We have reported that an intravenous anesthetic, ketamine, has a potent suppressive effect on lipopolysaccharide (LPS)-induced TNF-alpha production in vitro [Takenaka et al., Anesthesiology 80:402-408, 1994]. The purpose of the present study was to investigate the overall effects of ketamine on hemodynamics, serum TNF-alpha level, arterial blood gases (ABGs), blood glucose level, liver function, and lethality in carrageenan (CAR)-sensitized endotoxemic models. All animals were pretreated intraperitoneally with CAR (150 mg/kg) 16 hr before LPS stimulation. The control rats were injected LPS with 0.5 mg/kg intravenously (i.v.). The ketamine-treated rats were injected with 100 mg/kg of ketamine intramuscularly 30 min before LPS (0.5 mg/kg) i.v. injection, followed by an i.v. infusion at 0, 5, or 10 mg/kg/hr. Serum TNF-alpha, ABGs, blood glucose, and hematological studies were determined at 0, 2, and 6 hr after the LPS challenge. Serum hepatocellular enzyme levels were measured at 6 hr after the injection. In CAR-sensitized rats, serum TNF-alpha activity remarkably increased in accordance with the mild decrease of mean arterial pressure (MAP) at 2 hr after LPS stimulation. In addition, severe metabolic acidosis, hypoglycemia as well as severe hepatic injury were induced at 6 hr after the LPS challenge. By contrast, ketamine treatment significantly attenuated the decrease in MAP and LPS-induced TNF-alpha activity. Ketamine also significantly improved arterial oxygen tension (PaO2), metabolic acidosis and hypoglycemia, and attenuated endotoxin-induced hepatic injury in a dose-dependent fashion. In addition, ketamine treatment significantly improved LPS-induced lethality in CAR-sensitized mice.(ABSTRACT TRUNCATED AT 250 WORDS)