Nurse staffing and patient mortality in intensive care units.

BACKGROUND: Research evidence suggests that nurse staffing influences patient outcomes.

OBJECTIVES: To examine the relationship between nurse staffing and patient mortality in Korean intensive care units (ICUs).

METHODS: Using survey and administrative databases, this study included 27,372 ICU patients discharged from 42 tertiary and 194 secondary hospitals. Ownership (public vs. private), location (metropolitan city vs. province), size, specialization of ICUs (specialized vs. mixed), physician staffing and nurse staffing, and years of nurse experience were included as hospital and ICU characteristics. Nurse staffing was measured as the ratio of average daily census to the total number of full-time equivalent registered nurses in ICUs. Age, gender, 26 categories of primary diagnoses, 16 groups of comorbid conditions, and source of payment were used for risk adjustment. Mortality was defined as deaths that occurred in the hospital or on the date of hospital discharge. Using SAS GLIMMIX procedures, multivariate logistic regression analysis was employed separately for tertiary and secondary hospitals.

RESULTS: In tertiary hospitals, a greater likelihood of dying was found among patients who were admitted to a mixed ICU (odds ratio [OR] = 1.61, 95% confidence interval [CI] = 1.14-2.26) and where there was no board-certified physician present for 4 or more hours per day (OR = 1.56, 95% CI = 1.20-2.01). In secondary hospitals, every additional patient per RN was associated with a 9% increase in the odds of dying (OR = 1.09, 95% CI = 1.04-1.14). Nurse experience had no significant relationship with mortality.

DISCUSSION: Nurse and physician staffing and specialization of ICUs impacted patient mortality. Associations differed in tertiary and secondary hospitals. Further investigation of the impact of organizational environments in ICUs is needed.