Short-term nurse scheduling in response to daily fluctuations in supply and demand

Hourly changes in patient census and acuity require hospitals to update their staffing needs on a continuing basis. This paper discusses the problem that management faces several times a day as the demand for nursing services departs from the planned schedule. Prior to the start of each shift, the number of nurses who are scheduled to be on duty over the next 24 hours is compared with the number actually available, and if shortages exist a series of decisions have to be made to ensure that each unit in the hospital has sufficient coverage. These decisions involve the use of overtime, outside nurses, and floaters. To address this problem, we have developed an integer programming model that takes the current set of rosters for regular and pool nurses and the expected demand for the upcoming 24 hours as input, and produces a revised schedule that makes the most efficient use of the available resources. The model is formulated and solved at a hospital-wide level rather than for each unit separately. To determine its applicability, a representative set of scenarios was investigated using data obtained from a medium-size facility in the US with 14 units. The results indicate that problem instances with up to 120 nurses can be solved in a negligible amount of time.