Post-operative serious adverse events in a mixed surgical population - a retrospective register study

The number of surgical procedures is increasing, and knowledge of surgical risk factors, post-operative mortality and serious adverse events (SAE) is essential. The aim with our study was to determine the risk of a composite outcome of post-operative: death; myocardial infarction; pulmonary embolism; stroke; gastrointestinal bleeding; dialysis or reoperation.

Data of surgical procedures in the period from January 1, 2012 to June 30, 2012 were retrieved from the Danish Anaesthesia Database (DAD). Follow-up of all patients undergoing hip or knee replacement, abdominal or gynaecological surgery was conducted retrieving data from The Danish Civil Registration System and the National Patient Register. Total observation time was from January 1, 2012 to June 6, 2013.

A total7449 adult patients were included in the final analysis. The risk of the composite outcome during a follow-up until 342 days after inclusion of the last patient was estimated to 8.3%, 95% Confidence Intervals (CI) (7.8-9.0), with a median observation time of 437 days (IQR 387-485, range 0-522). The risk of the composite outcome within 90- and 180-day follow-up of each patient was 4.8% (4.4-5.3) and 5.9% (5.4-6.5), respectively. Mortality within longest follow-up as well as 90 and 180 days post-operatively was 3.6% (3.1-4.0), 1.7% (1.4-2.0), and 2.2% (1.9-2.6), respectively.

We found a risk of one or more events in the composite outcome within 342 days after inclusion of the last patients of 8.3% (7.8-9.0). The results are applicable in estimations of adequate sample sizes in future clinical trials investigating effects of interventions on SAEs.