Atracurium in clinical anaesthesia: effect of dosage on onset, duration and conditions for tracheal intubation.

Conditions for tracheal intubation at 90 seconds, time to onset of maximum block and duration of clinical relaxation after five different doses of atracurium, which ranged from 0.4 to 1.0 mg/kg were studied in 200 adult patients who were anaesthetized with nitrous oxide, oxygen and halothane or fentanyl. The conditions for intubation improved significantly with increasing doses, and were acceptable in 55% patients with a 0.4 mg/kg dose and in about 90% of those who received the two higher doses. The time to onset of complete block was 257 seconds with 0.4 mg/kg and decreased progressively to 124 seconds with 1.0 mg/kg. The duration of clinical relaxation under fentanyl anaesthesia averaged 29 minutes with 0.4 mg/kg and increased in a dose-related manner to 57 minutes with 1.0 mg/kg: halothane anaesthesia produced only a marginal increase. There was no evidence of cumulation with up to six repeat doses of 0.125 mg/kg. The only side effect noticed was cutaneous flushing observed in 42% of patients. This was again dose dependent, being 18% with 0.4 mg/kg and increasing to 73% after 1.0 mg/kg. There was associated hypotension and bronchospasm in one patient.