Cardiopulmonary bypass (CPB) has been proposed as a model for studying the inflammatory cascade associated with the systemic inflammatory response syndrome. Serum interleukin-6 (IL-6) concentration seems to be a good indicator of activation of the inflammatory cascade and predictor of subsequent organ dysfunction and death. Prolonged increases of circulating IL-6 are associated with morbidity and mortality after cardiac operations. In the present study, we compared the effects of adding ketamine 0.25 mg/kg to general anesthesia on serum IL-6 levels during and after elective coronary artery bypass grafting (CABG). Thirty-one patients undergoing elective CABG were randomized to one of two groups and prospectively studied in a double-blind manner. The patients received either ketamine 0.25 mg/kg or a similar volume of isotonic sodium chloride solution in addition to large-dose fentanyl anesthesia. Blood samples for analysis of serum IL-6 levels were drawn before the operation; after CPB; 4, 24, and 48 h after surgery; and daily for 6 days beginning the third day postoperatively. Ketamine suppressed the serum IL-6 response immediately after CPB and 4, 24, and 48 h postoperatively (P < 0.05). During the first 7 days after surgery, the serum IL-6 levels in the ketamine group were significantly lower than those in the control group (P < 0.05). On Day 8 after surgery, IL-6 levels were no different from baseline values in both groups. A single dose of ketamine 0.25 mg/kg administered before CPB suppresses the increase of serum IL-6 during and after CABG.
Implications: In this randomized, double-blind, prospective study of patients during and after coronary artery bypass surgery, we examined whether small-dose ketamine added to general anesthesia before cardiopulmonary bypass suppresses the increase of the serum interleukin-6 (IL-6) concentration. Serum IL-6 levels correlate with the patient's clinical course during and after coronary artery bypass. Ketamine suppresses the increase of serum IL-6 during and after coronary artery bypass surgery.