In the past 40 years there has been substantial progress in the ability to provide nutrition support to hospitalized patients, especially those that are critically ill. Small bore and percutaneous feeding tubes allow safe enteral
nutrition (EN) in circumstances and disease states previously considered impossible or inadvisable. Patients with a dysfunctional gastrointestinal tract can receive their full nutrition needs via parenteral nutrition (PN). However, while providing adequate nutrition reduces muscle breakdown, nutrition alone cannot completely preserve lean muscle mass in hospitalized adult patients.
In the early phase of critical illness, catabolism is unavoidable. Research has demonstrated that the negative nitrogen balance associated with the early stage of critical illness is not completely reversed even when calories and protein are provided far in excess of requirements. Furthermore, the lack of exercise and general immobilization that occurs in hospitalized patients results in breakdown of skeletal muscle regardless of nutrition intake. The loss of skeletal muscle during hospitalizations exacerbates muscle weakness, which can
hamper weaning from mechanical ventilation, delay recovery, and increase the need for and duration of rehabilitation services. A study of ARDS survivors revealed that discharge body weights were 18% less than preadmission weight, and there was a prolonged functional disability in many patients that persisted, even when pulmonary function returned to normal. Intensive Care Unit acquired weakness has been reported in 50% of patients ventilated > 1 week and was still present in 25% of ICU patients 7 days later.