Adverse events in New Zealand public hospitals II: preventability and clinical context

AIMS: To assess the preventability and clinical context of adverse events identified in New Zealand public hospitals. METHODS: Two-stage retrospective review of 6579 medical records randomly sampled from admissions for 1998 in 13 generalist hospitals providing acute care. Initial screening and medical review according to a standardised protocol. RESULTS: Eight hundred and fifty adverse events were identified, of which over one third (315) were preventable to a significant degree. Preventability of events increased with age of patient, and was more characteristic of certain diagnostic categories. Half of all events (413/850) were both preventable and occurred in hospital, giving an occurrence rate of 6.3%. This rate increased with patient age, as did impact on patients and extended stay. There were also variations by diagnostic category. Over half of the events were associated with surgery (489) and one third with medicine (303); operative incidents were predominant in the former, drug-related in the latter, and system issues in both. Events in medicine had greater patient impact, and were less likely to have occurred in a public hospital. System errors featured prominently as an area for prevention, being associated with nearly half of all preventable in-hospital events. Consultation and education were also important, resources less so. CONCLUSIONS: Preventable adverse events have a major impact on patient outcomes and extended hospital stay. A substantial proportion of these are system related and, hence, in principle susceptible to quality improvement.