ED50 of alfentanil for induction of anesthesia in unpremedicated young adults.
This study determined the ED50 and ED90 of alfentanil for unconsciousness and anesthesia. A bolus of alfentanil was given to 28 healthy unpremedicated adults undergoing gynecologic or orthopedic procedures in one of four dosages: 100, 150, 200, or 250 micrograms/kg. Three indicators of induction were assessed 90 s later: eyelid reflex, response to verbal commands to breathe, and response to placement of a nasopharyngeal airway. Succinylcholine, given at 90 s, was followed by tracheal intubation 1 min later. From probit analysis, the ED50 and ED90 for loss of voice response were 92 and 111 micrograms/kg, respectively, and for loss of nasopharyngeal airway response, 111 and 169 micrograms/kg. A high incidence of chest wall rigidity (75%) and movements of the limbs (54%) or eyes (25%) was seen. There were statistically significant increases of the heart rate prior to stimulation and of both the heart rate (21% rise) and systolic blood pressure (10% rise) from control to the peak value following intubation. Differences between alfentanil doses were not significant. Naloxone was required in 36% of patients for end-tidal PCO2 greater than 48 mmHg at emergence from anesthesia; no patient required additional naloxone. Nausea or vomiting occurred in 39% of all subjects. Two patients recalled placement of the nasopharyngeal airway. We conclude that alfentanil is an anesthetic, and its ED50 (analogous to MAC of inhalational agents) is 111 micrograms/kg. The blood pressure and heart rate responses to laryngoscopy and intubation were modest after doses that allowed for extubation as early as 51 min after induction.
D000759:Adjuvants, Anesthesia / Q000008:administration & dosage*; D000293:Adolescent; D000328:Adult; D015760:Alfentanil; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005283:Fentanyl / Q000008:administration & dosage / Q000031:analogs & derivatives*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans
D000759:Adjuvants, Anesthesia; D015760:Alfentanil; D005283:Fentanyl