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Unauthorized reproduction of this article is prohibited Copyright © 2019 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies. Unauthorized reproduction of this article is prohibited 776 www.pccmjournal.org August 2019 • Volume 20 • Number 8 Malnutrition at admission to the PICU is frequent and linked to suboptimal outcomes (1, 2). An early diagnosis of the nutritional status is important to establish an individualized plan for nutritional support (3). However, the potential deterioration of the nutritional clinical condition after admission has seldom been reported. Undernutrition in children has been defined as an imbalance between nutrient requirement and intake, resulting in cumulative deficits of energy, protein, or micronutrients that may negatively affect growth, development, and other relevant outcomes (4), like length of mechanical ventilation, length of hospital stay (LOS), infections, delayed wound healing, or even mortality. The same document also defines “acute” undernutrition as a condition with fewer than 3 months of duration and recommends that “dynamic” changes in anthropometric variables should be followed during the hospitalization (4). Failure to thrive and faltering growth (FG) are concepts included in these definitions. Current guidelines recommend that all children admitted to a PICU should have their nutritional status assessed. Green Corkins (5) has recently highlighted the importance of a full clinical evaluation—versus simple anthropometry—in the assessment of nutritional status in children. The nutritional evaluation should include anthropometric, clinical, biochemical, and dietary variables. Body composition should also be evaluated (6). As mentioned before, dynamic changes in weight and length velocity over time should also be recorded (4). Little is known about these dynamic acute changes in anthropometry “before” and “after” PICU admission. In a study published in 2018, Valla et al (7) reported dynamic anthropometric changes “before” admission to the PICU. FG was defined as a nonvoluntary weight deceleration greater than 1 z score in the previous 3 months. FG was present in 13.7% of the patients, mostly in children with normal body mass index (BMI), and was associated with extended length of PICU stay (7). In this issue of Pediatric Critical Care Medicine, the same group of investigators reports the results of their study on FG “after” the admission to the PICU (8). FG was defined as a BMI deterioration over PICU stay of greater than 1 z score; a deterioration between 0.5–1 was considered FG risk. A number of 579 patients that spent longer than 5 days in the PICU were studied. A total of 10.2% presented FG and 27.8% were at risk. Because weight for age (WA) is a better variable in children younger than 2 years, it was also noted a decline of WA z score greater than 0.5 sd in 27.8% of patients. FG was more frequent in older and well-nourished children, with higher severity of illness, neurologic failure, or sepsis. Suboptimal outcomes associated with FG were prolonged mechanical ventilation, LOS, and acquired infections (8). FG has been previously described only in hospitalized children with mild diseases (9, 10). It is known that in critically ill patients, anthropometric assessment is difficult to interpret because the measurements may be influenced by the disease itself, by the accompanying inflammation (e.g., fluid retention and swelling), and also by the quality and method of measurements, with large inter and intraobserver variability. BMI has been used to the nutritional assessment in a study conducted in a tertiary level PICU (utilizing a smaller population sample) without showing a good discrimination of nutritional status (11). BMI may be a valid nutrition marker as shown by Valla et al (8) and Bechard et al (12), but it may mask situations of muscle depletion since it does not discriminate among body compartments. Anthropometry continues to be a basic component of the nutritional assessment because it presents standardized reference values by age group, unlike biochemical indicators. However, other tools, like measurements to define body composition in more detail, have the potential to improve the accuracy of nutritional assessment and its interpretation. Some studies have shown that muscle mass reduction is an independent risk factor for mortality and is associated with longer LOS. Bioelectrical impedance analysis (BIA) can be a good adjunct marker to predict outcomes in a wide variety of clinical situations. The monitoring of phase angle utilizing BIA has been very useful to discriminate patients with muscle depletion and worse prognosis during PICU stay; is a noninvasive bedside tool, objective, reliable, inexpensive, and easy to use (6). *See also p. 714.