Outcomes of Nurse Practitioner-Delivered Critical Care: A Prospective Cohort Study

Abstract

Background: Acute care nurse practitioners (ACNPs) are increasingly being employed in ICUs to offset physician shortages, but no data exist about outcomes of critically ill patients continuously cared for by ACNPs.

Methods: Prospective cohort study of all admissions to an adult medical ICU in an academic, tertiary-care center between January 1, 2011, and December 31, 2013. The primary end point of 90-day survival was compared between patients cared for by ACNP and resident teams using Cox proportional hazards regression. Secondary end points included ICU and hospital mortality and ICU and hospital length of stay.

Results: Among 9,066 admissions, there was no difference in 90-day survival for patients cared for by ACNP or resident teams (adjusted hazard ratio [HR], 0.94; 95% CI, 0.85-1.04; P = .21). Although patients cared for by ACNPs had lower ICU mortality (6.3%) than resident team patients (11.6%; adjusted OR, 0.77; 95% CI, 0.63-0.94; P = .01), hospital mortality was not different (10.0% vs 15.9%; adjusted OR, 0.87; 95% CI, 0.73-1.03; P = .11). ICU length of stay was similar between the ACNP and resident teams (3.4 ± 3.5 days vs 3.7 ± 3.9 days [adjusted OR, 1.01; 95% CI, 0.93-1.1; P = .81]), but hospital length of stay was shorter for patients cared for by ACNPs (7.9 ± 11.2 days) than for resident patients (9.1 ± 11.2 days) (adjusted OR, 0.87; 95% CI, 0.80-0.95; P = .001).

Conclusion: Outcomes are comparable for critically ill patients cared for by ACNP and resident teams.

Keywords: acute care nurse practitioner; critical care; critical care manpower standards; intensive care units; nurse practitioner; outcome assessment (health care); patient care team; physician assistant; quality of health care; retrospective studies.

Figure 1

Derivation of the study cohort. All admissions to the ACNP service and resident services were included in analysis. ACNP = acute care nurse practitioners.

Figure 2

Survival by admitting service. (A) In a Cox proportional-hazards regression analysis adjusting for age, sex, ventilator use, vasopressor use, and University HealthSystem Consortium expected mortality, there was no difference between the NP and resident services in the primary outcome of 90-day survival. (B) The hazard ratio for death in the first 90 days was similar between services in subgroups defined by admitting diagnosis, number of ICU admissions during the study period, day of the week on which the admission occurred, and time of day of the admission. There was a suggestion of improved survival within the admitting diagnosis of glucose disorders on the NP service and with altered mental status on the resident service. Glucose disorder includes diabetic ketoacidosis, hyperosmolar hyperglycemic nonketotic syndrome, and hypoglycemia; weekday refers to Monday-Friday; daytime refers to 7 am through 7 pm. NP = nurse practitioner.

Figure 3

Observed relative to expected mortality by admitting service. For the acute care nurse practitioner (ACNP) service (red) and residents services (blue), the proportion of admissions that died before hospital discharge (mean and 95% CI) is displayed at each rate of expected in-hospital mortality as estimated by the UHC national data. Histograms display the distribution of expected mortality rates for patients admitted to each service. UHC = University HealthSystem Consortium. See Figure 2 legend for expansion of other abbreviation.