Perioperative morbidity and mortality are usually related to patients' co-morbidities, or intraoperative events such as hypotension or massive bleeding. Identifying and analyzing such relationships may help improve surgical outcomes. Indicators that predict patients' safety may help anesthetists to manage patients well. The concept of 'unplanned intensive care unit admission' (UIA) was first used in the US as a surrogate marker for patient safety and has potential for use in other countries [1,2]. Several studies indicated that UIA was associated with higher incidence of intraoperative adverse events such as cardiac arrest and hemodynamic instability; moreover, it was related to increased risk of respiratory fail-