ICG-liver test versus new biomarkers as prognostic markers for prolonged length of stay in critically ill patients - a prospective study of accuracy for prediction of length of stay in the ICU.

BACKGROUND: Prognostic abilities of medical parameters, which are scoring systems, measurements and biomarkers, are important for stratifying critically ill patients. Indocyanine green plasma disappearance (ICG-PDR) is an established clinical tool for the assessment of liver perfusion and function. Copeptin, MR-proANP and pro-ADM are biomarkers whose prognostic value is still unclear. The goal of this prospective study was to evaluate ICG-PDR, copeptin, MR-proANP and pro-ADM to predict prolonged length of stay (pLOS) in the ICU. METHODS: This study was conducted as a prospective single center study including 110 consecutively admitted ICU patients. Primary endpoint was prolonged length of stay (pLOS) in the ICU, defined as more than three days of stay there. RESULTS: ROC analysis showed an AUC of 0.73 for ICG-PDR, 0.70 for SAPS II, 0.65 for MR-proANP, 0.64 for pro-ADM and 0.54 for copeptin for pLOS in the ICU. CONCLUSIONS: The prediction of pLOS in the ICU might be better by means of ICG-PDR than with the new biomarkers copeptin, MR-proANP or pro-ADM. Nevertheless, there is more need for research to evaluate whether ICG-PDR is an overall prognostic marker for pLOS. TRIAL REGISTRATION: (ClinicalTrials.gov number, NCT01126554).

Influence on ICU course, outcome and costs for lung transplantation after implementation of the new Swiss transplantation law.

BACKGROUND: The Swiss organ allocation system for donor lungs was implemented on 1 July 2007. The effects of this implementation on patient selection, intensive care unit course, outcomes and intensive care costs are unknown. METHODS: The first 37 consecutive lung transplant recipients following the implementation of the new act were compared with the previous 42 lung transplant recipients. RESULTS: Following implementation of the new law, baseline characteristics and cumulative one-year patient survival were comparable in both groups (88.1% vs 83.8%, P = 0.58). The costs for each case increased by 35,000 euros after adoption of the new law. Stratifying patients after implementation of the law according to urgency status shows that urgent patients required longer mechanical ventilation (P = 0.04), a longer ICU stay (P = 0.045) and a longer hospital stay (P = 0.04) and ICU costs (median 64,050 euros) were higher compared to regular patients. CONCLUSION: The new transplantation law has increased ICU costs with the implementation of the Swiss organ allocation system. Patients listed as 'urgent' contribute significantly to the increase in ICU costs.

The combination of MELD score and ICG liver testing predicts length of stay in the ICU and hospital mortality in liver transplant recipients.

BACKGROUND: Early prediction of outcome would be useful for an optimal intensive care management of liver transplant recipients. Indocyanine green clearance can be measured non-invasively by pulse spectrophometry and is closely related to liver function. METHODS: This study was undertaken to assess the predictive value of a combination of the model of end stage liver disease (MELD) score and early indocyanine plasma disappearance rates (ICG-PDR) for length of stay in the intensive care unit (ICU), length of stay in the hospital and hospital mortality in liver transplant recipients. RESULTS: Fifty consecutive liver transplant recipients were included in this post Hoc single-center study. ICG-PDR was determined within 6 hours after ICU admission. Endpoints were length of stay in the ICU, length of hospital stay and hospital mortality. The combination of a high MELD score (MELD >25) and a low ICG-PDR clearance (ICG-PDR < 20%/minute) predicts a significant longer stay in the ICU (p = 0.004), a significant longer stay in the hospital (p < 0.001) and a hospital mortality of 40% vs. 0% (p = 0.003). CONCLUSION: The combination of MELD scores and a singular ICG-PDR measurement in the early postoperative phase is an accurate predictor for outcome in liver transplant recipients. This easy-to-assess tool might be valuable for an optimal intensive care management of those patients.

Extracorporeal membrane oxygenation: beneficial strategy for lung transplant recipients.

