Rapid reversal of acute kidney injury and hospital outcomes: a retrospective cohort study

Perioperative Acute Kidney Injury: Diagnosis, Prediction, Prevention, and Treatment

In this review, the authors define acute kidney injury in the perioperative setting, describe the epidemiologic burden, discuss procedure-specific risk factors, detail principles of management, and highlight areas of ongoing controversy and research.

Prevalence and mortality of transient acute kidney injury within 48 h, as new subtype, following coronary angiography: a cohort study

BACKGROUND

The association of transient acute kidney injury (AKI) with mortality was controversial. Our study aims to investigate the prevalence and impact of transient AKI on mortality in patients following coronary angiography (CAG).

METHODS

Our study retrospectively enrolled 3970 patients with pre-operative serum creatinine (Scr) and twice measurements within 48 h after procedure. Transient AKI defined as the diagnosis of AKI (Scr > 0.3 mg/dL or > 50% from the baseline level) on day 1 when Scr failed to meet the criteria for AKI on the day 2. Maintained AKI was defined as AKI not meeting the definition for transient AKI. The primary outcome was 1-year all-cause mortality. Multivariable logistic regression was used to assess the association between transient AKI and 1-year mortality.

RESULTS

Among 3,970 participants, 861 (21.7%) occurred AKI, of whom 128 (14.9%) was transient AKI and 733 (85.1%) was maintained AKI. 312 (7.9%) patients died within 1-year after admission. After multivariable analysis, transient AKI was not associated with higher 1-year mortality [adjusted odds ratio (aOR), 1.37; CI 0.68-2.51] compared without AKI. Among AKI patients, transient AKI was associated with a 52% lower 1-year mortality compared with maintained AKI. Additionally, maintained AKI was significantly associated with higher 1-year mortality (aOR, 2.67; CI 2.05-3.47).

CONCLUSIONS

Our data suggested that transient AKI within 48 h was a common subtype of AKI following CAG, without increasing mortality. More attention needs to be paid to the patients suffering from maintained AKI following CAG.

The effect of admission and pre-admission serum creatinine as baseline to assess incidence and outcomes of acute kidney injury in acute medical admissions

BACKGROUND

Acute kidney injury (AKI) in hospital-admitted patients is a common complication associated with increased mortality. The diagnosis of AKI relies on the ascertainment of peak increase in serum creatinine (SCr). This study evaluated the incidence of AKI using the increase from mean 7-365 days pre-admission (AKIpre) and admission (AKIadm) SCr levels, and examined the associations of AKI and changes in SCr levels with all-cause mortality.

METHODS

A total of 2436 patients admitted to a tertiary hospital were recruited and followed-up for a median of 47.70 (interquartile range 18.20) months. AKI incidence and severity were defined according to the Kidney Disease: Improving Global Outcomes-AKI Guidelines. Follow-up data were collected from the Hospital Episode Statistics and Office of National Statistics. Mortality was evaluated during a short- (30 days), mid- (1 year) and long-term (4 years) period.

RESULTS

No difference in the AKI rates using AKIpre and AKIadm (12.5% versus 12.2%; P = 0.695) or in the AKI severity (P = 0.261) was evident. Agreement between the two definitions was modest (Kappa-statistic = 0.596, P < 0.001). Patients with AKIpre or AKIadm had increased all-cause mortality compared with those without AKI during all follow-up periods. In fully adjusted regression analysis, AKIpre [hazard ratio (HR) = 2.226, 95% confidence interval (CI) 1.140-4.347; P = 0.027] and AKIadm (HR = 2.105, 95% CI 1.090-4.064; P = 0.027) remained associated with 30-day mortality. Results for the 1- and 4-year periods were similar. Increases of >4.00 μmol/L and >6.06% from pre-admission or >6.00 μmol/L and >17.24% from admission SCr levels presented increased mortality risk during follow-up.

CONCLUSIONS

Use of admission or pre-admission SCr provides similar incidence rates, but they diagnose different sets of patients. Even minor increases in SCr, below those required for the classification of AKI, were associated with increased mortality. These findings can help the clinicians to identify patients at higher risk for adverse outcomes.

Outcomes of early and reversible renal impairment in patients with ST segment elevation myocardial infarction undergoing percutaneous coronary intervention

Objective:

Acute kidney injury (AKI) is a frequent complication in patients with ST segment elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI). While AKI occurring post-PCI has been well studied, the incidence and clinical significance of early renal impairment evident on hospital admission prior to PCI and which resolves towards discharge has not been investigated.

Methods:

We retrospectively studied 2339 STEMI patients treated with primary PCI. The incidence of renal impairment and in-hospital complications as well as short and long-term mortality were compared between patients who did not develop renal impairment, patients who developed post-PCI AKI and those who presented with renal impairment on admission but improved their renal function during hospitalization (improved renal function). Improved renal function was defined as continuous and gradual decrease of ⩾ 0.3 mg/dL in serum creatinine levels obtained at hospital admission.

Results:

One hundred and nineteen patients (5%) had improved renal function and 230 patients (10%) developed post-PCI AKI. When compared with patients with no renal impairment, improved renal function and post-PCI AKI were associated with more complications and adverse events during hospitalization as well as higher 30-day mortality. Long-term mortality was significantly higher among those with post-PCI AKI (63/230, 27%) following STEMI than those without renal impairment (104/1990, 5%; p&lt;0.001), but there was no significant difference in long term mortality between patients with no renal impairment and those with improved renal function (5% vs. 7.5%, p=0.17).

Conclusion:

In STEMI patients undergoing primary PCI, the presence of renal impairment prior to PCI which resolves towards discharge is not uncommon and is associated with adverse short-term outcomes but better long-term outcomes compared with post-PCI AKI.

