Patient outcomes when hospitals experience a surge in admissions

In January 2004, a California law passed in 1999 became effective regulating minimum nurse to patient ratios in hospital units. This legislation was prompted by results from previous research showing higher adverse patient outcomes when hospital nurse/patient ratios are low. In this study, we use a census of hospital discharges in California over the 1996-2000 period to estimate the impact of hospital staff levels on adverse events by examining whether outcomes are correlated with the number of admissions in the hospital over the next 2 days. Because hospital staff levels are determined in advance, a large influx of patients to a hospital over the next 2 days will reduce the effective staff levels for patients admitted previously. We focus on the outcomes of patients admitted on Thursdays because hospital admissions are the most variable on Friday and Saturday and hospital staffs are lowest during the weekend. We find some evidence that large shocks to admissions on Friday and Saturday tend to reduce the length of stay and increase the chance of a subsequent readmission, but these coefficients are very small. We find quantitatively small and statistically insignificant effects of Friday and Saturday admission shocks on mortality rates of patients admitted on Thursdays. These results suggest that the portion of the California law designed to guarantee adequate staffing when the patient census increases unexpectedly should have little impact on patient outcomes.