Correlations between physiological parameters related with kidney function and minute-by-minute urine output.

AIM: Recently, devices capable of measuring minute-by-minute urine output (UOm) have become available. It is not known how UOm correlates with physiological parameters in normal conditions and in disease states characterized by vascular dysfunction. This paper analyzes correlations between UOm and physiological parameters related to kidney perfusion to provide some insight about UOm pathophysiological interpretation and its relationship with renal blood flow. METHODS: We studied 14 male pigs were anesthetized, tracheostomized, and mechanically ventilated. Mean systemic blood pressure (PART ), mean pulmonary artery blood pressure (PPA ), carotid artery blood flow (QCA ), as well as total (QREN ), cortical (QCOR ) and medullary (QMED ) renal blood flows, and the renal resistive index (RRI) were measured or calculated. Animals received an intravenous dose of live E. coli for the induction of sepsis (septic group), or an equivalent amount of normal saline (nonseptic group). Three groups were studied: nonseptic (n = 6) and septic (n = 4), both receiving for resuscitation NaCl 0.9% at 4 mL/kg per h; and septic (n = 4), receiving for resuscitation NaCl 0.9% at 17 mL/kg per h. Animals were monitored for 5 h after the induction of sepsis. RESULTS: In septic animals, UOm was strongly positively correlated with QREN (Kendall's τ = 0.770, P < 0.05), QCOR (τ = -0.566, P < 0.05) and QMED (τ = 0.632, P < 0.05); and negatively correlated with PPA (τ = -0.524, P < 0.05) and RRI (τ = -0.672, P < 0.05). Control animals exhibited weaker correlations. CONCLUSION: UOm is a good physiological surrogate marker of total and regional renal blood flows and vascular resistance, particularly under septic conditions, probably reflecting glomerulo-tubular dysfunction in sepsis.

A Metabolomic Approach to the Pathogenesis of Ventilator-induced Lung Injury.

BACKGROUND: Global metabolic profiling using quantitative nuclear magnetic resonance spectroscopy (MRS) and mass spectrometry (MS) is useful for biomarker discovery. The objective of this study was to discover biomarkers of acute lung injury induced by mechanical ventilation (ventilator-induced lung injury [VILI]), by using MRS and MS. METHODS: Male Sprague-Dawley rats were subjected to two ventilatory strategies for 2.5 h: tidal volume 9 ml/kg, positive end-expiratory pressure 5 cm H2O (control, n = 14); and tidal volume 25 ml/kg and positive end-expiratory pressure 0 cm H2O (VILI, n = 10). Lung tissue, bronchoalveolar lavage fluid, and serum spectra were obtained by high-resolution magic angle spinning and H-MRS. Serum spectra were acquired by high-performance liquid chromatography coupled to quadupole-time of flight MS. Principal component and partial least squares analyses were performed. RESULTS: Metabolic profiling discriminated characteristics between control and VILI animals. As compared with the controls, animals with VILI showed by MRS higher concentrations of lactate and lower concentration of glucose and glycine in lung tissue, accompanied by increased levels of glucose, lactate, acetate, 3-hydroxybutyrate, and creatine in bronchoalveolar lavage fluid. In serum, increased levels of phosphatidylcholine, oleamide, sphinganine, hexadecenal and lysine, and decreased levels of lyso-phosphatidylcholine and sphingosine were identified by MS. CONCLUSIONS: This pilot study suggests that VILI is characterized by a particular metabolic profile that can be identified by MRS and MS. The metabolic profile, though preliminary and pending confirmation in larger data sets, suggests alterations in energy and membrane lipids.SUPPLEMENTAL DIGITAL CONTENT IS AVAILABLE IN THE TEXT.

Metabolic Reprogramming in the Heart and Lung in a Murine Model of Pulmonary Arterial Hypertension.

