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Severe acute respiratory failure requiring mechanical ventilation is one of the most frequent reasons for admission to the intensive care unit. Among the most frequent causes for admission are exacerbation of chronic obstructive pulmonary disease and acute respiratory failure with acute lung injury (ALI) or with criteria of acute respiratory distress syndrome (ARDS). These patients have a high risk of malnutrition due to the underlying disease, their altered catabolism and the use of mechanical ventilation. Consequently, nutritional evaluation and the use of specialized nutritional support are required. This support should alleviate the catabolic effects of the disease, avoid calorie overload and, in selected patients, to use omega-3 fatty acid and antioxidant-enriched diets, which could improve outcome.

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. In these patients, relatively hypoproteic nutritional support is essential, using proteins with high biological value and limiting fluid and electrolyte intake according to the patient's individual requirements. Micronutrient intake should be adjusted, the only buffering agent used being bicarbonate. Limitations on fluid, electrolyte and nitrogen intake no longer apply when extrarenal clearance techniques are used but intake of these substances should be modified according to the type of clearance. 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.

Although it is considered that metabolic and nutritional support must be part of the management of septic patients, it has not been conclusively shown that nutritional support will improve survival or complications from sepsis. Specific data on this issue are scarce since there are few studies that have investigated specialized nutritional support in septic patients. Thus, most of the recommendations are based on outcomes obtained in severely ill patients with different pathologies. It is assumed that nutritional support should be carried out through the enteral route whenever possible, as in other critically ill patients. The energetic waste in these patients is highly variable, although in general terms the hypermetabolic situation may be classified as moderate. An adjustment factor of 1.25-1.30 is recommended for the Harris-Benedict's equation to calculate the caloric intake. Septic patients should receive a hyperproteic intake. The amount of glucose administered should not exceed 70% of non-protein calories, and lipids intake should not exceed 40%. With regards to micronutrients, it is recommended to increase the supply of those with antioxidant properties (vitamin E, carotenes, vitamin C, selenium). There are data to consider that the use of diets enriched with pharmaco-nutrients (both with parenteral and enteral routes) may be beneficial in septic patients, although there is some controversy when interpreting the outcomes.

The need to strictly control glucose levels, even in nondiabetic patients, has recently emerged following the publication of the results that indicate the possibility of reducing the morbidity and mortality in critically ill patients. Since hyperglycemia is one of the most frequent metabolic impairments in these patients, insulin therapy is a necessity in most of the cases. In order to prevent hyperglycemia and its associated complications, nutritional support must be adjusted to the patient's requirements, avoiding hyponutrition. Whenever possible, nutrients supply should be done through the digestive route. Parenteral nutrition is more often accompanied by hyperglycemia and requires an increase in insulin dosage to control it. There are two types of enteral diets designed to help controlling hyperglycemic conditions: carbohydrates rich diets, and fat rich diets. In general terms, carbohydrates rich diets may be recommended in type 1 diabetic patients who are in a stable condition, and fat rich diets in type 2 diabetes and in stress hyperglycemia. In both cases, the use of low glycemic index carbohydrates is recommended. Protein intake should be adjusted to the patients' metabolic stress level. In diabetic patients with acute disease, an increase in antioxidants intake is recommended.

Patients with chronic respiratory failure frequently have nutritional impairments that prompt nutritional support. This is more important during acute exacerbation episodes since, in this situation, the risk for hyponutrition is increased and recovery may be compromised. In order to prevent ventilatory overload, nutritional support should be normocaloric or mildly hypocaloric (using indirect calorimetry, if possible) with a fat content ratio of around 50% of the caloric intake. Micronutrients supply should be considered due to the effects of some of them (P, Mg, Se) on respiratory function. The aim of nutritional support in patients with acute respiratory failure (ARDS) is the requirements provision meanwhile the inflammatory response is modulated and repair mechanisms against acute damage are stimulated. Qualitative modification of lipids supply (by decreasing the intake of linoleic acid and increasing other eicosanoids-precursor lipids with a lesser inflammatory capability) and the use of antioxidants seem to be the most important mechanisms in this regard.

