1,721,147 research outputs found
Autonomic and circulatory alterations persist despite adequate resuscitation in a 5-day sepsis swine experiment.
Full text linkAutonomic and vascular failures are common phenotypes of sepsis, typically characterized by tachycardia despite corrected hypotension/hypovolemia, vasopressor resistance, increased arterial stiffness and decreased peripheral vascular resistance. In a 5-day swine experiment of polymicrobial sepsis we aimed at characterizing arterial properties and autonomic mechanisms responsible for cardiovascular homeostasis regulation, with the final goal to verify whether the resuscitation therapy in agreement with standard guidelines was successful in restoring a physiological condition of hemodynamic profile, cardiovascular interactions and autonomic control. Twenty pigs were randomized to polymicrobial sepsis and protocol-based resuscitation or to prolonged mechanical ventilation and sedation without sepsis. The animals were studied at baseline, after sepsis development, and every 24 h during the 3-days resuscitation period. Beat-to-beat carotid blood pressure (BP), carotid blood flow, and central venous pressure were continuously recorded. The two-element Windkessel model was adopted to study carotid arterial compliance, systemic vascular resistance and characteristic time constant τ. Effective arterial elastance was calculated as a simple estimate of total arterial load. Cardiac baroreflex sensitivity (BRS) and low frequency (LF) spectral power of diastolic BP were computed to assess autonomic activity. Sepsis induced significant vascular and autonomic alterations, manifested as increased arterial stiffness, decreased vascular resistance and τ constant, reduced BRS and LF power, higher arterial afterload and elevated heart rate in septic pigs compared to sham animals. This compromised condition was persistent until the end of the experiment, despite achievement of recommended resuscitation goals by administered vasopressors and fluids. Vascular and autonomic alterations persist 3 days after goal-directed resuscitation in a clinically relevant sepsis model. We hypothesize that the addition of these variables to standard clinical markers may better profile patients' response to treatment and this could drive a more tailored therapy which could have a potential impact on long-term outcomes
Comment on: "A novel 'shunt fraction' method to derive native cardiac output during liberation from central VA ECMO" by Lim, HS.
Full text linkGas exchange calculation may estimate changes in pulmonary blood flow during veno-arterial extracorporeal membrane oxygenation in a porcine model.
Full text linkBACKGROUND
Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used as rescue for severe cardiopulmonary failure. We tested whether the ratio of CO2 elimination at the lung and the ECMO (VCO2ECMO/VCO2Lung) would reflect the ratio of respective blood flows and could be used to estimate changes in pulmonary blood flow (QLUNG), i. e. native cardiac output.
METHODS
Four healthy pigs were centrally cannulated for VA-ECMO. We measured blood flows with an ultrasonic flow probes. VCO2ECMO and VCO2Lung were calculated from sidestream capnographs under constant pulmonary ventilation during ECMO weaning with changing sweep gas and/or ECMO blood flow. If ventilation/perfusion (V/Q) ratio of ECMO was not one, the VCO2ECMO was normalized to V/Q=1 (VCO2ECMONORM). Changes in pulmonary blood flow were calculated using the relationship between changes in CO2 elimination and ECMO blood flow.
RESULTS
QECMO correlated strongly with VCO2ECMONORM (r2 0.95 - 0.99). QLUNG correlated well with VCO2LUNG (r2 0.65 - 0.89, p<=0.002). Absolute QLung could not be calculated in a non-steady state. Calculated pulmonary blood flow changes had a bias of 76 (-266 to 418) ml/min and correlated with measured QLUNG (r2 0.974 - 1.000, p = 0.1 to 0.006) for cumulative ECMO flow reductions.
CONCLUSIONS
VCO2 of the lung correlated strongly with pulmonary blood flow. Our model could predict pulmonary blood flow changes within clinically acceptable margins of error. The prediction is made possible with a normalization to a V/Q of 1 for ECMO. This approach depends on measurements readily available and may allow immediate assessment of the cardiac output response
Persistent hyperammonia and altered concentrations of urea cycle metabolites in a 5-day swine experiment of sepsis.
