Shock : molecular, cellular, and systemic pathobiological aspects and therapeutic approaches : the official journal the Shock Society, the European Shock Society, the Brazilian Shock Society, the International Federation of Shock Societies
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Thermal injury results in reduced plasma levels of arginine (Arg). With reduced Arg availability, NOS produces superoxide instead of NO. We hypothesized that Arg supplementation after burn and smoke inhalation (B + S) injury would attenuate the acute insult to the lungs and, thus, protect pulmonary function. ⋯ Histopathological examinations also indicated a remarkably reduced histopathological scores associated with B + S injury. Nitrotyrosine stain in lung tissue was positive after B + S injury, but was significantly reduced in the group with Arg. Therefore, L-Arg supplementation improved gas exchange and pulmonary function in ovine after B + S injury via its, at least in part, effect on reduction of oxidative stress through the peroxynitrite pathway.
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Administration of fluids to maintain or restore intravascular volume is a common intervention after hemorrhagic shock, but there is uncertainty whether the choice of fluid significantly influences outcome. Systemic parameters, microvascular perfusion, and functional capillary density were used to characterize resuscitation from hemorrhagic shock with hydroxyethyl starch (HES) of different molecular weights. Studies were made in the hamster window chamber model to determine their effects on blood rheological properties, restoration of perfusion and coagulation changes. ⋯ Impairment of thrombus formation seems to be in part related to altered hemodynamics and transport inherent to hemodilution, leading to lowered platelet availability due to hemodilution and increased shear stress at the vessel wall when plasma viscosity is increased. The HES MW does not seem to be a factor in compromising platelet adherence on stimulated endothelium. The longer initial intravascular persistence of H-HES might result in longer-lasting volume effects.
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Shock and poor regional perfusion are common in asphyxiated neonates. We compared the systemic and regional hemodynamic effects of high-dose epinephrine (E) with those of dopamine combined with low-dose epinephrine (DE) infusions in a neonatal model of hypoxia-reoxygenation. Neonatal piglets (1-3 days, 1.5-2.5 kg) were acutely instrumented to continuously monitor systemic arterial pressure (SAP), pulmonary artery pressure, cardiac index (CI), and blood flows at the left common carotid, superior mesenteric, and renal arteries. ⋯ There were no differences in regional blood flows and oxygen delivery between groups. After hyperlactatemia with hypoxia, plasma lactate levels decreased with no difference between groups. Epinephrine given as the sole agent is as effective as dopamine and low-dose epinephrine combined in treating shock and hypotension that follow the resuscitation of hypoxic neonatal piglets, with no reduction in regional perfusion.
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Neonatal asphyxia may lead to cardiac and renal complications perhaps mediated by oxygen free radicals. Using a model of neonatal hypoxia-reoxygenation, we tested the hypothesis that N-acetylcysteine (NAC) would improve cardiac function and renal blood flow. Eighteen piglets (aged 1-4 days old, weighing 1.4-2.2 kg) were anesthetized and acutely instrumented for continuous monitoring of pulmonary and renal artery flow (cardiac index [CI] and renal artery flow index [RAFI], respectively) and mean blood pressure. ⋯ There were no significant differences in heart rate, pulmonary artery pressure, systemic oxygen uptake, and tissue lipid hydroperoxide levels between groups. No histologic injury was found in the heart or kidney. In this porcine model of neonatal hypoxia and 100% reoxygenation, NAC improved cardiac function and renal perfusion, with improved tissue glutathione content.
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Shock states are associated with an impaired tissue oxygen supply-demand relationship and perturbations within the microcirculation, leading to global tissue hypoxia, finally resulting in multiple-organ failure or even death. Two of the most frequent causes of shock are acute hemorrhage and sepsis. Although the origin and the pathophysiology of hemorrhagic and septic shock are basically different, the involvement of adenosine triphosphate-sensitive potassium (KATP) channels, as an important regulator of vascular smooth muscles tone, plays a pivotal role under both conditions. ⋯ The differences in the species, the comorbidity, and the difficulty in determining the exact onset of shock in clinical practice and, thus, any duration-related alterations in vascular responses and KATP channel activation may explain the discrepancy between the results obtained from experimental and clinical studies. Currently, two of the most relevant problems related to effective KATP blockade in shock states are represented by (1) the dose itself (benefit-risk ratio) and (2) the route of administration (oral vs. i.v.). This review article critically elucidates the published in vivo studies on the role of KATP channel inhibition in both described shock forms and discusses the advantages and the potential pitfalls related to the treatment of human shock states.