A significant glycolytic shift in the cells of the pulmonary vasculature and right ventricle during pulmonary arterial hypertension (PAH) has been recently described. Due to the late complications and devastating course of any variant of this disease, there is a great need for animal models that reproduce potential metabolic reprograming of PAH. Our objective is to study, in situ, the metabolic reprogramming in the lung and the right ventricle of a mouse model of PAH by metabolomic profiling and molecular imaging. PAH was induced by chronic hypoxia exposure plus treatment with SU5416, a vascular endothelial growth factor receptor inhibitor. Lung and right ventricle samples were analyzed by magnetic resonance spectroscopy. In vivo energy metabolism was studied by positron emission tomography. Our results show that metabolomic profiling of lung samples clearly identifies significant alterations in glycolytic pathways. We also confirmed an upregulation of glutamine metabolism and alterations in lipid metabolism. Furthermore, we identified alterations in glycine and choline metabolism in lung tissues. Metabolic reprograming was also confirmed in right ventricle samples. Lactate and alanine, endpoints of glycolytic oxidation, were found to have increased concentrations in mice with PAH. Glutamine and taurine concentrations were correlated to specific ventricle hypertrophy features. We demonstrated that most of the metabolic features that characterize human PAH were detected in a hypoxia plus SU5416 mouse model and it may become a valuable tool to test new targeting treatments of this severe disease.

On the minute by minute variations of urine output: a study in a porcine model.

BACKGROUND: Urine output (UO) is usually measured hourly in acutely ill patients. Devices capable of more continuous (minute by minute urine output, UOm) measurements have become available recently. This paper aims to (1) analyze the minute by minute variations of UO, (2) analyze the impact of sepsis on those variations and (3) test if UO measured over periods shorter than 60 min provides information not available in hourly measurements. METHODS: Fifteen male pigs were anesthetized, tracheostomized and mechanically ventilated. Sepsis was induced by the administration of live Escherichia coli. Three groups were studied: nonseptic (n = 7) and septic (n = 4), both receiving sodium chloride (NaCl) 0.9 % at 4 ml kg(-1) h(-1); and septic (n = 4) receiving NaCl 0.9 % at 17 ml kg(-1) h(-1). UOm was measured during 6 h. RESULTS: There was a significant variation of UOm over time, as assessed by the coefficient of variation of the root-mean-squared error (CV(RMSE)), which was significantly more pronounced under conditions of sepsis than under control conditions. A UO production pattern in sepsis was identified, characterized by low UO production compared to baseline levels for approximately 30 min, followed by high UO production for approximately 30 min after initiation of the septic challenge. This pattern was noticeable if UO was measured every 10 min but not over longer periods of time. CONCLUSIONS: UOm provides information not conveyed by hourly measurements, especially under the cardiovascular alterations associated to sepsis. This information could enable an early identification of sepsis.

Influence of mechanical ventilation and sepsis on redox balance in diaphragm, myocardium, limb muscles, and lungs.

Mechanical ventilation (MV), using high tidal volumes (V(T)), causes lung (ventilator-induced lung injury [VILI]) and distant organ injury. Additionally, sepsis is characterized by increased oxidative stress. We tested whether MV is associated with enhanced oxidative stress in sepsis, the commonest underlying condition in clinical acute lung injury. Protein carbonylation and nitration, antioxidants, and inflammation (immunoblotting) were evaluated in diaphragm, gastrocnemius, soleus, myocardium, and lungs of nonseptic and septic (cecal ligation and puncture 24 hours before MV) rats undergoing MV (n = 7 per group) for 150 minutes using 3 different strategies (low V(T) [V(T) = 9 mL/kg], moderate V(T) [V(T) = 15 mL/kg], and high V(T) [V(T) = 25 mL/kg]) and in nonventilated control animals. Compared with nonventilated control animals, in septic and nonseptic rodents (1) diaphragms, limb muscles, and myocardium of high-V(T) rats exhibited a decrease in protein oxidation and nitration levels, (2) antioxidant levels followed a specific fiber-type distribution in slow- and fast-twitch muscles, (3) tumor necrosis factor α (TNF-α) levels were higher in respiratory and limb muscles, whereas no differences were observed in myocardium, and (4) in lungs, protein oxidation was increased, antioxidants were rather decreased, and TNF-α remained unmodified. In this model of VILI, oxidative stress does not occur in distant organs or skeletal muscles of rodents after several hours of MV with moderate-to-high V(T), whereas protein oxidation levels were increased in the lungs of the animals. Inflammatory events were moderately expressed in skeletal muscles and lungs of the MV rats. Concomitant sepsis did not strongly affect the MV-induced effects on muscles, myocardium, or lungs in the rodents.

