Ebook Core topics in mechanical ventilation: Part 2
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Ebook Core topics in mechanical ventilation: Part 2
chapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2out by a variety of medical, surgical and traumatic events makes the optimum nutritional requirements of this group of patients difficult to determine. Nonetheless, nutritional support is an important adjunct to the management of patients in the intensive care unit, mechanically ventilated patients Ebook Core topics in mechanical ventilation: Part 2being especially vulnerable to complications of under- or over-feeding. This chapter will consider the nutritional requirements, route and timing of nEbook Core topics in mechanical ventilation: Part 2
utritional support, and complications associated with feeding mechanically ventilated, critically ill patients.Nutritional status and outcomeThe metabchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2haracterized by insulin resistance, increased metabolic rate and marked protein catabolism. The loss of lean body mass impairs function, delays recovery and rehabilitation and, at its most extreme, may delay weaning from artificial ventilation. The degree of catabolism and its impact on outcome depe Ebook Core topics in mechanical ventilation: Part 2nds on the duration and severity of the inflammatory response.Anthropometric techniques routinely used to measure changes in body mass and compositionEbook Core topics in mechanical ventilation: Part 2
areinaccurate in the presence of excess fluid retention and therefore the assessment and monitoring of the nutritional status in critically ill patiechapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2ive care unit (ICLI), acute changes in body weight largely reflect changes in fluid balance. Assessment of nutritional status should in such cases be based on clinical and bioc hem icaI para meter$.Malnourished critically ill patients are consistently found to have poorer clinical outcomes than (hei Ebook Core topics in mechanical ventilation: Part 2r well-nourished counterparts,I’I and up to 80% ofICLI patients are malnourished.'1' Complications occur more frequently in these patients resulting iEbook Core topics in mechanical ventilation: Part 2
n prolonged 1CLI and hospital length of stay and a greater risk of death.'11Nutritional requirementsDespite the negative impact of malnutrition on outchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2equirements of critically ill patients remain unknown.Energy requirementsResting energy expenditure of the ICll patient is variable, influenced by the impact of the illness and its treatment, but requirements rarely exceedCore Topics in Mechanical Ventilation, ed. lain Mackenzie. Published by Cambri Ebook Core topics in mechanical ventilation: Part 2dge University Press. © Cambridge University Press 2008.184CHAPTER 9: NUTRITION IN THE MECHANIC/2000 kcal per day.l2l Indirect calorimetry is considerEbook Core topics in mechanical ventilation: Part 2
ed the gold standard method for determining energy' expenditure despite having several limitations in the ICll setting.*'I Routine use of indirect calchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2 lack this methodology and must estimate nutritional goals based on predictive equations, of which there are more than 200. There are essentially two types of predictive equation. The first involves calculating basal metabolic rate, using equations previously derived from healthy subjects (e.g. Harr Ebook Core topics in mechanical ventilation: Part 2is Benedict), then adding a stress or correction factor to account for the illness or injury.!4! The addition of stress factors is very subjective andEbook Core topics in mechanical ventilation: Part 2
may introduce substantial error into estimates of energy expenditure. Typically, stress factors between 1.2 and 1.6 have been used for mechanically vchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2nergy' expenditure or parameters associated with resting energy' expenditure plus clinical variables that relate to the degree of hyper-metabolism. The Ireton-Jones equations are perhaps best known in the ICU and use categorical stress modifiers which take into account diagnosis, obesity' and ventil Ebook Core topics in mechanical ventilation: Part 2ator status.*5* Some studies have shown that these equations correlate well with measured energy expenditure.*6* An alternative and simpler method forEbook Core topics in mechanical ventilation: Part 2
estimating energy expenditure is to use a 'calorie per kilogram’ approach. The American College of Chest Physicians recommend using 25 kcal.kg-1 to echapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2difficult to assess true bodyweight and thus increase the inaccuracy'of these equations. Ideally, a pre-morbid weight should be used when calculating energy' needs.Comparison of these different approaches with indirect calorimetry' show that no single predictionequation is suitable in all patients a Ebook Core topics in mechanical ventilation: Part 2nd may' be dependent on age, adiposity and type of illness.*4,6* There is no evidence that achieving a positive energybalance in critically ill patienEbook Core topics in mechanical ventilation: Part 2
ts can prevent the loss of lean body mass or consistently improve clinical outcome; therefore, the level of accuracy' provided by prediction equationschapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2 be required if the complications associated with prolonged under- and over-feeding are to be prevented.Over-feedingOver-feeding critically' ill patients can negatively affect respiratory function. Any excessive intake, particularly excessive carbohydrate load, results in a significant increase in c Ebook Core topics in mechanical ventilation: Part 2arbon dioxide production.*7’ In order to expel excess carbon dioxide and to maintain normal blood gas concentrations, the body' increases alveolar venEbook Core topics in mechanical ventilation: Part 2
tilation (i.e. minute ventilation). This compensatory mechanism is limited in patients whose ventilatory' response is impaired and is further restrictchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2result in prolonged requirement for mechanical ventilation or even precipitate respiratory failure in the marginally' compensated patient.Enteral formulations have been marketed with reduced carbohydrate and increased lipid contents, specifically' for patients with respiratory' compromise, but their Ebook Core topics in mechanical ventilation: Part 2 use is rarely indicated provided that over-feeding is avoided.Hypocaloric feedingWeight-based predictive equations, used to estimate energy expendituEbook Core topics in mechanical ventilation: Part 2
re, increase the risk of overfeeding in overweight and obese patients.*6* With increasing evidence that a positive energy balance will not improve outchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2 sufficient energy 10 facilitate nitrogen retention without compromising organ function or outcome.Nitrogen retention increases with higher energy intakes but the effect is blunted as energy delivery increases above 60% of actual requirements. It has therefore been argued that providing energy intak Ebook Core topics in mechanical ventilation: Part 2es greater than 60% does not improve the efficacy of nutritional support.!8! Hypocaloric regimens aim to provide 50% to 60% of target energy intakes bEbook Core topics in mechanical ventilation: Part 2
ut 100% of protein requirements. The theory is that in overweight or obese patients the energy deficit caused by restricting energy intake will be comchapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2 associated with reduced ICU length of stay, decreased duration of antibiotic therapy and a trend towards a decrease in the number of days of mechanical ventilation.!9! In the absence of indirect calorimetry, it has been suggested that the ideal body weight or an adjusted body weight be used in pred Ebook Core topics in mechanical ventilation: Part 2ictive equations to avoid over-feeding. There is concern that using the ideal body weight of morbidly obese patients in equations will result in signiEbook Core topics in mechanical ventilation: Part 2
ficant under-feeding (<50% of energy requirements) and therefore an adjusted body weight may be more appropriate.To date, no reports in the literaturechapter 9Nutrition in the mechanically ventilated patientCLARE REIDIntroductionRespiratory failure and the need for mechanical ventilation brought abo Ebook Core topics in mechanical ventilation: Part 2but would be contraindicated in malnourished patients with little or no body fat reserve.Protein requirementsThe primary goal of nutritional support in critical illness is to presene lean body mass and function. However, seemingly adequate nutritional support, in the presence of a severe illness or Ebook Core topics in mechanical ventilation: Part 2injury, only attenuates the breakdown of lean tissue.!10'Total body protein losses of 12.5% (1.5 kg) have been reported in severely septic patients duEbook Core topics in mechanical ventilation: Part 2
ring the first 10 days of the illness.!11! Approximately 70% of protein losses came from muscle, which has serious implications for patient recovery aGọi ngay
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