Structure, process, and annual ICU mortality across 69 centers: United States Critical Illness and Injury Trials Group Critical Illness Outcomes Study

Abstract

Objective: Hospital-level variations in structure and process may affect clinical outcomes in ICUs. We sought to characterize the organizational structure, processes of care, use of protocols, and standardized outcomes in a large sample of U.S. ICUs.

Design: We surveyed 69 ICUs about organization, size, volume, staffing, processes of care, use of protocols, and annual ICU mortality.

Setting: ICUs participating in the United States Critical Illness and Injury Trials Group Critical Illness Outcomes Study.

Subjects: Sixty-nine intensivists completed the survey.

Measurements and main results: We characterized structure and process variables across ICUs, investigated relationships between these variables and annual ICU mortality, and adjusted for illness severity using Acute Physiology and Chronic Health Evaluation II. Ninety-four ICU directors were invited to participate in the study and 69 ICUs (73%) were enrolled, of which 25 (36%) were medical, 24 (35%) were surgical, and 20 (29%) were of mixed type, and 64 (93%) were located in teaching hospitals with a median number of five trainees per ICU. Average annual ICU mortality was 10.8%, average Acute Physiology and Chronic Health Evaluation II score was 19.3, 58% were closed units, and 41% had a 24-hour in-house intensivist. In multivariable linear regression adjusted for Acute Physiology and Chronic Health Evaluation II and multiple ICU structure and process factors, annual ICU mortality was lower in surgical ICUs than in medical ICUs (5.6% lower [95% CI, 2.4-8.8%]) or mixed ICUs (4.5% lower [95% CI, 0.4-8.7%]). We also found a lower annual ICU mortality among ICUs that had a daily plan of care review (5.8% lower [95% CI, 1.6-10.0%]) and a lower bed-to-nurse ratio (1.8% lower when the ratio decreased from 2:1 to 1.5:1 [95% CI, 0.25-3.4%]). In contrast, 24-hour intensivist coverage (p = 0.89) and closed ICU status (p = 0.16) were not associated with a lower annual ICU mortality.

Conclusions: In a sample of 69 ICUs, a daily plan of care review and a lower bed-to-nurse ratio were both associated with a lower annual ICU mortality. In contrast to 24-hour intensivist staffing, improvement in team communication is a low-cost, process-targeted intervention strategy that may improve clinical outcomes in ICU patients.