The role of extracorporeal membrane oxygenation (ECMO) as a therapeutic strategy has been very well documented for over a decade now with consistently positive remarks. The aim of the present study was analyzing the outcome of ECMO application in our lung transplant program, especially the feasibility and safety of our ECMO approach. Therefore, we retrospectively analyzed the data of 15 patients recipients requiring ECMO support. We analyzed clinical data, complications, and survival of the lung-transplanted population that needed ECMO support at our institution from 2006-2009. During that period, 19 applications of ECMO were done on 15 adult patients with the following indications: primary graft dysfunction (10 patients), "bridge to transplantation" (five), pulmonary hypertension (three), and severe acute respiratory distress syndrome (one). At 28 days, the overall survival was 93% (14 of 15 patients) and 12 of these patients (80%) survived at least 6 months. Complications included acute renal insufficiency with temporary need of renal replacement therapy (53%), bleeding (33%), critical illness polyneuropathy (66%), and reversible thrombocytopenia (73%). Based on the evaluation of the patients in this analysis, ECMO seems to be a safe therapeutic approach in lung transplant recipients with severe respiratory failure directly after transplantation.

Pretransplant dyslipidaemia determines outcome in lung transplant recipients.

BACKGROUND: There is little knowledge about the effect of dyslipidaemia on the outcome after lung transplantation. Thus, the aim of this retrospective single centre study was to analyse the impact of the plasma lipid profile on mortality in lung transplant recipients. From January 2000 to December 2008 the charts of 172 consecutive lung transplantation recipients were analysed. At baseline and after one year lipid profiles were routinely collected. During the follow-up major cardiovascular events (MCE; beginning of dialysis, cerebrovascular insult or myocardial infarction) were recorded. The follow-up period ended December 2010. FINDINGS: Over all total cholesterol (4.3 ± 1.6 vs. 5.4 ± 1.3 mmol/l, p < 0.0001), triglycerides (1.2 ± 0.7 vs. 2.4 ± 1.3 mmol/l, p < 0.0001), HDL (1.5 ± 0.6 vs. 1.7 ± 0.6 mmol/l, p = 0.003) and TC/HDL ratio (3.0 ± 1.0 vs. 3.6 ± 1.2, p = 0.002) increased significantly after 1 year.During the observational period 6.9% (10 patients) suffered a major cardiac event. In univariate analysis MCE was associated with baseline TC: on average the event-group had a 33% higher baseline TC (5.6 vs. 4.2 mmol/l, OR 1.6, CI 1.1 - 2.2, p = 0.02). The total mortality in the observational period was 25% (36 patients overall). In univariate analysis mortality was associated with increased TC/HDL ratio. The non-survivors had on average a 22% higher baseline TC/HDL ratio (3.6 vs. 2.8, HR 2.8, CI 1.2 - 3.5, p = 0.001). There was no association between mortality and TC (p = 0.33), triglycerides (p = 0.34), HDL (p = 0.78) and creatinine (p = 0.73). In a multivariate model the hazard ratio was 1.5 (1.2 - 1.9, p = 0.001) per increase of 0.4 TC/HDL ratio. CONCLUSIONS: This study shows that the total cholesterol before transplantation is associated with the incidence of MCE and the cholesterol/HDL ratio with mortality in lung transplanted recipients.

The relationship between preoperative creatinine clearance and outcomes for patients undergoing liver transplantation: a retrospective observational study.

BACKGROUND: Renal failure with following continuous renal replacement therapy is a major clinical problem in liver transplant recipients, with reported incidences of 3% to 20%. Little is known about the significance of postoperative acute renal failure or acute-on-chronic renal failure to postoperative outcome in liver transplant recipients. METHODS: In this post hoc analysis we compared the mortality rates of 135 consecutive liver transplant recipients over 6 years in our center subject to their renal baseline conditions and postoperative RRT. We classified the patients into 4 groups, according to their preoperative calculated Cockcroft formula and the incidence of postoperative renal replacement therapy. Data then were analyzed in regard to mortality rates and in addition to pre- and peritransplant risk factors. RESULTS: There was a significant difference in ICU mortality (p=.008), hospital mortality (p=.002) and cumulative survival (p<.0001) between the groups. The highest mortality rate occurred in the group with RRT and normal baseline kidney function (20% ICU mortality, 26.6% hospital mortality and 50% cumulative 1-year mortality, respectively). The hazard ratio in this group was 9.6 (CI 3.2-28.6, p=.0001). CONCLUSION: This study shows that in liver transplant recipient's acute renal failure with postoperative RRT is associated with mortality and the mortality rate is higher than in patients with acute-on-chronic renal failure and postoperative renal replacement therapy.

