ANESTHETIC OF CHOICE FOR OUTPATIENT IMMERSION LITHOTRIPSY

Abstract

S319 INTRODUCTION: Epidural anesthesia has been considered the anesthetic technique of choice for immersion lithotripsy. However, more recent studies have demonstrated that both intravenous sedation-analgesia [1] and general anesthesia [2] can offer advantages over epidural anesthesia with respect to an improved recovery profile. This study was designed to compare intravenous sedation-analgesic and volatile anesthetic-based techniques in outpatients undergoing immersion lithotripsy procedures. METHODS: 49 consenting adult outpatients undergoing extracorporeal shock wave lithotripsy (ESWL) were randomly assigned to one of two anesthetic treatment groups according to an IRB-approved protocol. All patients received midazolam 2 mg iv, and fentanyl, 0.5 [micro sign]g/kg iv, for premedication. In Group 1 received propofol, 50 [micro sign]g[center dot]kg-1[center dot]min-1, which was subsequently titrated to maintain an observer's assessment of alertness/sedation (OAA/S) score >3, with 1=awake/alert to 5=asleep. If the patient complained of pain during the procedure, fentanyl 12.5-25 [micro sign]g iv was administered. In Group 2, anesthesia was induced with propofol 1.5 mg[center dot]kg-1 iv, and following loss of consciousness, a cuffed oropharyngeal airway (COPA) device was inserted and connected to the airway circuit. Maintenance of anesthesia consisted of desflurane 2-4% and nitrous oxide (N2 O) 60% in oxygen. Tachypnea (respiratory rate >20 bpm) was treated with fentanyl 12.5-25 [micro sign]g iv. At the end of the procedure, the inhaled anesthetics were discontinued and droperidol 0.625 mg iv, was administered as a prophylactic antiemetic. Recovery times were recorded from discontinuation of the anesthetic drugs until the patient was awake and oriented. In addition, times to achieving an OAA/S score of 1 and to discharged home were noted. Postoperative side effects were assessed in the recovery area (Phase II step-down unit) and at 24 hr after the procedure. Data were analyzed using Students' t-test and Chi-square test, with a p-value <0.05 considered statistically significant (*). Values are means +/- SD. RESULTS: The two anesthetic treatment groups were similar demographically (Table 1). Although the general anesthetic group required a longer time interval to awaken, the time required for the patients to return to an OAA/S score of 1 and to be discharged home were similar in both anesthetic treatment groups. Finally, there were no significant differences in the incidences of perioperative side effects.Table 1DISCUSSION: General anesthesia with propofol-desflurane-N2 O was an acceptable alternative to an intravenous sedative-analgesic technique involving propofol and fentanyl for outpatient ESWL procedures. The ability to "bypass" the recovery room after general anesthesia was facilitated by using a COPA airway device and resulted in recovery times that were comparable to a sedation-analgesia technique for outpatient immersion lithotripsy.