Long-term continuous renal replacement therapy and anticoagulation with citrate in critically ill patients with severe liver dysfunction.

BACKGROUND: As of 2009, anticoagulation with citrate was standard practice in continuous renal replacement therapy (CRRT) for critically ill patients at the University Medical Centre of Saarland, Germany. Partial hepatic metabolism of citrate means accumulation may occur during CRRT in critically ill patients with impaired liver function. The aim of this study was to evaluate the actual influence of hepatic function on citrate-associated complications during long-term CRRT. METHODS: In a retrospective study conducted between January 2009 and November 2012, all cases of dialysis therapy performed in the interdisciplinary surgical intensive care unit were analysed. Inclusion criteria were CRRT and regional anticoagulation with citrate, pronounced liver dysfunction, and pathologically reduced indocyanine green plasma disappearance rate (ICG-PDR). RESULTS: A total of 1339 CRRTs were performed in 69 critically ill patients with liver failure. At admission, the mean Model for End-stage Liver Disease score was 19.2, and the mean ICG-PDR was 9.8%. Eight patients were treated with liver replacement therapy, and 30 underwent transplants. The mortality rate was 40%. The mean duration of dialysis was 19.4 days, and the circuit patency was 62.2 h. Accumulation of citrate was detected indirectly by total serum calcium/ionised serum calcium (tCa/iCa) ratio > 2.4. This was noted in 16 patients (23.2%). Dialysis had not to be discontinued for metabolic disorder or accumulation of citrate in any case. In 26% of cases, metabolic alkalosis occurred with pH > 7.5. Interestingly, no correlation between citrate accumulation and liver function parameters was detected. Moreover, most standard laboratory liver function parameters showed poor predictive capabilities for accumulation of citrate. CONCLUSIONS: Our findings indicate that extra-hepatic metabolism of citrate seems to exist, avoiding in most cases citrate accumulation in critically ill patients despite impaired liver function. Because the citric acid cycle is oxygen-dependent, disturbed microcirculation would result in inadequate citrate metabolism. Raising the tCa/iCa ratio would therefore be an indicator of severity of illness and mortality rather than of liver failure. However, further studies are warranted for confirmation.

A single preoperative FGF23 measurement is a strong predictor of outcome in patients undergoing elective cardiac surgery: a prospective observational study.

INTRODUCTION: Several scoring systems have been developed to predict postoperative mortality and complications in patients undergoing cardiac surgery. However, these computer-based calculations are time- and cost-intensive. A simple but highly predictive test for postoperative risk would be of clinical benefit with respect to increasingly scarce hospital resources. We therefore assessed the predictive power of fibroblast growth factor 23 (FGF23) measurement compared with an established scoring system. METHODS: We conducted a prospective interdisciplinary observational study at the Saarland University Medical Centre that included 859 patients undergoing elective cardiac surgery between January 2010 and March 2011 with a median follow-up after discharge of 822 days. We compared a single preoperative measurement of FGF23 as a prognostic tool with the 18 parameters comprising EuroSCORE II with respect to postoperative mortality, acute kidney injury, non-occlusive mesenteric ischemia, clinical course and long-term outcome. RESULTS: Preoperative FGF23 levels were highly predictive of postoperative outcome and complications. The predictive value of FGF23 for mortality in the receiver operating characteristic curve was greater than the EuroSCORE II (area under the curve: 0.800 versus 0.725). Moreover, preoperative FGF23 independently predicted postoperative acute kidney injury and non-occlusive mesenteric ischemia comparably to the EuroSCORE II. Finally, FGF23 was found to be an independent predictor of clinical course parameters, including duration of surgery, ventilation time and length of stay. CONCLUSIONS: In patients undergoing elective cardiac surgery, a simple preoperative FGF23 measurement is a powerful indicator of surgical mortality, postoperative complications and long-term outcome. Its utility compares to the widely used EuroSCORE II.

Novel insights into the critical role of bradykinin and the kinin B2 receptor for vascular recruitment of circulating endothelial repair-promoting mononuclear cell subsets: alterations in patients with coronary disease.

