Stable muscle relaxation during abdominal surgery using combined intravenous bolus and demand infusion: clinical appraisal with ORG NC45.

In order to obtain stable muscle relaxation for intra-abdominal operation, a continuous demand perfusion of ORG NC45 was administered following a loading dose of 0.07 mg . kg-1. The patients had previously been anaesthetized with methohexitone, fentanyl and nitrous oxide. The perfusion rate of ORG NC45 was regulated so that the mechanical muscular response of the adductor pollicis following a supra-maximal stimulation of the ulnar nerve was maintained at 10 per cent of its initial value. The level of relaxation thus obtained was always adequate for the surgeons. During the course of the operation the requirement for more relaxant decreased progressively, becoming stable after one half hour. Nevertheless, during stable administration, individual variations were quite marked, being 44 to 483 micrograms/M2 BSA/10 min (average 225 micrograms/M2 BSA/10 min). The duration of the infusion varied from 60 to 107 minutes (average 103 minutes). After its termination the time taken from recovery varied between 3 and 82 minutes (average 27 minutes). Having regained a single twitch height of 75 per cent patients awoke rapidly after the administration of nitrous oxide was terminated. No signs of recurarization were noticed in any of the patients. In conclusion, this method of administration of ORG NC45 assures a stable level of curarization without side-effects. However, because of the different individual levels of sensitivity which were noted, this mode of administration requires careful monitoring to avoid inappropriate dosage.