Pancreatitis is an illness that can bring about nutritional changes in connection with the underlying cause, the metabolic reaction to stress or the limitations that this pathology may represent for the processes of digesting and absorbing nutrients or for tolerating the diet. Although nutritional support is well accepted as a therapeutic measure in patients with severe acute pancreatitis, there is some dispute over the route of administration. In patients with mild pancreatitis, the use of parenteral nutrition may be accompanied by an increase in complications, particularly due to catheter-related sepsis, but in severe cases, early parenteral nutrition has been associated with a lower incidence of complications and a drop in mortality. Although parenteral nutrition is the preferred conventional method for the nutritional support of patients with pancreatitis, enteral nutrition offers the advantages of being more physiological, safer and less costly, at the same time as it seems to have a favourable influence on the progress of the pancreatitis. For this reason, the current recommendations suggest the use of enteral nutrition via the jejunum in those cases where the severity of the pancreatitis indicates nutritional support. Further research is, however, necessary in this field to clarify the group of patients in which the benefits of nutritional support would be most evident, the most appropriate type of diet, and the role of enteral nutrition on the evolution, both locally and systemically, of the changes brought about by the inflammation of the pancreas.

Objective: To compare tolerance of two sources of isocaloric intake (fructose-glucose-xylitol mixture [FGX] versus glucose) in parenteral nutrition for patients with systemic inflammatory response syndrome (SIRS)., Design: Open, prospective, cohort and randomized study., Setting: Intensive Care Unit., Subjects and Methods: Two groups of patients admitted in ICU: acute pneumonia with sepsis, and necro-hemorrhagic pancreatitis. Criteria of exclusion were: diabetes, previous hypertriglyceridemia, renal failure with serum creatinine > 3 mg/dL on admission in ICU, or hyperbilirrubinemia > 2.5 mg/dL. Parenteral nutrition (TPN), consisting of 1.4 g AA + Lipids 1.3 g + carbohydrates 4 g/kg/d, (either glucose or FGX at random) was administered. Basal levels and days 1st, 4th and 10th plasma glucose, triglycerides, cholesterol, uric acid were determined, and blood venous gases as well. Capillary glycemia was measured every 6 hours and insulin given if glucose levels rose above 180 mg/dL., Statistics: Fisher's exact test; Student t-test; Mann-Whitney test. Data as mean and SD., Results and Conclusions: During 48 months, 119 patients admitted in the ICU (72 with pneumonia and 47 with pancreatitis) were included. In pneumonia, tolerance was similar with both intakes; glycemia was kept at the same level in both, but the amount of insulin given was significantly more in those patients fed on glucose (p < 0.05). Nevertheless, resting blood glucose and triglyceride levels were higher in pancreatitic patients, and more insulin was required. Those on FGX had lower triglyceride plasma levels (p < 0.05) and less insulin was given throughout the study. Glycemia was kept lower though no statistical significance was reached (p < 0.1). No hyperuricemia nor lactic acidosis was found.

The application of artificial nutritional treatment in critical patients, nowadays is a completely accepted fact. To a large degree this is due to the advances made in the understanding of the metabolic response shown by patients against a severe and persistent aggression. One of the entities which presents the highest mortality in critical patients, is the Acute Respiratory Distress Syndrome (ARDS), which one understands as the pulmonary response to different types of aggression. To understand the metabolic implications in the face of the development of this syndrome, would permit a better understanding of the need to treat these patients and to establish the nutritional standards which are most adequate to each different metabolic alteration. It would not only be important to understand the most effective method for calculating the caloric needs of these patients, but we shall also have to deepen our understanding of possible harmful effects of the different substrates, which undoubtedly could condition morbidity. This is why in this review we focus on the intimate pulmonary mechanism, both in healthy conditions as in those of disease, in order to extrapolate conclusions which are potentially applicable to patients suffering from an acute pulmonary lesion, as those suffering from ARDS: A main role shall be played the assessment of the administration of macronutrients in the form carbohydrates, lipids, and amino acid particles, due to the implications which each of these may have on the lesioned lung and its ventilatory capacity.

Large burn patients make up a subgroup of critical patients in whom the nutro-metabolic support reaches its maximum importance, due to the fact thermal aggression induces a hypermetabolic response which is prolonged until the wounds heal. In fact, there are few deubt with regard to the importance of nutritional support tin the management of these patients for reducing the complications and facilitating the closing of the wounds and the recovery of the patients. Thermal trauma induces the release of counter-regulatory hormones and of other mediators which favor proteineic catabolism, mainly muscular, lipolysis, and gluconeogenesis; as well, there is an alteration of thermoregulation, raising the equilibrium point. The estimate of the energetic requirements may be done by means of predictive equations, although these tend to over-estimate it; indirect calorimetry is the most exact method and this permits monitorization of the evolution, which is very variable in time, it gives the metabolic response to the thermal aggression, at the same time as permitting the analysis of the use of the administrated substrates. Its use has meant a dramatic decrease in the supply of calories administered to burn patients, with the present recommendation being 35-40 kcal/kg/d. The supply of non-proteineic calories has also been modified: It is recommended that at least 60-70% of the calories administered, be in the form of carbohydrates, without surpassing 1600 kcal/kg/d. The optimal relation of non-proteineic kcal:nitrogen, is 150:1. The administration route of the artificial nutrition support should be individualized in each patient, with the enteral route being the route of choice, as this is the most physiologic, the cheapest, and the safest; its use prevents the appearance of certain complications (Curling ulcer, cholecystitis, bacterial translocation); however, if his does not cover nutritional requirements of the burn patient, parenteral nutrition should be associated to this.

