Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Ambulatory Anesthesia
INTRODUCTION: The blood gas partition coefficient of S would predict more rapid emergence than other inhalation agents.  A large multicenter study demonstrated a time to response to command of 12.8 +/- 0.7 min and orientation of 17.2 +/- 0.8 min after 1.52 +/- 0.1 MAC hours of anesthesia.  A second study demonstrated a response to command of 7.5 min after 2.5 +/- 0.1 MAC hours of S.  All of these reports were on patients anesthestized for surgery with concomitant agents such as fentanyl, non-depolarizing neuromuscular blocking agents and N2 O. The addition of these agents might cause a longer awakening and orientation time. We report the recovery time and orientation parameters utilizing specific measures of recovery in normal volunteers exposed solely to S Anesthesia for 8 hours.
METHODS: After IRB approval and informed consent, 11 healthy male volunteers between the ages of 18 to 30 and weighing >or=to 80 kg participated in this open label study. Volunteers were familiarized with the Treiger Dot (TD) and digit symbol substitution tests (DSST) prior to administration of anesthesia and baseline measures were obtained. Anesthesia was induced with propofol 2-3 mg/kg and tracheal intubation facilitated with vecuronium 0.1 mg/kg. 3% end-tidal S (2.4% MAC) was achieved using an inflow of 8 L/m for the first 5 min. The flow was then reduced to 2 L/m for 8 hours. After 8 hrs, anesthesia was terminated abruptly and the circuit transformed into a nonrebreathing system. Every 1 min after the termination of anesthesia the volunteers were instructed to open their eyes. Additionally, volunteers were quizzed concerning orientation to person, time and place. TD and DSST were administered every 30 min post anesthesia for up to 120 min. Nausea and vomiting were also recorded and measured utilizing a 10cm VAS. Data were analyzed using descriptive statistics and are reported as Mean +/- SD.
RESULTS: The mean times to verbal response and orientation were 25 +/- 9 and 31 +/- 12 min, respectively. 4 of 11 volunteers were not able to perform a TD test at 90 min and 2 of 11 were unable to perform a DST at 90 min. Of the 7 subjects that could perform the TD test, 4 had not reached baseline at 90 min. 4 of 11 volunteers were nauseated and/or vomited by 90 min after anesthetic exposure.
DISCUSSION: There is a discrepancy in what the term recovery implies. Anesthetists may claim that this is when consciousness and psychologic abilities return; while patients consider recovery to be when they can resume their lifestyle. Some have suggested that recovery is correlated with duration of hospital stay. With rapidly eliminated anesthetics patients may leave the hospital sooner. As previously demonstrated S has been associated with more rapid recovery from anesthesia as compared to isoflurane. One would argue that a time to response to command of 12 min and orientation of 17 min after significant S Anesthesia is relatively short. This study however demonstrates that the time to orientation after S anesthesia may take much longer then previously reported with significant nausea, vomiting, and impairment occurring. S, therefore, may not be an ideal anesthetic for long procedures.
1. Anesth Analg 1987; 66:654-6
2. J Clin Anesth 1996;8:557-63
3. Anesth Analg 1992;74:241-5