury at this site contributes to organ failure. During apoptosis, well-orchestrated events converge at the mitochondrion, the organelle that integrates life and death signals generated by the BCL2 (B-cell lymphoma 2) protein family. Death requires the 'perfect storm' for outer mitochondrial membrane injury to release its cellular 'executioners'. The complexity of this process affords new targets for effective interventions, both before and after renal insults. Inhibiting apoptosis appears to be critical, because circulating factors released by the injured kidney induce apoptosis and inflammation in distant organs including the heart, lung, liver, and brain, potentially contributing to the high morbidity and mortality associated with AKI. Manipulation of known stress kinases upstream of mitochondrial injury, induction of endogenous, anti-apoptotic proteins, and improved understanding of the timing and consequences of renal cell apoptosis will inevitably improve the outcome of human AKI.

Acute kidney injury: controversies revisited

This paper addresses the epidemiology of AKI specifically in relation to recent changes in AKI classification and revisits the controversies regarding the timing of initiation of dialysis and the use of peritoneal dialysis as a renal replacement therapy for AKI. In summary, the new RIFLE/AKIN classifications of AKI have facilitated more uniform diagnosis of AKI and clinically significant risk stratification. Regardless, the issue of timing of dialysis initiation still remains unanswered and warrants further examination. Furthermore, peritoneal dialysis as a treatment modality for AKI remains underutilised in spite of potential beneficial effects. Future research should be directed at identifying early reliable biomarkers of AKI, which in conjunction with RIFLE/AKIN classifications of AKI could facilitate well-designed large randomised controlled trials of early versus late initiation of dialysis in AKI. In addition, further studies of peritoneal dialysis in AKI addressing dialysis dose and associated complications are required for this therapy to be accepted more widely by clinicians.

GSK3beta promotes apoptosis after renal ischemic injury

The mechanism by which the serine-threonine kinase glycogen synthase kinase-3beta (GSK3beta) affects survival of renal epithelial cells after acute stress is unknown. Using in vitro and in vivo models, we tested the hypothesis that GSK3beta promotes Bax-mediated apoptosis, contributing to tubular injury and organ dysfunction after acute renal ischemia. Exposure of renal epithelial cells to metabolic stress activated GSK3beta, Bax, and caspase 3 and induced apoptosis. Expression of a constitutively active GSK3beta mutant activated Bax and decreased cell survival after metabolic stress. In contrast, pharmacologic inhibition (4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione [TDZD-8]) or RNA interference-mediated knockdown of GSK3beta promoted cell survival. Furthermore, RNA interference-mediated knockdown of Bax abrogated the cell death induced by constitutively active GSK3beta. In a cell-free assay, TDZD-8 inhibited the phosphorylation of a peptide containing the Bax serine(163) site targeted by stress-activated GSK3beta. In rats, TDZD-8 inhibited ischemia-induced activation of GSK3beta, Bax, and caspase 3; ameliorated tubular and epithelial cell damage; and significantly protected renal function. Taken together, GSK3beta-mediated Bax activation induces apoptosis and tubular damage that contribute to acute ischemic kidney injury.

Acute renal failure during sepsis: potential role of cell cycle regulation

OBJECTIVES

This study aimed to evaluate cell cycle regulation in acute kidney injury after intraperitoneal sepsis in rats.

METHODS

Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) in rats. At 0, 6, 12, 24, 48, and 72 h after CLP, serum creatinine was evaluated. DNA content of isolated kidney cells was analyzed using flow cytometer. Furthermore, the expression of p21, p53, cyclin D1, cyclin E, CDK2, CDK4 and P-pRb was also measured by western blot.

RESULTS

After sepsis-induced by CLP, kidney injury of rat was associated with G1 cell cycle arrest, however, recovery of renal function related to cell cycle progression 48h after CLP. Results also showed that the upregulation of p53 and p21 was correlated with G1 cell arrest in 48h after CLP. Nevertheless, upregulation of cyclin D1/CDK4 and cyclin E/CDK2 induced pRb phosphorylation, which resulted in the G1/S transition 48 h after CLP.

CONCLUSION

The data suggest that G1 cell cycle arrest may play a role in the initiation of kidney injury, whereas, through regulating cell cycle, p53, p21, CDKs, cyclins and P-pRb may be involved in the injury or recovery of renal function after intraperitoneal sepsis.