BACKGROUND: Endothelial injury is considered critical for progression of atherosclerosis and its complications in coronary artery disease (CAD). The endothelial-supportive effects of bradykinin have mainly been attributed to activation of the resident endothelium. Here we newly investigate the role of bradykinin and its B2 receptor for the recruitment and functional activation of circulating mononuclear cell subsets with endothelial-repair promoting capacity, such as CD34(+)CXCR4(+)cells, at sites of arterial injury. METHODS AND RESULTS: Bradykinin-B2-receptor (B2R) blockade by icatibant substantially impaired recruitment of circulating CD34(+)CXCR4(+) mononuclear cells (expressing high levels of B2R) to endothelial cells in vitro and to injured arterial wall in vivo, whereas recruitment of CD14(hi) monocytes (expressing low levels of B2R) was unchanged. Moreover, the capacity of genetically B2R-deficient bone marrow cells to promote endothelial repair in vivo was markedly impaired as compared with wild-type bone marrow cells. B2R expression was reduced on CD34(+)CXCR4(+)mononuclear cells and endothelial repair-promoting early outgrowth cells, but not on CD14(hi)monocytes, from CAD patients as compared with healthy subjects. B2R stimulation induced CD18 activation in early outgrowth cells of healthy subjects, but not in early outgrowth cells of CAD patients. Adenoviral B2R overexpression enhanced in vivo vascular recruitment and rescued impaired endothelial repair capacity of early outgrowth cells from CAD patients. CONCLUSIONS: We newly report that bradykinin/B2R signaling may promote endothelial repair after arterial injury by selective recruitment and functional activation of B2R-expressing circulating mononuclear cell subsets. In CAD patients, B2R downregulation on endothelial repair-promoting circulating mononuclear cells substantially impairs the bradykinin-dependent endothelial repair, representing a novel mechanism promoting endothelial injury in CAD patients.

Total-to-ionized calcium ratio predicts mortality in continuous renal replacement therapy with citrate anticoagulation in critically ill patients.

INTRODUCTION: Regional citrate anticoagulation is safe, feasible and increasingly used in critically ill patients on continuous renal replacement therapy (CRRT). However, in patients with hepatic or multi-organ dysfunction, citrate accumulation may lead to an imbalance of calcium homeostasis. The study aimed at evaluating the incidence and prognostic relevance of an increased total to ionized calcium ratio (T/I Ca(2+) ratio) and its association to hepatic dysfunction. METHODS: We performed a prospective observational study on n = 208 critically ill patients with acute kidney injury (AKI) and necessity for CRRT with regional citrate anticoagulation (CRRT-citrate) between September 2009 and September 2011. Critical illness was estimated by Simplified Acute Physiology Score II; hepatic function was measured with indocyanine green plasma disappearance rate. After achieving a steady state of calcium homeostasis patients were classified into tertiles according to the T/I Ca(2+) ratio (<2.0 versus 2.0 - 2.39 versus ≥ 2.4). RESULTS: The T/I Ca(2+) ratio was determined as an independent predictor for 28-day mortality in critically ill patients with AKI on CRRT-citrate confirmed by receiver operating characteristics and multivariate analysis (Area under the curve 0.94 ± 0.02; p<0.001). A T/I Ca(2+) ratio ≥ 2.4 independently predicted a 33.5-fold (p<0.001) increase in 28-day mortality-rate. There was a significant correlation between the T/I Ca(2+) ratio and the hepatic clearance (p<0.001) and the severity of critical illness (p<0.001). The efficacy and safety of citrate anticoagulation, determined by blood urea nitrogen, mean filter patency and bleeding episodes, were not significantly different between the tertiles. CONCLUSIONS: In patients on CRRT-citrate T/I Ca(2+) ratio is closely related to the clinical outcome and emerged as an independent predictor of 28-day mortality. Larger studies are required to define the cut-off and predictive value for the T/I Ca(2+) ratio. This ratio is associated with hepatic and/or multi-organ dysfunction and therefore an important therapeutic target.

