Clinical experience with atracurium during prolonged anaesthesia

The pharmacodynamic properties of repeated injections of atracurium were studied in twenty-two patients. A control group received narcotic-based anaesthesia while another group received the same narcotic-based anaesthesia subsequently modified by the addition of 0.5% isoflurane. The twitch response of the adductor pollicis muscle was recorded after train-of-four (TOF) stimulation of the ulnar nerve at the wrist. Duration of effect and recovery time were measured. A bolus dose of atracurium (0.5 mg/kg b.w.) was given for tracheal intubation and maintenance doses of 0.2 mg/kg b.w. were given during anaesthesia at a TOF ratio of 0.25. Mean duration of anaesthesia was 7.5 hours (range 3-19). In the control group mean duration of effect and mean recovery time remained unchanged (six doses studied). A noteworthy inter-individual variation was found. In the isoflurane group mean duration of effect increased from 36.1 (SD 6.3) minutes to 42.2 (SD 8.1) minutes (P less than 0.05) following the addition of isoflurane. Corresponding recovery times remained unchanged. We conclude that during repeated administration of atracurium during narcotic-based anaesthesia, each patient shows a constant interval between requirements for maintenance doses of atracurium of 0.2 mg/kg b.w. Addition of 0.5% isoflurane causes a moderate prolongation of the duration of effect, but recovery time remains unchanged.