Effect of stress hyperglycaemia on acute kidney injury in non-diabetic critically ill patients?

BACKGROUND

Stress hyperglycaemia (SH) and acute kidney injury (AKI) occur frequently in critically ill patients, and particularly non-diabetics are associated with adverse outcome. Data is scarce on the effect of SH on AKI. We assessed whether SH (i) preceded AKI, (ii) was a risk factor of subsequent AKI, and (iii) how SH and tubular injury interacted in AKI development in critically ill, non-diabetics.

METHODS

Case-control study of 82 patients each with and without SH matched by propensity score for multiple demographic characteristics. AKI was defined by KDIGO criteria, SH either as blood glucose (BG) > 140 mg/dl (BG140), > 200 mg/dl (BG200), or stress hyperglycemia rate (SHR) ≥ 1.47 (SHR1.47) as measured 2 days before AKI. Urinary cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) indicated tubular injury.

RESULTS

In AKI, SH rates were frequent using all 3 definitions applied, but highest when BG140 was applied. SH by all 3 definitions was consistently associated with AKI. This was independent of established risk factors of AKI such as sepsis and shock. Increments of BG, urinary NGAL or cystatin C, and its products, were independently associated with the likelihood of subsequent AKI, demonstrating their reciprocal potentiating effects on AKI development.

CONCLUSIONS

SH is frequent in critically ill, non-diabetics with AKI. SH was identified as an independent risk factor of AKI. Higher BG combined with tubular injury may potentiate their adverse effects on AKI.

Incidence, severity, risk factors and outcomes of acute kidney injury in older adults: systematic review and meta-analysis

OBJECTIVES

Old age was identified as a strong risk factor for acute kidney injury (AKI). Our objectives were to provide estimates of AKI, risk factors and outcomes in patients ≥ 75 years for whom data are scarce.

METHODS

Observational studies and randomized controlled trials between 2005 and 2021 with patients of mean or median age ≥ 75 years, reporting AKI according to current definitions. Data on AKI incidence, risk factors and mortality were analyzed separately in unselected (UC) and acute heart failure (AHF) cohorts.

RESULTS

Twenty-six observational studies and 4 randomized controlled trials with 51,111 UC and 25,414 AHF patients were included. Ages averaged 79.4 and 79.8 years, respectively. Pooled risk ratios (RRs) of AKI rates were 26.29% (95% confidence intervals (CI) 13.20-41.97) (UC) and 24.21% (95% CI 20.03-28.65) (AHF). In both cohorts, AKI was associated with decreased estimated glomerular filtration rate at baseline, chronic kidney disease (UC: RR 1.80 (95% CI 1.15-2.80), AHF: RR 1.51 (95% CI 1.26-1.95) and hypertension (UC: RR 1.30 (95% CI 1.09-1.56), AHF: RR 1.07 (95% CI 1.05-1.09). RRs of AKI in patients on renin-angiotensin-inhibitors were 0.87 (95% CI 0.78-0.97) and 0.88 (95% CI 0.78-0.98) in UC and AHF, respectively. AKI was consistently associated with increased risk of in-hospital mortality (UC: RR 3.15 (95% CI 2.28-4.35), AHF: RR 4.28 (95% CI 2.53-7.24).

CONCLUSION

AKI is frequent in patients ≥ 75 years. While reduced renal function at baseline, CKD and hypertension were associated with AKI development, renin-angiotensin-inhibitors may be protective. Older AKI patients showed higher short-term mortality rates.

Health-Related Quality of Life according to Renal Function: Results from a Nationwide Health Interview and Examination Survey

BACKGROUND

Most studies on health-related quality of life (HRQoL) in chronic kidney disease (CKD) focus on patients with end-stage kidney disease although they represent a small proportion of patients with CKD. We aimed to analyze HRQoL according to glomerular filtration rate (GFR) categories in a population-based sample of adults living in Germany.

METHODS

Data from the German health interview and examination survey conducted from 2008 to 2011 were used. Participants with valid interview and examination data aged 40-79 years were included (n = 5,159). Serum creatinine levels were used to calculate estimated GFR via the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. We classified kidney function in GFR categories according to the Kidney Disease Improving Global Outcomes Initiative (KDIGO) guidelines on CKD: G1 (high): ≥90 mL/min/1.73 m2, G2 (normal): 60-89 mL/min/1.73 m2, G3a (mildly decreased): 45-59 mL/min/1.73 m2, G3b (moderately decreased): 30-44 mL/min/1.73 m2, G4/5 (severely decreased/end-stage kidney disease): <30 mL/min/1.73 m2. HRQoL was evaluated with the Short Form Health Survey (SF-36). Different multivariate linear and logistic regression models were used to analyze the association of HRQoL with GFR categories.

RESULTS

Overall, 5.9% had a GFR <60 mL/min/1.73 m2 (corresponding to categories G3a, G3b, and G4/5). Compared to category G2 linear regression showed a decline in physical HRQoL in categories G3a (-2.34, p = 0.004), G3b (-5.37, p = 0.009), and G4/5 (-4.82, p = 0.117). No decline in mental HRQoL was detected with increasing GFR categories. Categories G3a to G4/5 were significantly associated with a low perceived general state of health (G3a: odds ratio [OR] = 2.03, p = 0.001; G3b: OR = 3.01, p = 0.009; G4/5: OR = 8.70, p = 0.016) when compared to category G2.

CONCLUSION

In a representative sample of adults living in Germany, both physical HRQoL and the perceived general state of health are already significantly reduced in category G3a.

