Sarcopenia and a physiologically low respiratory quotient in patients with cirrhosis: a prospective controlled study

Abstract

Patients with cirrhosis have increased gluconeogenesis and fatty acid oxidation that may contribute to a low respiratory quotient (RQ), and this may be linked to sarcopenia and metabolic decompensation when these patients are hospitalized. Therefore, we conducted a prospective study to measure RQ and its impact on skeletal muscle mass, survival, and related complications in hospitalized cirrhotic patients. Fasting RQ and resting energy expenditure (REE) were determined by indirect calorimetry in cirrhotic patients (n = 25), and age, sex, and weight-matched healthy controls (n = 25). Abdominal muscle area was quantified by computed tomography scanning. In cirrhotic patients we also examined the impact of RQ on mortality, repeat hospitalizations, and liver transplantation. Mean RQ in patients with cirrhosis (0.63 ± 0.05) was significantly lower (P < 0.0001) than healthy matched controls (0.84 ± 0.06). Psoas muscle area in cirrhosis (24.0 ± 6.6 cm(2)) was significantly (P < 0.001) lower than in controls (35.9 ± 9.5 cm(2)). RQ correlated with the reduction in psoas muscle area (r(2) = 0.41; P = 0.01). However, in patients with cirrhosis a reduced RQ did not predict short-term survival or risk of developing complications. When REE was normalized to psoas area, energy expenditure was significantly higher (P < 0.001) in patients with cirrhosis (66.7 ± 17.8 kcal/cm(2)) compared with controls (47.7 ± 7.9 kcal/cm(2)). We conclude that hospitalized patients with cirrhosis have RQs well below the traditional lowest physiological value of 0.69, and this metabolic state is accompanied by reduced skeletal muscle area. Although low RQ does not predict short-term mortality in these patients, it may reflect a decompensated metabolic state that requires careful nutritional management with appropriate consideration for preservation of skeletal muscle mass.

Fig. 1.

Respiratory quotient in hospitalized patients with cirrhosis (n = 25) was significantly lower than that in matched healthy control subjects (n = 25). ***P < 0.01.

Fig. 2.

Scatterplot showing that respiratory quotient is highly directly correlated with psoas muscle area (used as a measure of skeletal muscle mass). r² = 0.71; P < 0.001.

Fig. 3.

Scatterplot showing that resting energy expenditure was significantly correlated with psoas muscle area in cirrhotic and control subjects. r² = 0.19; P < 0.05.

Fig. 4.

Resting energy expenditure normalized to muscle area was significantly higher in patients with cirrhosis than controls. ***P < 0.01.

Fig. 5.

Scatterplot showing that respiratory quotient is directly correlated with visceral fat mass (on CT). r² = 0.39; P = 0.01.

Fig. 6.

Scatterplot showing that respiratory quotient is directly correlated with subcutaneous fat mass (on CT). r² = 0.46; P = 0.01.