Phenotypes and Baseline Risk Factors of Acute Kidney Injury in Children After Allogeneic Hematopoietic Stem Cell Transplantation

Background: Acute kidney injury (AKI) is a frequent and widely recognized complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Despite relatively high prevalence, AKI after allo-HSCT and its risk factors in children remain obscure. The aim of this study was to describe the prevalence and course of AKI during the first 100 days after allo-HSCT in children and to investigate its associations with baseline characteristics. Methods: Retrospective single-center chart review of all patients under 18 who underwent allo-HSCT during 2011-2017 was performed. AKI was defined using the pediatric RIFLE criteria and only the patients with pRIFLE stage I (eGFR decrease by 50% or more) or higher were considered for the analysis. Recurrent AKI and acute kidney disease (AKD) were defined according to the Acute Disease Quality Initiative consensus. Demographic, clinical, and procedure-related characteristics were recorded at the day of HSCT. Results: Fifty-one patients (68.6% boys) with a median age of 9 years (range: 0.25-17) were included. During a median follow-up of 82 (IQR, 60-98) days, 27 (52.9%) patients experienced a total of 39 AKI episodes, translating into one AKI episode per 100 patient days. Multiple AKIs occurred in 11 (21.6%) patients and 18 (35.3%) progressed to AKD. Four patients died, all with ongoing or previous AKI. Patients with AKD were, on average, older (10 vs. 6 years; p = 0.03) and had higher baseline body mass index (BMI) [standard deviation score (SDS) 0.83 vs. 0.04, p = 0.05], whereas patients with recurrent AKI had higher baseline estimated glomerular filtration rate (eGFR) (244.1 vs. 193.9 ml/min/1.73 m², p = 0.02). In the adjusted Cox models (HR; 95% CI), older age (1.10; 1.01-1.20) was associated with higher risk of overall AKI and higher eGFR (1.02; 1.01-1.04) was associated with higher risk of recurrent AKI, while older age (1.17; 1.04-1.31), higher eGFR (HR 1.01; 1.0-1.02), and higher BMI SDS (1.66; 1.01-2.72) were associated with higher risk of AKD. Conclusions: AKI is a frequent early complication of allo-HSCT in children, and approximately one fifth experience AKI recurrence and one third develop AKD. Older age, higher BMI, and higher eGFR at the day of transplant may have an effect on the risk of AKI development and its course.

Clinical Outcomes Depending on Acute Blood Pressure After Cerebral Hemorrhage

OBJECTIVE

To determine the association between clinical outcomes and acute systolic blood pressure (SBP) levels achieved after intracerebral hemorrhage (ICH).

METHODS

Eligible patients who were randomized to the ATACH-2 (Antihypertensive Treatment in Intracerebral Hemorrhage 2) trial (ClinicalTrials.gov: NCT01176565) were divided into 5 groups by 10-mmHg strata of average hourly minimum SBP (<120, 120-130, 130-140, 140-150, and ≥ 150 mmHg) during 2 to 24 hours after randomization. Outcomes included: 90-day modified Rankin Scale (mRS) 4 to 6; hematoma expansion, defined as an increase ≥6 ml from baseline to 24-hour computed tomography; and cardiorenal adverse events within 7 days.

RESULTS

Of the 1,000 subjects in ATACH-2, 995 with available SBP data were included in the analyses. The proportion of mRS 4 to 6 was 37.5, 36.0, 42.8, 38.6, and 38.0%, respectively. For the "140 to 150" group relative to the "120 to 130," the odds ratio (OR), adjusting for sex, race, age, onset-to-randomization time, baseline National Institutes of Health Stroke Scale score, hematoma volume, and hematoma location, was 1.62 (95% confidence interval [CI], 1.02-2.58). Hematoma expansion was identified in 16.9, 13.7, 21.4, 18.5, and 26.4%, respectively. The 140 to 150 (OR, 1.80; 95% CI, 1.05-3.09) and "≥150" (1.98; 1.12-3.51) showed a higher frequency of expansion than the 120 to 130 group. Cardiorenal events occurred in 13.6, 16.6, 11.5, 8.1, and 8.2%, respectively. The 140 to 150 (0.43; 0.19-0.88) and ≥ 150 (0.44; 0.18-0.96) showed a lower frequency of the events than the 120 to 130.

INTERPRETATION

Beneficial effects of lowering and maintaining SBP at 120 to 130 mmHg during the first 24 hours on clinical outcomes by suppressing hematoma expansion was somewhat offset by cardiorenal complications. ANN NEUROL 2019;85:105-113.

Impact of Isolyte Versus 0.9% Saline on Postoperative Event of Acute Kidney Injury Assayed by Urinary [TIMP-2] × [IGFBP7] in Patients Undergoing Cardiac Surgery

OBJECTIVE

Administration of excess chloride in 0.9% normal saline (NS) decreases renal perfusion and glomerular filtration rate, thereby increasing the risk for acute kidney injury (AKI). In this study, the effect of NS versus Isolyte use during cardiac surgery on urinary levels of tissue inhibitor of metalloproteinase 2 and insulin-like growth factor-binding protein 7 [TIMP-2] × [IGFBP7] and postoperative risk of AKI were examined.

DESIGN

Prospective, randomized, and single-blinded trial.

SETTING

Single university medical center.

PARTICIPANTS

Thirty patients over 18 years without chronic renal insufficiency or recent AKI undergoing elective cardiac surgery.

