Medicina intensiva
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Electrical impedance tomography has been described as a new method of monitoring critically ill patients on mechanical ventilation. It has recently gained special interest because of its applicability for monitoring ventilation and pulmonary perfusion. ⋯ This review explains the physical concept of bioimpedance and its clinical application, and summarizes the scientific evidence published to date with regard to the implementation of electrical impedance tomography as a method for monitoring ventilation and perfusion, mainly in the patient with acute lung injury, and other possible applications of the technique in the critically ill patient. The review also summarizes the limitations of the technique and its potential areas of future development.
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Nutritional support in acute renal failure must take into account the patient's catabolism and the treatment of the renal failure. Hypermetabolic failure is common in these patients, requiring continuous renal replacement therapy or daily hemodialysis. In patients with normal catabolism (urea nitrogen below 10 g/day) and preserved diuresis, conservative treatment can be attempted. ⋯ Depending on their hemofiltration flow, continuous renal replacement systems require high daily nitrogen intake, which can sometimes reach 2.5 g protein/kg. The amount of volume replacement can induce energy overload and therefore the use of glucose-free replacement fluids and glucose-free dialysis or a glucose concentration of 1 g/L, with bicarbonate as a buffer, is recommended. Monitoring of electrolyte levels (especially those of phosphorus, potassium and magnesium) and of micronutrients is essential and administration of these substances should be individually-tailored.
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Patients with liver failure have a high prevalence of malnutrition, which is related to metabolic abnormalities due to the liver disease, reduced nutrient intake and alterations in digestive function, among other factors. In general, in patients with liver failure, metabolic and nutritional support should aim to provide adequate nutrient intake and, at the same time, to contribute to patients' recovery through control or reversal of metabolic alterations. In critically-ill patients with liver failure, current knowledge indicates that the organ failure is not the main factor to be considered when choosing the nutritional regimen. ⋯ Despite the physiopathological basis classically described by some authors who consider amino acid imbalance to be a triggering factor and key element in maintaining encephalopathy, there are insufficient data to recommend "specific" solutions (branched-chain amino acid-enriched with low aromatic amino acids) as part of nutritional support in patients with acute liver failure. In patients undergoing liver transplantation, nutrient intake should be started early in the postoperative period through transpyloric access. Prevention of the hepatic alterations associated with nutritional support should also be considered in distinct clinical scenarios.