Local Anesthetics Time-Dependently Inhibit Staphylococcus aureus Phagocytosis, Oxidative Burst and CD11b Expression by Human Neutrophils

Background and Objectives Local anesthetics have been shown to modulate neutrophil functions in a time-dependent manner, which might help to prevent inflammatory injury to the organism. However, if host defense mechanisms are affected similarly, the ability to eliminate bacteria might be reduced. We hypothesized that local anesthetics have time-dependent effects on phagocytosis of S. aureus , oxidative burst, and CD11b expression by human neutrophils. To test this hypothesis, we reanalyzed data from a previous study. Methods Blood samples from 11 healthy volunteers were incubated with lidocaine (1,846 μmol/L), bupivacaine (770 μmol/L) or ropivacaine (801 μmol/L) for 30 minutes. Thereafter, bacteria were added, either fluorescently labeled for determination of phagocytosis, or unstained for determination of oxidative burst and CD11b expression. After an additional incubation for 0, 10, 30, or 60 minutes, phagocytosis was stopped and neutrophils were stained with monoclonal antibodies for flow cytometric analysis. Data were analyzed by analysis of variance for repeated measurements. Results Lidocaine and bupivacaine inhibited neutrophil functions in a time-dependent manner ( P P Conclusions Our results indicate that in a whole blood model, time-dependent effects of local anesthetics affect key neutrophil functions necessary for bacterial elimination. However, these effects only occur at concentrations that are unlikely to be routinely attained in the clinical setting, and concern about interfering with the host defense is likely unwarranted.