SARS-CoV-2: Viral Loads of Exhaled Breath and Oronasopharyngeal Specimens in Hospitalized Patients with COVID-19

Background

SARS-CoV-2 seems mainly transmissible via respiratory droplets. We compared the time-dependent SARS-CoV-2 viral load in serial pharyngeal swab with exhaled breath (EB) samples of hospitalized COVID-19 patients.

Methods

In this prospective proof of concept study, we examined hospitalized patients who initially tested positive for SARS-CoV-2. Paired oronasopharyngeal swab and EB specimens were taken at different days of hospitalization. EB collection was performed through a simple, noninvasive method using an electret air filter-based device. SARS-CoV-2 RNA detection was determined with real-time quantitative reverse transcription polymerase chain reaction.

Results

Of 187 serial samples from 15 hospitalized patients, 87/87 oronasopharyngeal swabs and 70/100 EB specimens tested positive. Comparing the number of SARS-CoV-2 copies, the viral load of the oronasopharyngeal swabs was significantly higher (CI 99%, P<<0,001) than for EB samples. The mean viral load per swab was 7.97 × 10⁶ (1.65 × 10²-1.4 × 10⁸), whereas EB samples showed 2.47 × 10³ (7.19 × 10¹-2.94 × 10⁴) copies per 20 times exhaling. Viral loads of paired oronasopharyngeal swab and EB samples showed no correlation.

Conclusions

Assessing the infectiousness of COVID-19 patients merely through pharyngeal swabs might not be accurate. Exhaled breath could represent a more suitable matrix for evaluating infectiousness and might allow screening for superspreader individuals and widespread variants such as Delta.

Capnocytophaga canimorsus - a potent pathogen in immunocompetent humans - systematic review and retrospective observational study of case reports

Purpose: Severe and fatal Capnocytophaga canimorsus infection has been described in immunocompromised patients. Data of C. canimorsus infection in immunocompetent and risk factors of severe courses are missing. Our aims were to describe the epidemiology of C. canimorsus infection and to identify potential risk factors of sepsis and fatal outcome.Methods: Observational study and systematic review of all cases reported in immunocompetent subjects between 2002 and 2019.Results: A total of 128 cases of C. canimorsus infection in immunocompetent individuals were reported. Male gender comprised 74.2%, the median age was 58 years and 47.7% were admitted with sepsis. Case-fatality rate was 29.7% and especially high in septic patients (55.7%). Transmission by bite (OR = 2.37, 95% CI: 1.05-6.52) and incubation time ≤3 d (OR = 7.98; 95% CI: 2.33-27.34) were identified as risk factors of sepsis on admission, and early wound cleansing as protective (OR = 0.42; 95% CI: 0.14-0.96). Sepsis (OR = 23.67; 95% CI: 2.85-197.89) and septic shock (OR = 45.50; 95% CI: 3.08-676.55) were risk factors of fatal outcome, whereas early wound cleansing (OR = 0.05; 95% CI: 0.01-0.72), initial penicillin therapy with beta-lactamase inhibitors (OR = 0.48; 95% CI: 0.16-0.92) and surgical removal of infectious focus (OR = 0.38; 95% CI: 0.06-0.95) were protective factors.Conclusions: Immunocompetent patients with C. canimorsus infection frequently develop sepsis. A shorter incubation period in cases of sepsis might be related to higher infectious dose. Fatal outcome may be prevented by early wound cleansing, initial use of penicillins in combination with beta-lactamase inhibitors and surgical removal of an infectious focus.

Being Licked by a Dog Can Be Fatal: Capnocytophaga canimorsus Sepsis with Purpura Fulminans in an Immunocompetent Man

Bite infections caused by Capnocytophaga canimorsus are rare. Severe and fatal infections are more frequently reported in patients with immunodeficiency, splenectomy or alcohol abuse. We describe the case of a 63-year-old man who developed flu-like symptoms and presented after some delay with severe sepsis and purpura fulminans. He was found to be infected with C. canimorsus without a bite injury and did not demonstrate immunodeficiency or any other typical predisposition. Despite extensive intensive care, his conditions deteriorated and he died from multiorgan failure.

Combined use of drugs inhibiting the renin-angiotensin system: prescribing patterns and risk of acute kidney injury in German nursing home residents

Background/aims

In 2012, the European Medicines Agency reviewed the safety of dual renin-angiotensin system (RAS) blockade because of potentially increased risks for inter alia acute kidney injury (AKI). Since residents of nursing homes are particularly vulnerable to adverse drug outcomes, the aims of our study were to describe RAS-inhibiting drug use in German nursing home residents and examine the risk of AKI associated with dual RAS blockade.

Methods

Based on claims data, a nested case-control study within a cohort of RAS-inhibiting drug users was conducted. Using conditional logistic regression, confounder-adjusted odds ratios (aORs) and 95% confidence intervals (CI) were obtained for the risk of AKI associated with dual RAS blockade. Subgroup analyses were performed in patients with diabetes or chronic kidney disease and both comorbidities.

Results

Of all 127,227 nursing home residents, the study cohort included 64,567 (50.7%) who were treated with at least one RAS-inhibiting drug. More than three quarters of the study population were female (77.1%). Mean age was 86.0 ± 6.8 years. Most residents were treated with angiotensin-converting enzyme inhibitors (77.8%), followed by angiotensin II receptor blockers (21.6%) and aliskiren (0.2%). Annual prevalence of dual RAS blockade declined from 9.6 (95% CI 7.8-11.8) in 2010 to 4.7 (95% CI 4.0-5.4) per 1,000 users in 2014. In the overall cohort, AKI was not significantly associated with dual RAS blockade (aOR 1.99; 0.77-5.17). However, significantly increased aORs were observed when considering patients with diabetes (3.47; 1.27-9.47), chronic kidney disease (4.74; 1.24-18.13) or both (11.17; 2.65-47.15).

