Acute renal failure and mechanical ventilation: reality or myth?

Receipt of high-frequency ventilation is associated with acute kidney injury in very preterm neonates

BACKGROUND

High-frequency ventilation (HFV) is frequently used in critically ill preterm neonates. We aimed to determine the incidence of acute kidney injury (AKI) in neonates less than 29 weeks gestation who received HFV in the first week of life and to determine if the rates of AKI differed in those who received other forms of respiratory support.

METHODS

This retrospective cohort study of 24 international, level III/IV neonatal intensive care units (NICUs) included neonates less than 29 weeks gestation from the AWAKEN study database. Exclusion criteria included the following: no intravenous fluids ≥ 48 h, admission ≥ 14 days of life, congenital heart disease requiring surgical repair at < 7 days of life, lethal chromosomal anomaly, death within 48 h, severe congenital kidney abnormalities, inability to determine AKI status, insufficient data on ventilation, and when the diagnosis of early AKI was unable to be made. Subjects were grouped into three groups based on ventilation modes (CPAP/no ventilation, conventional ventilation, and HFV).

RESULTS

The incidence of AKI was highest in the CPAP/no ventilation group, followed by HFV, followed by conventional ventilation (CPAP/no ventilation 48.5% vs. HFV 42.6% vs. conventional ventilation 28.4% (p = 0.009). An increased risk for AKI was found for those on HFV compared to CPAP/no ventilation (HR = 2.65; 95% CI:1.22-5.73).

CONCLUSIONS

HFV is associated with AKI in the first week of life. Neonates on HFV should be screened for AKI. The reasons for this association are not clear. Further studies should evaluate the relationship between ventilator strategies and AKI in premature neonates. A higher resolution version of the Graphical abstract is available as Supplementary information.

Sepsis associated acute kidney injury

Sepsis is defined as organ dysfunction resulting from the host's deleterious response to infection. One of the most common organs affected is the kidneys, resulting in sepsis associated acute kidney injury (SA-AKI) that contributes to the morbidity and mortality of sepsis. A growing body of knowledge has illuminated the clinical risk factors, pathobiology, response to treatment, and elements of renal recovery that have advanced our ability to prevent, detect, and treat SA-AKI. Despite these advances, SA-AKI remains an important concern and clinical burden, and further study is needed to reduce the acute and chronic consequences. This review summarizes the relevant evidence, with a focus on the risk factors, early recognition and diagnosis, treatment, and long term consequences of SA-AKI. In addition to literature pertaining to SA-AKI specifically, pertinent sepsis and acute kidney injury literature relevant to SA-AKI was included.

AKI in the very elderly patients without preexisting chronic kidney disease: a comparison of 48-hour window and 7-day window for diagnosing AKI using the KDIGO criteria

Objectives

To compare the differences between the Kidney Disease Improving Global Outcomes (KDIGO) criteria of the 48-hour window and the 7-day window in the diagnosis of acute kidney injury (AKI) in very elderly patients, as well as the relationship between the 48-hour and 7-day windows for diagnosis and 90-day mortality.

Patients and methods

We retrospectively enrolled very elderly patients (≥75 years old) from the geriatrics department of the Chinese PLA General Hospital between January 2007 and December 2015. AKI patients were divided into 48-hour and 7-day groups by their diagnosis criteria. AKI patients were divided into survivor and nonsurvivor groups by their outcomes within 90 days after diagnosis of AKI.

Results

In total, 652 patients were included in the final analysis. The median age of the cohort was 87 (84–91) years, the majority (623, 95.6%) of whom were male. Of the 652 AKI patients, 334 cases (51.2%) were diagnosed with AKI by the 48-hour window for diagnosis, while 318 cases (48.8%) were by the 7-day window for diagnosis. The 90-day mortality was 42.5% in patients with 48-hour window AKI and 24.2% in patients with 7-day window AKI. Kaplan–Meier curves showed that 90-day mortality was lower in the 7-day window AKI group than in the 48-hour window AKI group (log rank: P<0.001). Multivariate analysis by the Cox model revealed that 48-hour window for diagnosis hazard ratio (HR=1.818; 95% CI: 1.256–2.631; P=0.002) was associated with higher 90-day mortality.

Conclusion

The 90-day mortality was higher in 48-hour window AKI than in 7-day window AKI in very elderly patients. The 48-hour KDIGO window definition may be less sensitive. The 48-hour KDIGO window definition is significantly better correlated with subsequent mortality and is, therefore, still appropriate for clinical use. Finding early, sensitive biomarkers of kidney damage is a future direction of research.

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.

Ventilação mecânica e a lesão renal aguda em pacientes na unidade de terapia intensiva

Objetivo Verificar o impacto do emprego da ventilação mecânica em pacientes internados na Unidade de Terapia Intensiva e a ocorrência de lesão renal aguda. Métodos Estudo de coorte, prospectivo, quantitativo, desenvolvido com 27 pacientes sob suporte de ventilação mecânica internados na unidade de terapia intensiva em um hospital público. Resultados A maioria (55,6%) dos pacientes foi classificada no estágio de lesão renal, de acordo com a classificação Risk, Injury, Failure, Loss, End-Stage (RIFLE). Dentre os pacientes, 45,8% estavam sob ventilação mecânica com pressão expiratória final positiva entre 5cmH2O e 10cmH2O, os quais evoluíram com lesão renal aguda. Acute Physiology and Chronic Health Disease Classification System II (APACHE II) apresentou associação significativa com disfunção renal (p=0,046). Conclusão O emprego da ventilação mecânica invasiva com pressão expiratória final positiva em pacientes graves pode determinar prejuízos à função renal dos pacientes internados em unidade de terapia intensiva.

