肌肉减少在重症监护病房普遍并且可能与高热量相关

　　肌肉减少在重症监护病房（ICU）普遍，既往有研究表明补充高热量不利于ICU患者的结局。为了探讨ICU肌肉减少人群高热量暴露与不良结局之间的相关性，美国拉什大学、伊利诺伊大学回顾分析了95例（女性占52%，年龄平均60.2±15.3岁，体重指数28.7±9.4）需营养支持的急性呼吸窘迫综合征（ARDS）重症患者。

　　该研究测量了24小时热量供给量并通过CT第三腰椎平面估算患者骨骼肌横截面积，计算出热量/估算去脂体重比（kcal/ELBM）。

　　结果发现，肌肉减少患者占77%（73例），主要为老年（P=0.01）和男性（P=0.001）。经过排除疾病严重程度影响后，平均每增加1个单位的kcal/ELBM，患者机械通气时间增加0.32天（P＜0.001），ICU住院天数增加0.37天（P＜0.001），总住院时间增加0.63天（P＜0.001），并且高kcal/ELBM与高感染率有相关趋势（比值比：1.09，P=0.08）。

　　因此，该ARDS患者人群的肌肉减少发生率高于预计。单位去脂体重供热较高，与感染并发症较多、机械通气持续时间延长、住院时间增加有相关性，这可能由于未根据肌肉减少患者入院时体重精准估计代谢需求引起非意向性过度喂养造成。需要更多研究直接测量肌肉减少患者的能量消耗，以准确确定热量需求、避免非意向性过度喂养。

JPEN J Parenter Enteral Nutr. 2017;41(2):272.

Low muscle mass is prevalent in the ICU and may be associated with toxic calorie exposure.

Sarah Peterson, Carol Braunschweig.

Food and Nutrition, Rush University Medical Center, Chicago, Illinois, USA; Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA.

PURPOSE: Increased calorie exposure has been associated with worse outcome in the intensive care unit (ICU). We recently conducted a PRCT to assess the impact of intensive medical nutrition therapy from diagnosis of mild, moderate, or severe acute respiratory distress syndrome (ARDS) through hospital discharge vs standard care on clinical outcomes (INTACT). The trial was stopped at 40% of goal recruitment (78/200) due to significantly greater mortality in the intervention compared with control group (40 vs 16%, P = .02). Mypoenia, or decreased muscle mass, is prevalent in the ICU. In the absence of indirect calorimetry, we suspect utilization of predictive equations among myopenic patients may lead to a toxic calorie exposure and result in worse outcomes. The objective of the current retrospective study was to discern the prevalence of myopenia and the influence of increased energy delivery among myopenic patients in a population of intubated ARDS patients comparable to INTACT.

METHODS: Patients who met eligibility INTACT criteria during the recruitment period but did not participate in the trial were identified. A subset of patients with a diagnostic abdominal computed tomography (CT) scan within 7 days (before or after) of determining eligibility for INTACT was included in the current analysis. Baseline demographics included age, sex, body mass index (BMI), and severity of illness parameters. Calorie delivery (including delivery of enteral nutrition, parenteral nutrition, propofol, and dextrose-containing intravenous fluids) was collected from 24 hours of ARDS diagnosis through diet advancement or ICU discharge. Slice-O-Matic software was used to measure skeletal muscle cross-sectional area at the third lumbar region (L3). Skeletal muscle mass index (skeletal muscle cross-sectional area at L3 [cm2]/height [m2]) was calculated; myopenia was defined as a skeletal muscle index <38.5 cm2/m2 for females and <52.4 cm2/m2 for males. Estimated lean body mass (ELBM [kg], 0.3 × cm2 skeletal muscle cross-sectional area at L3 + 6.06) was calculated. Linear (mechanical ventilation and length of stay) and logistic (infection and mortality) regression models were used to describe the relationship between calorie exposure per ELBM and ICU outcomes.

RESULTS: The final sample included 95 patients (52% female) with a mean age of 60.2 ± 15.3 years and BMI of 28.7 ± 9.4. A total of 77% (73/95) of patients were classified as mypoenic by CT scans. Myopenic patients were older (P = .01) and more likely to be male (P = .001). Duration of mechanical ventilation, ICU, and hospital length of stay all increased significantly with higher kcal/ELBM delivery. After controlling for severity of illness, every 1-kcal/ELBM increase in calorie delivery increased the duration of mechanical ventilation by 0.32 days (β = 0.32, P < .0001), increased ICU length of stay by 0.37 days (β = 0.37, P < .0001), and increased hospital length of stay by 0.63 days (β = 0.63, P < .0001). There was a trend between kcal/ELBM and higher likelihood of infection (odds ratio [OR], 1.09; 95% CI, 0.99-1.11; P = .08). There was no relationship between mortality and kcal/ELBM delivery.

CONCLUSIONS: Overall prevalence of myopenia was higher than expected in our population of ARDS patients. Higher kcal/ELBM delivery was associated with more infectious complications, prolonged duration of mechanical ventilation, and increased length of stay. We suspect this effect represents the impact of unintentional overfeeding due to the inherent inaccuracy of using admission weights as dosing weights to estimate metabolic demand in patients with low muscle mass. More research is needed to directly measuring energy expenditure in myopenic patients to accurately determine calorie requirements and avoid unintentional overfeeding.

DOI: 10.1177/0148607116686023