Protein catabolism and oxygen consumption are increased in septic adults in proportion to degree of illness. Inflammatory cytokines are thought to mediate proteolysis to maintain synthesis of acute phase proteins (e.g. C-reactive protein [CRP]) during sepsis. Septic neonates have immature immunologic responses characterized by elevated IL-6, but not tumor necrosis factor (TNF) levels. To study the impact of sepsis on cytokines and protein metabolism in neonates, we studied 25 newborns (36±3 wks EGA; 2910±840g) divided into three groups: Group 1 (septic, positive blood culture [BC]), Group 2 (sick, negative BC), Group 3 (healthy, rule out sepsis). Infants had oxygen consumption (VO2 [mL/kg/min]), 6 hour nitrogen balance (N Bal[g/kg/d]), urinary 3-methyl Histidine/Creatinine (3MH/Cr), serum TNF & IL-6 (pg/mL), CRP (mg/dL), and Score for Neonatal Acute Physiology (SNAP) measured at 12-36 hours after onset of illness. Data are mean±SD.Table
In the septic infants, the degree of illness (SNAP) correlated with VO2(r=0.98; p<0.001), but not with N Bal or 3MH/Cr. The septic infants' IL-6 levels correlated with CRP concentrations, but their TNF and IL-6 levels did not correlate with either N Bal or 3MH/CR. Conclusions: In septic neonates, energy but not protein needs are dependent on the degree of illness. The cytokine mediated acute phase response seen in adults is present in neonates without the characteristic muscle proteolysis of adult sepsis. Thus, there appears to be a dissociation of the nitrogen wasting from the acute phase protein producing effects of cytokines in babies.