Magnesium is an important element in health and in disease, it is the organism's second most abundant intracellular cation, after potassium, and it is the main divalent intracellular cation. Its metabolic importance is well known, as it has been identified as a cofactor in more than 300 enzymatic reactions which affect the energetic metabolism, and the synthesis of proteins and nucleic acids, Hypomagnesemia is a frequent finding in hospitalized patients, even more so when the patients are critical (+/-65%). Although low serum levels of magnesium imply the presence of intracellular depletion, normal serum magnesium levels may be present in situations of intracellular magnesium depletion, with important clinical repercussions. Keeping in mind that only 1% of the body's magnesium is in the extracellular fluid, the serum magnesium levels may not adequately reflect the situation, which is why techniques have been proposed which determine the intracellular concentración. The identification of the patients who may potentially present a magnesium depletion, requires a clear knowledge of the risk factors associated with magnesium deficiency: poorly controlled diabetes mellitus, excessive alcohol intake, severe diarrhea, important steatorrhea, and the use of drugs which favor their renal excretion. The present review gives an up date of the most frequent causes of magnesium deficits, giving a series of practical recommendations to prevent this situation, and to undertake a correct replacement therapy. Finally, and although hypermagnesemia appears in a reduced number of circumstances, the presence of kidney failure of diverse etiology, as well as the broadening of the indications of magnesium salts, have increased its incidence, which is why special emphasis is made in this section.

In the last 25 years, the mortality of renal failure, far from decreasing, has shown a slight tendency towards increasing, despite continuously more sophisticated and expensive therapeutic measures. As an explanation, the greater frequency of intrahospital renal failures, as past of the systemic inflammatory response syndrome which covers dysfunction of various organs and systems, is brought into this. This relative treatment inefficiency leads to the need of investigating new lines of treatment. After reviewing the conservative treatment of acute renal failure, the main alternatives which exist at present, are reviewed, some of which are in the experimental phase. As prognostically poor renal failure appears in relation to the inflammatory response syndrome, the possibility of eliminating mediators there of by means of continuous hemofiltration systems, is being considered. Despite some positive effects, the majority of authors have not managed to achieve a significant reduction of acute renal failure. The theoretical possibility of improving renal function by administration of certain amino acids (Arginine and Glycine), is not confirmed in practice, possibly due to the incidence of oxidative stress. This stress may be a determining factor in the evolution of renal failure, as it induces many risk factors in these patients. However, carefully, the bases for the anti-oxidant therapy are being established. Finally, the treatment with hormones and growth factors, with the aim of stimulating the rapid regeneration of the renal tubule, represents a very attractive therapeutic alternative, though still in the experimental phase.

The complications derived from the puncture and catheterization of the veins of the neck, cause symptoms and signs on physical examination which facilitate their diagnosis. The phrenic paralysis which we present, is characterized by few accompanying symptoms, with the elevation of the hemidiaphragm being a radiological finding. The suspicion is confirmed by fluoroscopy. We reviewed the mechanisms, the cases described in the literature, and the possible risk factors.

We studied the behavior of the cholesterol of 118 septic patients on entering Intensive Care and on receiving parenteral nutritional support, to establish its utility as malnutrition and/or monitoring marker. On admission, there was more intensive hypocholesterolemia (104 +/- 39 mg/dl) in those who had developed multi-organ failure (87 +/- 34 mg/dl, p < 0.001). There was no correlation between cholesterol and gravity (APACHE II). Basal cholesterol values were correlated with transferrin (r = 0.58), prealbumin (r = 0.43), retinol-linked protein (r = 0.32) and albumin (r = 0.32) and albumin (r = 0.54). During twelve days' parenteral nutrition, cholesterol and visceral protein levels recovered, and the good correlation was maintained between cholesterol and transferrin while that between cholesterol and prealbumin increased and that between cholesterol and retinol-linked virtually disappeared. There ceased to be a relation between albumin and cholesterol as from day six. In cases where the septic situation was maintained, with clinical deterioration, cholesterol levels did not rise. This, along with the close correlation with transferrin, led us to think that cholesterol is influenced by inflammation mediators, acting as a marker for this more as nutritional parameter. However, in practice, it provides the same information as short-life visceral proteins, and its determination is more accessible.(ABSTRACT TRUNCATED AT 250 WORDS)