Propofol, remifentanil and mivacurium: fast track surgery with poor intubating conditions.

BACKGROUND: Mivacurium is widespread used because it is the non-depolarizing muscle relaxant with the shortest duration time. Therefore, it seems to be ideal for fast track or ambulatory surgery. However, especially in combination with propofol and remifentanil onset time remains unclear and incidence of poor intubating conditions seems to be higher than in other regimes of anesthesia. METHODS: We included 35 ear, nose and throat (ENT) patients in this study. Muscle relaxation was measured by acceleromyograhpy at the adductor pollicis muscle (a.p.m.) and intubating conditions were evaluated. Anesthesia was induced with 2.5 mg kg-1 propofol and 1 µg kg-1 remifentanil and intubation was performed three minutes after the administration of 0.2 mg kg-1 mivacurium. Open vocal cords conjoined with full relaxation of the a.p.m., easy mouth opening and prevention of coughing and bucking represented the primary endpoint in this study. RESULTS: Only 20% of patients (N.=7) had optimal intubating conditions and achieved the primary endpoint. In 21 patients (60%) a complete block of the a.p.m. could not be achieved and in six patients (17%) the vocal cords were closed. In seven patients (20%) we observed difficult mouth opening and in 11 patients (31%) coughing and bucking. In addition, we found a prolonged onset time of 228±95 seconds (mean±SD). CONCLUSION: In combination with propofol and remifentanil the muscle relaxant agent mivacurium led to uncertain muscle relaxation and to poor intubating conditions. Therefore the study was aborted after 35 patients. Probably mivacurium is not a useful muscle relaxant agent if fast and deep muscle relaxation is needed. The advantage of a short duration time is foiled by intubation complications due to insufficient muscle relaxation.