Increased Utilization of Overtime and Agency Nurses and Patient Safety.

Importance: The use of nurse overtime and agency nurses has increased in recent years, making it important to understand the opportunities and limits of these alternative staffing strategies on patient safety outcomes.

Objective: To examine the association between overtime and agency nurse staffing hours and hospital patient safety.

Design, setting, and participants: This quality improvement study used data from 70 US hospitals, from January 2019 through December 2022. Participants included patients and nurse staff across the 70 hospitals.

Exposure: The use of overtime and agency nursing.

Main outcomes and measures: The main outcomes were 10 of the US Agency for Healthcare Research and Quality's patient safety indicators and their associations with regular, overtime, and agency nursing hours per patient day: pressure ulcers, iatrogenic pneumothorax, in-hospital fall with hip fracture, perioperative hemorrhage or hematoma, postoperative acute kidney injury requiring dialysis, postoperative respiratory failure, perioperative thromboembolism, postoperative sepsis, postoperative wound dehiscence, and accidental puncture or laceration. A baseline Poisson regression model and a structural breakpoint analysis were used to identify safety thresholds. Pairwise interactions between staffing intensity variables and hospital bed size were also included. Adjustments were made for the COVID-19 hospital census, patient case mix, and hospital characteristics.

Results: The sample included 46 hospitals in the South, 20 in the West, and 4 in the Northeast; 48 hospitals were urban, 32 hospitals had fewer than 200 beds, 26 had between 200 and 399 beds, and 12 had 400 or more beds. The average use of nurse overtime and agency nurse hours exceeded safe thresholds for pressure ulcers by 140.0% for agency staffing and by 63.6% for overtime, representing a 6.44% increase associated with excess agency nurse hours and a 2.09% increase for excess use of overtime. There also was a statistically significant association of agency hours with postsurgery hemorrhage or hematoma rates, but no breakpoint threshold. There were no significant associations with other outcomes.

Conclusions and relevance: These findings suggest that both nurse overtime and nurse agency hours are associated with increased rates of pressure ulcers, a measure that is one of the most sensitive to nursing care. In future research, hospitals could use their own data to track safe thresholds.