Onset of neuromuscular block is the same if the ipsilateral or contralateral limb to the injection site is used for monitoring.

We studied 40 healthy adult patients undergoing elective surgery who were premedicated with flunitrazepam. Before induction of anaesthesia, one of the upper limbs was cannulated and an i.v. infusion of 0.9% saline commenced. Patients were given fentanyl and thiopentone for induction of anaesthesia and then 50% (20 patients) received atracurium 0.5 mg kg-1 and the other 50% vecuronium 0.1 mg kg-1. Neuromuscular block (maximum degree of depression of the elicited first twitch and the onset time of depression of twitch height to 50%, 90% and 100% of control) and skin temperature (at the thenar eminence) were monitored in both the limb with the i.v. infusion and the non-cannulated upper limb. There was no difference in onset time and degree of neuromuscular block between the two upper limbs. Skin temperature was not significantly different between the two upper limbs. We conclude that each upper limb, irrespective of whether an i.v. infusion is in progress, may be used for monitoring onset of neuromuscular block.