Onset Time, Recovery Duration, and Drug Cost with Four Different Methods of Inducing General Anesthesia Edith Fleischmann, MD*‡, Ozan Akc¸a, MD*‡, Thomas Wallner, MD*‡, Cem F. Arkilic¸, MD*‡, Andrea Kurz, MD*‡, Randy S. Hickle, MD‡§, Michael Zimpfer, MD*‡, and Daniel I. Sessler, MD*‡i Department of Anesthesia and General Intensive Care (*A) and (†B), and ‡Outcomes Research™, University of Vienna; §Apotheus Laboratories, Ltd., Lubbock, Texas; iDepartment of Anesthesia, University of California-San Francisco, San Francisco, California; and iLudwig Boltzmann Institute for Clinical Anesthesia and Intensive Care, Vienna, Austria We compared two conventional induction techniques times were comparable with each method. Recovery (thiopental and propofol), an inhaled induction with duration was shortest with sevoflurane, intermediate sevoflurane using a circle system, and a rebreathing with propofol, and longest with thiopental. Induction method. Fentanyl 1 mg/kg was given to women under- drug costs were lowest with Sevo/Bag and thiopental, going 10- to 20-min procedures. Anesthesia was in- intermediate with Sevo/Circle, and highest with duced (n 5 20 each) with one of the following: propofol. However, sevoflurane (by either method) 1) sevoflurane and N2O from a rebreathing bag (Sevo/ caused considerable nausea and vomiting that required Bag). A 5-L bag was prefilled with a mixture of sevoflu- treatment. Consequently, total drug cost was least with rane 7% and N2O 60% in oxygen. The bag was con- thiopental, intermediate with Sevo/Bag and propofol, nected between the normal circle system, separated by and greatest with Sevo/Circle. Thus, no single tech- a spring-loaded valve; 2)sevoflurane 8% and N2O 60% nique was clearly superior. Implications: Anesthetic from a circle system on a conventional anesthesia ma- induction techniques influence awakening time, recov- chine with a total fresh gas flow of 6 L/min (Sevo/Cir- ery duration, and drug costs. We tested two IV methods cle); 3) propofol 3 mg/kg as an IV bolus; 4) thiopental and two inhaled techniques. However, none of the four sodium 5 mg/kg as an IV bolus. Postoperative nausea tested methods was clearly superior to the others. and vomiting was treated with ondansetron. Induction (Anesth Analg 1999;88:930–5) arious induction anesthetics and methods have rapid onset, be inexpensive, and provide rapid post- been advocated, but none has proven over- anesthetic recovery with little nausea and vomiting. V whelmingly superior. The drugs and technique Sevoflurane and desflurane share a short duration of chosen influence the ease, speed, and cost of induc- action. Desflurane, however, is pungent, and rapid con- tion. Furthermore, drugs given during induction in- centration increases provoke autonomic nervous system fluence the rate and characteristics of postanesthetic hyperactivity and hemodynamic instability (1). In con- recovery. An additional factor is that the easiest and trast, sevoflurane is suitable for inhaled inductions and is fastest techniques tend to be expensive or require used extensively for this purpose in pediatric patients drugs that may prolong postanesthetic recovery. The (2). A limitation of sevoflurane is that the drug is rela- ideal method would be easy to implement, have a tively expensive. This expense can be reduced somewhat during maintenance anesthesia by reducing the fresh gas flow to 2 L/min, which is currently the lowest recom- Supported by National Institutes of Health Grant GM58273, the mended rate in the United States and several other coun- Joseph Drown Foundation (Los Angeles, CA), the Fonds zur Fo¨rde- tries. During induction, however, flows near 10 L/min rung der Wissenschaftlichen Forschung (Vienna, Austria), Apotheus Laboratories, Ltd., and Abbott GesmbH (Vienna, Austria). are required to rapidly fill the circle system and to com- RSH is President and CEO of Apotheus Laboratories, a company pensate for absorption of the anesthetic into the patient’s that manufactures a mask designed to restrict waste-anesthetic gas lungs and circulation. The result is that an inhaled in- exposure among postanesthesia care personnel. The other authors do not consult for, accept honoraria from, or own stock or stock duction with sevoflurane can contribute substantially to options in any anesthesia-related company. the total cost of anesthetic drugs, especially during short Accepted for publication December 22, 1998. procedures. Address correspondence to Dr. Ozan Akc¸a, Department of Anes- The cost and time required for an inhaled induction thesia and General Intensive Care (A), University of Vienna, Wa¨hringer-Gu¨ rtel 18–20, A-1090 Vienna, Austria. Address e-mail to with sevoflurane can potentially be reduced by avoid- [email protected]. ing the circle system with its large (approximately 7 L) ©1999 by the International Anesthesia Research Society 930 Anesth Analg 1999;88:930–5 0003-2999/99/$5.00 ANESTH ANALG FLEISCHMANN ET AL. 931 1999;88:930–5 A COMPARISON OF INDUCTION METHODS MAC) (4). The bag was connected between the normal circle system and the endotracheal tube, separated by a spring-loaded valve. Depressing the valve isolated the routine breathing system so that the patient breathed and rebreathed from the 5-L bag (Fig. 1). 