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Patient Outcomes After the Introduction of Statewide ICU Nurse Staffing Regulations*

Law, Anica C., MD1,2; Stevens, Jennifer P., MD, MS1,2; Hohmann, Samuel, PhD, MS3,4; Walkey, Allan J., MD, MS5,6,7

doi: 10.1097/CCM.0000000000003286
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Objectives: To assess whether Massachusetts legislation directed at ICU nurse staffing was associated with improvements in patient outcomes.

Design: Retrospective cohort study; difference-in-difference design to compare outcomes in Massachusetts with outcomes of other states (before and after the March 31, 2016, compliance deadline).

Setting: Administrative claims data collected from medical centers across the United States (Vizient).

Patients: Adults between 18 and 99 years old who were admitted to ICUs for greater than or equal to 1 day.

Interventions: Massachusetts General Law c. 111, § 231, which established 1) maximum patient-to-nurse assignments of 2:1 in the ICU and 2) that this determination should be based on a patient acuity tool and by the staff nurses in the unit.

Measurements and Main Results: Nurse staffing increased similarly in Massachusetts (n = 11 ICUs, Baseline patient-to-nurse ratio 1.38 ± 0.16 to Post-mandate 1.28 ± 0.15; p = 0.006) and other states (n = 88 ICUs, Baseline 1.35 ± 0.19 to Post-mandate 1.31 ± 0.17; p = 0.002; difference-in-difference p = 0.20). Massachusetts ICU nurse staffing regulations were not associated with changes in hospital mortality within Massachusetts (Baseline n = 29,754, standardized mortality ratio 1.20 ± 0.04 to Post-mandate n = 30,058, 1.15 ± 0.04; p = 0.11) or when compared with changes in hospital mortality in other states (Baseline n = 572,952, 1.15 ± 0.01 to Post-mandate n = 567,608, 1.09 ± 0.01; difference-in-difference p = 0.69). Complications (Massachusetts: Baseline 0.68% to Post-mandate 0.67%; other states: Baseline 0.72% to Post-mandate 0.72%; difference-in-difference p = 0.92) and do-not-resuscitate orders (Massachusetts: Baseline 13.5% to Post-mandate 15.4%; other states: Baseline 12.3% to Post-mandate 14.5%; difference-in-difference p = 0.07) also remained unchanged relative to secular trends. Results were similar in interrupted time series analysis, as well as in subgroups of community hospitals and workload intensive patients receiving mechanical ventilation.

Conclusions: State regulation of patient-to-nurse staffing with the aid of patient complexity scores in intensive care was not associated with either increased nurse staffing or changes in patient outcomes.

1Center for Healthcare Delivery Science, Beth Israel Deaconess Medical Center, Boston, MA.

2Division of Pulmonary, Critical Care, and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA.

3Vizient, Center for Advanced Analytics, Chicago, IL.

4Department of Health Systems Management, Rush University, Chicago, IL.

5Evans Center for Implementation and Improvement Sciences, Department of Medicine, Boston University School of Medicine, Boston, MA.

6The Pulmonary Center, Boston University School of Medicine, Boston, MA.

7Department of Health Law, Policy and Management, Boston University School of Public Health, Boston, MA.

*See also pp. 1681 and 1683.

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Supported, in part, by grants from National Institute on Aging (1F32AG058352 to Dr. Law); Agency for Healthcare Research and Quality (5K08HS024288) and Doris Duke Charitable Foundation (to Dr. Stevens); and National Heart, Lung, and Blood Institute (1R01HL136660, K01HL116768) and Boston University School of Medicine Department of Medicine Career Investment Award (to Dr. Walkey).

Dr. Law’s institution received funding from the National Institute on Aging; the Agency for Healthcare Research and Quality (AHRQ); and the National Heart, Lung, and Blood Institute. She received support for article research from the National Institutes of Health. Dr. Stevens was supported by grant number K08HS024288 from the AHRQ. The content is solely the responsibility of the authors and does not represent the official views of the AHRQ. The remaining authors have disclosed that they do not have any potential conflicts of interest.

Address requests for reprints to: Anica C. Law, MD, Center for Healthcare Delivery Science, Division of Pulmonary, Critical Care, and Sleep Medicine, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215. E-mail:

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