Effects of Ketamine on Endotoxin and Traumatic Brain Injury Induced Cytokine Production in the Rat

Background: Endotoxemia from lipopolysaccharide (LPS) induces systemic cytokine production, whereas traumatic brain injury (TBI) increases intracerebral cytokine production. In anesthetic doses, ketamine has potent anti-inflammatory properties. However, its anti-inflammatory effects at subanesthetic doses and its effects on TBI-induced inflammation have not been fully investigated. We hypothesized that ketamine would attenuate both LPS- and TBI-induced inflammatory responses. Methods: Male rats received intraperitoneal (i.p.) ketamine (70 mg/kg, 7 mg/kg, or 1 mg/kg) or saline 1 hour before LPS (20 mg/kg i.p.) or saline. Five hours after LPS, rats were killed. Serum was collected for cytokine analysis. In other experiments, male rats were given ketamine (7 mg/kg i.p.) or saline 1 hour before induction of TBI with controlled cortical impact (or sham). One hour and 6 hours after injury, brain was extracted for analysis of cerebral edema and cytokine production. Results: LPS increased the serum concentrations of interleukin (IL)-1 alpha, IL-1 beta, IL-6, IL-10, tumor necrosis factor-alpha, and interferon-gamma. Ketamine dose dependently attenuated these changes. TBI caused cerebral edema and increased concentrations of cerebral IL-1 alpha, IL-1 beta, IL-6, IL-10, and tumor necrosis factor-alpha. However, ketamine had minimal effect on TBI-induced inflammation. Conclusions: Although ketamine did not seem to exert any beneficial effects against TBI in the rat, it did not exacerbate cytokine production or enhance cerebral edema as some studies have suggested.