Articles: splanchnic-circulation-physiology.
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The organs of the hepatosplanchnic system are considered to play a key role in the development of multiorgan failure during septic shock. Impaired oxygenation of the intestinal mucosa can lead to disruption of the intestinal barrier, which may promote a vicious cycle of inflammatory response, increased oxygen demand and inadequate oxygen supply. ⋯ These therapies may have beneficial or detrimental effects not only on systemic haemodynamics but also on splanchnic haemodynamics, at both the macrocirculatory and microcirculatory levels. This clinical review focuses on the splanchnic haemodynamic and metabolic effects of standard therapies used in patients with septic shock, as well as on the recently described nonconventional therapies such as vasopressin, prostacyclin and N-acetyl cysteine.
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A number of papers have suggested that the splanchnic circulation and oxidative metabolism are compromised in critical illness. This review discusses this hypothesis and outlines the recent advances in the understanding of splanchnic metabolism with special focus on acute liver failure and hyperdynamic sepsis. ⋯ There is increasing evidence that both acute liver failure and sepsis are accompanied by a hypermetabolic state in the hepatosplanchnic area, characterized by enhanced glycolysis and hyperlactatemia. This should not be rigorously interpreted as an indication of hypoxia. In fact, clinically important splanchnic hypoxia may be a relatively uncommon phenomenon in such patients.
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Inadequate splanchnic perfusion is associated with increased morbidity and mortality, particularly if liver dysfunction coexists. Heart failure, increased intra-abdominal pressure, haemodialysis and the presence of obstructive sleep apnoea are among the multiple clinical conditions that are associated with impaired splanchnic perfusion in critically ill patients. Total liver blood flow is believed to be relatively protected when gut blood flow decreases, because hepatic arterial flow increases when portal venous flow decreases (the hepatic arterial buffer response [HABR]). ⋯ Unfortunately, no drugs are yet available that increase total hepato-splanchnic blood flow selectively and to a clinically relevant extent. The present review discusses old and new concepts of splanchnic vasoregulation from both experimental and clinical viewpoints. Recently published trials in this field are discussed.
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For supportive therapy in sepsis adequate volume loading is probably the first, and possibly the most important step in the treatment of patients with septic shock. An elevated global O2-supply (DO2) may be necessary and beneficial in most of these patients, but the increase in DO2 should be guided by measurement of parameters assessing global and regional oxygenation. Routine strategies for elevating DO2 by the use of very high dosages of catecholamines cannot be recommended. ⋯ Dopexamine has been suggested for improvement of splanchnic perfusion, but since these effects remain somewhat controversial there are no current grounds for a general recommendation in favour of dopexamine in septic patients. These recommendations are currently limited by the lack of sufficient outcome studies and studies evaluating regional perfusion. Until the various catecholamine regimes are more fully examined, recommendations for catecholamine support in sepsis must be considered "conditional".
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Sepsis and SIRS are characterised by increased hepatosplanchnic blood flow and oxygen transport due to sepsis-associated hypermetabolism with enhanced oxygen uptake. Regional hypermetabolism may be linked with a mismatch of oxygen availability and demand potentially resulting in a pathological splanchnic oxygen uptake/supply dependency. ⋯ The response of splanchnic haemodynamics and oxygen kinetics, however, to therapeutic interventions does not necessarily parallel the different metabolic pathways. Therefore, understanding of both tissue perfusion and oxygenation as well as metabolism is pivotal for evaluating the effects of different therapeutic strategies in intensive care medicine.