ObjectiveTo test the efficacy of a recombinant endotoxin neutralizing protein as compared with saline in rats with Escherichia coli sepsis.DesignProspective, controlled animal trial.SettingHospital animal research laboratory.SubjectsMale Wistar rats challenged with intraperitoneal E. coli, O18ac K1, and treated 1 hr later with ceftriaxone and gentamicin.InterventionsRecombinant endotoxin neutralizing protein, 50 mg/kg, was administered to rats 1, 2, or 3 hrs after E. coli challenge; saline was administered to control animals.Measurements and Main ResultsQuantitative bacteremia, 1 hr after challenge and before antibiotic administration, was not significantly different between treatment groups (range geometric mean 451 to 621 colony-forming units [cfu]/mL). The endotoxin concentration, measured immediately before recombinant endotoxin neutralizing protein administration, was significantly higher in animals sampled and treated at 2 hrs (geometric mean 260 EU/mL; 95% confidence interval 140 to 480 EU/mL), or 3 hrs (geometric mean 697 EU/mL; 95% confidence interval 307 to 1585 EU/mL) after E. coli challenge, compared with animals sampled and treated at 1 hr (geometric mean 17 EU/mL; 95% confidence interval 7 to 69 EU/mL). Survival rate was significantly greater in rats treated with recombinant endotoxin neutralizing protein at 1 hr (23/27; p < .001) or 2 hrs (8/30; p < .01) after E. coli challenge than in controls (1/32).ConclusionAdministration of recombinant endotoxin neutralizing protein delayed up to 2 hrs after challenge with E. coli improves survival in antibiotic-treated rats with Gram-negative sepsis.(Crit Care Med 1996; 24:1514-1517)