ICU nurse to patient ratio greater than 1 to 2 associated with an increased risk of complications in abdominal aortic surgery patients

Introduction: We previously reported having an ICU nurse to patient ratio less than 1 to 2 during the day was associated with a 49% mean increase in ICU LOS for patients who had abdominal aortic surgery in Maryland 1994 to 1996. We hypothesized that this increase in ICU LOS is due to an increase risk of complications. Methods: We analyzed hospital discharge data on all patients in non-federal acute care hospitals in Maryland who had a principal procedure code for abdominal aortic surgery from 1/94-12/96 (N = 2987). We obtained information on ICU organizational characteristics by surveying ICU medical directors at the 46 Maryland hospitals that performed abdominal aortic surgery. Thirty-nine (85%) of the ICU directors completed this survey. The primary outcomes were risk of specific medical and surgical complications. Using multilevel modeling with logistic regression and adjusting for patient demographic characteristics, comorbid diseases, severity of illness, and surgeon and hospital volume, we evaluated the association between complications and having a nurse to patient greater than 1 to 2. Results: 2128 patients at 31 hospitals had an ICU nurse to patient ratio less than 1 to 2 while 478 patients at 7 hospitals had a nurse to patient ratio greater than 1 to 2. The median ICU LOS was 3 days for those hospitals with a nurse to patient ratio greater than 1:2 versus 2 days for those less than 1:2. In unadjusted analysis, pulmonary insufficiency after a procedure (Odds Ratio [OR] 3.1; 95% Confidence interval 2.4-4.0), cardiac complications after a procedure (OR 1.5; CI 1.1-1.9), and reintubation (OR 1.6; CI 1.3-2.1) were associated with having an ICU nurse to patient ratio greater than 1 to 2 during the day. In adjusted analysis, pulmonary insufficiency after procedure (OR 4.4; CI 1.5-13.3), and reintubation (OR 2.1;CI 1.0-4.6) were associated with having an ICU nurse to patient ratio greater than 1 to 2 during the day. Conclusion: Having an ICU nurse to patient ratio greater than 1 to 2 during to day is associated with an increase risk of several specific complications after abdominal aortic surgery and likely leads to an increased ICU LOS.