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

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

A secondary analysis of cross-sectional survey data.

We 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.

Ratios 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.

The 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.

This study did not include patient or public involvement in its design, conduct, or reporting.

Minimum ratios should be complemented by nurse-driven tools and flexible staffing strategies to account for contextual and resource variability.

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.

This study adheres to STROBE guidelines.