Induction of anaesthesia: a guide to drug choice.

In developed countries, the choice of an anaesthetic agent for induction of anaesthesia remains based mainly on its pharmacodynamic properties. Until now, cardiovascular effects were the main factor in this decision. However, other factors, such as the depth of anaesthesia and effects on cortisol synthesis, can modify this simplistic view. A better understanding of the relationships between the pharmacokinetics and pharmacodynamics of these drugs, and the availability of new techniques, such as target-controlled infusions of anaesthetic drugs and inhalation induction, have led practitioners to the understanding that the way a drug is administered is a far more important factor for maintaining haemodynamic stability than the specific agent used. The ability of a drug to maintain spontaneous ventilation and to relax the upper airway is another factor in this decision, especially when considering difficult intubation, laryngeal mask insertion or tracheal intubation without neuromuscular blockade. Beyond the factors mentioned above, anaesthetists adapt current practice to suit patients' willingness to comply with anaesthesia and to avoid the adverse effects that are most often feared by the patient. Although most practitioners are not concerned with the cost of anaesthesia, cost-containment policies have led some institutions to restrict the use of the more expensive drugs to particular indications. However, this is too simplistic an approach for the reduction of global costs, as other direct medical costs, such as those for staffing, form a greater proportion of total costs than do direct drug costs. Cost-benefit and cost-efficacy studies of the anaesthetics used for induction of anaesthesia are needed to help anaesthetists to choose a drug based on both cost and pharmacodynamic or pharmacokinetic properties.