ObjectivesTo investigate a possible relationship between plasma erythropoietin and interleukin-6 (IL-6) in critically ill children with sepsis or septic shock. To examine the modulatory effects of plasma from these patients on erythropoietin production in vitro, employing a cell culture system that uses the erythropoietin-producing Hep 3B cell line.DesignA prospective, controlled clinical and laboratory study.SettingA pediatric intensive care unit and research laboratory facility at a children's hospital.PatientsChildren admitted to the pediatric intensive care unit with the diagnosis of sepsis or septic shock (n = 16), and control patients without infection or anemia (n = 16) were admitted to the study.InterventionsNone.Measurements and Main ResultsBlood samples were obtained from 16 children with sepsis or septic shock, and 16 age-matched controls. Plasma erythropoietin and IL-6 concentrations were measured using an enzyme-linked immunoassay. Plasma erythropoietin concentrations were significantly higher in children with sepsis or septic shock (120 +/- 26 mIU/mL) than in controls (10 +/- 2 mIU/mL) (p < .001). Plasma IL-6 concentrations were greater in children diagnosed with sepsis or septic shock (12,405 +/- 6662 pg/mL) than in control patients (7 +/- 1 pg/mL) (p < .001), and higher in septic shock patients (27,469 +/- 13,647 pg/mL) than sepsis patients (688 +/- 258 pg/mL) (p = .03). Hep 3B cells were incubated under hypoxic conditions in media containing plasma from control patients, or patients diagnosed with sepsis or septic shock. Media concentrations of erythropoietin were measured using an enzyme-linked immunoassay. Hep 3B cells incubated with plasma from patients diagnosed with sepsis or septic shock produced more erythropoietin (216 +/- 23 mIU/mL) than Hep 3B cells incubated under the same conditions in media containing plasma from control patients (152 +/- 11 mIU/mL) (p = .04). Hypoxic Hep 3B cell erythropoietin production in media incubated with plasma from patients diagnosed with sepsis or septic shock correlated significantly (although weakly) with plasma IL-6 values from these same patients (p = .03, r2= .28).ConclusionsPlasma erythropoietin and IL-6 values are increased in critically ill children with sepsis or septic shock in comparison with controls. The data indicate that one or more plasma factors are responsible for stimulation of hypoxia-induced erythropoietin production in the Hep 3B cell line and suggest a possible role for IL-6 in the regulation of erythropoietin production in critically ill children with sepsis or septic shock.(Crit Care Med 1996; 24:1455-1459)