Conclusions

Prescribing of drugs inhibiting the RAS is common in German nursing homes. Though the prevalence of dual RAS blockade declined, our study showed an increased risk of AKI in patients with diabetes and/or chronic kidney disease. Therefore, cautious use is warranted in these vulnerable patients.

Use of oral anticoagulants in German nursing home residents: drug use patterns and predictors for treatment choice

AIMS

Information on utilization of oral anticoagulants (OACs) in nursing homes is scarce. This study aimed to (i) describe OAC use in German nursing home residents, (ii) examine factors influencing whether treatment is initiated with vitamin K antagonists (VKAs) or non-VKA oral anticoagulants (NOACs) and (iii) assess which conditions predict switching to NOAC instead of continuing VKA.

METHODS

Using claims data (2010-2014), we studied a cohort of new nursing home residents aged ≥65 years receiving OAC. Further, OAC use in patients with atrial fibrillation (AF) was examined over the years.

RESULTS

Overall, 16 804 patients (median age: 85 years, 75% female, 44% with renal disease) were included. The majority received phenprocoumon as first OAC (58.0%), followed by rivaroxaban (28.1%). Over the study period, NOAC use increased substantially. Initiating NOAC instead of VKA was predicted by a previous stroke (adjusted odds ratio: 1.76; 95% confidence interval: 1.49-2.08). In contrast, renal disease predicted VKA initiation (0.66; 0.59-0.75) as did the presence of a prosthetic heart valve. Switching from VKA to NOAC was predicted by a stroke (2.55; 2.00-3.24), bleeding events and a recent hospitalization. During 2010-2014, the proportion of AF patients with a CHADS2 score ≥2 receiving OAC increased from 27% to 46%.

CONCLUSIONS

NOACs are increasingly used in German nursing homes, both for initial anticoagulation but also in VKA pre-treated patients. Switching from VKA to NOAC was substantially influenced by aspects such as intended higher effectiveness and safety but probably also practicability due to less blood monitoring.

Improving Outcomes from Acute Kidney Injury (AKI): Report on an Initiative

Acute Kidney Injury (AKI) is a complex disorder for which currently there is no accepted definition. We describe an initiative to develop uniform standards for defining and classifying AKI and establish a forum for multidisciplinary interaction to improve care for patients with, or at risk for AKI. Members representing key societies in critical care and nephrology along with additional experts in adult and pediatric AKI participated in a 2-day conference in Amsterdam in September 2005 to draft consensus recommendations for diagnosing and staging AKI. This report describes the proposed diagnostic and staging criteria for AKI and the formation of a multidisciplinary collaborative network (Acute Kidney Injury Network (AKIN) focused on improving outcomes from AKI.

Inappropriate Medication in Non-Hospitalized Patients With Renal Insufficiency: A Systematic Review

OBJECTIVES

Renal insufficiency is common among older patients and, accordingly, renally excreted drugs may require an adjustment in dosage for them. Rates of non-adherence to renal dosing guidelines range from 19% to 70% across all settings, with the highest rate occurring in outpatient care. However, there is a paucity of research in this field. The main objective of this systematic review is to assess how often drugs are inappropriately prescribed in non-hospitalized patients with renal insufficiency.

DESIGN

A systematic literature search was performed. Data were identified from three electronic databases: PubMed, CINAHL, and Scopus. Studies were included if they reported quantitative data on inappropriate drug use with respect to renal function in non-hospitalized patients.

RESULTS

Our search strategy resulted in 2,403 hits, of which 18 articles satisfied the criteria for inclusion. Mean estimated glomerular filtration rate ranged from 36.0 to 60.4 mL/min. Prevalence of renally inappropriate drug use ranged from 1% to 37% in outpatient settings other than nursing homes, and from 6% to 43% in nursing homes. Eight of the studies we included identified predictors for use of drugs inappropriate for kidney function. Most frequently determined risk factors were increasing age and a high number of prescribed drugs.

CONCLUSION

Lack of dose adjustment for renal impairment seems to be a common problem, even in outpatients. However, the differences in methodologies used in these studies hampered any direct comparison. Accepted and comparable standards regarding the drugs included in the studies as well as estimation of renal function would be beneficial.

Renal Insufficiency and Medication in Nursing Home Residents. A Cross-Sectional Study (IMREN)

BACKGROUND

Nursing home residents often suffer from a multiplicity of medical conditions and take many different drugs. Many drugs are eliminated via the kidneys and thus require dose adjustment in patients with renal insufficiency. This is the first study to address the prevalence of renal insufficiency among nursing home residents in Germany, and the extent to which such persons take drugs that are contraindicated or incorrectly dosed because of renal insufficiency.

METHODS

We carried out a cross-sectional study in nursing homes in the German regions of Bremen and Lower Saxony. Data were collected by nursing staff and given to us anonymously. Whenever the nursing home data did not include a current creatinine value, the patient's general practitioner was asked to supply this value. The estimated creatinine clearance (eCCr) was calculated with the Cockcroft-Gault formula.

RESULTS

852 residents of 21 nursing homes were included in the study; eCCr values were obtainable for 685 (80.4%) of them (average age, 83.3 years; 75.2% female). 48.2% of these patients (95% confidence interval [CI] 41.8-54.5) had moderate renal insufficiency (eCCr 59-30 mL/min), and 15.5% (95% CI 12.4-18.6) had severe renal insufficiency (eCCr <30 mL/min). 19.7% were regularly taking at least one medication that was contraindicated or incorrectly dosed in the light of renal insufficiency. Predictors for such inappropriate drug use were advanced age, female sex, arterial hypertension, and polypharmacy. The drugs that were most often inappropriately used were metformin, ramipril, and potassium chloride.

