Suxamethonium and atracurium: sequential and simultaneous administration.

The interaction between suxamethonium and atracurium was investigated during anaesthesia with thiopentone, fentanyl, enflurane and nitrous oxide in oxygen with controlled ventilation. Electromyographic data (Relaxograph, Datex) from 30 patients in three, equal groups were analyzed. Group 1 received atracurium 0.23 mg kg-1. Group 2 received suxamethonium 1 mg kg-1 followed by atracurium 0.23 mg kg-1 when the EMG had recovered to 20% of its control value: a sequence intended to be representative of clinical practice. Group 3 received suxamethonium 1 mg kg-1 and atracurium 0.23 mg kg-1 in rapid succession. Plasma cholinesterase concentrations and Dibucaine and fluoride numbers were within normal limits in all patients. Suxamethonium given for endotracheal intubation (group 2) neither potentiated the subsequent atracurium blockade nor delayed spontaneous recovery. When suxamethonium and atracurium were given in rapid succession (group 3), the duration of suxamethonium blockade was reduced considerably but the recovery from the atracurium component of the blockade was not significantly different from groups 1 and 2. Although the intubation score at 60s was no worse in group 3, the duration of profound blockade suitable for intubation was reduced to such an extent that the simultaneous administration of suxamethonium and atracurium cannot be recommended in clinical practice when there is a requirement for rapid endotracheal intubation.