Bleeding complications after cardiac surgery, before anticoagulation start and then with argatroban or heparin in the early postoperative setting.

OBJECTIVES: After elective cardiac surgery a postoperative anticoagulation is obligatory. With critically ill patients the conventional anticoagulation standard heparin is sometimes impossible, e.g. based on HIT II. Then, argatroban is currently a possible alternative, however, due to its impaired metabolism in critically ill patients, anticoagulation effect is harder to anticipate, thus resulting in higher bleeding risk. Furthermore, to date no antidote is available. Hence, severe postoperative bleeding incidents under anticoagulation are commonly mono-causal attributed to the anticoagulation itself. This study concentrates on the number of well-defined postoperative bleeding incidents before any anticoagulation started, then actually under argatroban as well as compared to those under heparin (or switched from heparin to argatroban). MATERIAL AND METHODS: Retrospective study including 215 patients undergoing elective cardiac surgery with a postoperative stay in ICU ≥48 h. Postoperative bleeding complications before and after start of anticoagulation were evaluated. Definition of bleeding complications were: decrease of hemoglobin by more than 2 g/dl without dilution (mean value of volume balance plus one standard deviation) and/or increased need of red blood cell transfusion/day (average transfusion rate + 2 standard deviations). RESULTS: Within the study group of 215 patients, 143 were treated with heparin, 43 with argatroban, 29 switched from heparin to argatroban. Overall, 26.5% (57/215) postoperative bleeding complications occurred. In 54.4% (31/57) bleeding complications occurred before start of anticoagulation; in 43.6% (26/57) after. Of these, 14 bleeding incidents occurred under heparin 9.8% (14/143), 6 under argatroban 14% (6/43) and 6 switched 20.7% (6/29). Higher bleeding complications before start of anticoagulation was related to concomitant factors influencing the overall bleeding risk; e.g. score of severity of illness. These observations further correlate with postoperative, but not anticoagulation induced mortality rate of 2.8% of then given heparin, 20.9% then argatroban, 20.7% then switched. CONCLUSIONS: Postoperative bleeding complications cannot simply be attributed to anticoagulation since occurring often before anticoagulation was started. The risk for bleeding complications after start of anticoagulation was quite comparable for argatroban and heparin. Accordingly, the influence of argatroban on bleeding complications in the postoperative period may be less significant than previously thought.

Bias in recent miRBase annotations potentially associated with RNA quality issues.

Although microRNAs are supposed to be stable in-vivo, degradation processes potentially blur our knowledge on the small oligonucleotides. We set to quantify the effect of degradation on microRNAs in mouse to identify causes for distorted microRNAs patterns. In liver, we found 298, 99 and 8 microRNAs whose expression significantly correlated to RNA integrity, storage time at room temperature and storage time at 4 °C, respectively. Expression levels of 226 microRNAs significantly differed between liver samples with high RNA integrity compared to liver samples with low RNA integrity by more than two-fold. Especially the 157 microRNAs with increased expression in tissue samples with low RNA integrity were most recently added to miRBase. Testing potentially confounding sources, e.g. in-vitro degraded RNA depleted of small RNAs, we detected signals for 350 microRNAs, suggesting cross-hybridization of fragmented RNAs. Therefore, we conclude that especially microRNAs added in the latest miRBase versions might be artefacts due to RNA degradation. The results facilitate differentiation between degradation-resilient microRNAs, degradation-sensitive microRNAs, and likely erroneously annotated microRNAs. The latter were largely identified by NGS but not experimentally validated and can severely bias microRNA biomarker research and impact the value of microRNAs as diagnostic, prognostic or therapeutic tools.

Vascular effects of oxysterols and oxyphytosterols in apoE -/- mice.