CONCLUSION

Nursing home residents often suffer from renal insufficiency and should therefore have their creatinine levels measured regularly. A knowledge of the creatinine level is a prerequisite for the proper adjustment of drug doses (if necessary). A practical and compact summary of dose-adjustment recommendations for patients with renal insufficiency would be desirable but is not yet available.

Polypharmacy and Renal Failure in Nursing Home Residents: Results of the Inappropriate Medication in Patients with Renal Insufficiency in Nursing Homes (IMREN) Study

BACKGROUND

Polypharmacy has become an emerging public health issue in recent years, since use of multiple medications or polypharmacy is beneficial for many conditions, but may also have negative effects like adverse drug reactions. The risk further increases in patients with chronic renal failure, a comorbidity very frequent in nursing home residents. Since more than 50% of all drugs were renally excreted, dose adjustments in patients with renal failure are required.

OBJECTIVE

To assess polypharmacy in German nursing homes, in particular in residents with renal failure.

METHODS

Multi-center cross-sectional study in 21 nursing homes in Bremen and Lower Saxony/Germany. Baseline data were analysed using descriptive statistics. Multivariable logistic regression model and 95% confidence intervals were used to study the association of renal failure and polypharmacy.

RESULTS

Of all 852 residents, the analysis comprised those 685 with at least one serum creatinine value so that the estimated creatinine clearance could be calculated. Of those, 436 (63.6%) had a severe or moderate renal failure, defined as estimated creatinine clearance <60 mL/min. Polypharmacy (5-9 drugs) was found in 365 (53.3%) and excessive polypharmacy (≥10 drugs) in 112 (16.4%) residents. Diuretics and psycholeptics were the most commonly used drug classes. Severe renal failure (estimated creatinine clearance <30 mL/min) was associated with polypharmacy (OR: 2.8, 95% CI 1.4-5.7).

CONCLUSION

Both, polypharmacy and renal failure are common in German nursing home residents and an association of both could be found. Further studies are needed to assess the appropriateness of polypharmacy in these patients.

Acute kidney injury prediction in cardiac surgery patients by a urinary peptide pattern: a case-control validation study

Background

Acute kidney injury (AKI) is a prominent problem in hospitalized patients and associated with increased morbidity and mortality. Clinical medicine is currently hampered by the lack of accurate and early biomarkers for diagnosis of AKI and the evaluation of the severity of the disease.

In 2010, we established a multivariate peptide marker pattern consisting of 20 naturally occurring urinary peptides to screen patients for early signs of renal failure. The current study now aims to evaluate if, in a different study population and potentially various AKI causes, AKI can be detected early and accurately by proteome analysis.

Methods

Urine samples from 60 patients who developed AKI after cardiac surgery were analyzed by capillary electrophoresis-mass spectrometry (CE-MS). The obtained peptide profiles were screened by the AKI peptide marker panel for early signs of AKI. Accuracy of the proteomic model in this patient collective was compared to that based on urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) ELISA levels. Sixty patients who did not develop AKI served as negative controls.

Results

From the 120 patients, 110 were successfully analyzed by CE-MS (59 with AKI, 51 controls). Application of the AKI panel demonstrated an AUC in receiver operating characteristics (ROC) analysis of 0.81 (95 % confidence interval: 0.72–0.88). Compared to the proteomic model, ROC analysis revealed poorer classification accuracy of NGAL and KIM-1 with the respective AUC values being outside the statistical significant range (0.63 for NGAL and 0.57 for KIM-1).

Conclusions

This study gives further proof for the general applicability of our proteomic multimarker model for early and accurate prediction of AKI irrespective of its underlying disease cause.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1344-z) contains supplementary material, which is available to authorized users.

Progressive chronic kidney disease in primary care: modifiable risk factors and predictive model

OBJECTIVE

To determine the incidence and prevalence of CKD and of progressive GFR decline, to identify modifiable risk factors of and to develop a predictive risk model for progressive GFR decline in high risk primary care patients.

METHODS

Retrospective observational study of 803 patients with or at high risk of CKD exclusively managed in primary care. Baseline data was collected in 2003, follow-up data in 2006. High risk was defined as inadequately controlled hypertension or diabetes, and GFR<60, progressive GFR decline as annual GFR decline >2.5mlmin(-1) 1.73m(-2).

RESULTS

CKD was present in 25.4% at baseline and developed in further 13.7% during follow-up, 42.5% demonstrated progressive GFR decline. Obesity, proteinuria, heart failure, inadequate hypertension and diabetes control, lacking angiotensin-converting-enzyme-inhibitors or angiotensin-receptor-blockers, radio contrast, and dual renin-angiotensin-aldosterone-system blockade were identified as modifiable, independent risk factors of progressive GFR decline. The risk model, containing 7 readily obtainable variables, showed good discriminative ability.

CONCLUSIONS

High risk primary care patients demonstrated high CKD prevalence and incidence, and rate of progressive GFR decline. Identified risk factors can be modified in primary care. Our risk model may aid primary care physicians to predict patients at high risk of progressive GFR decline.

Validation of treatment strategies for enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome: case-control study

OBJECTIVE

To evaluate the effect of different treatment strategies on enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome.

DESIGN

Multicentre retrospective case-control study.

SETTING

23 hospitals in northern Germany.

PARTICIPANTS

298 adults with enterohaemorrhagic E coli induced haemolytic uraemic syndrome.