Vascular dysfunction in sepsis: effects of the peroxynitrite decomposition catalyst MnTMPyP.

The mechanisms contributing to sepsis vascular dysfunction are not well known. We tested the hypothesis that peroxynitrite scavenging ameliorates sepsis-induced macrovascular and microvascular dysfunction. Male Sprague-Dawley rats were killed 48 h after cecal ligation (n = 15) and puncture or sham procedure (n = 15). Their aortas and mesenteric vessels were mounted in organ baths for isometric tension recording. We studied contraction in resting vessels (norepinephrine 1 nM-10 µM and 10 nM-10 µM) and endothelium-dependent relaxation (acetylcholine, 10 nM-10 µM and 1 nM-10 µM) for aortas and microvessels, respectively. Vascular rings were preincubated for 30 min with the superoxide scavenger Cu-Zn-superoxide dismutase (SOD) (100 U/mL), the SOD mimetic and peroxynitrite scavenger tempol (10 M), the NO synthase inhibitor N-nitro-l-arginine methyl ester (10 M), or the peroxynitrite decomposition catalyst manganese tetrakis(4-N-methylpyridyl)porphyrin (MnTMPyP) (10 M). Fluorescence to 3-nitrotyrosine, oxidized dihydroethidium, and NOS2 was assessed in vascular tissue. Vascular NOS2, endothelial nitric oxide synthase (NOS1), NADPH-oxidase-1 (NOX-1), and SOD expression was analyzed by reverse transcription-polymerase chain reaction. Sepsis induced (i) in macrovessels, impairment of norepinephrine-induced contractions; (ii) in microvessels, impairment in norepinephrine-induced contractions and acetylcholine-induced relaxations; (iii) aortic and microvascular tissue increased reactivity to 3-nitrotyrosine, oxidized dihydroethidium, NOS2, and increased expression of NOS2, as well as increased expression of NOX-1 in microvascular tissue. Contractile responses in aortic and microvascular rings improved by ex vivo treatment with MnTMPyP and tempol, whereas vascular relaxation in microvessels improved only with MnTMPyP. Peroxynitrite scavenging protects from vascular dysfunction in sepsis.

A metabolomic approach for diagnosis of experimental sepsis.

BACKGROUND: The search for reliable diagnostic biomarkers of sepsis remains necessary. Assessment of global metabolic profiling using quantitative nuclear magnetic resonance (NMR)-based metabolomics offers an attractive modern methodology for fast and comprehensive determination of multiple circulating metabolites and for defining the metabolic phenotype of sepsis. OBJECTIVE: To develop a novel NMR-based metabolomic approach for diagnostic evaluation of sepsis. METHODS: Male Sprague-Dawley rats (weight 325-375 g) underwent cecal ligation and puncture (n = 14, septic group) or sham procedure (n = 14, control group) and 24 h later were euthanized. Lung tissue, bronchoalveolar lavage (BAL) fluid, and serum samples were obtained for (1)H NMR and high-resolution magic-angle spinning analysis. Unsupervised principal components analysis was performed on the processed spectra, and a predictive model for diagnosis of sepsis was constructed using partial least-squares discriminant analysis. RESULTS: NMR-based metabolic profiling discriminated characteristics between control and septic rats. Characteristic metabolites changed markedly in septic rats as compared with control rats: alanine, creatine, phosphoethanolamine, and myoinositol concentrations increased in lung tissue; creatine increased and myoinositol decreased in BAL fluid; and alanine, creatine, phosphoethanolamine, and acetoacetate increased whereas formate decreased in serum. A predictive model for diagnosis of sepsis using these metabolites classified cases with sensitivity and specificity of 100%. CONCLUSIONS: NMR metabolomic analysis is a potentially useful technique for diagnosis of sepsis. The concentrations of metabolites involved in energy metabolism and in the inflammatory response change in this model of sepsis.