INTERVENTIONS

Subjects were randomized to receive either NS or Isolyte during the intraoperative period.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the change in urinary levels of [TIMP2] × [IGFBP7] from before surgery to 24 hours postoperatively. Secondary outcomes included serum creatinine pre- and postoperatively at 24 and 48 hours, serum chloride pre- and postoperatively at 24 and 48 hours, need for dialysis prior to discharge, and arterial pH measured 24 hours postoperatively. Sixteen patients received NS and 14 patients received Isolyte. Three patients developed AKI within the first 3 postoperative days, all in the NS group. The authors found increases in [TIMP-2] × [IGFBP7] in both groups. However, the difference in this increase between study arms was not significant (p = 0.92; -0.097 to 0.107).

CONCLUSION

The authors observed no change in urinary [TIMP-] × [IGFBP7] levels in patients receiving NS versus Isolyte during cardiac surgery. Future larger studies in patients at higher risk for AKI are recommended to evaluate the impact of high- versus lower-chloride solutions on the risk of postoperative AKI after cardiac surgery.

Seasonal pattern of incidence and outcome of Acute Kidney Injury: A national study of Welsh AKI electronic alerts

OBJECTIVES

To identify any seasonal variation in the occurrence of, and outcome following Acute Kidney Injury.

METHODS

The study utilised the biochemistry based AKI electronic (e)-alert system established across the Welsh National Health Service to collect data on all AKI episodes to identify changes in incidence and outcome over one calendar year (1st October 2015 and the 30th September 2016).

RESULTS

There were total of 48 457 incident AKI alerts. The highest proportion of AKI episodes was seen in the quarter of January to March (26.2%), and the lowest in the quarter of October to December (23.3%, P < .001). The same trend was seen for both community-acquired and hospital-acquired AKI sub-sets. Overall 90 day mortality for all AKI was 27.3%. In contrast with the seasonal trend in AKI occurrence, 90 day mortality after the incident AKI alert was significantly higher in the quarters of January to March and October to December compared with the quarters of April to June and July to September (P < .001) consistent with excess winter mortality reported for likely underlying diseases which precipitate AKI.

CONCLUSIONS

In summary we report for the first time in a large national cohort, a seasonal variation in the incidence and outcomes of AKI. The results demonstrate distinct trends in the incidence and outcome of AKI.

Acute kidney injury electronic alerts in primary care - findings from a large population cohort

BACKGROUND

Electronic reporting of AKI has been used to aid early AKI recognition although its relevance to CA-AKI and primary care has not been described.

AIMS

We described the characteristics and clinical outcomes of patients with CA-AKI, and AKI identified in primary care (PC-AKI) through AKI e-Alerts.

DESIGN

A prospective national cohort study was undertaken to collect data on all e-alerts representing adult CA-AKI.

METHOD

The study utilized the biochemistry based AKI electronic (e)-alert system that is established across the Welsh National Health Service.

RESULTS

28.8% of the 22 723 CA-AKI e-alerts were classified as PC-AKI. Ninety-day mortality was 24.0% and lower for PC-AKI vs. non-primary care (non-PC) CA-AKI. Hospitalization was 22.3% for PC-AKI and associated with greater disease severity, higher mortality, but better renal outcomes (non-recovery: 18.1% vs. 21.6%; progression of pre-existing CKD: 40.5% vs. 58.3%). 49.1% of PC-AKI had a repeat test within 7 days, 42.5% between 7 and 90 days, and 8.4% was not repeated within 90 days. There was significantly more non-recovery (24.0% vs. 17.9%) and progression of pre-existing CKD (63.3% vs. 47.0%) in patients with late repeated measurement of renal function compared to those with early repeated measurement of renal function.

CONCLUSION

The data demonstrate the clinical utility of AKI e-alerts in primary care. We recommend that a clinical review, or referral together with a repeat measurement of renal function within 7 days should be considered an appropriate response to AKI e-alerts in primary care.

A decrease in serum creatinine after ICU admission is associated with increased mortality

Background

The elevation of serum creatinine (SCr), acute kidney injury (AKI), is associated with an increase of mortality in critically ill patients. However, it is uncertain whether a decrease in SCr in the intensive care unit (ICU) has an effect on outcomes.

Methods

In a retrospective study, we enrolled 486 patients who had been admitted to an urban tertiary center ICU between Jan 2014 and Dec 2014. The effect of changes in SCr after ICU admission on 90 day mortality was analyzed. Patients were classified into 3 groups based on change in SCr after ICU admission: a stable SCr group (Δ SCr < 0.3mg/dL during ICU stay), a decreased SCr group (Δ SCr ≥ -0.3 mg/dL during ICU stay) and an increased SCr group with criteria based on the KDIGO AKI criteria.

Results

In total, 486 patients were identified. SCr decreased in 123 (25.3%) patients after ICU admission. AKI developed in 125 (24.4%) patients. The overall 90-day mortality rate was 29.0%. In a Kaplan-Meyer analysis, the mortality of the AKI group was higher than that of other groups (p<0.0001). Patients with a decrease in SCr had a higher mortality rate than those with stable SCr (p<0.0001). A Cox analysis showed that both a decrease in SCR (HR, 3.56; 95% CI, 1.59–7.97; p = 0.002) and an increase in SCr (AKI stage 1, HR, 9.35; 95% CI, 4.18–20.9; p<0.0001; AKI stage 2, HR, 11.82; 95% CI, 3.85–36.28; p<0.0001; AKI stage 3, HR, 17.41; 95% CI, 5.50–55.04; p<0.0001) were independent risk factors for death compared to stable SCr.

Conclusion

Not only an increase in SCr, but also a decrease in SCr was associated with mortality in critically ill patients.

The impact of transient and persistent acute kidney injury on short-term outcomes in very elderly patients

Objectives

Acute kidney injury (AKI) is a common complication in elderly patients and is associated with poor outcomes. However, the effect of transient and persistent geriatric AKI on short-term mortality is unclear. We aimed to study the incidence, clinical characteristics, and prognostic impact of transient and persistent AKI in such patients.

