Intravenous lidocaine for ambulatory anesthesia: good to go or not so fast?

Spencer S. Liu, MD† In this issue of the journal, McKay et al. report the results of randomizing patients undergoing ambulatory surgery to an IV infusion of lidocaine or saline. Although rarely used as a component of ambulatory anesthesia, perioperative infusion of IV lidocaine is attractive. Low-dose IV lidocaine is easy to administer, has well-established analgesic, antihyperalgesic, and antiinflammatory effects, and has minimal toxicity in commonly studied doses (typically 1.5–3 mg kg 1 h ). Researchers examining infusion of IV lidocaine for various major abdominal procedures in previous randomized controlled trials reported quite favorable effects that have been summarized in a recent meta-analysis. Use of lidocaine significantly reduced the incidence of nausea and vomiting (32% vs 52%), marginally reduced pain scores ( 5/100 mm visual analog scale), and decreased duration of postoperative ileus ( 8.4 h) and hospital stay ( 0.84 days). These are impressive results from a simple intervention and compare favorably with the effects from the more technically cumbersome and expensive use of epidural analgesia. Thus, it makes sense to investigate whether such positive outcomes from IV lidocaine can be transported to the field of ambulatory anesthesia. Currently, most surgeries in the United States are performed on an ambulatory basis (60% of all procedures in 2007), and an inexpensive, technically simple, and time-limited intervention that provides long-lasting benefit would be valuable. However, the effects of IV lidocaine in this study were much less gratifying than previously reported for major abdominal surgery. Opioid consumption was reduced but without affecting the incidence of opioidrelated side effects, such as nausea and vomiting. Pain scores were temporarily reduced in the postoperative care unit but only for a few hours. Finally, length of stay was not affected. Why would lidocaine not demonstrate greater efficacy? Part of the reason may be attributable to the proposed mechanism for the effects of low-dose IV infusions of lidocaine for perioperative analgesia. It is speculated that sodium channel block by lidocaine plays a minor role, whereas suppression of the inflammatory process may have accounted for the reduction in ileus and hospital stay after major abdominal surgery. Previous studies have observed much greater blood levels of inflammatory mediators after major abdominal surgery versus less extensive procedures. For example, pancreatoduodenectomy resulted in dramatic increases in inflammatory mediators (e.g., tumor necrosis factorand interleukin-6) that are not suppressed by epidural anesthesia, whereas hip replacement surgery did not result in increases in these mediators. Martin et al., who conducted a recent study examining perioperative IV infusion of lidocaine versus saline in patients undergoing total hip replacement, did not report any effects on pain, opioid-sparing, or postoperative rehabilitation with lidocaine. Thus, it may simply be that most ambulatory surgical procedures are too minimally invasive to benefit from IV infusion of lidocaine. Another key consideration is that, by simply transferring the usual outcome measurements (e.g., length of stay) for hospitalized patients to ambulatory anesthesia studies, we are simply looking at the wrong outcomes. From the *Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University, Baltimore, Maryland; and †Department of Anesthesiology, Hospital for Special Surgery, Weill College of Medicine of Cornell University, New York, New York. Accepted for publication August 3, 2009. Supported by the Department of Anesthesiology, Hospital for Special Surgery, New York, NY. Reprints will not be available from the author. Address correspondence to Spencer S. Liu, MD, Department of Anesthesiology, Hospital for Special Surgery, 535 East 70th St., New York, NY 10021. Address e-mail to liusp@hss.edu. Copyright © 2009 International Anesthesia Research Society DOI: 10.1213/ANE.0b013e3181bbc6e1