EFFECTS OF ANESTHESIA BASED ON LARGE VERSUS SMALL DOSES OF FENTANYL ON NATURAL-KILLER-CELL CYTOTOXICITY IN THE PERIOPERATIVE PERIOD

Surgical stress and general anesthesia suppress immune functions, incl uding natural killer cell cytotoxicity (NKCC). This suppression could be attributable, at least in part, to opiates. We have previously show n that large-dose fentanyl administration suppressed NKCC in rats. The present study sought to compare the effects of two anesthetic protoco ls, based on large- (LDFA) versus small (SDFA)-dose fentanyl anesthesi a on NKCC in the perioperative period. Forty patients were included in this study; half were assigned to each protocol of anesthesia. In eac h anesthetic group, half the patients were undergoing surgery for mali gnant diseases, and half for benign conditions. Blood samples were col lected during the perioperative period. NKCC was assessed using the ch romium release assay. Initially, both types of anesthesia similarly su ppressed NKCC, with a peak effect 24 h after surgery. The two types of anesthesia, however, differed in the rate of recovery of NKCC suppres sion. By the second postoperative day, NKCC returned to control values in the SDFA patients, whereas NKCC was still significantly suppressed after LDFA. These results indicate that LDFA causes prolonged suppres sion of NK cell function. Whether this suppression might have a long-t erm impact on the overall outcome, especially in cancer patients, rema ins to be determined.