Study of deadliest form of stroke demostrates much lower mortality rates at high caseload hospitals
Published in today's Journal of Neurosurgery, study has national implications for emergency medical care in cases of confirmed or suspected SAH
FAIRFAX, Va., November 5, 2003 – A study published today in the Journal of Neurosurgery found a strong relationship between in-hospital mortality following subarachnoid hemorrhage (SAH), the deadliest form of stroke, and the volume of such cases seen at the treating hospital. The study, which is the most comprehensive to date evaluating the volume-mortality relationship in SAH cases, showed patients treated at high volume SAH centers had 40 percent better chance of leaving the hospital alive than patients treated at low volume centers. Study authors attributed this finding, in part, to differences in the availability of specialized personnel, equipment and protocols at low and high volume SAH centers. The study found that the in-hospital mortality rate of low volume hospitals (those treating less than 10 per year) was 38.7 percent compared to only 27 percent in high volume centers (those treating more than 35 per year). The large difference in hospital mortality provides compelling evidence that surviving a SAH is more likely if a patient is admitted to a high volume hospital and suggests that there may be significant benefits to centralizing SAH care for these catastrophic strokes.
"The 40% reduction in relative risk seen at high-volume SAH centers represents one of the largest impacts demonstrated in any medical study examining mortality differences at low and high volume centers," said DeWitte T. Cross, M.D., lead author of the study and director of Interventional Neuroradiology at the Mallinckrodt Institute of Radiology at Washington University's Barnes-Jewish Hospital. "This is the most comprehensive study of its kind to date involving patients from 18 states, representing nearly 60 percent of the U.S. population. Its findings suggest that centralizing treatment of this disease in high volume centers may mean significantly more patients will survive their SAH."
Characteristics of a High Volume SAH Center The study's authors point to a variety of factors that are likely to account for the large difference in mortality. Compared to their low volume counterparts, high volume hospitals tend to have more specialists on staff, rely on more sophisticated and less invasive imaging equipment and use a defined team approach to treatment. In addition, they benefit from experienced neuro-intensive care units and offer both surgical and endovascular treatment. For example, the study showed that only two percent of low volume hospitals offered endovascular treatment.
"It's important to emphasize that the data does not show that physicians and hospitals are delivering low quality care. Rather, the data demonstrates that on average, high volume centers generate better medical outcomes due to a multiplicity of factors related to specialized stroke care," said Daniel L. Barrow, M.D. chairman of neurosurgery at Emory University in Atlanta. "The patterns of care for patients with SAH are complex and indicate that opportunities may exist to improve outcomes through the development of high-volume multi-disciplinary centers. The key is specialization involving multi disciplinary teams, access to surgical and endovascular treatment and dedicated specialized after care. Volume brings experience and most high volume centers are specialized but there are also some smaller centers that specialize and offer excellent care. Unfortunately, a significant number of patients are not taken to specialized centers when they suffer a SAH. We need more of these centers and we need to make sure that the medical personnel who first care for these patients recognize the potential benefits of getting these patients to high volume multi-disciplinary centers whenever possible."
"This is a compelling study and it suggests that we re-examine the Emergency Medicine Services protocols that outline where a patient is first taken for treatment, and how a patient ideally should be transferred to a high volume center when indicated. We need to better define and implement 'best practices' in stroke care," said American Society of Interventional and Therapeutic Neuroradiology president John J. (Buddy) Connors III, M.D., Medical Director, Interventional Neuroradiology at Baptist Hospital's Miami Cardiac & Vascular Institute. "We have an enormous and exciting opportunity to improve treatment for SAH," added Dr. Connors.
About SAH Subarachnoid Hemorrhage is defined as bleeding into the compartment around the brain. The most common cause of SAH is a ruptured brain aneurysm, which is a weak spot in a brain artery that has "ballooned" out. Other origins of hemorrhagic stroke are vascular malformations, high blood pressure that leads to the rupture of a tiny artery or vein, and drugs that create a dysfunction of the clotting system. Blood from the burst aneurysm can severely injure the brain, making SAH a catastrophic event that requires as early treatment as possible to increase chance of survival and/or minimize neurological dysfunction. Nearly 30,000 Americans fall victim to SAH each year. Ten to 15 percent of SAH patients die before reaching a hospital. More than 50 percent of SAH victims die within the first 30 days after the attack, and of those who survive, about half suffer a permanent deficit.
Study Design Using data from 18 different states, which represented nearly 60 percent of the U.S. population, researchers conducted a retrospective database analysis of hospital discharge data to examine the relationship between in-hospital mortality and the volume of SAH cases seen at the treating hospitals. The study cohort comprised 16,399 emergency department admissions with a diagnosis of SAH that spanned 1,546 different hospitals. All non-emergency admissions were excluded from the study population to ensure similarity of health status among the study subjects. Researchers also analyzed a subset of 9,290 cases, representing 1,312 SAH centers, in order to control for the potential impact of combined variables (age, sex, Medicaid status, region, data source year, hospital volume quartile and co-morbidity) on outcomes.
Conclusion The authors of this study concluded that SAH outcomes could be immediately improved by ensuring that suspected or confirmed cases of SAH are treated at hospitals with a high caseload of SAH. Additionally, researchers cited the availability of specialized staff, equipment and protocols as factors that likely contributed to the higher survival rates at high volume hospitals. Further research and development of care guidelines for comprehensive SAH/stroke centers, such as those presently being developed by the Brain Attack Coalition, may also assist in defining an optimal treatment environment and care protocols. In addition, guidelines for development and implementation of Interventional Stroke Therapy Centers are being defined by a multi-specialty coalition including neuroradiologists, neurologists and other stroke experts from the ASITN, the American Society of Neuroradiology, and the Society of Interventional Radiology to delineate the necessary hospital resources to optimally utilize minimally-invasive catheter-based techniques for the treatment and prevention of stroke.
About the American Society of Interventional & Therapeutic Neuroradiology The American Society of Interventional & Therapeutic Neuroradiology is the specialty society representing physician experts in minimally invasive, targeted neurological treatments performed using radiological imaging guidance. Innovations from the field of interventional neuroradiology include, among others, the endovascular treatment of cerebral aneurysms, carotid stents, intracranial stents, emergency stroke treatment, intracranial angioplasty, and vertebroplasty. More information about ASITN can be found on our Web site at http://www.asitn.org.