OBJECTIVES: The aim of our study was to investigate vascular effects of oxysterols and oxyphytosterols on reactive oxygen species (ROS), endothelial progenitor cells, endothelial function and atherogenesis. METHODS: Male apoE-/-mice were treated with cholesterol, sitosterol, 7-ß-OH-cholesterol, 7-ß-OH-sitosterol, or cyclodextrin by daily intraperitoneal application. The respective concentrations in the plasma and in the arterial wall were determined by gas chromatography-flame ionization or mass spectrometry. ROS production was assessed by electron-spin resonance spectroscopy in the aorta, endothelial function of aortic rings and atherosclerosis in the aortic sinus was quantitated after 4 weeks. RESULTS: Compared to vehicle, there was no difference in plasma cholesterol levels and arterial wall concentrations after i.p. application of cholesterol. 7-ß-OH-cholesterol concentrations were increased in the plasma (33.7±31.5 vs. 574.57.2±244.92 ng/ml) but not in the arterial wall (60.1±60.1 vs. 59.3±18.2 ng/mg). Sitosterol (3.39±0.96 vs. 8.16±4.11 mg/dL; 0.08±0.04 vs. 0.16±0.07 µg/mg, respectively) and 7-ß-OH-sitosterol concentrations (405.1±151.8 vs. 7497±3223 ng/ml; 0.24±0.13 vs. 16.82±11.58 ng/mg, respectively) increased in the plasma and in the aorta. The i.p-application of the non-oxidized cholesterol or sitosterol did not induce an increase of plasma oxysterols or oxyphytosterols concentrations. Oxidative stress in the aorta was increased in 7-ß-OH-sitosterol treated mice, but not in mice treated with cholesterol, sitosterol, or 7-ß-OH-cholesterol. Moreover, cholesterol, sitosterol, 7-ß-OH-cholesterol, and 7-ß-OH-sitosterol did not affect endothelial-dependent vasodilation, or early atherosclerosis. CONCLUSION: Increased oxyphytosterol concentrations in plasma and arterial wall were associated with increased ROS production in aortic tissue, but did not affect endothelial progenitor cells, endothelial function, or early atherosclerosis.

Dimethylarginines ADMA and SDMA: the real water-soluble small toxins?

Uremia occurs if the kidney loses the ability to eliminate toxic compounds at a sufficient rate into the urine. In 1970, N-N, N-G- and N-G,N׳-G-dimethyl-arginine (asymmetric dimethylarginine [ADMA] and symmetric dimethylarginine) were isolated from human urine. It was anticipated that both substances might be important in the pathophysiology and for the diagnosis of various pathologic states. It took 22 years, however, before this idea materialized when it was found that ADMA, which is increased in hemodialysis patients, inhibits the synthesis of the endothelial-derived relaxing factor, identified as nitric oxide. ADMA correlates with traditional and nontraditional cardiovascular risk factors and is a strong predictor of cardiovascular events and death in both patients with chronic kidney disease and in the general population. It also seems to mediate adverse cardiovascular effects of drugs such as proton pump inhibitors. To date, we have no specific pharmacologic therapy at hand to neutralize the deleterious effects of ADMA, curbing the enthusiasm for this marker and mediator of cardiovascular disease.

Short-term inhibition of DPP-4 enhances endothelial regeneration after acute arterial injury via enhanced recruitment of circulating progenitor cells.

BACKGROUND: Endothelial injuries regularly occur in atherosclerosis and during interventional therapies of the arterial occlusive disease. Disturbances in the endothelial integrity can lead to insufficient blood supply and bear the risk of thrombus formation and acute vascular occlusion. At present, effective therapeutics to restore endothelial integrity are barely available. We analyzed the effect of pharmacological DPP-4-inhibition by Sitagliptin on endogenous progenitor cell-based endothelial regeneration via the SDF-1α/CXCR4-axis after acute endothelial damage in a mouse model of carotid injury. METHODS AND RESULTS: Induction of a defined endothelial injury was performed in the carotid artery of C57Bl/6 mice which led to a local upregulation of SDF-1α expression. Animals were treated with placebo, Sitagliptin or Sitagliptin+AMD3100. Using mass spectrometry we could prove that Sitagliptin prevented cleavage of the chemokine SDF-1α. Accordingly, increased SDF-1α concentrations enhanced recruitment of systemically applied and endogenous circulating CXCR4+ progenitor cells to the site of vascular injury followed by a significantly accelerated reendothelialization as compared to placebo-treated animals. Improved endothelial recovery, as well as recruitment of circulating CXCR4+ progenitor cells (CD133+, Flk1+), was reversed by CXCR4-antagonization through AMD3100. In addition, short-term Sitagliptin treatment did not significantly promote neointimal or medial hyperplasia. CONCLUSION: Sitagliptin can accelerate endothelial regeneration after acute endothelial injury. DPP-4 inhibitors prevent degradation of the chemokine SDF-1α and thus improve the recruitment of regenerative circulating CXCR4+ progenitor cells which mediate local endothelial cell proliferation without adversely affecting vessel wall architecture.

