Background/Purpose Serum C-reactive protein (CRP) levels reflect the severity of the metabolic response to injury in critically ill children. During this per iod, caloric overfeeding can increase complications and delay recovery. The auth ors hypothesized that by avoiding excessive caloric delivery, the effect of inju ry severity would be the major factor determining clinical outcome. Methods Twen ty-eight surgical infants who had indirect calorimetry measurements while in th e Neonatal Intensive Care Unit between August 2000 and January 2002 were studied . Serum CRP concentrations, mean energy expenditure (MEE), respiratory quotient (RQ), length of hospital stay (LOS), and caloric intake (I) at the time of indir ect calorimetry were recorded. Data were analyzed using the Pearson product-mom ent correlation. Results Peak serum CRP was significantly correlated to LOS in a ll patients (r = 0.79, P < .0001). When net caloric balance (I-MEE) did not e xceed 5 kcal/kg/d (n = 9), peak serum CRP was correlated positively with RQ (r = 0.66, P = .05). When I-MEE exceeded 5 kcal/kg/d (n = 19), the positive corre lation of serum CRP with RQ was diminished (r = 0.23, P = . 33). Conclusions CR P-measured injury severity is a major determinant of clinical outcome in surgic al infants. In addition, overfeeding causes additional RQ elevation. Background / Purpose Serum C-reactive protein (CRP) levels reflect the severity of the metabolic response to injury in critically ill children. During this per iod, caloric overfeeding can increase complications and delay recovery. The auth ors hypothesized that by avoiding excessive caloric delivery , the effect of inju ry severity would be the major factor determining clinical outcome. Methods Twen ty-eight surgical infants who had indirect calorimetry measurements while in e Neonatal Intensive Care Unit were August 2000 and January 2002 were studied. Serum CRP concentrations, mean Energy expenditure (MEE), respiratory quotient (RQ), length of hospital stay (LOS), and caloric intake (I) at the time of indir ect calorimetry were recorded. Data were analyzed using the Pearson product-mom ent correlation. Results Peak Serum CRP was significantly correlated with LOS in a ll patients (r = 0.79, P <.0001). When net caloric balance (I-MEE) did not e xceed 5 kcal / kg / d When I-MEE exceeded 5 kcal / kg / d (n = 19), the positive correlativity of serum CRP with RQ was diminished (r = 0.23, P = P = .33). Conclusions CR P-measure injury severity is a major determinant of clinical outcome in surgic al infants. In addition, overfeeding causes additional RQ elevation.