Methods

We retrospectively enrolled very elderly patients (≥75 years) from the geriatric department of the Chinese PLA General Hospital between 2007 and 2015. AKI was defined according to the 2012 Kidney Disease: Improving Global Outcomes criteria. AKI patients were divided into transient or persistent AKI groups based on their renal function at 3 days post-AKI. Renal function recovery was defined as a return to the baseline serum creatinine (SCr) levels.

Results

In total, 668 geriatric patients (39.0%) experienced AKI, and 652 satisfied the inclusion criteria. Of these 652 patients, 270 (41.4%) had transient AKI, and 382 (58.6%) had persistent AKI. The 90-day mortality was 5.9% in patients with transient AKI and 53.1% in patients with persistent AKI. Multivariate analysis revealed that low hemoglobin levels (odds ratio [OR] =0.989; 95% CI: 0.980–0.999; P=0.025), low mean aortic pressure (OR =0.985; 95% CI: 0.971–1.000; P=0.043), peak SCr (OR =1.020; 95% CI: 1.015–1.026; P<0.001) levels, high uric acid (OR =1.002; 95% CI: 1.000–1.003; P=0.040) levels, high blood urea nitrogen (OR =1.028; 95% CI: 1.000–1.056; P=0.047) levels, and mechanical ventilation requirements (OR =1.610; 95% CI: 1.012–2.562; P=0.044) were associated with persistent AKI. Persistent AKI (hazard ratio [HR] =5.741; 95% CI: 3.356–9.822; P<0.001) and more severe AKI stages (stage 2: HR =3.363; 95% CI: 1.973–5.732; P<0.001 and stage 3: HR =4.741; 95% CI: 2.807–8.008; P<0.001) were associated with 90-day mortality.

Conclusion

AKI is common in very elderly patients, with transient renal injury representing close to 42% of all cases of geriatric AKI. More frequent SCr measurements may be helpful for the early diagnosis of transient geriatric AKI. Persistent geriatric AKI is independently associated with a significantly higher risk of 90-day mortality.

The Pattern of Longitudinal Change in Serum Creatinine and 90-Day Mortality After Major Surgery

OBJECTIVE

Calculate mortality risk that accounts for both severity and recovery of postoperative kidney dysfunction using the pattern of longitudinal change in creatinine.

BACKGROUND

Although the importance of renal recovery after acute kidney injury (AKI) is increasingly recognized, the complex association that accounts for longitudinal creatinine changes and mortality is not fully described.

METHODS

We used routinely collected clinical information for 46,299 adult patients undergoing major surgery to develop a multivariable probabilistic model optimized for nonlinearity of serum creatinine time series that calculates the risk function for 90-day mortality. We performed a 70/30 cross validation analysis to assess the accuracy of the model.

RESULTS

All creatinine time series exhibited nonlinear risk function in relation to 90-day mortality and their addition to other clinical factors improved the model discrimination. For any given severity of AKI, patients with complete renal recovery, as manifested by the return of the discharge creatinine to the baseline value, experienced a significant decrease in the odds of dying within 90 days of admission compared with patients with partial recovery. Yet, for any severity of AKI, even complete renal recovery did not entirely mitigate the increased odds of dying, as patients with mild AKI and complete renal recovery still had significantly increased odds for dying compared with patients without AKI [odds ratio: 1.48 (95% confidence interval: 1.30-1.68)].

CONCLUSIONS

We demonstrate the nonlinear relationship between both severity and recovery of renal dysfunction and 90-day mortality after major surgery. We have developed an easily applicable computer algorithm that calculates this complex relationship.

Acute kidney injury in the ICU: from injury to recovery: reports from the 5th Paris International Conference

The French Intensive Care Society organized its yearly Paris International Conference in intensive care on June 18-19, 2015. The main purpose of this meeting is to gather the best experts in the field in order to provide the highest quality update on a chosen topic. In 2015, the selected theme was: "Acute Renal Failure in the ICU: from injury to recovery." The conference program covered multiple aspects of renal failure, including epidemiology, diagnosis, treatment and kidney support system, prognosis and recovery together with acute renal failure in specific settings. The present report provides a summary of every presentation including the key message and references and is structured in eight sections: (a) diagnosis and evaluation, (b) old and new diagnosis tools,

Acute kidney injury in the ICU: from injury to recovery: reports from the 5th Paris International Conference

The French Intensive Care Society organized its yearly Paris International Conference in intensive care on June 18-19, 2015. The main purpose of this meeting is to gather the best experts in the field in order to provide the highest quality update on a chosen topic. In 2015, the selected theme was: "Acute Renal Failure in the ICU: from injury to recovery." The conference program covered multiple aspects of renal failure, including epidemiology, diagnosis, treatment and kidney support system, prognosis and recovery together with acute renal failure in specific settings. The present report provides a summary of every presentation including the key message and references and is structured in eight sections: (a) diagnosis and evaluation, (b) old and new diagnosis tools,

Physician Prevention of Acute Kidney Injury

BACKGROUND

The frequency of acute kidney injury has become substantially greater over the recent past. Acute kidney injury, moreover, is associated with increased mortality and morbidity over both the short and long term. Despite these facts, its therapy has not changed significantly for many decades. Currently, therefore, prevention is the only action that can reduce the frequency and consequences of acute kidney injury.

METHODS

Charts of 492 patients were reviewed retrospectively for the presence of acute kidney injury based on creatinine elevation. One hundred seventy patients were found to have acute kidney injury defined as a sustained elevation of serum creatinine ≥ 0.3 mg/dL for 48 hours or more. An agent or event was determined to be responsible for renal injury if there was the defined increase in serum creatinine within 48 hours of exposure. Charts were reviewed to determine if the renal injury was preventable.