Association of intraoperative transfusion of blood products with mortality in lung transplant recipients.

BACKGROUND: The impact of intraoperative transfusion on postoperative mortality in lung transplant recipients is still elusive. METHODS: Univariate and multivariate analysis were performed to investigate the influence of red blood cells (RBCs) and fresh frozen plasma (FFP) on mortality in 134 consecutive lung transplants recipients from September 2003 until December 2008. RESULTS: Intraoperative transfusion of RBCs and FFP was associated with a significant increase in mortality with odds ratios (ORs) of 1.10 (1.03 to 1.16, P = 0.02) and 1.09 (1.02 to 1.15, P = 0.03), respectively. For more than four intraoperatively transfused RBCs multivariate analysis showed a hazard ratio for mortality of 3.8 (1.40 to 10.31, P = 0.003). Furthermore, non-survivors showed a significant increase in renal replacement therapy (RRT) (36.6% versus 6.9%, P <0.0001), primary graft dysfunction (PGD) (39.3% versus 5.9%, P <0.0001), postoperative need of extracorporeal membrane oxygenation (ECMO) (26.9% versus 3.1%, P = 0.0019), sepsis (24.2% versus 4.0%, P = 0.0004), multiple organ dysfunction syndrome (MODS) (26.9% versus 3.1%, P <0.0001), infections (18.1% versus 0.9%, P = 0.0004), retransplantation (12.1% versus 6.9%, P = 0.039) and readmission to the ICU (33.3% versus 12.8%, P = 0.024). CONCLUSIONS: Intraoperative transfusion is associated with a strong negative influence on outcome in lung transplant recipients.

Aldosterone stimulates vacuolar H(+)-ATPase activity in renal acid-secretory intercalated cells mainly via a protein kinase C-dependent pathway.

Urinary acidification in the collecting duct is mediated by the activity of H(+)-ATPases and is stimulated by various factors including angiotensin II and aldosterone. Classically, aldosterone effects are mediated via the mineralocorticoid receptor. Recently, we demonstrated a nongenomic stimulatory effect of aldosterone on H(+)-ATPase activity in acid-secretory intercalated cells of isolated mouse outer medullary collecting ducts (OMCD). Here we investigated the intracellular signaling cascade mediating this stimulatory effect. Aldosterone stimulated H(+)-ATPase activity in isolated mouse and human OMCDs. This effect was blocked by suramin, a general G protein inhibitor, and GP-2A, a specific G(αq) inhibitor, whereas pertussis toxin was without effect. Inhibition of phospholipase C with U-73122, chelation of intracellular Ca(2+) with BAPTA, and blockade of protein kinase C prevented the stimulation of H(+)-ATPases. Stimulation of PKC by DOG mimicked the effect of aldosterone on H(+)-ATPase activity. Similarly, aldosterone and DOG induced a rapid translocation of H(+)-ATPases to the luminal side of OMCD cells in vivo. In addition, PD098059, an inhibitor of ERK1/2 activation, blocked the aldosterone and DOG effects. Inhibition of PKA with H89 or KT2750 prevented and incubation with 8-bromoadenosine-cAMP mildly increased H(+)-ATPase activity. Thus, the nongenomic modulation of H(+)-ATPase activity in OMCD-intercalated cells by aldosterone involves several intracellular pathways and may be mediated by a G(αq) protein-coupled receptor and PKC. PKA and cAMP appear to have a modulatory effect. The rapid nongenomic action of aldosterone may participate in the regulation of H(+)-ATPase activity and contribute to final urinary acidification.

Angiotensin II stimulates vacuolar H+ -ATPase activity in renal acid-secretory intercalated cells from the outer medullary collecting duct.