2. Sevoflurane and nitrous oxide from a circle sys- tem on a conventional anesthesia machine (Sevo/Circle). The sevoflurane concentration on the vaporizer was set to 8% and was adminis- tered with nitrous oxide 60% in a total fresh gas flow of 8 L/min. Figure 1. The sevoflurane rebreathing bag and spring-loaded valve and their interface with the conventional circle system. 3. Propofol 3 mg/kg (Propofol). Propofol was given as an IV bolus. 4. Thiopental sodium 5 mg/kg (Thiopental). Thio- intrinsic volume. As an alternative, we considered a pental was given as an IV bolus. 5-L bag prefilled with sevoflurane 7% in nitrous oxide 60%. This bag was connected to a valve inserted be- Lung ventilation was initially spontaneous in each tween the circle system and the face mask. Depressing case, then assisted at a rate of approximately 10 breaths/ the spring-loaded valve disconnected the circle system min when apnea prevailed. The specified induction so that the patient was directly connected to the bag. method was continued until eyelid reflexes were lost, Anesthesia then resulted from breathing and rebreath- and an additional minute. A lubricated laryngeal mask ing from this bag (Fig. 1). We tested two conventional was then inserted using standard technique (the cuff was induction techniques (thiopental and propofol), an in- slightly inflated to facilitate insertion). Additional propo- haled induction with sevoflurane using a circle sys- fol or thiopental was given if required clinically in the tem, and the rebreathing method described above. patients assigned to IV induction. Fresh gas flow was Our purpose was to evaluate the effects of induction discontinued during laryngeal mask insertion. technique on induction time, recovery characteristics, Anesthesia was subsequently maintained with and drug cost. sevoflurane (1.2%–1.4% end-tidal concentration) in ni- trous oxide 60%, using a 6-L/min fresh gas flow via a circle circuit. Patients breathed spontaneously, their Methods breathing was assisted as necessary to maintain a Petco2 With approval of the Ethics Committee of the Univer- near 35 mm Hg. Minimal peak airway pressures were sity of Vienna and written, informed consent, we stud- used, consistent with maintaining physiological Petco2 ied 80 women undergoing short gynecological proce- concentrations with a respiratory rate of 10 breaths/min. dures (e.g., hysteroscopy, curettage, cervical conic Additional fentanyl (50 mg IV) was given when it was excision) with an anticipated duration of 10–20 min. clinically indicated. All patients were aged 20–60 yr and were ASA phys- Sevoflurane and nitrous oxide concentrations were ical status I or II. not reduced toward the end of surgery; instead, both Patients who were seriously obese, claimed allergy were abruptly discontinued when the operation was to any of the study drugs, were pregnant or nursing, complete. After spontaneous breathing resumed and air- or used opioids or sedatives were excluded. We also way reflexes were reestablished, the laryngeal mask was excluded patients who refused either IV or inhaled removed. Patients were observed until they responded induction and those at risk of regurgitation. to command and were then transferred to the postanes- None of the patients was premedicated. Each was thesia care unit. Postoperatively, patients were given IV preoxygenated for 1 min with 100% oxygen, and then boluses of the opioid piritramid as necessary for treat- given 1 mg/kg IV fentanyl. One of the following ran- ment of pain. Postoperative nausea and vomiting was 5 domly assigned anesthetic induction techniques (n treated by the IV administration of ondansetron (4– 20 each) was then started at elapsed time zero: 8 mg). Antiemetic treatment was determined by the 1. Sevoflurane and nitrous oxide from a rebreathing patient’s reported sensation of nausea or when emesis or bag (Sevo/Bag). A 5-L bag was prefilled with a retching was observed. The treating anesthesiologists, mixture of nitrous oxide 60% (0.6 minimum al- who were blinded to group assignment and intraopera- veolar anesthetic concentration [MAC]) (3) and tive management, based their treatments on direct pa- oxygen 30% that was passed through a vaporizer tient observation and their 5-min queries (see below). set to 8% sevoflurane. This produced an actual Standard morphometric and demographic charac- sevoflurane concentration in the bag of 7% (3.5 teristics of the participating patients were recorded, 932 FLEISCHMANN ET AL. ANESTH ANALG A COMPARISON OF INDUCTION METHODS 1999;88:930–5 Table 1. Fitness for Discharge Scoring System 01 2 Activity No movement No purposeful movement Raises one arm on command Respiration Apnea Dyspnea or limited breathing Breathes deeply and coughs freely , . Spo2 on room air (%) 90 90–95 95 Consciousness Unresponsive Arouses to verbal stimuli Fully awake Blood pressure (% of baseline) .