RESULTS

Fifty-one cases were considered to be preventable. Of these, 16 had not received saline prophylaxis for intravenous contrast when appropriate, 15 were not treated appropriately for hemodynamic instability or for hypertension, 9 had inappropriate use of medications, and 11 received multiple nephrotoxic agents.

CONCLUSIONS

In a retrospective analysis of 170 hospitalized patients who developed acute kidney injury during admission, 30% of episodes could have been avoided if physicians had taken appropriate preventive actions.

Epidemiology and Clinical Correlates of AKI in Chinese Hospitalized Adults

BACKGROUND AND OBJECTIVES

Comprehensive epidemiologic data on AKI are particularly lacking in Asian countries. This study sought to assess the epidemiology and clinical correlates of AKI among hospitalized adults in China.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a multicenter retrospective cohort study of 659,945 hospitalized adults from a wide range of clinical settings in nine regional central hospitals across China in 2013. AKI was defined and staged according to Kidney Disease Improving Global Outcomes criteria. The incidence of AKI in the cohort was estimated using a novel two-step approach with adjustment for the frequency of serum creatinine tests and other potential confounders. Risk factor profiles for hospital-acquired (HA) and community-acquired (CA) AKI were examined. The in-hospital outcomes of AKI, including mortality, renal recovery, length of stay, and daily cost, were assessed.

RESULTS

The incidence of CA-AKI and HA-AKI was 2.5% and 9.1%, respectively, giving rise to an overall incidence of 11.6%. Although the risk profiles for CA-AKI and HA-AKI differed, preexisting CKD was a major risk factor for both, contributing to 20% of risk in CA-AKI and 12% of risk in HA-AKI. About 40% of AKI cases were possibly drug-related and 16% may have been induced by Chinese traditional medicines or remedies. The in-hospital mortality of AKI was 8.8%. The risk of in-hospital death was higher among patients with more severe AKI. Preexisting CKD and need for intensive care unit admission were associated with higher death risk in patients at any stage of AKI. Transiency of AKI did not modify the risk of in-hospital death. AKI was associated with longer length of stay and higher daily costs, even after adjustment for confounders.

CONCLUSION

AKI is common in hospitalized adults in China and is associated with significantly higher in-hospital mortality and resource utilization.

Relationship between duration of hospital-acquired acute kidney injury and mortality: a prospective observational study

BACKGROUND/AIMS

New definitions of acute kidney injury (AKI) have recently emerged. Some studies have suggested that duration of AKI is an additional predictive parameter for mortality. Here, we evaluated whether AKI duration was predictive of long-term mortality in patients with hospital-acquired acute kidney injury (HAAKI).

METHODS

We prospectively enrolled patients who developed HAAKI at an urban university hospital, from September 2007 to August 2008 and followed them until December 2011. Patients were divided into two groups by duration of the AKI (1 to 5 days vs. ≥ 6 days), and long-term mortality was compared.

RESULTS

HAAKI developed in 1.2% of patients during the enrollment period. The median follow-up period was 240 days (interquartile range, 53 to 1,428). In 42.3% of patients (n = 52), the AKI lasted 1 to 5 days, while it lasted ≥ 6 days in 57.7% (n = 71). Survival analysis showed that a longer duration of AKI increased the risk of death. Long-term survival was significantly different in the two groups.

CONCLUSIONS

The duration of AKI influenced mortality rates in hospitalized patients. Thus, AKI duration is a parameter affecting mortality in HAAKI.

Relation of in-hospital serum creatinine change patterns and outcomes among ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention

BACKGROUND

The worsening of serum creatinine (sCr) level is a frequent finding among ST-segment elevation MI (STEMI) patients undergoing primary percutaneous coronary intervention (PCI), associated with adverse short-term and long-term outcomes. No information is present, however, regarding the incidence and prognostic implications associated with an improvement in sCr levels throughout hospitalization, as compared with admission levels.

HYPOTHESIS

Reversible renal impairment prior to PCI is not associated with adverse outcomes.

METHODS

We retrospectively studied 1260 STEMI patients undergoing primary PCI. The incidence of in-hospital complications and long-term mortality was compared between patients having stable, worsened (>0.3 mg/dL increase), or improved (>0.3 mg/dL decrease) sCr levels throughout hospitalization.

RESULTS

Overall, 127 patients (10%) had worsening in sCr levels, whereas 44 (3.5%) had an improvement of sCr compared with admission levels. Patients with worsening sCR had more complications during hospitalization, higher 30-day (13% vs 1%; P < 0.001) and up to 5-year all-cause mortality (28% vs 5%; P < 0.001) compared with those with stable sCR. No significant difference was found regarding complications and mortality between patients having an improvement in sCr and stable sCr. Compared with patients with stable sCr, the adjusted hazard ratio for all-cause mortality in patients with worsened sCr was 6.68 (95% confidence interval: 2.1-21.6, P = 0.002).

CONCLUSIONS

In STEMI patients undergoing primary PCI, renal impairment prior to PCI is a frequent finding. In contrast to post-PCI sCr worsening, this entity is not associated with adverse short-term and long-term outcomes.

