Interhospital transfer: an independent risk factor for mortality in the surgical intensive care unit

Interhospital transfer (IHT) is associated with mortality in medical and mixed intensive care units (ICUs), but few studies have examined this relationship in a surgical ICU (SICU) setting. We hypothesized that IHT is associated with increased mortality in SICU patients relative to ICU patients admitted within the hospital. We reviewed SICU and transfer center databases from a tertiary academic center over a 2-year period. Inclusion criteria included age 18 years or older and SICU admission 24 hours or greater. Demographic data, admission service, and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were captured. The primary end point was ICU mortality. Univariate logistic regression was used to test the association between variables and mortality. Factors found to be associated with mortality at P < 0.1 were entered into a multivariable model. Of 4542 admissions, 416 arrived by IHT. Compared with the non-IHT group, the IHT group was older (age 58.3 years [interquartile range, 47.8 to 70.6] vs. 57.8 years [interquartile range, 44.1 to 68.8] years, P = 0.036), sicker (APACHE II score 16.5 [interquartile range, 12 to 23] vs. 14 [interquartile range, 10 to 20], P < 0.001), and more likely to be white (82% [n = 341] vs. 69% [n = 2865], P < 0.001). Mortality rates in IHT patients were highest on the emergency surgery (18%), transplant surgery (16%), and gastrointestinal surgery (8%) services. After adjusting for age and APACHE II score, IHT remained a risk factor for ICU mortality (odds ratio, 1.60; 95% confidence interval, 1.04 to 2.45; P = 0.032) in SICU patients. Interhospital transfer is an independent risk factor for mortality in the SICU population; this risk is unevenly distributed through service lines. Further efforts to determine the cause of this association are warranted.