Anesthesiology 2005; 103:495–9 © 2005 American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc. Desﬂurane Enhances Reactivity during the Use of the Laryngeal Mask Airway Shahbaz R. Arain, M.D.,* Hariharan Shankar, M.D.,† Thomas J. Ebert, M.D., Ph.D.‡ Background: Desﬂurane and sevoﬂurane have markedly different pungencies. The tested hypothesis was that patients breathing equivalent concentrations of desﬂurane or sevoﬂu- rane through a laryngeal mask airway (LMA) would have simi- lar responses. Methods: After institutional review board approval and in- formed consent were obtained, 60 patients were enrolled and given intravenous midazolam (14 g/kg) and fentanyl (1 g/kg) 5 min before induction of anesthesia. The LMA was inserted at loss of consciousness after 2 mg/kg propofol. When spontane- ous breathing returned, a randomly assigned volatile anesthetic was started at an inspired concentration of either 1.8% sevoﬂu- rane or 6% desﬂurane at a fresh gas ﬂow of 6 l/min in air: oxygen (50:50). After 5 min, a controlled movement of the LMA took place. Three minutes later, the inspiratory anesthetic con- centration was changed to either 3.6% sevoﬂurane or 12% des- ﬂurane for 3 min. A blinded observer recorded movements and airway events during the start of anesthetic, LMA movement, deepening of the anesthetic, and emergence before LMA re- moval. Results: There were no differences at anesthetic start and LMA movement. Desﬂurane titration to 12% increased heart rate, increased mean arterial blood pressure, and initiated fre- quent coughing (53% vs. 0% sevoﬂurane) and body movements (47% vs. 0% sevoﬂurane). During emergence, there was a two- fold greater incidence of coughing and a ﬁvefold increase in breath holding in the desﬂurane group. Conclusions: When airway responses to sevoﬂurane and desﬂurane were compared in elective surgical patients breath- ing through an LMA, there were signiﬁcantly more adverse responses with desﬂurane at 12% concentrations and during emergence. DESFLURANE and sevoﬂurane represent our newest vol- atile anesthetics in clinical use and are unique in their low blood:gas solubilities. They seem to have different cardiovascular and respiratory effects. 1,2 Recent data have suggested that compared with sevoﬂurane, patients anesthetized with desﬂurane experienced greater re- sponses to tracheal stimulation at 1 mean alveolar con- centration (MAC) level of anesthesia. 3 In addition, des- ﬂurane has been associated with increases in airway resistance at inspired concentrations of 6% when com- pared to equipotent concentrations of sevoﬂurane, an effect that has been attributed to the greater pungency and irritant properties of desﬂurane. 2 These ﬁndings suggest that desﬂurane might be less well tolerated in patients who are not provided muscle relaxants and are breathing 1–2 MAC inspired concentrations via a laryn- geal mask airway (LMA). However, a recent study sug- gested that desﬂurane via an LMA was associated with a similar low incidence of adverse airway responses com- pared with sevoﬂurane when these anesthetics were used with nitrous oxide and 2– 4 g/kg fentanyl. 4 The current study evaluated the airway responses and patient movement when administering desﬂurane and sevoﬂu- rane without nitrous oxide and minimal fentanyl at low and higher inspired concentrations. We tested the hy- pothesis that clinically relevant concentrations of sevoﬂurane and desﬂurane would result in similar airway and movement responses in spontaneously breathing patients. Materials and Methods After institutional review board approval was obtained (Zablocki VA Medical Center, Milwaukee, Wisconsin), patients who had an American Society of Anesthesiolo- gists physical status classiﬁcation of I–III and were sched- uled to undergo elective surgery of less than 2 h in duration provided written, informed consent and were included in the study. Patients were excluded for a history of gastroesophageal reﬂux disease, hiatal hernia, morbid obesity, nonelective surgery, and any procedure requiring muscle relaxants; smokers were not excluded. Demographic data were collected. After measuring base- line vital signs, an intravenous line was established, and patients were provided with 14 g/kg midazolam in the holding area and 1 g/kg fentanyl 5 min before induc- tion of anesthesia. At the time of arrival in the operating room, standard monitors were applied, and ﬂuid deﬁcits from fasting were replaced with 0.9% saline. After preoxygenation with 6 l/min oxygen through a facemask for 2–3 min, intravenous pretreatment with 30 mg lido- caine, 1%, was followed by induction of anesthesia with 2 mg/kg propofol. After loss of eyelash reﬂex, the ap- propriate size LMA, lubricated with plain water-soluble lubricant, was inserted. The cuff was inﬂated with the minimum amount of air required to maintain a seal at a pressure of 20 cm H 2 O and a leak above this value. Fresh gas ﬂow was set at 3 l each of air and oxygen. The patient was randomly assigned to receive either sevoﬂu- rane or desﬂurane. At the start of spontaneous breathing, the volatile anesthetic was started to keep the inspired concentration at 1 MAC equivalent (1.8% sevoﬂurane, 6% desﬂurane). During this time, heart rate (HR), mean arterial blood pressure (MAP), end-tidal carbon dioxide, * Clinical Research Fellow, ‡ Staff Anesthesiologist, VA Medical Center. † Clinical Fellow, Medical College of Wisconsin, Milwaukee, Wisconsin. Received from the Department of Anesthesiology, Zablocki VA Medical Cen- ter, Milwaukee, Wisconsin. Submitted for publication February 24, 2005. Ac- cepted for publication June 6, 2005. Supported by a contract with Abbott Laboratories, Abbott Park, Illinois. Address correspondence to Dr. Ebert: VAMC, Anesthesiology/CC-112A, 5000 West National Avenue, Milwaukee, Wisconsin 53295. Address electronic mail to: tjebert@mcw.edu. Individual article reprints may be purchased through the Journal Web site, www.anesthesiology.org. Anesthesiology, V 103, No 3, Sep 2005 495 Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/103/3/495/428376/0000542-200509000-00011.pdf by guest on 19 December 2021