The definition of acute kidney injury and its use in practice

Acute kidney injury (AKI) is a common syndrome that is independently associated with increased mortality. A standardized definition is important to facilitate clinical care and research. The definition of AKI has evolved rapidly since 2004, with the introduction of the Risk, Injury, Failure, Loss, and End-stage renal disease (RIFLE), AKI Network (AKIN), and Kidney Disease Improving Global Outcomes (KDIGO) classifications. RIFLE was modified for pediatric use (pRIFLE). They were developed using both evidence and consensus. Small rises in serum creatinine are independently associated with increased mortality, and hence are incorporated into the current definition of AKI. The recent definition from the international KDIGO guideline merged RIFLE and AKIN. Systematic review has found that these definitions do not differ significantly in their performance. Health-care staff caring for children or adults should use standard criteria for AKI, such as the pRIFLE or KDIGO definitions, respectively. These efforts to standardize AKI definition are a substantial advance, although areas of uncertainty remain. The new definitions have enabled the use of electronic alerts to warn clinicians of possible AKI. Novel biomarkers may further refine the definition of AKI, but their use will need to produce tangible improvements in outcomes and cost effectiveness. Further developments in AKI definitions should be informed by research into their practical application across health-care providers. This review will discuss the definition of AKI and its use in practice for clinicians and laboratory scientists.

The effect of acute kidney injury and discharge creatinine level on mortality following cardiac surgery*

OBJECTIVES

Acute kidney injury after cardiac surgery is associated with increased operative and late mortality. The objective was to determine if short and long term mortality are systematically improved with completeness of postoperative acute kidney injury reversal or with amount of residual renal function.

DESIGN

Retrospective, single center study.

SETTING

Tertiary care hospital.

PATIENTS

One thousand five hundred and forty-three cardiac surgery patients divided into acute kidney injury groups based on Kidney Disease International Group Outcome criteria.

MEASUREMENTS AND MAIN RESULTS

Operative mortality was 3.1% overall and was progressively worse with increasing acute kidney injury: none (0.8%), minimal (1.6%), Kidney Disease International Group Outcome stage 1 (4.3%), stage 2 (17%), and stage 3 (29%). Similar to the operative outcomes, late outcomes were progressively worse with rising amounts of acute kidney injury. The risk of late death was related to amount of acute kidney injury and remaining renal function at discharge.

CONCLUSIONS

Acute kidney injury was associated with higher operative and late mortality. Lesser amounts of residual renal function were associated with increased late mortality.

Early reversible acute kidney injury is associated with improved survival in septic shock

INTRODUCTION

The fact that acute kidney injury (AKI) is associated with worse clinical outcomes forms the basis of most AKI prognostic scoring systems. However, early reversibility of renal dysfunction in acute illness is not considered in such systems. We sought to determine whether early (≤24 hours after shock documentation) reversibility of AKI was independently associated with in-hospital mortality in septic shock.

METHODS

Patient information was derived from an international database of septic shock cases from 28 different institutions in Canada, the United States and Saudi Arabia. Data from a final cohort of 5443 patients admitted with septic shock between Jan 1996 and Dec 2009 was analyzed. The following 4 definitions were used in regards to AKI status: (1) reversible AKI = AKI of any RIFLE severity prevalent at shock diagnosis or incident at 6 hours post-diagnosis that reverses by 24 hours, (2) persistent AKI = AKI prevalent at shock diagnosis and persisting during the entire 24 hours post-shock diagnosis, (3) new AKI = AKI incident between 6 and 24 hours post-shock diagnosis, and (4) improved AKI = AKI prevalent at shock diagnosis or incident at 6 hours post followed by improvement of AKI severity across at least one RIFLE category over the first 24 hours. Cox proportional hazards were used to determine the association between AKI status and in-hospital mortality.

RESULTS

During the first 24 hours, reversible AKI occurred in 13.0%, persistent AKI in 54.9%, new AKI in 11.7%, and no AKI in 22.4%. In adjusted analyses, reversible AKI was associated with improved survival (HR, 0.64; 95% CI, 0.53-0.77) compared to no AKI (referent), persistent AKI (HR, 0.99; 95% CI, 0.88-1.11), and new AKI (HR, 1.41; 95% CI, 1.22-1.62). Improved AKI occurred in 19.1% with improvement across any RIFLE category associated with a significant decrease in mortality (HR, 0.53; 95% CI, 0.45-0.63). More rapid antimicrobial administration, lower Acute Physiology and Chronic Health Evaluation II score, lower age, and a smaller number of failed organs (excluding renal) on the day of shock as well as community-acquired infection were independently associated with reversible AKI.

CONCLUSION

In septic shock, reversible AKI within the first 24 hours of admission confers a survival benefit compared to no, new, or persistent AKI. Prognostic AKI classification schemes should consider integration of early AKI reversibility into the scoring system.

Continuous venovenous hemofiltration versus extended daily hemofiltration in patients with septic acute kidney injury: a retrospective cohort study

INTRODUCTION

Whether continuous venovenous hemofiltration (CVVHF) is superior to extended daily hemofiltration (EDHF) for the treatment of septic AKI is unknown. We compared the effect of CVVHF (greater than 72 hours) with EDHF (8 to 12 hours daily) on renal recovery and mortality in patients with severe sepsis or septic shock and concurrent acute kidney injury (AKI).

METHODS

A retrospective analysis of 145 septic AKI patients who underwent renal replacement therapy (RRT) between July 2009 and May 2013 was performed. These patients were treated by CVVHF or EDHF with the same polyacrylonitrile membrane and bicarbonate-based buffer. The primary outcomes measured were occurrence of renal recovery and all-cause mortality by 60 days.

RESULTS

Sixty-five and eighty patients were treated with CVVHF and EDHF, respectively. Patients in the CVVHF group had significantly higher recovery of renal function (50.77% of CVVHF group versus 32.50% in the EDHF group, P = 0.026). Median time to renal recovery was 17.26 days for CVVHF patients and 25.46 days for EDHF patients (P = 0.039). Sixty-day all-cause mortality was similar between CVVHF and EDHF groups (44.62%, and 46.25%, respectively; P = 0.844). 55.38% of patients on CVVHF and 28.75% on EDHF developed hypophosphatemia (P = 0.001). The other adverse events related to RRT did not differ between groups. On multivariate analysis, including physiologically clinical relevant variables, CVVHF therapy was significantly associated with recovery of renal function (HR 3.74; 95% CI 1.82 to 7.68; P < 0.001), but not with mortality (HR 0.69; 95% CI 0.34 to 1.41; P = 0.312).

