[Intubation conditions and the development of neuromuscular blockade with rocuronium in endoscopic ORL surgery].

UNLABELLED: Rocuronium is a new nondepolarizing muscle relaxant for which a fast onset has been described. The goal of this study was to examine whether the characteristics of rocuronium could make it an appropriate relaxant for the anaesthetic management of operations of intermediate duration such as endoscopic upper airway surgery. These operations, which require the anaesthesiologist and surgeon to "share" the patient's airway, require good muscle relaxation for endotracheal intubation and placement of endoscopic instruments. In addition, the time course of neuromuscular blockade and its relation to the quality of intubating conditions were analysed.

METHODS: The study was approved by the local ethics committee; 30 patients (ASA status 1-3) scheduled for elective endoscopic upper airway surgery were included after written informed consent. Exclusion criteria were suspected difficult intubating conditions, neuromuscular disease, or antibiotic therapy with aminoglycosides during the last 24 h. Anaesthesia was induced by propofol 2 mg/kg and alfentanil 1 mg after volume loading with 500 ml Ringer's lactate and preoxygenation, and was maintained by propofol infusion 5-8 mg/kg/h and repetitive alfentanil injections according to clinical needs. Endotracheal intubation was performed by a senior anaesthesiologist 90 s after injection of rocuronium 0.6 mg/kg (2 x ED95). Intubating conditions were graded 1 to 4 (1 = excellent, 2 = good, 3 = sufficient, 4 = inadequate). Acceleromyography was used for neuromuscular monitoring by means of the TOF-guard (organon Teknika/Biometer). The adduction movement of the thumb was measured by an acceleration transducer while stimulating the ulnar nerve at the wrist via surface electrodes in a supramaximal train-of-four (TOF) mode (2 Hz every 15 s). Twitch height and TOF ratio were documented during the course of neuromuscular blockade. Data are presented as mean +/- standard deviation.

RESULTS: Patients were aged 37 to 64 years (mean 54 +/- 7). Intubating conditions were excellent in 17 cases and good in 7. In 2 cases intubating conditions were graded sufficient, as patients could be easily intubated but showed clear diaphragmatic movements at intubation. In 4 patients intubating conditions could not be judged, as a laryngoscopic view of the glottic structures was impossible for anatomic reasons. Neuromuscular block at intubation was 78 +/- 22%, onset time 152 +/- 62 s, clinical duration 30 +/- 8 min, and recovery index 11 +/- 4 min. The TOF ratio required 51 +/- 14 min to return to 0.7.

CONCLUSIONS: Good to excellent intubating conditions can be expected 90 s after injection of rocuronium 0.6 mg/kg. Diaphragmatic reactions cannot be excluded. Complete relaxation of the adductor pollicis muscle is not necessary for endotracheal intubation. Intubation at a certain time interval, for example, 90 s after injection of rocuronium 0.6 mg/kg, can be recommended. Onset and recovery characteristics of rocuronium make it an appropriate relaxant for the anaesthetic management of operations of intermediate duration such as endoscopic upper airway surgery. Care should be given, however, to detect inadequate recovery of neuromuscular transmission, as there are considerable interindividual differences in recovery.