The Australian Patient Safety Foundation was formed in 1987; it was decided to set up and coordinate the Australian Incident Monitoring Study as a function of this Foundation; 90 hospitals and practices joined the study. Participating anaesthetists were invited to report, on an anonymous and voluntary basis, any unintended incident which reduced, or could have reduced, the safety margin for a patient. Any incident could be reported, not only those which were deemed "preventable" or were thought to involve human error. The Mark 1 AIMS form was developed which incorporated features and concepts from several other studies. All the incidents in this symposium were reported using this form, which contains general instructions to the reporter, key words and space for a narrative of the incident, structured sections for what happened (with subsections for circuitry incidents, circuitry involved, equipment involved, pharmacological incidents and airway incidents), why it happened (with subsections for factors contributing to the incident, factors minimising the incident and suggested corrective strategies), the type of anaesthesia and procedure, monitors in use, when and where the incident happened, the experience of the personnel involved, patient age and a classification of patient outcome. Enrolment, reporting and data-handling procedures are described. Data on patient outcome are presented; this is correlated with the stages at which the incident occurred and with the ASA status of the patients. The locations at which the incidents occurred and the types of procedures, the sets of incidents analysed in detail and a breakdown of the incidents due to drugs are also presented. The pattern and relative frequencies of the various categories of incidents are similar to those in "closed-claims" studies, suggesting that AIMS should provide information of relevance to those wishing to develop strategies to reduce the incidence and/or impact of incidents and accidents.

Human error is a pervasive and normal part of everyday life and is of interest to the anaesthetist because errors may lead to accidents. Definitions of, and the relationships between, errors, incidents and accidents are provided as the basis to this introduction to the psychology of human error in the context of the work of the anaesthetist. Examples are drawn from the Australian Incident Monitoring Study (AIMS). An argument is put forward for the use of contemporaneous incident reporting (eliciting relevant contextual information as well as details of use to cognitive psychologists), rather than the use of accident investigation after the event (with the inherent problems of scant information, altered perception and outcome bias). A classification of errors is provided. ';4ctive" errors may be classified into knowledge-based, rule-based, skill-based and technical errors. Different strategies are required for the prevention of each type and it may now be useful to place more emphasis in anaesthetic practice on categories to which little attention has been directed in the past. "Latent" errors make an enormous contribution to problems in anaesthesia and several categories are discussed (e.g. environment, physiological state, equipment, work practices, personnel training, social and cultural factors). An approach is provided for the prevention and management of errors, incidents and accidents which allows clinical problems to be categorized, the relative importance of various contributing factors to be established, and appropriate preventative strategies to be devised and implemented on the basis of priorities determined from the AIMS data. Accidents cannot be abolished; however, an understanding of the factors underlying them can lead to the rational direction of resources and effort to prevent them and minimise their effects.