Relationship between auditory intensity discrimination in noise and olivocochlear efferent system activity in humans

The intravenous (i.v.) steroid anesthetic, eltanolone, compares favorably to propofol with respect to its induction characteristics. This double-blind investigation was designed to compare the induction and recovery profile of eltanolone (versus propofol) when it was used for both induction and maintenance of ambulatory anesthesia. Eighty-three consenting ASA physical status I-III outpatients undergoing minor gynecologic or urologic procedures lasting 10-40 min were randomly assigned to one of three anesthetic treatment groups. All patients received midazolam, 2 mg i.v., and fentanyl, 50 micrograms i.v., before induction of anesthesia. The control group (Group 1) was induced with propofol, 2.4 mg/kg i.v. (18-60 yr or ASA physical status I or II) or 1.6 mg/kg i.v. (61-80 yr and/or ASA physical status III), followed by intermittent bolus doses of 0.6 mg/kg i.v. in combination with N2O 67% for maintenance of anesthesia. In Group 2, anesthesia was induced with eltanolone, 0.75 mg/kg i.v., (18-60 yr and/or ASA physical status I or II) or 0.5 mg/kg i.v. (61-80 yr and/or ASA physical status III), and maintained with intermittent bolus injections of 0.2 mg/kg i.v. and N2O 67%. Group 3 received eltanolone, 1.0 mg/kg i.v. (18-60 yr and/or ASA physical status I or II), or 0.75 mg/kg i.v. (61-80 yr and/or ASA physical status III), followed by intermittent bolus injections of 0.2 mg/kg i.v. and N2O 67%. In addition to recording the induction and recovery times and side effects, psychomotor testing was performed before and at 30-min intervals after anesthesia. Induction times (57 +/- 23, 67 +/- 26, and 61 +/- 22s, respectively) were similar in all three groups. Although eltanolone produced no pain on injection (versus 52% in the propofol group), 10% of the eltanolone-treated patients (versus none in the propofol group) developed transient cutaneous (rash-like) reactions. The total dose of study medication used during the anesthetic period was 9.2 +/- 3.7 mg.kg-1.h-1 in the propofol group compared with 3.3 +/- 1.4 mg.kg-1.h-1 and 3.3 +/- 1.9 mg.kg-1.h-1 in Groups 2 and 3, respectively. Early recovery times were significantly shorter after propofol anesthesia. However, times to ambulation, micturition, and being judged "fit for discharge," as well as recovery of cognitive function, were similar in all three groups. Although ethanolone seems to be a safe and effective i.v. anesthetic, these data suggest that it is unlikely to replace propofol in the ambulatory setting. Implications: Eltanolone is an investigational steroid anesthetic that causes less pain on injection and less cardiovascular depression than propofol (the most widely used intravenous anesthetic in the outpatient setting). Unfortunately, emergence from anesthesia after ambulatory surgery is slower with eltanolone compared with propofol. Therefore, it is unlikely that eltanolone will replace propofol for outpatient anesthesia.