MAIN OUTCOME MEASURES

Dialysis, seizures, mechanical ventilation, abdominal surgery owing to perforation of the bowel or bowel necrosis, and death.

RESULTS

160 of the 298 patients (54%) temporarily required dialysis, with only three needing treatment long term. 37 patients (12%) had seizures, 54 (18%) required mechanical ventilation, and 12 (4%) died. No clear benefit was found from use of plasmapheresis or plasmapheresis with glucocorticoids. 67 of the patients were treated with eculizumab, a monoclonal antibody directed against the complement cascade. No short term benefit was detected that could be attributed to this treatment. 52 patients in one centre that used a strategy of aggressive treatment with combined antibiotics had fewer seizures (2% v 15%, P = 0.03), fewer deaths (0% v 5%, p = 0.029), required no abdominal surgery, and excreted E coli for a shorter duration.

CONCLUSIONS

Enterohaemorrhagic E coli induced haemolytic uraemic syndrome is a severe self limiting acute condition. Our findings question the benefit of eculizumab and of plasmapheresis with or without glucocorticoids. Patients with established haemolytic uraemic syndrome seemed to benefit from antibiotic treatment and this should be investigated in a controlled trial.

Effects of fractionated plasma separation and adsorption on survival in patients with acute-on-chronic liver failure

BACKGROUND & AIMS

Fractionated plasma separation and adsorption (FPSA) is an extracorporeal procedure that supports liver function by removing endogenous toxins that cause complications from acute-on-chronic liver failure (AOCLF). We performed a randomized trial to investigate survival of patients with AOCLF treated with FPSA.

METHODS

Patients with AOCLF were randomly assigned to groups given a combination of FPSA and standard medical therapy (SMT) (FPSA group, n = 77) or only SMT (SMT group, n = 68). The Prometheus liver support system was used to provide 8 to 11 rounds of FPSA (minimum of 4 hours each) for 3 weeks. Primary end points were survival probabilities at days 28 and 90, irrespective of liver transplantation.

RESULTS

Baseline clinical parameters and number of transplant patients were similar between study arms. Serum bilirubin level decreased significantly in the FPSA group but not in the SMT group. In an intention-to-treat analysis, the probabilities of survival on day 28 were 66% in the FPSA group and 63% in the SMT group (P = .70); on day 90, they were 47% and 38%, respectively (P = .35). Baseline factors independently associated with poor prognosis were high SOFA score, bleeding, female sex, spontaneous bacterial peritonitis, intermediate increases in serum creatinine concentration, and combination of alcoholic and viral etiology of liver disease. There were no differences between the 2 groups in the incidence of side effects.

CONCLUSIONS

Among all patients with AOCLF, extracorporeal liver support with FPSA does not increase the probability of survival. Further studies are needed to assess whether therapy might be beneficial in specific subsets of patients.

Prognostic significance of serum cystatin C in multiple myeloma

Multiple myeloma (MM) is frequently complicated by renal insufficiency, which is associated with an unfavorable prognosis. Serum cystatin C is a new and accurate marker of glomerular filtration rate. Global gene expression analysis has revealed serum cystatin C as one of the most highly upregulated genes in MM. Recent data have shown serum cystatin C as an independent prognostic marker in MM. To further elucidate the prognostic significance of serum cystatin C, we investigated pretreatment serum cystatin C levels in 68 newly diagnosed patients homogeneously treated with high-dose melphalan followed by autologous stem cell transplantation. Median serum cystatin C level in MM patients was significantly higher than in the 66 healthy controls (1.07 vs. 0.74 mg/L [p = 0.002]). Median serum cystatin C levels significantly increased with higher International Staging System (ISS) stages (stage I 0.72 mg/L; stage II 0.89 mg/L; stage III 1.28 mg/L; p < 0.0001). Higher serum cystatin C was positively correlated with higher serum levels of creatinine (r = 0.84; p < 0.0001), β2-microglobulin (r = 0.72; p < 0.0001), LDH (r = 0.43; p = 0.0003), white blood cell counts (r = 0.61; p < 0.0001) and calcium (r = 0.29; p = 0.016), and negatively correlated with lower serum albumin levels (r = 0.44; p < 0.0001) and hemoglobin levels (r = 0.31; p = 0.01). Using ROC analysis, patients with serum cystatin C levels ≥0.95 mg/L (n = 24) had a significantly shorter event-free survival (EFS) and overall survival (OS) than patients with serum cystatin C levels <0.95 mg/L (median EFS: 26 vs. 44 months, p < 0.0001; median OS: 54 vs. 68 months, p = 0.05). Moreover, the combination of serum cystatin C level and genomic aberrations further refined the prognostic information (EFS and OS) provided by either one of the factors. The level of serum cystatin C is not only a sensitive marker of renal function, but also reflects tumor burden and delivers prognostic information in MM.

Definition and risk factors of rapidly declining residual renal function in peritoneal dialysis: an observational study

BACKGROUND

It is critical to preserve residual renal function (RRF) in peritoneal dialysis (PD), as RRF is associated with lower morbidity and mortality. There is no uniform definition of RRF, and rapidly declining RRF has rarely been studied and predominately limited to single factor analysis and not corrected for lead-time bias.

METHODS

An observational study in 71 incident PD patients. RRF was defined as urine output (UO) ≥500 ml/day and renal glomerular filtration rate (rGFR) ≥2 ml/min/1.73 m(2), rapid declining RRF as UO <500 ml/day and rGFR <2 ml/min/1.73 m(2) occurring within 6 months which were separately evaluated. Independent risk factors associated with rapid RRF decline were identified while correcting for lead-time bias.

