pass, and Congress to consider, proposed legislation to protect consumers (Derlet and Young, 1997; ACEP, 1998). Specifically, managed care has been charged with the delay of emergency care through preauthorization requirements; denial or undercoverage at EDs that are not part of a managed care network of providers; inadequate information about the use of 9-1-1; and premature discharge from acute care or rehabilitation (ACEP, 1993, 1998; Kilborn, 1997). The net effect may be an interruption in the continuity of care and poorer patient outcomes (Derlet, 1997). Counterbalancing these charges are the purported benefits of managed care. Among them is the possibility of promoting a better match between available resources and patient needs; reducing unnecessary costs; and emphasizing prevention, cost-effectiveness, data acquisition, and the use of treatment guidelines (IOM, 1996). What may be lost amidst the entry of managed care into trauma systems is the fact that some underlying goals of managed care and trauma care are similar, particularly the emphasis on prevention and on a match between available resources and patient needs. Congress is currently considering the passage of proposed federal legislation requiring public and private health insurance coverage for ED visits that any "prudent layperson" considers to be medically necessary.
The remainder of this section describes the modest body of peer-reviewed literature on the impact of managed care on trauma systems utilization, costs, and outcome. To place this literature in the context of managed care across all types of health care, a comprehensive literature analysis of studies since 1980 found HMOs, in comparison with fee-for-service plans, to have lower hospital admission rates, shorter lengths of stay (LOS), the same or more physician office visits per enrollee, less use of expensive procedures and tests, greater use of preventive services, mixed results on outcomes, and somewhat lower enrollee satisfaction with services (Miller and Luft, 1994).
With respect to managed care and trauma systems, the main measures of utilization have been 9-1-1 access, emergency room visits, and LOS. In terms of 9-1-1 access, one study found that virtually all Chicago-based HMOs surveyed in the late 1980s advised enrollees in case of emergency to contact the HMO office, primary physician, or a toll-free number, whereas only one HMO advised enrollees to go to the nearest hospital, yet made no mention of calling 9-1-1 (Hossfeld and Ryan, 1989). This study may be limited in applicability or dated, but it was among the first and only study of its kind. In another study, ED visits were reduced by at least 15 percent during one hospital's transition to managed care that was mandated by the State of Connecticut for all Medicaid recipients (Powers, 1997). Since access to emergency services is crucial, it is important for research to monitor the impact of managed care on trauma system access and related outcomes.
Under managed care, LOS would be expected to be lower for trauma patients. Yet two published studies that bear either directly or indirectly on LOS offer conflicting results. In the first study, Campbell and coworkers (1995) found that the mean LOS for 89 HMO trauma center patients in San Francisco from 1989 to 1993 were actually higher than those for non-HMO controls matched for