Final urinary acidification is mediated by the action of vacuolar H(+)-ATPases expressed in acid-secretory type A intercalated cells (A-IC) in the collecting duct. Angiotensin II (AngII) has profound effects on renal acid-base transport in the proximal tubule, distal tubule, and collecting duct. This study investigated the effects on vacuolar H(+)-ATPase activity in A-IC in freshly isolated mouse outer medullary collecting ducts. AngII (10 nM) stimulated concanamycin-sensitive vacuolar H(+)-ATPase activity in A-IC in freshly isolated mouse outer medullary collecting ducts via AT(1) receptors, which were also detected immunohistochemically in A-IC. AngII increased intracellular Ca(2+) levels transiently. Chelation of intracellular Ca(2+) with BAPTA and depletion of endoplasmic reticulum Ca(2+) stores prevented the stimulatory effect on H(+)-ATPase activity. The effect of AngII on H(+)-ATPase activity was abolished by inhibitors of small G proteins and phospholipase C, by blockers of Ca(2+)-dependent and -independent isoforms of protein kinase C and extracellular signal-regulated kinase 1/2. Disruption of the microtubular network and cleavage of cellubrevin attenuated the stimulation. Finally, AngII failed to stimulate residual vacuolar H(+)-ATPase activity in A-IC from mice that were deficient for the B1 subunit of the vacuolar H(+)-ATPase. Thus, AngII presents a potent stimulus for vacuolar H(+)-ATPase activity in outer medullary collecting duct IC and requires trafficking of stimulatory proteins or vacuolar H(+)-ATPases. The B1 subunit is indispensable for the stimulation by AngII, and its importance for stimulation of vacuolar H(+)-ATPase activity may contribute to the inappropriate urinary acidification that is seen in patients who have distal renal tubular acidosis and mutations in this subunit.

Differential localization of vacuolar H+-ATPases containing a1, a2, a3, or a4 (ATP6V0A1-4) subunit isoforms along the nephron.

Vacuolar H(+)-ATPase are multi-subunit containing pumps important for several processes along the nephron such as receptor mediated endocytosis, acidification of intracellular organelles, bicarbonate reabsorption and secretion, and H(+)- extrusion. Mutations in the human a4 (ATP6V0A4) subunit cause distal renal tubular acidosis (dRTA). There are 4 known isoforms of the 'a' subunit (a1-a4). Here we investigated the expression and localization of all four isoforms in mouse kidney. Real-time PCR detected mRNAs encoding all four 'a' isoforms in mouse kidney with a relative abundance in the following order: a4>a2=a1>a3. Immunolocalization demonstrated expression of all 'a' subunits in the proximal tubule and in the intercalated cells of the collecting system. In intercalated cells a1 and a4 isoforms appeared on both the apical and basolateral side and were expressed in all subtypes of intercalated cells. In contrast, a2, and a3 were only found in the apical membrane. a1 and a4 were colocalized in the same cells with AE1 or pendrin, whereas a2 was only found in AE1 positive cells but absent from pendrin expressing intercalated cells. These results suggest that vacuolar H(+)-ATPases containing different 'a' isoforms may serve specific and distinct functions and may help explaining why loss of the a4 isoform causes only dRTA without an apparent defect in the proximal tubule.

Distal renal tubular acidosis in mice lacking the AE1 (band3) Cl-/HCO3- exchanger (slc4a1).

Mutations in the human gene that encodes the AE1 Cl(-)/HCO(3)(-) exchanger (SLC4A1) cause autosomal recessive and dominant forms of distal renal tubular acidosis (dRTA). A mouse model that lacks AE1/slc4a1 (slc4a1-/-) exhibited dRTA characterized by spontaneous hyperchloremic metabolic acidosis with low net acid excretion and, inappropriately, alkaline urine without bicarbonaturia. Basolateral Cl(-)/HCO(3)(-) exchange activity in acid-secretory intercalated cells of isolated superfused slc4a1-/- medullary collecting duct was reduced, but alternate bicarbonate transport pathways were upregulated. Homozygous mice had nephrocalcinosis associated with hypercalciuria, hyperphosphaturia, and hypocitraturia. A severe urinary concentration defect in slc4a1-/- mice was accompanied by dysregulated expression and localization of the aquaporin-2 water channel. Mice that were heterozygous for the AE1-deficient allele had no apparent defect. Thus, the slc4a1-/- mouse is the first genetic model of complete dRTA and demonstrates that the AE1/slc4a1 Cl(-)/HCO(3)(-) exchanger is required for maintenance of normal acid-base homeostasis by distal renal regeneration of bicarbonate in the mouse as well as in humans.

