Impact of California mandated acute care hospital nurse staffing ratios: a literature synthesis.

California is the first state to enact legislation mandating minimum nurse-to-patient ratios at all times in acute care hospitals. This synthesis examines 12 studies of the impact of California's ratios on patient care cost, quality, and outcomes in acute care hospitals. A key finding from this synthesis is that the implementation of minimum nurse-to-patient ratios reduced the number of patients per licensed nurse and increased the number of worked nursing hours per patient day in hospitals. Another finding is that there were no significant impacts of these improved staffing measures on measures of nursing quality and patient safety indicators across hospitals. A critical observation may be that adverse outcomes did not increase despite the increasing patient severity reflected in case mix index. We cautiously posit that this finding may actually suggest an impact of ratios in preventing adverse events in the presence of increased patient risk.