Abstract
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<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.