Nurse-Patient Staffing Relationship in the ICU: More Than Just Numbers.

Critical Care Medicine www.ccmjournal. org 1681 What constitutes an optimal nurse-to-patient ratio? Mandating specific nurse-to-patient ratios in critical care units remains controversial because 1) single metrics do not adequately describe staffing and 2) all measurements are limited in the precision with which they capture size, components, and deployment of nursing teams (1). Studies investigating patient outcomes associated with nurse staffing in critical care units have yielded mixed results (2–10). Those mixed results have led to divergent policies. Thus, in Victoria (Australia) and California (United States), mandated nurse-to-patient staffing ratios have been in effect for over 10 years. Elsewhere, authorities suggest and even recommend— but do not mandate—staffing levels in critical care units (11). A recent systematic review and meta-analysis reported the effects of nurse-to-patient ratios in acute specialist units, (including ICUs), emergency departments, and cardiovascular ICUs. The included studies were contemporary (2006–2017), each had at least one nurse-sensitive outcome, and all reported mortality. Outcomes of more than 175,000 patients were analyzed. The analysis concluded that a higher level of nurse staffing lowers the risk of inhospital mortality: for every increase of one nurse, patients were 14% less likely to experience inhospital mortality. Yet the authors noted considerable heterogeneity in the ways nursing staffing levels were measured and reported. There was also sufficient heterogeneity in reporting of nurse-patient sensitive outcomes in the studies that further meta-analysis would be unreliable (11). In this issue of Critical Care Medicine, Law et al (12) report the effect of nurse-to-patient ratios in ICUs on mortality and on nurse-patient sensitive outcomes in a large study that leveraged a newly legislated mandate. They analyzed cohorts using a difference-in-difference design to compare outcomes in ICUs in Massachusetts (with newly mandated ICU nurse-topatient ratios) with contemporaneous outcomes in other states with no legislative mandates. The authors evaluated changes inhospital mortality, central catheter-associated bloodstream infections, catheter-associated urinary tract infections, hospital-acquired pressure ulcers, patient falls with injury, and rates of do not resuscitate orders. The authors evaluated outcomes during three time periods (relative to the nurse staffing compliance date) for academic hospitals: a baseline (April 1, 2014, to March 31, 2015), a preparation period (April 1, 2015, to March 31,2016), and a postmandate period (April 1, 2016, to March 31, 2017). The authors observed 1) no improvements following the mandated staffing change in any of the patient outcomes that were measured and 2) nurse staffing in Massachusetts after the implementation of the mandate was not significantly higher than staffing in states that did not pass the same mandate for ICU nurse-to-patient ratios. In other words, legislation mandating nurse-to-patient ratios in the ICU created bureaucracy without apparent benefit to staffing or outcomes. The data should be interpreted with caution and further in a larger context. The first caution is that the study by Law et al (12) used administrative claims data collected from medical centers across the United States. Administrative claims data are typically collected in retrospect, aim for standardization, and thus may not entirely describe the clinical course. Also, patients may differ in required care for reasons not captured in administrative data, for example, overcoming language barriers. The clinical outcomes reported in the study by Law et al (12) were limited to quality metric data supplied to regulatory bodies—surely convenient for analysis—yet those data often blur morbidity. Patient-centered outcomes including unplanned extubation, failure to rescue, shock, cardiac arrest, hospital-acquired pneumonia, respiratory failure, medication errors, and deep vein thrombosis are other domains reported to change with varying nurse-to-patient ratios (11). Nurse-to-patient ratios also affect staff well-being, which was not evaluated in the current study by Law et al (12). Healthy work environment factors first established by the American Association of Critical Care Nurses in 2005 and updated in 2016 speak to appropriate staffing and to attributes beyond ratios—skilled collaboration, true collaboration, effective decision-making, meaningful recognition, and authentic leadership are important (13). These additional attributes may be affected by the composition and schedules of staff: education level, years of ICU experience, specialty certification (Critical Care Registered Nurse), status of hire (temporary or *See also p. 1563.