Renal acid-base transport: old and new players.

Systemic acid-base homeostasis is the product of complex interactions between metabolism, regulated exhalation of CO2 by the lungs and acid or base excretion by the kidneys. The importance of renal acid-base transport has been highlighted by mutations identified in several proteins involved in this task in patients with inborn forms of renal tubular acidosis. The underlying mechanisms of disease have been further studied in genetically altered mouse models and cell culture. An interesting field of research has focused on the question how changes in metabolism or acid-base homeostasis are sensed and result in altered excretion of acid or bases by the kidney. Several hormonal pathways including aldosterone and endothelin were implicated, a novel subfamily of proton-sensing receptors has been identified, and signaling molecules described that are activated by changes in pH.

Cystinuria-specific rBAT(R365W) mutation reveals two translocation pathways in the amino acid transporter rBAT-b0,+AT.

Apical reabsorption of dibasic amino acids and cystine in kidney is mediated by the heteromeric amino acid antiporter rBAT/b(0,+)AT (system b(0,+)). Mutations in rBAT cause cystinuria type A, whereas mutations in b(0,+)AT cause cystinuria type B. b(0,+)AT is the catalytic subunit, whereas it is believed that rBAT helps the routing of the rBAT/b(0,+)AT heterodimeric complex to the plasma membrane. In the present study, we have functionally characterized the cystinuria-specific R365W (Arg(365)-->Trp) mutation of human rBAT, which in addition to a trafficking defect, alters functional properties of the b(0,+) transporter. In oocytes, where human rBAT interacts with the endogenous b(0,+)AT subunit to form an active transporter, the rBAT(R365W) mutation caused a defect of arginine efflux without altering arginine influx or apparent affinities for intracellular or extracellular arginine. Transport of lysine or leucine remained unaffected. In HeLa cells, functional expression of rBAT(R365W)/b(0,+)AT was observed only at the permissive temperature of 33 degrees C. Under these conditions, the mutated transporter showed 50% reduction of arginine influx and a similar decreased accumulation of dibasic amino acids. Efflux of arginine through the rBAT(R365W)/b(0,+)AT holotransporter was completely abolished. This supports a two-translocation-pathway model for antiporter b(0,+), in which the efflux pathway in the rBAT(R365W)/b(0,+)AT holotransporter is defective for arginine translocation or dissociation. This is the first direct evidence that mutations in rBAT may modify transport properties of system b(0,+).

Localization and regulation of the ATP6V0A4 (a4) vacuolar H+-ATPase subunit defective in an inherited form of distal renal tubular acidosis.

Vacuolar-type H(+)-ATPases (V-H(+)-ATPases) are the major H(+)-secreting protein in the distal portion of the nephron and are involved in net H(+) secretion (bicarbonate generation) or H(+) reabsorption (net bicarbonate secretion). In addition, V-H(+)-ATPases are involved in HCO(3)(-) reabsorption in the proximal tubule and distal tubule. V-H(+)-ATPases consist of at least 13 subunits, the functions of which have not all been elucidated. Mutations in the accessory ATP6V0A4 (a4 isoform) subunit have recently been shown to cause an inherited form of distal renal tubular acidosis in humans. Here, the localization of this subunit in human and mouse kidney was studied and the regulation of expression and localization of this subunit in mouse kidney in response to acid-base and electrolyte intake was investigated. Reverse transcription-PCR on dissected mouse nephron segments amplified a4-specific transcripts in proximal tubule, loop of Henle, distal convoluted tubule, and cortical and medullary collecting duct. a4 protein was localized by immunohistochemistry to the apical compartment of the proximal tubule (S1/S2 segment), the loop of Henle, the intercalated cells of the distal convoluted tubule, the connecting segment, and all intercalated cells of the entire collecting duct in human and mouse kidney. All types of intercalated cells expressed a4. NH(4)Cl or NaHCO(3) loading for 24 h, 48 h, or 7 d as well as K(+) depletion for 7 and 14 d had no influence on a4 protein expression levels in either cortex or medulla as determined by Western blotting. Immunohistochemistry, however, demonstrated a subcellular redistribution of a4 in response to the different stimuli. NH(4)Cl and K(+) depletion led to a pronounced apical staining in the connecting segment, cortical collecting duct, and outer medullary collecting duct, whereas NaHCO(3) loading caused a stronger bipolar staining in the cortical collecting duct. Taken together, these results demonstrate a4 expression in the proximal tubule, loop of Henle, distal tubule, and collecting duct and suggest that under conditions in which increased V-H(+)-ATPase activity is required, a4 is regulated by trafficking but not protein expression. This may allow for the rapid adaptation of V-H(+)-ATPase activity to altered acid-base intake to achieve systemic pH homeostasis. The significance of a4 expression in the proximal tubule in the context of distal renal tubular acidosis will require further clarification.