RESULTS

RRF declined rapidly by both definitions in 65% patients 2.5 years after PD start. Both definitions of RRF decline were consistent in 96%. Nephrotoxic drugs, renal transplant failure and absent angiotensin-converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARB) were independent risk factors associated with rapidly declining RRF defined both by definitions, intravascular radiocontrast additionally for UO decline.

CONCLUSIONS

Most PD patients demonstrated rapid RRF decline, independent of its definition. Both definitions are highly consistent and interchangeable. Nephrotoxic drugs and radiocontrast were identified as risk factors of acute, absent ACEI or ARB, and renal transplant failure of chronic renal injury.

Proteomic biomarkers for the early detection of acute kidney injury

Acute kidney injury (AKI) comprises several syndromes that are associated with a sudden decrease in renal function. AKI is a common condition especially among critically ill patients. It is typically multifactorial and of great prognostic significance. The incidence of AKI has increased while the associated mortality rate has remained unchanged over the last years. Recent definitions of AKI, namely the Risk, Injury, Failure, Loss of renal function and End-stage kidney disease (RIFLE) classifycation or the Acute Kidney Injury Network (AKIN) criteria, incorporate serum creatinine and urine output as the principal markers to define and detect AKI. However, elevated serum creatinine or oliguria were demonstrated to detect AKI at late stages of renal injury when preventive strategies may be less effective. Therefore, there has recently been a great scientific interest in obtainng valuable markers for early AKI detection. In the last 5 years numerous new markers such as neutrophil-gelatinase associated lipo-calin, interleukin-18, cystatin C and kidney injury molecule 1 in the urine and/or serum have been studied and proposed as early detection markers of AKI. Persistently, these markers performed well in initial pilot trials. However, these promising results could often not be confirmed in later, larger multicentre trials and limitation of these biomarkers in the early diagnosis of renal injury were discovered. Furthermore, as AKI is multi-factorial and heterogeneous in origin, it seems likely that not one single marker but a panel of biomarkers will be required to detect all subtypes of AKI early during their evolution. This has initiated proteomic studies to develop panels of biomarkers which may facilitate early detection of AKI. The present review will focus on the most important clinical studies evaluating the ability of single AKI biomarkers and on those in clinical proteomics that attempted to establish panels of biomarkers in urine for early and accurate AKI diagnosis and prognosis.

How does late nephrological co-management impact chronic kidney disease? - an observational study

AIMS

To assess the impact of late referral (LR) for nephrological co-management compared with early referral (ER) on morbidity and mortality in chronic kidney disease (CKD) and to identify individual factors associated with higher mortality in LR, correcting for lead-time and immortal time bias.

PATIENTS AND METHODS

Retrospective observational study comparing 46 LR patients with 103 ER patients. The quality of CKD management was assessed by measures to prevent CKD progression and to modify CKD complications and cardiovascular risk factors according to current guidelines. One-year mortality of LR and ER was compared and factors associated with mortality were identified. Analysis was performed with equivalent GFR (glomerular filtration rate) of ER and LR at baseline to correct for lead-time and immortal time bias.

RESULTS

Late referral was associated with inferior control of most risk factors for CKD progression, CKD complications and cardiovascular risk factors. In particular, glycaemic control, the use of angiotensin converting enzyme inhibitors and angiotensin-2-receptor blockers in diabetic nephropathy or proteinuria, the control of nutritional and volume status were inferior in LR. One-year mortality was significantly higher in LR (RR 5.9 (95% CI 1.5-19.6); p < 0.01). Inadequate control of blood pressure, anaemia, volume status, malnutrition and emergency initial dialysis, but not LR itself were independently associated with mortality.

CONCLUSIONS

Late referral was associated with a substantially lower survival after correction for lead-time and immortal time bias and with inferior control of most risk factors for CKD progression, complications and cardiovascular risk factors. CKD patients may particularly profit from adequate control of blood pressure, anaemia, nutritional and volume status, and avoidance of emergency initial dialysis as these factors may predominately contribute to survival.

Naturally occurring human urinary peptides for use in diagnosis of chronic kidney disease

Because of its availability, ease of collection, and correlation with physiology and pathology, urine is an attractive source for clinical proteomics/peptidomics. However, the lack of comparable data sets from large cohorts has greatly hindered the development of clinical proteomics. Here, we report the establishment of a reproducible, high resolution method for peptidome analysis of naturally occurring human urinary peptides and proteins, ranging from 800 to 17,000 Da, using samples from 3,600 individuals analyzed by capillary electrophoresis coupled to MS. All processed data were deposited in an Structured Query Language (SQL) database. This database currently contains 5,010 relevant unique urinary peptides that serve as a pool of potential classifiers for diagnosis and monitoring of various diseases. As an example, by using this source of information, we were able to define urinary peptide biomarkers for chronic kidney diseases, allowing diagnosis of these diseases with high accuracy. Application of the chronic kidney disease-specific biomarker set to an independent test cohort in the subsequent replication phase resulted in 85.5% sensitivity and 100% specificity. These results indicate the potential usefulness of capillary electrophoresis coupled to MS for clinical applications in the analysis of naturally occurring urinary peptides.

Plasma cystatin C and acute kidney injury after cardiopulmonary bypass

BACKGROUND AND OBJECTIVES

Little is known about the performance of plasma cystatin C (CysC) in patients undergoing cardiopulmonary bypass (CPB) and its utility in the early diagnosis of acute kidney injury (AKI). In this post hoc analysis, the goal was to determine whether plasma cystatin C, measured 2 hours after the conclusion of CPB, is a reliable marker of AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma CysC was measured in 150 patients undergoing CPB at the following times: preoperatively, 2 hours after the conclusion of CPB, postoperative day 1, and postoperative day 2. Plasma CysC levels were related to the development of AKI as defined by an increase in serum creatinine of >or=50% or >or=0.3 mg/dl from baseline up to 3 days postoperative. Mixed linear models were used to evaluate the relationship of serial plasma CysC values with AKI. The discriminatory capacity of plasma CysC was estimated using receiver operating characteristic curves. Logistic regression was utilized to assess the adjusted relationship between plasma CysC and subsequent AKI.

