Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 393

Cachexia syndromes associate anorexia, fatigue/asthenia, hypercatabolism/antianabolism, and weight loss in the long term. Cachexia is the cytokine‐associated wasting of protein and energy stores due to the effects of disease. Systemic inflammation mediated through cell injury or activation of the immune system triggers an inflammatory response. People with cachexia lose roughly equal amounts of fat and fat‐free mass while maintaining extracellular water and intracellular potassium. The loss of fat‐free mass is mainly from the skeletal muscle.

Cytokines are related to a number of disease conditions, including organ failure (heart, lung, kidney), neurodegenerative diseases, cancer, rheumatoid arthritis, and AIDS⁵⁰ (Figure 14.1). For each pathology, a different cytokines profile is shown.^51,52 Cardiac cachexia due to heart failure–associated inflammation is particularly frequent in NYHA stage III.⁵¹ Cancer cachexia is defined as an weight loss >5% in the last six months not due to simple starvation, BMI <20 kg/m² and any degree of weight loss >2%, or appendicular muscle mass consistent with sarcopenia.⁵³ During chemotherapy, very low intake of protein and weight loss induce impairment in quality of life, particularly fatigue.⁵⁴ Decreased food intake and low calf circumference (a hallmark of sarcopenia) are independent risk factors for one‐year mortality.⁵⁵

Cytokines have a direct negative effect on muscle mass, and increased concentrations of inflammatory markers have been associated with a reduced lean mass.^56‐58 This direct effect also has been associated with a decline in muscle strength in older adults.

Increasingly, a consensus on the differential effects of starvation and cachexia is developing.⁵⁹ Starvation can frequently be distinguished from cachexia (Table 14.2). However, in later stages, this distinction is more difficult. The hallmark of starvation is a rapid response to refeeding.

Table 14.2 Distinguishing starvation from cachexia.

Source: Thomas,⁵⁰ © 2002 Elsevier.

	Starvation	Cachexia
Appetite	Suppressed in late phase	Suppressed in early phase
Body mass index	Not predictive of mortality	Predictive of mortality
Serum albumin	Low in late phase	Low in early phase
Transthyretin	Low in late phase	Low in early phase
Transferrin	Low	Low
Retinol‐binding protein	Low	Low
Cholesterol	May remain normal	Low
Total lymphocyte count	Low, responds to refeeding	Low, unresponsive to refeeding
C‐reactive protein	Few data	Elevated
Inflammatory disease	Usually not present	Present
Response to refeeding	Reversible	Resistant