Full text linkWe measured plasma and cerebrospinal fluid (CSF) metabolite concentrations in a 5-day porcine sepsis model of fecal peritonitis. The objectives were: (i) to verify whether the expected pathways that had emerged in previous studies pertain only to the early inflammatory response or persist for the subsequent days; (ii) to identify metabolic derangements that arise later; (iii) to verify whether CSF metabolite concentrations were altered and if these alterations were similar to those in the blood or delayed. We observed an early response to inflammation and cytokine storms with alterations in lipid and glucose metabolism. The arginine/asymmetric dimethylarginine (ADMA) and phenylalanine/tyrosine balances changed 24 h after resuscitation in plasma, and later in CSF. There was a rise in ammonia concentration, with altered concentrations of metabolites in the urea cycle. Whether persistent derangement of these pathways have a role not only on short-term outcomes but also on longer-term comorbidities, such as septic encephalopathy, should be addressed in further studies
Perioperative metabolic changes in patients undergoing cardiac surgery
No full textPerioperative metabolic changes in cardiac surgical patients are not only induced by tissue injury and extracorporeal circulation per se: the systemic inflammatory response to surgical trauma and extracorporeal circulation, perioperative hypothermia, cardiovascular and neuroendocrine responses, and drugs and blood products used to maintain cardiovascular function and anesthesia contribute to varying degrees. The pathophysiologic changes include increased oxygen consumption and energy expenditure; increased secretion of adrenocorticotrophic hormone, cortisol, epinephrine, norepinephrine, insulin, and growth hormone; and decreased total tri-iodothyronine levels. Easily measurable metabolic consequences of these changes include hyperglycemia, hyperlactatemia, increased aspartate, glutamate and free fatty acid concentrations, hypokalemia, increased production of inflammatory cytokines, and increased consumption of complement and adhesion molecules. Nutritional risk before elective cardiac surgery-defined as preoperative unintended pathologic weight loss/low amount of food intake in the preceding week or low body mass index-is related to adverse postoperative outcome. Improvements in surgical techniques, anesthesia, and perioperative management have been designed to minimize the stressful stimulus to catabolism, thereby slowing the wasting process to the point where much less nutrition is required to meet metabolic requirements. Early nutrition in cardiac surgery is safe and well tolerated
Wave separation analysis to assess cardiovascular alterations induced by sepsis
Full text linkObjective: Sepsis induces a severe decompensation of arterial and cardiac functional properties, leading to important modifications of arterial blood pressure (ABP) waveform, not resolved by recommended therapy, as shown by previous works. The aim of this study is to quantify the changes in ABP waveform morphology and wave reflections during a long-term swine experiment of polymicrobial sepsis and resuscitation, to deepen the understanding of the cardiovascular response to standard resuscitation therapy. Methods: We analyzed 14 pigs: polymicrobial sepsis was induced in 9 pigs followed by standard resuscitation and 5 pigs were treated as sham controls. Septic animals were studied at baseline (T1), after sepsis development (T2), and after 24h (T3) and 48h (T4) of therapy administration, and sham controls at the same time points. ABP and arterial blood flow were measured in the left and right carotid artery, respectively. Pulse wave analysis and wave separation techniques were used to estimate arterial input impedance, carotid characteristic impedance, forward and backward waves, indices of wave reflections such as reflection magnitude and reflection index, and augmentation index. Results: Sepsis led to an acute alteration of ABP waveform passing from type A to type B or C; consistently, the reflection phenomena were significantly reduced. The resuscitation was successful in reaching targeted hemodynamic stability, but it failed in restoring a physiological blood propagation and reflection. Conclusion: Septic pigs persistently showed altered reflected waves even after 48 hours of successful therapy according to guidelines, suggesting a persistent hidden cardiovascular disorder. Significance: The proposed indices may be useful to unravel the complex cardiovascular response to therapy administration in septic patients and could potentially be used for risk stratification of patient deterioration. Whether alterations of blood propagation and reflection contribute to persisting organ dysfunction after hemodynamic stabilization should be further investigated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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