Beyond the Ratios: Evidence for Optimal Minimum Nurse-Patient-Ratios in Medical-Surgical Settings.

aimTo evaluate the maximum number of patients per nurse before quality and safety outcomes deteriorate in medical-surgical settings.

designA secondary analysis of cross-sectional survey data.

methodsWe analysed data from 609 direct care nurses working in British Columbia's medical-surgical areas. The relationship between nurse-to-patient ratios and quality and safety outcomes was analysed using both two-level and one-level regression models, including visualisations such as boxplots and scatterplots with LOESS curves. The analysis controlled for nurse demographics and hospital clustering effects.

resultsRatios ranged from 1:1 to 1:9, with outliers above 1:9 excluded. For desirable outcomes, last shift quality of care, unit safety grade, and recommending units to friends/family and to colleagues, the means were generally positive for ratios ranging from 1:2 or 1:3 to 1:4 but negative for ratios ranging from 1:5 to 1:8 or 1:9. This pattern was reversed for adverse outcomes, undone tasks and emotional exhaustion; the means were generally negative for ratios between 1:1 and 1:3 to 1:4 but became positive for ratios between 1:5 and 1:6 to 1:8. A turning point (crossing zero) was found between the ratios of 1:4 and 1:5 for all outcomes except patient adverse events, where the turning point was between the ratio of 1:3-1:4.

conclusionThe findings provide preliminary evidence in support of minimum nurse-to-patient ratios of 1:4 in British Columbia's medical-surgical areas. Policy-makers and decision-makers should augment minimum nurse-to-patient ratios with other nurse-driven tools and nurse-management staffing methods that provide more flexibility to better meet fluctuating environmental, patient and staffing needs. NO PATIENT OR PUBLIC INVOLVEMENT: This study did not include patient or public involvement in its design, conduct, or reporting. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: Minimum ratios should be complemented by nurse-driven tools and flexible staffing strategies to account for contextual and resource variability. IMPACT: This secondary analysis of 2015 survey data from 609 medical-surgical nurses in British Columbia, Canada supported a minimum nurse-to-patient ratio of 1:4 using a series of quality and safety outcomes for patients and nurses. This finding provides important preliminary evidence in support of the specific minimum nurse-to-patient ratios of 1:4 as the province prepares to implement this ratio in medical-surgical settings. Existing staffing models using minimum nurse-to-patient ratios may be augmented by employing additional staffing tools and methodologies that provide more flexible resource allocation. REPORTING

methodThis study adheres to STROBE guidelines.