RESULTS

AKI developed in 47 (31.3%) patients. Plasma CysC was higher at all times among patients who developed AKI compared with those who did not (P < 0.0001). The discriminatory capacity of plasma CysC measured preoperatively and 2 hours after the conclusion of CPB was modest.

CONCLUSIONS

Serial measures of plasma CysC are highly correlated with the development of AKI. However, the discriminatory capacity of plasma CysC as an early marker of AKI remains limited.

Uremic toxins in acute kidney injury

Acute kidney injury (AKI) is a serious and frequent condition which may fully resolve but is associated with markedly increased mortality. Mortality in AKI is caused by nonrenal, distant organ failure. Renal recovery from AKI is often not achieved on account of new injuries in the repair phase. Uremic toxins may be the missing link between AKI and nonrenal organ failure, tubular and endothelial injury. Compared with chronic kidney disease (CKD), research of uremic toxins in AKI is in its infancy. This review presents the current knowledge on uremic toxins in AKI which is predominately derived from experimental studies. Most uremic toxins investigated have previously been identified in CKD. The review focuses on those uremic toxins with biologic effect on the respective nonrenal organs failing in AKI and on the renal tubule and the endothelium. These uremic toxins may insofar be specific mediators of pathophysiological processes in AKI.

Dinucleoside polyphosphates and uremia

Dinucleoside polyphosphates constitute a group of endogenous vasoregulatory purines and pyrimidines with a strong impact on physiologic and pathophysiologic processes of the cardiovascular system. Recently, the importance of dinucleoside polyphosphates in chronic kidney disease (CKD) and uremia gained increasing interest. Although our knowledge about the impact of dinucleoside polyphosphates in CKD and uremia is just at the beginning, this article reviews the current knowledge of the physiologic and pathophysiologic role of dinucleoside polyphosphates in CKD and uremia.

CE-MS analysis of the human urinary proteome for biomarker discovery and disease diagnostics

Owing to its availability, ease of collection, and correlation with pathophysiology of diseases, urine is an attractive source for clinical proteomics. However, many proteomic studies have had only limited clinical impact, due to factors such as modest numbers of subjects, absence of disease controls, small numbers of defined biomarkers, and diversity of analytical platforms. Therefore, it is difficult to merge biomarkers from different studies into a broadly applicable human urinary proteome database. Ideally, the methodology for defining the biomarkers should combine a reasonable analysis time with high resolution, thereby enabling the profiling of adequate samples and recognition of sufficient features to yield robust diagnostic panels. Capillary electrophoresis coupled to mass spectrometry (CE-MS), which was used to analyze urine samples from healthy subjects and patients with various diseases, is a suitable approach for this task. The database of these datasets compiled from the urinary peptides enabled the diagnosis, classification, and monitoring of a wide range of diseases. CE-MS exhibits excellent performance for biomarker discovery and allows subsequent biomarker sequencing independent of the separation platform. This approach may elucidate the pathogenesis of many diseases, and better define especially renal and urological disorders at the molecular level.

Coronary artery bypass surgery and acute kidney injury--impact of the off-pump technique

BACKGROUND

Acute kidney injury (AKI) is a serious and frequent complication after coronary artery bypass grafting (CABG). Cardiopulmonary bypass (CPB) was identified as a major AKI risk factor after CABG. Our aim was to assess the impact of the off-pump coronary artery bypass (OPCAB) compared to the on-pump coronary artery bypass (ONCAB) technique on the rate and severity of AKI, while taking other risk factors for AKI into account.

METHODS

An observational study of 201 consecutive adult patients was conducted; 100 were operated by the OPCAB and 101 by the ONCAB technique. All patients in each group were operated by a single, experienced surgeon. Fifteen pre-, intra- and postoperative variables that were repeatedly identified in previous studies as independent AKI risk factors were included in this analysis. AKI was defined as an increase of serum creatinine >/=50% or >/=0.3 mg/dL within 48 h and AKI severity was classified, according to current AKIN definitions.

RESULTS

Significantly fewer OPCAB patients developed AKI compared to ONCAB (14.0 versus 27.7%; P = 0.03). OPCAB was associated with milder stages of AKI, whereas ONCAB patients had more severe AKI. Congestive heart failure and chronic kidney disease were independent risk factors for AKI. The OPCAB technique for CABG was identified as the only independent factor associated with lower incidence of AKI.

CONCLUSIONS

Using current AKI definitions and classifications, the OPCAB technique for CABG, which avoids CPB; was associated with a significantly lower rate and less severe AKI compared to ONCAB. The OPCAB technique was identified as the only modifiable and potentially protective factor against postoperative AKI.

A framework and key research questions in AKI diagnosis and staging in different environments

BACKGROUND AND OBJECTIVES

Acute Kidney Injury (AKI) is common worldwide, and associated with significant morbidity, mortality, and resource utilization. The RIFLE system of staging AKI correlates with survival in AKI in several settings. A similar AKI definition and staging system that also incorporates lesser degrees of serum creatinine elevation was proposed at the inaugural Acute Kidney Injury Network (AKIN) meeting in 2005. At the Second AKIN meeting in Vancouver, Canada in September 2006, our group developed a research agenda that would test the utility of these diagnostic and staging criteria to predict patient outcomes in a variety of clinical settings and patient groups.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

Three-day, international, consensus conference. A multidisciplinary stakeholder committee was divided into work groups. Recommendations for clinical practice and for future research were developed by the committee as an iterative process. This procedure consisted of a literature review phase and focus group interactions with presentations to the entire committee.

