The role of muscle relaxants in total intravenous anaesthesia.

For total intravenous anaesthesia (TIVA), all drugs that are required as part of the anaesthetic method are administered intravenously. This is usually taken to imply the use of intravenous infusions. It is normal practice to administer muscle relaxants intravenously, although other routes have been used. A muscle relaxant is required firstly to secure paralysis and secondly to maintain paralysis. The rate of onset of all the nondepolarizing neuromuscular blocking agents which are routinely available at present is similar; it takes about 3-6 min for a normal clinical dose to reach maximum effect. Maintenance of an adequate level of block is necessary, and it is usually helpful to the surgeon for the level of block to be relatively constant. The choice of drug is important. It should cause negligible side-effects. For administration by infusion, an agent with an intermediate (e.g., atracurium) or short (e.g., mivacurium) duration of action is essential to ensure a rapid recovery of effect on termination of the infusion. The routine use of neuromuscular monitoring is recommended when a continuous infusion of a relaxant is used.