Molecular cloning and characterization of Atp6v1b1, the murine vacuolar H+ -ATPase B1-subunit.

The multisubunit vacuolar-type proton-translocating ATPases (H(+)-ATPases) mediate the acidification of various intracellular organelles. In a subset of tissues, they also mediate H(+) secretion at the plasma membrane. Two isoforms of the H(+)-ATPase B-subunit exist in humans; we have shown that mutations in ATP6V1B1, encoding the B1-isoform, cause the clinical condition distal renal tubular acidosis. Here we report the cloning and characterization of murine Atp6v1b1, which encodes a 513-amino acid (aa) protein with 93% identity to human ATP6V1B1. Genomic organization is conserved between the murine and human H(+)-ATPase B1-subunits, and Atp6v1b1 maps to a region of mouse chromosome 6 syntenic to human 2p13, the location of ATP6V1B1. Northern blotting detects a 2.2-kb Atp6v1b1 transcript in the kidney and testis, but not other major organs. In mouse kidney, the B1-subunit localizes to intercalated cells of the cortical and medullary collecting duct. B1 protein levels were not increased in either mouse renal cortex or medulla after either 2 or 7 days of oral acid loading. These results demonstrate that Atp6v1b1 encodes the murine ortholog of human ATP6V1B1 and provides a tool for future development of animal models based on manipulation of the Atp6v1b1 genomic locus.

Regulation of the expression of the Cl-/anion exchanger pendrin in mouse kidney by acid-base status.

BACKGROUND: Pendrin belongs to a superfamily of Cl-/anion exchangers and is expressed in the inner ear, the thyroid gland, and the kidney. In humans, mutations in pendrin cause Pendred syndrome characterized by sensorineural deafness and goiter. Recently pendrin has been localized to the apical side of non-type A intercalated cells of the cortical collecting duct, and reduced bicarbonate secretion was demonstrated in a pendrin knockout mouse model. To investigate a possible role of pendrin in modulating acid-base transport in the cortical collecting duct, we examined the regulation of expression of pendrin by acid-base status in mouse kidney. METHODS: Mice were treated orally either with an acid or bicarbonate load (0.28 mol/L NH4Cl or NaHCO3) or received a K+-deficient diet for one week. Immunohistochemistry and Western blotting was performed. RESULTS: Acid-loading caused a reduction in pendrin protein expression levels within one day and decreased expression to 23% of control levels after one week. Concomitantly, pendrin protein was shifted from the apical membrane to the cytosol, and the relative abundance of pendrin positive cells declined. Similarly, in chronic K+-depletion, known to elicit a metabolic alkalosis, pendrin protein levels decreased and pendrin expression was shifted to an intracellular pool with the relative number of pendrin positive cells reduced. In contrast, following oral bicarbonate loading pendrin was found exclusively in the apical membrane and the relative number of pendrin positive cells increased. CONCLUSIONS: These results are in agreement with a potential role of pendrin in bicarbonate secretion and regulation of acid-base transport in the cortical collecting duct.