To evaluate the associations between strained ICU capacity and patient outcomes.Methods:
Multi-center population-based cohort study of nine integrated ICUs in Alberta, Canada. Path-analysis modeling was adopted to investigate direct and indirect associations between strain (available beds ≤1; occupancy ≥95%) and outcomes. Mixed-effects multivariate regression was used to measure the association between strain and acuity (APACHE II score), and both acuity and strain measures on ICU mortality and length of stay.Results:
12,265 admissions comprise the study cohort. Available beds ≤1 and occupancy ≥95% occurred for 22.3% and 17.0% of admissions. Lower bed availability was associated with higher APACHE II score (p < 0.0001). The direct effect of ≤1 available beds at ICU admission on ICU mortality was 11.6% (OR 1.116; 95% CI, 0.995–1.252). Integrating direct and indirect effects resulted in a 16.5% increased risk of ICU mortality (OR 1.165; 95% CI, 1.036–1.310), which exceeded the direct effect by 4.9%. Findings were similar with strain defined as occupancy ≥95%. Strain was associated with shorter ICU stay, primarily mediated by greater acuity.Conclusions:
Strained capacity was associated with increased ICU mortality, partly mediated through greater illness acuity. Future work should consider both the direct and indirect relationships of strain on outcomes.