RESULTS

We first proposed a conceptual framework of disease that describes a series of AKI stages, antecedents and outcomes, and allows a description of research recommendations based on transition between AKI stages. We further proposed methods for testing of the definition and development of research questions to establish the utility of new biomarkers for the diagnosis and staging of AKI and associated illnesses.

CONCLUSIONS

Retrospective studies should be conducted to initiate the process of validating the AKIN definition of AKI, followed by comprehensive prospective studies that incorporate sampling for emerging AKI biomarkers.

Uridine adenosine tetraphosphate acts as an autocrine hormone affecting glomerular filtration rate

Recently, uridine adenosine tetraphosphate (Up(4)A) was described as a strong vasoconstrictor released from endothelial cells after stimulation with mechanical stress. In this study, we isolated and identified Up(4)A from kidney tissue, and we characterized the essential varying effects of Up(4)A on the afferent and efferent arterioles. Porcine and human kidney tissue was fractionated by size exclusion chromatography, affinity chromatography, anion exchange chromatography and reverse phase chromatography. In fractions purified to homogeneity, Up(4)A was identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), MALDI-LIFT fragment mass spectrometry (MALDI-TOF/TOF MS), retention-time comparison and enzymatic cleavage analysis. We analysed the release of Up(4)A from cultivated renal proximal tubule cells after stimulation of protein kinase C with oleoyl-2-acetyl-sn-glycerol (OAG). Up(4)A was identified in renal tissue, and the effect of Up(4)A on the vascular tone of isolated perfused afferent and efferent arterioles was tested. Stimulation of tubule cells with OAG increased the release rate of Up(4)A from tubule cells about tenfold. Up(4)A acts as a strong vasoconstrictive mediator on afferent arterioles, but has no significant effect on the tone of efferent arterioles, suggesting a functional role of Up(4)A as an autocrine hormone for glomerular perfusion. Because of the predominant effect of the Up(4)A on afferent arterioles, we assume that Up(4)A may decrease glomerular perfusion, intra-glomerular pressure and, hence, glomerular filtration rate. The release of Up(4)A from renal tubular cells may be an additional mechanism whereby tubular cells could affect renal perfusion. Up(4)A release may further contribute to renal vascular autoregulation mechanisms. In conclusion, as Up(4)A occurs in renal tissue and has marked effects on afferent but not efferent arterioles, Up(4)A may play a role in renal hemodynamics and possibly blood pressure regulation.

Increased urinary cystatin C reflects structural and functional renal tubular impairment independent of glomerular filtration rate

OBJECTIVES

The ratio of the urinary mass concentrations of cystatin C and creatinine (UcysC/Ucrea)>/=11.3 mg/mmol has recently been proposed as an accurate marker for the detection of GFR</=60 mL/min/1.73 m(2).

DESIGN AND METHODS

We prospectively evaluated the diagnostic performance of UcysC/Ucrea>/=11.3 mg/mmol and factors associated with increased UcysC/Ucrea in 72 children and adults with a wide variety of renal disorders. UcysC/Ucrea was calculated, and GFR wad estimated from serum creatinine and cystatin C by equations.

RESULTS

UcysC/Ucrea>/=11.3 mg/mmol had a low diagnostic value to detect GFR values</=60 mL/min/1.73 m(2) estimated by creatinine or cystatin-C-based equations with sensitivities of 72% and 63%, and specificities of 42% and 34%. ROC curves for UcysC/Ucrea to detect GFR</=60 mL/min/1.73 m(2) confirmed this with AUCs of 0.59 for creatinine and 0.57 for cystatin-C-based equations. Multivariate analysis identified tubular proteinuria, tubulointerstitial disease and heavy proteinuria, but not GFR</=60 mL/min/1.73 m(2), as factors independently associated with increased UcysC/Ucrea.

CONCLUSIONS

UcysC/Ucrea>/=11.3 mg/mmol is not an accurate marker to detect GFR</=60 mL/min/1.73 m(2), but reflects tubular dysfunction and proteinuria due to heavy proteinuria and tubulointerstitial disease.

Paracrine stimulation of vascular smooth muscle proliferation by diadenosine polyphosphates released from proximal tubule epithelial cells

The purinergic receptor system plays an important role in the regulation of both vascular and tubular functions within the kidney; however, the release of purinergic agonists other than ATP by renal tissue is not known. In this investigation, we determine if kidney tissue is a source of diadenosine polyphosphates, which have high affinity for the P(2X) and P(2Y) receptors. Both diadenosine pentaphosphate and hexaphosphate were identified by matrix-assisted laser desorption ionization-mass spectrometry in extracts purified from both whole porcine kidney and from cloned cells of the LLC-PK1 cell line. Both polyphosphates in nanomolar concentrations were found to significantly stimulate the proliferation of vascular smooth muscle cells derived from rat thoracic aortas. The purinergic-receptor antagonist, suramin, did not significantly affect the growth-stimulatory properties of the polyphosphates. The growth stimulation of vascular smooth muscle cells by platelet-derived growth factor was potentiated by both diadenosine polyphosphates. We conclude that diadenosine polyphosphates are endogenous purinergic agonists of the kidney that have physiologic and pathophysiologic relevance. These epithelial cell metabolic products have vasoregulatory properties while linking the energy supply and tubular function.