Respiratory care clinics of North America最新文献

Enteral nutrition is increasingly becoming the standard of care for critically ill patients with the goal of providing nutritional support that prevents nutritional deficiencies and reduces morbidity. Furthermore, the development of nutritional strategies that dampen inflammation is an encouraging advance in the management of patients who have acute respiratory distress syndrome. This article discusses evidence from randomized, controlled studies that the use of a specialized nutritional formula containing eicosapentaenoic acid plus gamma-linolenic acid and elevated antioxidants offer physiologic and anti-inflammatory benefits over standard formulas.

Obesity and its many metabolic and physiologic comorbidities are becoming more common. Thus, a strategy to approach the nutritional needs of obese critically ill patients is warranted. The adverse effect of obesity on the respiratory system is well established. The obesity may be an inciting event or merely an additional burden in the obese critically ill patient. A strategy of hypocaloric nutrition support avoids the many detrimental effects of overfeeding and has been considered for all critically ill patients. In the obese patient, the strategy addresses the additional problem of the excessive fat store and has the additional benefit of fat reduction while sparing lean body mass. In the patient with normal renal and hepatic function, hypocaloric nutrition support simplifies care and may improve outcome.

Indirect calorimetry provides an important adjunctive monitor for the provision of nutrition support in the critically ill patient. Accuracy in determining caloric requirements may serve to optimize benefit from nutrition therapy and improve patient outcome. A number of strategies in nutrition management in the intensive care setting (eg, dosing of enteral nutrition, monitoring cumulative caloric balance, and deliberate but "permissive" underfeeding) necessitate the determination of a fairly specific goal for caloric provision. Inaccuracy leading to inappropriate under- or overfeeding may generate additional morbidity and adverse clinical consequences for patients already at high risk from hypermetabolic stress response to injury.

Malnutrition in patients with COPD is associated with an impaired pulmonary status, reduced diaphragmatic mass, lower exercise capacity, and higher mortality rate when compared with adequately nourished individuals with COPD. Deterioration in patients with COPD may be the result of malnutrition. In addition, malnutrition could be a sign of other factors directly altered by the disease.

IC is the standard for determining energy expenditure in critically ill patients. The measured REE is an objective, patient-specific caloric reference that serves as the most accurate method of determining energy expenditure. Protocols addressing IC methodology are necessary to ensure technical accuracy and clinically useful results. The measured REE should be the caloric target without the addition of stress or activity factors for nutrition support regimens in the ICU. The RQ should be used primarily as an indicator of test validity. Optimal nutrition intervention requires continuous evaluation of all pertinent clinical data and careful monitoring of each patient's response to therapy.

Although the nutrition support literature is limited and therefore does not provide robust evidence to promote grade A or strong recommendations, there is a "signal" from all of these studies taken a a whole that critically ill patients may benefit from nutritional manipulation. The acutely ventilated patient that is likely to still be intubated by day three is a classic example of the critically ill patient who has the potential to achieve positive outcomes with nutritional support. Initiating nutrition support early improves the chances of benefit. However, nutrition cannot be provided in a vacuum. It is only one part of a multitude of treatments and therapies that must be optimally applied by a multidisciplinary team of professionals dedicated to the care of ICU patients. The exact makeup of the enteral (or parenteral) formula that is most likely to improve survival is unclear. More research is needed. Further study may demonstrate the possibility for nutritional manipulation to be one of the most important treatments physicians can offer to critically ill ventilated patients. Nutrition may have as much survival benefit as activated protein C, a drug costing over $7000 per course of therapy. No longer can it be said that nutrition makes no difference.

This article discusses issues related to nutrition support for the critically ill (CCI), especially those who are dependent on ventilators for long periods. A large and growing population of patients survives acute critical illness only to become CCI with profound debilitation, weeks to months of hospitalization, and often permanent dependence on mechanical ventilation and other life-sustaining modalities. Despite resource-intensive treatment, outcomes for CCI remain poor. Topics addressed in this article include neuroendocrine profiles in CCI patients, allostatic overload, causes of prolonged mechanical ventilation, and the metabolism of chronic ventilator dependence. The article also describes issues related to assessing the nutrition, determining nutrition requirements, and deciding the route of nutrient delivery for CCI patients.

It is improbable that aspiration and aspiration-pneumonia can be entirely prevented, but application of one or more of the strategies described in this article probably can reduce these potentially life threatening conditions. Fortunately, many of these strategies are relatively easy and inexpensive to incorporate into routine care.

It is clear that mechanical ventilation strategies influence the course of lung disease, and the choice of a ventilation strategy that avoids volutrauma and atelectrauma is firmly based on experimental literature and clinical experience. The application of a lung-protective strategy with reduced tidal volumes, effective lung recruitment, adequate PEEP to minimize alveolar collapse during expiration, and permissive hypercapnia has been shown to be advantageous in adult patients who have ARDS, although it has not been systematically studied in children. A significant body of literature confirms the beneficial effects of hypercapnic acidemia in the setting of acute lung injury. As a corollary, experimental evidence indicates that buffering hypercapnic acidosis abrogates its protective effects. The use of permissive hypercapnia as part of a lung-protective strategy in children should be accepted and perhaps even desired, provided it does not result in significant hemodynamic instability. This acceptance should be tempered with the recognition that a low-stretch, reduced-tidal volume strategy without hypercapnia has also been shown to improve outcomes in adults who have ARDS and that HFOV can generally provide lung-protective ventilation without necessarily inducing hypercapnia. Thus, a synthesis of the available clinical and research data strongly supports a graded approach to managing patients who have acute lung injury requiring intubation. The highest priority should be a mechanical ventilation strategy that limits the tidal volume, with the allowance of hypercapnia to a degree that does not compromise hemodynamic status.

The ventilator goals of the ICU clinician faced with caring for a critically ill child who has ALI/ARDS remain relatively simple: provide adequate ventilation and oxygenation without overdistending alveoli or furthering lung injury. How one obtains these goals is much less simple. The current use of CV calls for the use of relatively low V(T)s and limiting peak inspiratory pressure and plateau pressure while accepting a certain degree of respiratory acidosis. The ICU team can also often achieve these same goals with HFOV. How, then, does one use evidenced-based medicine to pick the best mode of mechanical ventilation for a particular patient? The answer is controversial, to say the least. Does one start with a gentle, open-lung mode of CV then switch to HFOV if the child deteriorates? Or does one use HFOV from the very early stages of ALI? Animal data appear to point to advantages of HFOV when used early in the course of ALI. Most of these studies report a beneficial effect of HFOV when applied on expanded lungs in the early stages of the disease process. These beneficial effects encompass improved gas exchange, oxygenation, lung tissue morphology and pulmonary mechanics. The studies by Arnold and colleagues in the pediatric population also help to answer our questions. In their work, the early initiation of HFOV was associated with improved gas exchange and a trend toward a lower mortality. In adults, Derdak and colleagues demonstrated the superiority of HFOV in terms of gas exchange and oxygenation; however, no statistical significant difference was found for mortality. So, where is the clinician left after a review of these data? It would appear that (1) low-V(T) CV remains a cornerstone of therapy for the pediatric patient who has ALI/ARDS; (2) HFOV is a safe and well-tolerated mode of mechanical ventilation; (3) early use of HFOV (as opposed to the rescue use of this mode) may be of benefit based on animal and human data; and (4) like so many areas of pediatric critical care, clinicians must await new data and trials that will help them continue to improve the care they provide.