Timing of Onset, Burden, and Postdischarge Mortality of Persistent Critical Illness in Scotland, 2005–2014: A Retrospective, Population-Based, Observational Study

Objectives: We aimed to understand the prevalence, timing of onset, resource use, and long-term outcomes of patients who developed persistent critical illness in a national dataset. Design: Retrospective cohort. Using a physiologic risk adjustment model from ICU admission, we examined the relative ability of acute (related to reason for ICU presentation) and antecedent (demographics, comorbidities) characteristics to discriminate hospital mortality models. Persistent critical illness was defined as the point during an ICU stay when, at the population-level, patients' acute diagnoses and physiologic disturbance are no longer more accurate at discriminating who survives than are baseline demographics and comorbidity. We examined the change across ICU stay in the relative discrimination of those characteristics, and short-term (in-hospital and 30 d after admission) and medium-term (90 d after admission) survival. Finally, we analyzed the changes in the population definition of persistent critical illness over time. Setting: Patients admitted as level 3 to Scottish ICUs between 2005 and 2014. Patients: Seventy-two-thousand two-hundred fifty-three adult level 3 ICU admissions in 23 ICUs across Scotland. Interventions: None. Measurements and Main Results: The onset of persistent critical illness, occurs at an average of 5.0 days (95% CI, 3.9-6.4 d) across this dataset. The crossing point increased across the decade, by an average of 0.36 days (95% CI, 0.22-0.50 d) per year. In this dataset, 24,425 (33.8%) remained in the ICU long enough to meet this greater than 5-day definition of persistent critical illness. The care of such patients involved 72.3% ICU days used by any level 3 patient; 46.5% of all Scottish ICU bed-days were after day 5. Although rates of 30 days after admission survival rose dramatically during the decade under study, these rates were similar for those with shorter or longer ICU stays, as were the rates of 90-day survival among those who survived at least 30 days. Conclusions: Persistent critical illness occurred in one in three ICU patients in Scotland. These minority of patients accounted for disproportionate hospital resources but did not have worse 30- or 90-day postadmission survival.