Endovascular treatment, which was more often used in the elderly, was also associated with significantly higher mortality rates in smaller hospitals (P 0.001) and steadily increasing morbidity rates (45%). Large academic centers were associated with better results, particularly for surgical clip placement.161 Prior studies have also indi- cated that 82% of US hospitals admitted 19 patients with aSAH annually, and the 30-day mortality rate was signif- icantly higher in hospitals that admitted 10 patients with aSAH versus 35 patients with aSAH (39% versus 27%; odds ratio, 1.4).80 Two factors associated with better outcomes were greater use of endovascular services and a higher percentage of patients transferred from other hospitals.79 81 Institutions that used endovascular coil embolization more frequently had lower in-hospital mortality rates, a 9% reduction in risk for every 10% of cases treated. In addition, there was a 16% reduction in risk of in-hospital death at institutions that used interventional therapies such as balloon angioplasty to treat arterial vasospasm.2,81,162 Therefore, hospital treatment vol- umes and availability of both endovascular and neurological intensive care services at hospitals are important determinants of improved outcomes in aSAH.163 In addition, a cost-utility analysis estimated that transferring a patient with aSAH from a low- to a high-volume hospital would result in a gain of 1.6 quality-adjusted life-years at a cost of $10 548.162,163 Although 1 study suggested that care was uniformly delivered within an institution when weekend and weekday admissions were compared,164 others have shown that inten- sive care specialists followed evidence-based recommenda- tions very inconsistently, and these variations in practice did not depend on the quality of the supporting data.165 Signifi- cant practice differences were noted between respondents from North America and Europe and between those working in high- and low-volume centers. 