The Primary Target of Nutritional Support: Body Composition or Muscle Function?

摘要

In a 70-kg man, skeletal muscle accounts for 40-50% of the total body mass. A loss of the muscle mass due to the net breakdown of muscle proteins is a common feature of many acute and long-term illnesses. During the initial flow phase, patients with an acute critical illness (multiple trauma and sepsis) lose 1-2 kg muscle mass per day and up to half the muscle mass in periods of 1-2 weeks [1]. Many chronic diseases that impair the function of the lungs, liver, kidney and heart including cancer and AIDS (affecting multiple systems) are attended by a generally slower, gradual loss of muscle mass. A very slow, but in the end substantial, loss of muscle mass is also observed during aging (sarcopenia) [2]. The reduction in muscle mass in all these conditions is the major component of the reduction in lean body mass. Impairments are also seen in muscle function, with a reduction in strength and endurance capacity being most evident [2, 3j. This again limits the ability of the patients to walk and perform normal activities of daily living. In some of the chronic diseases, the reduction in muscle function forms a serious disability or even handicap that dramatically reduces their quality of life [3]. This limitation in physical performance and continuous subjective feelings of fatigue are experienced as the most distressing phenomenon of many acquired chronic diseases [3, 4], In patients with multiple trauma and sepsis, the loss of muscle mass and functions leads to life-threatening complications (e.g. respiratory failure) and is a major cause of death [5].