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Objective To investigate the effect of different doses of ketamine on inflammatory cytokines in rabbits with severe burn at early stage and preliminarily approach its regulatory action on early stage of inflammatory reaction due to stress of trauma.Methods Forty healthy male New Zealand rabbits were randomly divided into four groups in accord with the random number table method: normal control group, scald model group, ketamine analgesia group and ketamine anesthesia group. Before scald, pentobarbital sodium was used for anesthesia, afterwards catheters were inserted into internal jugular vein and internal carotid artery respectively ready for use, and 24 hours later, Ⅲ degree scald at the animal back and buttocks occupying 30% total body surface area (TBSA) was performed as the scald model for all the rabbits except those in normal control group. In ketamine analgesia group, after scald for 0.5 hour, 0.5 mg/kg ketamine intravenous injection was given to the rabbits as the loading dosage and then persistent intravenous pump infusion of 9μg·kg-1·min-1 ketamine was applied for all together 24 hours. In ketamine anesthesia group, after scald for 0.5 hour, 1.5 mg/kg ketamine intravenous injection was given to the rabbits, and then persistent intravenous pump infusion of 45μg·kg-1·min-1 ketamine was applied for 4 hours to maintain systemic anesthesia. In normal control and scald model groups, only intravenous infusion of equal amount of normal saline was given to the rabbits. The amount of intravenous transfusion in each group and the total dosages of ketamine used in ketamine analgesia group and ketamine anesthesia group were recorded. Before scald and 0.5, 6, 12, 24 hours after scald, arterial blood gas analyses were made, and the levels of serum interleukins (IL-1, IL-6) and tumor necrosis factor-α (TNF-α) were determined.Results Although the indexes of blood gas analysis were changed in the four groups, they were all in the normal range, showing that the respiratory function was in the normal range and indirectly reflecting that the circulatory function was also in the normal range, thus the effects on cytokines by factors of respiratory and circulatory functions were ruled out. The levels of IL-1, IL-6 and TNF-α before scald showed no statistically significant differencesamong the four groups (allP > 0.05). From 0.5 hour after scald, the levels of IL-1, IL-6 and TNF-α were markedly higher in model group than those of normal control group [IL-1 (ng/L): 30.27±0.93 vs. 13.79±1.11, IL-6 (ng/L): 47.22±1.49 vs. 46.31±4.12, TNF-α (ng/L): 243.39±20.85 vs. 190.95±14.97, allP < 0.05], and the situation continued until 24 hours after scald; the levels of IL-1, IL-6 and TNF-α from 6 hours after scald were significantly decreased in ketamine analgesia and ketamine anesthesia groups compared with those in the model group, and from 12 hours after scald, the degrees of descent in levels of the above indexes in ketamine analgesia group were more obvious than those in ketamine anesthesia group [IL-1 (ng/L): 19.28±2.51 vs. 40.12±10.31, IL-6 (ng/L): 52.10±4.23 vs. 72.20±10.11, TNF-α (ng/L): 246.03±20.74 vs. 313.71±27.34, allP < 0.05].Conclusion The low-dose ketamine analgesia and ketamine anesthesia have certain degree of inhibitory effect on the expression and release of inflammatory cytokines at the early stage in rabbits with severe burn, the effect of long-term low-dose ketamine analgesia being more significant.