Preliminary studies of perioperative stellate ganglion block (SGB) in cardiac surgery suggest that this technique may reduce or prevent episodes of POAF requiring treatment. The investigator's ultimate goal is to determine whether SGB reduces the incidence of POAF in specific cardiac surgery populations at MMC. First, however, the investigator proposes to test the hypothesis that SGB, performed perioperatively by cardiac anesthesiologists in a population of patients undergoing cardiac surgery, is both safe and clinically feasible.