EFFECTS ON RECOVERY WHEN ISOFLURANE IS USED TO SUPPLEMENT PROPOFOL-NITROUS OXIDE ANESTHESIA

During propofol-nitrous oxide (N2O) anesthesia, volatile anesthetics a re frequently administered to treat signs of inadequate anesthesia and to decrease the possibility of intraoperative awareness. Because the clinical effects of this combination have not been examined rigorously , we used data from the 1989-90 Phase IV clinical trial with propofol to evaluate recovery from propofol-N2O anesthesia with and without sup plementation with isoflurane. In this study involving 15,806 patients at 1722 institutions, propofol was administered for induction and main tenance of anesthesia with N2O for procedures lasting less than 60 min . At the discretion of the anesthesiologist, volatile anesthetics were administered as needed during maintenance of anesthesia (the incidenc e of use of inhaled anesthetics was 14.7% for isoflurane, 2.2% for enf lurane, and 0.2% for halothane). Other intraoperative medications incl uded opioid analgesics, muscle relaxants, and anticholinergic drugs. T he present study concerns the subset of 7796 patients given propofol-N 2O maintenance anesthesia (intermittent bolus or continuous infusion) with or without isoflurane supplementation for procedures lasting less than 60 min. Isoflurane was used more frequently for procedures lasti ng 30-60 min than for those less than 30 min. Nevertheless, the mainte nance dose of propofol was significantly (P < 0.05) less with isoflura ne (178 vs 235 mg). Adjunctive use of isoflurane prolonged the time to awakening and to becoming oriented, but discharge times were similar for the two groups. The incidence of postoperative nausea, vomiting, r ecall, and excitement did not differ between the two groups. We conclu de that the addition of isoflurane to a propofol-N2O anesthetic does n ot alter recovery from anesthesia.