Prognosis-related factors in intensive care unit (ICU) patients with hematological malignancies: A retrospective cohort analysis in a Chinese population

OBJECTIVES

This study investigates the link between patient characteristics and mortality in patients with hematological malignancies (HM) in three university-affiliated hospitals in Hunan, China.

METHODS

We conducted a detailed retrospective chart review of 121 sequential intensive care unit (ICU) admissions with HM over a 5-year period. Outcome measures were short- and long-term mortality rates and were correlated with physiologic and therapeutic factors. We also evaluate the performance of two severity-of-illness scoring systems in this population, particularly the value and trend of the sequential organ failure assessment (SOFA).

RESULTS

The rates for ICU, 1-month and 6-month mortalities were 60.3, 85.9, and 90.9%, respectively. Invasive mechanical ventilation (IMV) was associated with worse outcomes at all time points. Both acute physiology and chronic health evaluation and SOFA scores had positive correlation with ICU mortality. An increase or no change in SOFA over the course of the admission or during the first 48 hours after admission was the most powerful adverse predictor. IMV use and renal dysfunction had a negative effect on the 1-month survival.

CONCLUSION

Patients with HM have less access to intensive care resources in Hunan, China. The use of IMV, APACHII at admission, and SOFA trend have a strong predictive value in this population. Based on our results, we propose a panel of parameters for use when considering ICU transfer to guide patient management.

Special nutrition challenges: current approach to acute kidney injury

Acute kidney injury (AKI), previously known as acute renal failure, is defined as a sudden decline in glomerular filtration rate with accumulation of metabolic waste products, toxins, and drugs, as well as alteration in the intrinsic functions of the kidney. Reports of mortality are as high as 80%, with numerous contributing causes including infection, cardiorespiratory complications, and cardiovascular disease. Concurrent with the high prevalence of critical illness in this population is the protein energy wasting (PEW), seen in up to 42% of patients upon intensive care unit admission. The pathophysiologic derangements of critical illness, the low energy and protein stores, and uremic complications require early nutrition intervention to attenuate the inflammatory response and oxidative stress, improve endothelial function, stabilize blood sugar, and preserve lean body mass. This article addresses the unique challenges of nutrition support for the patient with AKI in the setting of critical illness and renal replacement therapy. Evidence-based recommendations are provided to meet the macronutrient and micronutrient requirements of this heterogeneous and complex patient population.

Predicting restoration of kidney function during CRRT-free intervals

Background

Renal failure is common in critically ill patients and frequently requires continuous renal replacement therapy (CRRT). CRRT is discontinued at regular intervals for routine changes of the disposable equipment or for replacing clogged filter membrane assemblies. The present study was conducted to determine if the necessity to continue CRRT could be predicted during the CRRT-free period.

Materials and methods

In the period from 2003 to 2006, 605 patients were treated with CRRT in our ICU. A total of 222 patients with 448 CRRT-free intervals had complete data sets and were used for analysis. Of the total CRRT-free periods, 225 served as an evaluation group. Twenty-nine parameters with an assumed influence on kidney function were analyzed with regard to their potential to predict the restoration of kidney function during the CRRT-free interval. Using univariate analysis and logistic regression, a prospective index was developed and validated in the remaining 223 CRRT-free periods to establish its prognostic strength.

Results

Only three parameters showed an independent influence on the restoration of kidney function during CRRT-free intervals: the number of previous CRRT cycles (medians in the two outcome groups: 1 vs. 2), the "Sequential Organ Failure Assessment"-score (means in the two outcome groups: 8.3 vs. 9.2) and urinary output after the cessation of CRRT (medians in two outcome groups: 66 ml/h vs. 10 ml/h). The prognostic index, which was calculated from these three variables, showed a satisfactory potential to predict the kidney function during the CRRT-free intervals; Receiver operating characteristic (ROC) analysis revealed an area under the curve of 0.798.

Conclusion

Restoration of kidney function during CRRT-free periods can be predicted with an index calculated from three variables. Prospective trials in other hospitals must clarify whether our results are generally transferable to other patient populations.

Sensing, physiological effects and molecular response to elevated CO2 levels in eukaryotes

Carbon dioxide (CO₂) is an important gaseous molecule that maintains biosphere homeostasis and is an important cellular signalling molecule in all organisms. The transport of CO₂ through membranes has fundamental roles in most basic aspects of life in both plants and animals. There is a growing interest in understanding how CO₂ is transported into cells, how it is sensed by neurons and other cell types and in understanding the physiological and molecular consequences of elevated CO₂ levels (hypercapnia) at the cell and organism levels. Human pulmonary diseases and model organisms such as fungi, C. elegans, Drosophila and mice have been proven to be important in understanding of the mechanisms of CO₂ sensing and response.