CONCLUSIONS

Patients undergoing CVVHF therapy had significantly improved renal recovery independent of clinically relevant variables. The patients with septic AKI had similar 60-day all-cause mortality rates, regardless of type of RRT.

Xenobiotic metabolism: the effect of acute kidney injury on non-renal drug clearance and hepatic drug metabolism

Acute kidney injury (AKI) is a common complication of critical illness, and evidence is emerging that suggests AKI disrupts the function of other organs. It is a recognized phenomenon that patients with chronic kidney disease (CKD) have reduced hepatic metabolism of drugs, via the cytochrome P450 (CYP) enzyme group, and drug dosing guidelines in AKI are often extrapolated from data obtained from patients with CKD. This approach, however, is flawed because several confounding factors exist in AKI. The data from animal studies investigating the effects of AKI on CYP activity are conflicting, although the results of the majority do suggest that AKI impairs hepatic CYP activity. More recently, human study data have also demonstrated decreased CYP activity associated with AKI, in particular the CYP3A subtypes. Furthermore, preliminary data suggest that patients expressing the functional allele variant CYP3A5*1 may be protected from the deleterious effects of AKI when compared with patients homozygous for the variant CYP3A5*3, which codes for a non-functional protein. In conclusion, there is a need to individualize drug prescribing, particularly for the more sick and vulnerable patients, but this needs to be explored in greater depth.

Reactive oxygen species and IRF1 stimulate IFNα production by proximal tubules during ischemic AKI

We previously reported that expression of the transcription factor interferon regulatory factor 1 (IRF1) is an early, critical maladaptive signal expressed by renal tubules during murine ischemic acute kidney injury (AKI). We now show that IRF1 mediates signals from reactive oxygen species (ROS) generated during ischemic AKI and that these signals ultimately result in production of α-subtypes of type I interferons (IFNαs). We found that genetic knockout of the common type I IFN receptor (IFNARI-/-) improved kidney function and histology during AKI. There are major differences in the spatial-temporal production of the two major IFN subtypes, IFNβ and IFNαs: IFNβ expression peaks at 4 h, earlier than IFNαs, and continues at the same level at 24 h; expression of IFNαs also increases at 4 h but continues to increase through 24 h. The magnitude of the increase in IFNαs relative to baseline is much greater than that of IFNβ. We show by immunohistology and study of isolated cells that IFNβ is produced by renal leukocytes and IFNαs are produced by renal tubules. IRF1, IFNαs, and IFNARI were found on the same renal tubules during ischemic AKI. Furthermore, we found that ROS induced IFNα expression by renal tubules in vitro. This expression was inhibited by small interfering RNA knockdown of IRF1. Overexpression of IRF1 resulted in the production of IFNαs. Furthermore, we found that IFNα stimulated production of maladaptive proinflammatory CXCL2 by renal tubular cells. Altogether our data support the following autocrine pathway in renal tubular cells: ROS > IRF1 > IFNα > IFNARI > CXCL2.

N-acetylcysteine does not prevent contrast nephropathy in patients with renal impairment undergoing emergency CT: a randomized study

BACKGROUND

Patients admitted to the emergency room with renal impairment and undergoing a contrast computed tomography (CT) are at high risk of developing contrast nephropathy as emergency precludes sufficient hydration prior to contrast use. The value of an ultra-high dose of intravenous N-acetylcysteine in this setting is unknown.

METHODS

From 2008 to 2010, we randomized 120 consecutive patients admitted to the emergency room with an estimated clearance lower than 60 ml/min/1.73 m2 by MDRD (mean GFR 42 ml/min/1.73 m2) to either placebo or 6000 mg N-acetylcysteine iv one hour before contrast CT in addition to iv saline. Serum cystatin C and creatinine were measured one hour prior to and at day 2, 4 and 10 after contrast injection. Nephrotoxicity was defined either as 25% or 44 μmol/l increase in serum creatinine or cystatin C levels compared to baseline values.

RESULTS

Contrast nephrotoxicity occurred in 22% of patients who received placebo (13/58) and 27% of patients who received N-acetylcysteine (14/52, p = 0.66). Ultra-high dose intravenous N-acetylcysteine did not alter creatinine or cystatin C levels. No secondary effects were noted within the 2 groups during follow-up.

CONCLUSIONS

An ultra-high dose of intravenous N-acetylcysteine is ineffective at preventing nephrotoxicity in patients with renal impairment undergoing emergency contrast CT.

TRIAL REGISTRATION

The study was registered as Clinical trial (NCT01467154).

Acute kidney injury: the beginning of the end of the dark ages

There has been enormous progress in the understanding of acute kidney injury (AKI) over the past 5 years. This article reviews some of the salient new findings, the challenges revealed by these findings and new insights into the pathogenesis of ischemic AKI. Clinical studies have demonstrated that even a small, transient rise in serum creatinine increases the risk of mortality in hospitalized patients and that a single event of AKI increases the risk for developing chronic kidney disease. Although the overall mortality rate from AKI has improved over the past 2 decades, it continues to be significant. Current treatment is focused on maintaining renal perfusion and avoiding volume overload. However, new therapeutic targets are emerging for the treatment of AKI as our understanding of the pathogenesis of ischemic injury and inflammation increases. Early diagnosis, however, continues to be challenging as the search continues for sensitive and specific biomarkers.

