Critical care : the official journal of the Critical Care Forum
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The microcirculation is a complex and integrated system that supplies and distributes oxygen throughout the tissues. The red blood cell (RBC) facilitates convective oxygen transport via co-operative binding with hemoglobin. In the microcirculation oxygen diffuses from the RBC into neighboring tissues, where it is consumed by mitochondria. ⋯ Nitric oxide (NO) maintains microvascular homeostasis by regulating arteriolar tone, RBC deformability, leukocyte and platelet adhesion to endothelial cells, and blood volume. NO also regulates mitochondrial respiration. During sepsis, NO over-production mediates systemic hypotension and microvascular reactivity, and is seemingly protective of microvascular blood flow.
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Hypertension is an extremely common clinical problem, affecting approximately 50 million people in the USA and approximately 1 billion individuals worldwide. Approximately 1% of these patients will develop acute elevations in blood pressure at some point in their lifetime. ⋯ Immediate reduction in blood pressure is required only in patients with acute end-organ damage. This article reviews current concepts, and common misconceptions and pitfalls in the diagnosis and management of patients with acutely elevated blood pressure.
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Comparative Study
Does the tube-compensation function of two modern mechanical ventilators provide effective work of breathing relief?
An endotracheal tube (ETT) imposes work of breathing on mechanically ventilated patients. Using a bellows-in-a-box model lung, we compared the tube compensation (TC) performances of the Nellcor Puritan-Bennett 840 ventilator and of the Dräger Evita 4 ventilator. ⋯ Although both ventilators provided effective TC, even when set to 100% TC they could not entirely compensate for a ventilator and ETT-imposed work of breathing. The effect of TC is less than that of pressure support ventilation. Physicians should be aware of this when using TC in weaning trials.
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Apoptosis is a process of controlled cellular death whereby the activation of specific death-signaling pathways leads to deletion of cells from tissue. The importance of apoptosis resides in the fact that several steps involved in the modulation of apoptosis are susceptible to therapeutic intervention. ⋯ The second hypothesis, the 'epithelial hypothesis', suggests that epithelial injury in acute lung injury is associated with apoptotic death of alveolar epithelial cells triggered by soluble mediators such as soluble Fas ligand. We also review recent studies that suggest that the rate of clearance of apoptotic neutrophils may be associated with resolution of neutrophilic inflammation in the lungs, and data showing that phagocytosis of apoptotic neutrophils can induce an anti-inflammatory phenotype in activated alveolar macrophages.
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We describe a case of systemic inflammatory response syndrome associated with air embolism following the removal of a central line catheter, coupled with a deep inspiratory maneuver. The presence of a patent foramen ovale allowed the passage of a clinically significant amount of air from the venous circulation to the systemic circulation. The interaction of air with the systemic arterial endothelium may have triggered the release of endothelium-derived cytokines, resulting in the physiologic response of systemic inflammatory response syndrome.