Background and objective Factors which lead to prolonged stay in the day–care unit and unplanned admission after day-case surgery are poorly understood.

Methods Data sets of 3152 day-case patients were collected with a computerized online record keeping system (NarkoData). Predictors of prolonged postoperative stay including unanticipated admission were identified using univariate analysis. Charts of patients, who needed admission, were reviewed.

Results 13.2% of day–case patients had a postoperative stay ≤3 h, 55.3% 3–6 h and 26.2%≥6h. The rate of unanticipated admission was 5.4%. Intraoperative haemoglobin concentration and blood loss were the best predictors of a prolonged postoperative stay. Other significant predictors were female gender, advanced age, longer duration of surgery, larger volume of infusions, intubation, spinal anaesthesia, intraoperative use of opioids and non–depolarizing muscle relaxants, high pain score, nausea and vomiting and prolonged preoperative waiting time. Chart review of patients admitted to hospital confirmed the validity of the statistically significant predictors.

Conclusions In day-case surgery, the predictors of prolonged stay in the day-care unit and unplanned Hospital admission are mainly related to the surgical procedure.