Background: Granulocyte-Colony Stimulating Factor (G-CSF) is a key cytokine for activation of neutrophile granulocytes in bacterial infection. Recombinant G-CSF administered i.v. to neutropenic patients with myelosupression is removed from the circulation by first order kinetics with a half-life of 259 min (109-353) and in healthy subjects with a half-life of 231 min (212-269).

Study Type/Setting: Prospective cohort study in a tertiary neonatal and pediatric intensive care unit.

Patients: 30 patients with sepsis and elevated G-CSF levels(>750 pg/ml, norm 10.5 pg/ml), 13 of these were already hospitalized when acquiring sepsis thus allowing to assess kinetics before intention to treat.

Measurments: Serial measurements of routine parameters and G-CSF before, at intention to treat, 2-4, 8-12, 24 and 48 hours thereafter. ELISA with a detection range of 39-5000 pg/ml.

Results: At onset of clinical symptoms, elevated G-CSF levels were detected in 10 of 13 patients with G-CSF positive hospital acquired sepsis. G-CSF levels rose with great interpatient variability: median time for doubling of G-CSF was 168 min (58-424). G-CSF levels peaked between 2 to 6 hours after initiation of antimicrobial therapy. If treatment was effective, levels above 1500 pg/ml initially declined following first order kinetics. Half-life showed intepatient variability. Median was 336 min (85-605). Moderately elevated levels (750-1500 pg/ml) declined with a longer half -life of 573 min (220-814), p<0.05, Mann-Whitney U Test. Ineffective control of infection resulted in further increase of G-CSF levels or a half-life above 16h.

Conclusions: In G-CSF positive sepsis, measurements of this cytokine monitor efficiency of therapy.