In Response: We appreciate the interesting comments from Dr. Benumof regarding our study evaluating the use of the laryngeal mask airway (LMA) as an alternative to the tracheal tube (TT) during ambulatory surgery [1]. Dr. Benumof suggested that in the TT group, the use of muscle relaxants may have contributed to a lower volatile anesthetic requirements because isoflurane was titrated "to avoid purposeful movements." However, as noted in the Methods section, the concentrations of volatile anesthetic were adjusted to provide adequate anesthesia as indicated not only by the absence of purposeful movements, but also hemodynamic stability. Supplemental doses of fentanyl were administered only if changes in the inspired concentration of the volatile anesthetic failed to achieve adequate hemodynamic stability. Therefore, the use of muscle relaxants would not necessarily alter the requirements for isoflurane. We agree that the "combined" anesthetic and analgesic requirements (i.e., volatile anesthetic and opioid) were significantly higher in the LMA (vs. TT) group. However, this difference was not considered clinically-significant because recovery times from anesthesia and the incidence of postoperative adverse effects (e.g., nausea and vomiting) were similar in both groups. The studies by Wilkins et al. [2] and Cork et al. [3] are difficult to interpret because of their small sample sizes and possible flaws in their study design. Wilkins et al. [2] studied only 18 patients (10 and 8 in each group) and Cork et al. [3] studied a total of 44 patients randomized to 4 groups (9 or 13 in each group). Furthermore, Wilkins et al. [2] did not evaluate the volatile anesthetic and analgesic requirements throughout the operative period. These investigators only reported the end-tidal concentrations of isoflurane at which the two airways devices were tolerated during emergence from anesthesia. Similarly, Cork et al. [3] did not report the intra-operative opioid requirements in their study. Although the isoflurane concentrations in patients receiving TT were higher than those receiving LMA devices, these differences were not found to be statistically significant. Interestingly, there was no effect of the mode of ventilation (spontaneous versus controlled) on the end-tidal isoflurane concentrations in the two groups. Finally, the lack of statistically-significant difference in the anesthetic requirements of outpatients receiving oropharyngeal airway and the LMA may also be due to an inadequate sample size [4]. While it is possible that confounding factors may have obscured differences in the anesthetic requirements with the two airway devices, there is no convincing evidence to support Dr. Benumof's conclusion. Girish P. Joshi, MB BS, MD, FFARCSI Paul F. White, PhD, MD, FANZCA Department of Anesthesiology and Pain Management; University of Texas Southwestern Medical Center at Dallas; Dallas, TX 75235-9068