The neonatal intensive care unit (NICU) is a setting with high nurse-to-patient ratios. Little is known about the factors that determine nurse workload and assignment. The goals of this study were to (1) develop a measure of NICU infant acuity; (2) describe the acuity distribution of NICU infants; (3) describe the nurse/infant ratio at each acuity level, and examine the factors other than acuity, including nurse qualifications and the availability of physicians and other providers, that determined staffing ratios; and (4) explore whether nurse qualifications were related to the acuity of assigned infants. In a two-stage cohort study, data were collected in 104 NICUs in 2008 by nurse survey (6,038 nurses and 15,191 infants assigned to them) and administrators reported on unit-level staffing of non-nurse providers; in a subset of 70 NICUs in 2009-2010, census data were collected on four selected shifts (3,871 nurses and 9,276 infants assigned to them). Most NICU infants (62%) were low-acuity (Levels 1 and 2); 12% of infants were high-acuity (Levels 4 and 5). The nurse-to-infant ratio ranged from 0.33 for the lowest-acuity infants to 0.95 for the highest-acuity infants. The staffing ratio was significantly related to the acuity of assigned infants but not to nurse education, experience, certification, or availability of other providers. There was a significant but small difference in the percentage of high-acuity (Levels 4 and 5) infants assigned to nurses with specialty certification (15% vs. 12% for nurses without certification). These staffing patterns may not optimize patient outcomes in this highly intensive pediatric care setting.
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