Association between AKI, recovery of renal function, and long-term outcomes after hospital discharge

BACKGROUND AND OBJECTIVES

This study aimed to determine if recovery of kidney function after AKI modifies the association between AKI during hospitalization and adverse outcomes after discharge.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The effect of renal recovery after AKI was evaluated in a population-based cohort study (n=190,714) with participants identified from a provincial claims registry in Alberta, Canada, between November 1, 2002 and December 31, 2007. AKI was identified by a two-fold increase between prehospital and peak in-hospital serum creatinine (SCr). Recovery was assessed using SCr drawn closest to 90 days after the AKI event. All-cause mortality and a combined renal outcome of sustained doubling of SCr or progression to kidney failure were evaluated.

RESULTS

Overall, 3.7% of the participants (n=7014) had AKI, 62.7% of whom (n=4400) survived 90 days. In the 3231 patients in whom recovery could be assessed over a median follow-up of 34 months, 30.8% (n=1268) of AKI survivors died and 2.1% (n=85) progressed to kidney failure. Participants who did not recover kidney function had a higher risk for mortality and adverse renal outcomes when AKI participants who recovered to within 25% of baseline SCr were used as the reference group (adjusted mortality hazard ratio (HR), 1.26; 95% confidence interval, 1.10, 1.43) (adjusted renal outcomes HR, 4.13; 95% confidence interval, 3.38, 5.04). Mortality HR was notably higher when participants failed to recover within 55% of baseline.

CONCLUSIONS

Renal recovery after AKI is associated with a lower risk of death or adverse renal outcomes after hospital discharge.

Peri-operative renal protection: The strategies revisited

Postoperative acute renal failure (ARF) is a serious complication which can result in a prolonged hospital stay and a high mortality and morbidity. Underlying renal disease, cardiac diseases, nephrotoxin exposure and renal hypoperfusion are the possible predisposing risk factors which can create a high probability for the development of ARF. The incidence of ARF is highest after major vascular, cardiac and high-risk thoraco-abdominal surgery. Among the various renal protection strategies, adequate peri-operative volume expansion and avoidance of hypovolemia is the most accepted and practiced strategy. Numerous bio-markers of renal injury are used to estimate the presence and extent of renal insult and various new are currently under trial. Traditional pharmacological interventions like dopamine, diuretics and calcium antagonists are not currently the first line of reno-protective agents. The new non-pharmacological and pharmacological methods may improve outcome in renal transplantation, contrast-induced nephropathy and in various other settings of ARF. The current review is an attempt to refresh the knowledge and put forth the various renal protection strategies during the peri-operative period.

The meaning of the blood urea nitrogen/creatinine ratio in acute kidney injury

Background.

A blood urea nitrogen (BUN)/creatinine ratio (BCR) >20 (0.081 in international unit) is used to distinguish pre-renal azotemia (PRA) and acute tubular necrosis (ATN). However, there is little evidence that BCR can distinguish between these two conditions and/or is clinically useful.

Methods.

We conducted a retrospective study using a large hospital database. Patients were divided into three groups: ‘low BCR’ (if BCR when acute kidney injury (AKI) developed was ≤20), ‘high BCR’ (if BCR when AKI developed was >20) and ‘no AKI’ if patients did not satisfy any of the Risk, Injury, Failure, Loss and End-stage kidney disease criteria for AKI during hospitalization.

Results.

Among 20 126 study patients, 3641 (18.1%) had AKI. Among these patients, 1704 (46.8%) had a BCR <20 at AKI diagnosis (‘low BCR’) and 1937 (53.2%) had a BCR >20 (‘high BCR’). The average BCR for the two groups was 15.8 versus 26.1 (P < 0.001). Hospital mortality was significantly less in the ‘low-BCR’ group (18.4 versus 29.9%, P < 0.001). Multivariable logistic regression analysis for hospital mortality (‘no AKI’ as a reference) showed that the odds ratio of ‘high BCR’ (5.73) was higher than that of ‘low BCR’ (3.32).

Conclusions.

Approximately half of the patients with AKI have a BCR >20, the traditional threshold of diagnosing PRA. Unlike PRA patients who have a lower mortality than ATN patients, high BCR patients had higher hospital mortality compared with low BCR patients, which was confirmed with multivariable analysis. These findings do not support BCR as a marker of PRA.

[Acute kidney injury]

Acute kidney injury (AKI) is defined as an abrupt decline in the glomerular filtration rate with accumulation of nitrogenous waste products and the inability to maintain fluid and electrolyte homeostasis. Occurring in 7% of all hospitalized patients and 28% to 35% of those in intensive care units, AKI increases hospital mortality. Early evaluation should include differentiating prerenal and postrenal components from intrinsic renal disease. Biological markers can give early warning of AKI and assist with differential diagnosis and assessment of prognosis. The most effective preventive measure is to maintain adequate circulation and cardiac output, avoiding ischemia- or nephrotoxin-induced injury. To that end, patients and situations of risk must be identified, hemodynamics and diuresis monitored, hypovolemia reversed, and nephrotoxins avoided. Protective agents such as sodium bicarbonate, mannitol, prostagiandins, calcium channel blockers, N-acetyl-L-cysteine, sodium deoxycholate, allopurinol, and pentoxifylline should be used. Treatment includes the elimination of prerenal and postrenal causes of AKI; adjustment of doses according to renal function; avoidance of both overhydration and low arterial pressure; maintenance of electrolytic balance, avoiding hyperkalemia and correcting hyperglycemia; and nutritional support, assuring adequate protein intake. For severe AKI, several modalities of renal replacement therapy, differentiated by mechanism and duration, are available. Timing--neither the best moment to start dialysis nor the optimal duration--has been not established. Early detection of AKI is necessary for preventing progression and starting renal replacement therapy at adjusted doses that reflect metabolic requirements.