Best practice & research. Clinical anaesthesiology
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Best Pract Res Clin Anaesthesiol · Dec 2016
ReviewRed blood cell transfusion and its effect on microvascular dysfunction in shock states.
Among critically ill patients, red blood cell (RBC) transfusion is often prescribed for anemia in the absence of active or recent bleeding. The failure of RBC transfusion to improve physiological parameters and clinical outcomes in this setting may be explained by current understanding of the relationship between the RBCs and the microcirculation. It is now evident that the circulating RBCs contribute to microcirculatory hypoxic vasodilation by regulated nitric oxide (NO)-dependent vasodilation, thereby facilitating delivery of oxygen to oxygen-deprived tissue. ⋯ In recent years, there has been a significant focus on the dysfunctional interaction between stored RBCs and the microcirculation, with emphasis on understanding the mechanisms that drive erythrocyte NO-mediated vasodilation. The development of technology that allows noninvasive observation of the microcirculation in humans has allowed for direct observation of the microcirculation immediately before and after RBC transfusion. The current understanding of RBC NO-mediated vasodilation and the results of direct observation of the microcirculation in the setting of RBC transfusion are reviewed.
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Best Pract Res Clin Anaesthesiol · Dec 2016
ReviewLactate levels and hemodynamic coherence in acute circulatory failure.
In this review, the relationship between changes in macrohemodynamics during the development and treatment of acute circulatory failure is discussed in the context of coherence with microcirculation and changes in lactate. In models of circulatory failure, coherence between changes in macrocirculatory and microcirculatory perfusion and coherence with subsequent changes in lactate levels are more or less preserved. ⋯ Resuscitation should therefore aim at adequate tissue perfusion where systemic hemodynamics, microcirculatory perfusion parameters, and lactate levels should be used in their relevant context. This results in treating the individual patient as an n = 1 experiment.
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Over the last decade, there has been an increased interest in the use of goal-directed therapy (GDT) in patients undergoing high-risk surgery, and various haemodynamic monitoring tools have been developed to guide perioperative care. Both the complexity of the patient and surgical procedure need to be considered when deciding whether GDT will be beneficial. ⋯ Although global haemodynamic parameters may be optimised with the use of GDT, microvascular impairment can still persist. This review will provide an overview of both haemodynamic optimisation and microvascular assessment in the perioperative period.
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Best Pract Res Clin Anaesthesiol · Dec 2016
ReviewEffect of non-adrenergic vasopressors on macro- and microvascular coupling in distributive shock.
The present review initially describes the rationale for the use of non-adrenergic vasopressors in the treatment of distributive shock and then provides an overview of the individual vasopressin-receptor agonists, namely arginine vasopressin, terlipressin, and selepressin. Following a brief summary of their current use in clinical practice, the present review focuses on the influence of vasopressin-receptor agonists on macro- and microvascular coupling, also referred to as hemodynamic coherence. ⋯ A higher selectivity for the V1a-receptor seems to be beneficial; however, future clinical trials are warranted to verify this assumption. Notably, the optimal treatment regime for non-adrenergic vasopressors with respect to compound, dose, and timing still needs to be defined.
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In case of haemorrhage, a combination of low volume fluid resuscitation and permissive hypotension is used to avoid the adverse effects of early aggressive fluid resuscitation. During this phase, occult microvascular hypoperfusion can possibly develop over time. After controlling the bleeding, it is expected that optimization of macrocirculation will result in an improvement in microcirculation. ⋯ However, haemorrhagic shock, reperfusion, traumatic injury and inflammation can damage microcirculation and thus lead to a loss of haemodynamic coherence. In these cases, a systemic haemodynamic-driven resuscitation would not be effective in restoring microcirculation and tissue oxygenation. A real-time technique enabling microcirculation monitoring can create an opportunity for microcirculatory haemodynamic-driven resuscitation to become the gold standard in the future.