The wealth of nations and the dissemination of cardiovascular research.

BACKGROUND: This study aimed at understanding whether investigators from less wealthy countries were at a disadvantage in disseminating their research, after accounting for potential differences in research quality and infrastructure. METHODS AND RESULTS: In this bibliometric analysis a representative random selection of 10% (n=1002 studies) of all abstracts submitted to the European Society of Cardiology (ESC) congress 2006 was followed for publication and citation from September 2006 to December 2011. The main variable of interest was the per-capita gross domestic product (GDP) of the country of the principal investigator. Using multivariable models that adjusted for socioeconomic indicators and previously identified markers of research quality, we examined the relationship between per-capita GDP and three study endpoints: Acceptance at the ESC congress, full-text publication, and number of two-year citations. Among 1002 abstracts from 63 countries, per-capita GDP was positively correlated with all three study endpoints. After adjusting for markers of research quality and infrastructure, per-capita GDP remained a strong predictor for acceptance at the ESC congress (adjusted OR for every 10,000 USD increase in per-capita GDP, 1.44; 95% CI, 1.15 to 1.80), full-text publication within 5years (adjusted OR, 1.49; 95% CI, 1.17 to 1.90), and high citation frequency (adjusted OR, 2.30; 95% CI, 1.31 to 4.04). These findings were largely consistent in a subgroup of abstracts of high-quality, prospective clinical trials. CONCLUSION: Investigators in less wealthy countries face challenges to disseminate their research, even after accounting for potential differences in the quality of their work and research infrastructure.

Inhibition of nicotinamide phosphoribosyltransferase reduces neutrophil-mediated injury in myocardial infarction.

AIMS: Nicotinamide phosphoribosyltransferase (Nampt) is a key enzyme for nicotinamide adenine dinucleotide (NAD(+)) biosynthesis, and recent evidence indicates its role in inflammatory processes. Here, we investigated the potential effects of pharmacological Nampt inhibition with FK866 in a mouse myocardial ischemia/reperfusion model. In vivo and ex vivo mouse myocardial ischemia/reperfusion procedures were performed. RESULTS: Treatment with FK866 reduced myocardial infarct size, neutrophil infiltration, and reactive oxygen species (ROS) generation within infarcted hearts in vivo in a mouse model of ischemia and reperfusion. The benefit of FK866 was not shown in the Langendorff model (ex vivo model of working heart without circulating leukocytes), suggesting a direct involvement of these cells in cardiac injury. Sera from FK866-treated mice showed reduced circulating levels of the neutrophil chemoattractant CXCL2 and impaired capacity to prime migration of these cells in vitro. The release of CXCL8 (human homolog of murine chemokine CXCL2) by human peripheral blood mononuclear cells (PBMCs) and Jurkat cells was also reduced by FK866, as well as by sirtuin (SIRT) inhibitors and SIRT6 silencing, implying a pivotal role for this NAD(+)-dependent deacetylase in the production of this chemokine. INNOVATION: The pharmacological inhibition of Nampt might represent an effective approach to reduce neutrophilic inflammation- and oxidative stress-mediated tissue damage in early phases of reperfusion after a myocardial infarction. CONCLUSIONS: Nampt inhibition appears as a new strategy to dampen CXCL2-induced neutrophil recruitment and thereby reduce neutrophil-mediated tissue injury in mice.