ObjectiveIncreased release of intracellular calcium has been implicated in cell death and organ failure in endotoxemia and sepsis. We sought to test this hypothesis in a rat model of antibiotic-treated intraperitoneal sepsis with the use of dantrolene sodium, a specific inhibitor of intracellular calcium release.DesignA prospective, randomized controlled trial.SettingAn experimental animal laboratory in a university hospital.SubjectsTwo hundred fourteen male Sprague-Dawley rats.InterventionsRats were rendered septic by intraperitoneal implantation of sterile feces mixed with live Escherichia coli and allocated to control, vehicle, or dantrolene treatment. A separate group of rats had arterial catheters implanted to allow blood sampling for determination of circulating tumor necrosis factor (TNF)-alpha and lactate concentrations. Additional rats were randomized to receive vehicle or dantrolene after intravenous injection of endotoxin.Measurements and Main ResultsOver the 7-day study period, survival was significantly worse among rats that received dantrolene at a dose of 10 mg/kg, irrespective of whether treatment was started before or after induction of peritonitis. Mean whole blood lactate for each group peaked at 6 hrs after induction of infection. There were no significant differences in lactate concentration among the groups at any of the time points examined. Similarly, there were no differences among any of the groups for circulating concentrations of TNF-alpha. In rats challenged with endotoxin, dantrolene affected neither survival nor circulating concentrations of TNF-alpha.ConclusionsWe conclude that dantrolene decreases survival in bacterial sepsis and has no effect on survival in endotoxemia in rats. The importance of excessive intracellular calcium release in sepsis remains to be elucidated. (Crit Care Med 1996; 24:1537-1542)