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Intensive care unit nurse staffing and the risk for complications after abdominal aortic surgery
P J Pronovost1, D Dang, T Dorman
1Johns Hopkins University Schools of Medicine, and Hygiene and Public Health, Baltimore, Md., USA. ppronovo@jhmi.edu
Context:
We previously found that length of stay in the intensive care unit (ICU) after abdominal aortic surgery increased when fewer ICU nurses were available per patient. We hypothesized that having fewer nurses increases the risk for medical complications.
Objective:
To evaluate the association between nurse-to-patient ratio in the ICU and risk for medical and surgical complications after abdominal aortic surgery.
Design:
Observational study.
Setting:
All nonfederal acute care hospitals in Maryland.
Data Sources:
Information about patients came from hospital discharge data on all patients in Maryland with a principal procedure code for abdominal aortic surgery from 1994 through 1996 (n = 2606). The organizational characteristics of ICUs were obtained by surveying ICU medical and nursing directors in 1996 at the 46 Maryland hospitals that performed abdominal aortic surgery. Thirty-nine of the ICU directors (85%) completed the survey.
Exposure:
Surgery in hospitals with fewer ICU nurses (in which each nurse cared for three or four patients) compared with hospitals with more ICU nurses (in which each nurse cared for one or two patients).
Outcome:
Proportion of patients who developed postoperative complications.
Results:
Seven hospitals with 478 patients had fewer ICU nurses, and 31 hospitals with 2128 patients had more ICU nurses. Patients in hospitals with fewer nurses were more likely than patients in hospitals with more nurses to have complications: 47% vs. 34% had any complication, 43% vs. 28% had any medical complication, 24% vs. 9% had pulmonary insufficiency after a procedure, and 21% vs. 13% were reintubated (P < 0.001 for all comparisons). After adjustment for patient, hospital, and surgeon characteristics, having fewer versus more ICU nurses was associated with an increased risk for any complication (relative risk, 1.7 [95% CI, 1.3 to 2.4]), any medical complication (relative risk, 2.1 [CI, 1.5 to 2.9]), pulmonary insufficiency after procedure (relative risk, 4.5 [CI, 2.9 to 6.9]) and reintubation (relative risk, 1.6 [CI, 1.1 to 2.5]).
Conclusion:
Having fewer ICU nurses per patient is associated with increased risk for respiratory-related complications after abdominal aortic surgery.