Distinct functions of activated protein C differentially attenuate acute kidney injury

Administration of activated protein C (APC) protects from renal dysfunction, but the underlying mechanism is unknown. APC exerts both antithrombotic and cytoprotective properties, the latter via modulation of protease-activated receptor-1 (PAR-1) signaling. We generated APC variants to study the relative importance of the two functions of APC in a model of LPS-induced renal microvascular dysfunction. Compared with wild-type APC, the K193E variant exhibited impaired anticoagulant activity but retained the ability to mediate PAR-1-dependent signaling. In contrast, the L8W variant retained anticoagulant activity but lost its ability to modulate PAR-1. By administering wild-type APC or these mutants in a rat model of LPS-induced injury, we found that the PAR-1 agonism, but not the anticoagulant function of APC, reversed LPS-induced systemic hypotension. In contrast, both functions of APC played a role in reversing LPS-induced decreases in renal blood flow and volume, although the effects on PAR-1-dependent signaling were more potent. Regarding potential mechanisms for these findings, APC-mediated PAR-1 agonism suppressed LPS-induced increases in the vasoactive peptide adrenomedullin and infiltration of iNOS-positive leukocytes into renal tissue. However, the anticoagulant function of APC was responsible for suppressing LPS-induced stimulation of the proinflammatory mediators ACE-1, IL-6, and IL-18, perhaps accounting for its ability to modulate renal hemodynamics. Both variants reduced active caspase-3 and abrogated LPS-induced renal dysfunction and pathology. We conclude that although PAR-1 agonism is solely responsible for APC-mediated improvement in systemic hemodynamics, both functions of APC play distinct roles in attenuating the response to injury in the kidney.

Do-not-resuscitate orders in the critically ill patient--an observational study with special emphasis on withholding of renal replacement therapy

We examined the process, consequences and impact of writing a Do-Not-Resuscitate (DNR) order in a cohort of critically-ill ICU patients. Special emphasis was given to the DNR order including withholding renal replacement therapy. A DNR code was mainly written in the first week following ICU admission and more often given to medical, older and sicker patients. Patients never actively participated in the decision and in only half of the cases the DNR order was discussed with relatives. Mortality of all patients studied was 21% of whom 67% died with a DNR order. In our population, the final in-hospital mortality rate of DNR-coded patients was 100%, because the DNR status was ordered when the patients were already very sick. DNR-coded patients died after a longer mean length of ICU stay than patients without a code. Withholding renal replacement therapy was commonly added to the DNR order even if renal failure either was not present or never developed.

Tight blood glucose control is renoprotective in critically ill patients

Two large, prospective, randomized, controlled trials have shown a beneficial effect of intensive insulin therapy (IIT) on the kidney function of critically ill patients. The data from these trials were combined for performance of a more detailed analysis of the renoprotective effect of IIT. After exclusion of 41 patients with preadmission ESRD, the study sample comprised 2707 critically ill patients who were randomly assigned to conventional or IIT. A modified risk-injury-failure-loss-ESRD (mRIFLE) system was used to classify acute kidney injury such that mRIFLE-Injury and -Failure (mR-IF) corresponded to peak serum creatinine levels >/=2x and >/=3x the admission levels, respectively. IIT significantly reduced the incidence of mR-I or -F from 7.6 to 4.5% (P = 0.0006), and this renoprotective effect was most pronounced in patients who achieved strict normoglycemia. In surgical patients, IIT also significantly reduced oliguria (from 5.6 to 2.6%; P = 0.004) and the need for renal replacement therapy (from 7.4 to 4.0%; P = 0.008). In medical patients, the incidence of mR-I or -F decreased to a lesser extent, perhaps because a greater severity of illness at admission may have rendered preventive therapies less effective. In conclusion, this secondary analysis of two large, randomized, controlled trials suggests that IIT, with a goal of achieving normoglycemia, protects the renal function of critically ill patients.

Role of protein C in renal dysfunction after polymicrobial sepsis

Protein C (PC) plays an important role in vascular function, and acquired deficiency during sepsis is associated with increased mortality in both animal models and in clinical studies. This study explored the consequences of PC suppression on the kidney in a cecal ligation and puncture model of polymicrobial sepsis. This study shows that a rapid drop in PC after sepsis is strongly associated with an increase in blood urea nitrogen, renal pathology, and expression of known markers of renal injury, including neutrophil gelatinase-associated lipocalin, CXCL1, and CXCL2. The endothelial PC receptor, which is required for the anti-inflammatory and antiapoptotic activity of activated PC (APC), was significantly increased after cecal ligation and puncture as well as in the microvasculature of human kidneys after injury. Treatment of septic animals with APC reduced blood urea nitrogen, renal pathology, and chemokine expression and dramatically reduced the induction of inducible nitric oxide synthase and caspase-3 activation in the kidney. The data demonstrate a clear link between acquired PC deficiency and renal dysfunction in sepsis and suggest a compensatory upregulation of the signaling receptor. Moreover, these data suggest that APC treatment may be effective in reducing inflammatory and apoptotic insult during sepsis-induced acute renal failure.

The changing epidemiology of acute renal failure

Different definitions of acute renal failure (ARF) abound. The existence of multiple definitions makes it difficult to determine the true epidemiological characteristics of this condition. Despite this difficulty, it has been possible to detect notable variations in the epidemiology of ARF during the past few decades. The absolute incidence of ARF has increased, while associated mortality rate has remained relatively static. Several factors have contributed to this altered epidemiology. Here, we discuss the relative contribution of these factors, which include site of disease onset (developed or developing countries, community or hospital or intensive care unit), patient age, infections (HIV, malaria, leptospirosis and hantavirus), concomitant illnesses (cardiopulmonary failure, hemato-oncological disease), and interventions (hematopoietic progenitor cell and solid organ transplantation).