Impact on mortality of prompt admission to critical care for deteriorating ward patients: an instrumental variable analysis using critical care bed strain

Abstract

PurposeTo estimate the effect of prompt admission to critical care on mortality for deteriorating ward patients.MethodsWe performed a prospective cohort study of consecutive ward patients assessed for critical care. Prompt admissions (within 4 h of assessment) were compared to a ‘watchful waiting’ cohort. We used critical care strain (bed occupancy) as a natural randomisation event that would predict prompt transfer to critical care. Strain was classified as low, medium or high (2+, 1 or 0 empty beds). This instrumental variable (IV) analysis was repeated for the subgroup of referrals with a recommendation for critical care once assessed. Risk-adjusted 90-day survival models were also constructed.ResultsA total of 12,380 patients from 48 hospitals were available for analysis. There were 2411 (19%) prompt admissions (median delay 1 h, IQR 1–2) and 9969 (81%) controls; 1990 (20%) controls were admitted later (median delay 11 h, IQR 6–26). Prompt admissions were less frequent (p < 0.0001) as strain increased from low (22%), to medium (15%) to high (9%); the median delay to admission was 3, 4 and 5 h respectively. In the IV analysis, prompt admission reduced 90-day mortality by 7.4% (95% CI 1.7–18.5%, p = 0.117) overall, and 16.2% (95% CI 1.1–31.3%, p = 0.036) for those recommended for critical care. In the risk-adjust survival model, 90-day mortality was similar.ConclusionAfter allowing for unobserved prognostic differences between the groups, we find that prompt admission to critical care leads to lower 90-day mortality for patients assessed and recommended to critical care.Electronic supplementary materialThe online version of this article (10.1007/s00134-018-5148-2) contains supplementary material, which is available to authorized users.

Discrete-Event Simulation Modeling of Critical Care Flow: New Hospital, Old Challenges

“…In general, DTOC is associated with high occupancy levels, which in turn has been shown to have detrimental effect on mortality due to the increased acuity of admitted patients ( 8 ). Our data support the previous findings that reducing congestion may improve timely access to critical care, with potentially improved patient outcomes ( 9 , 10 ). Based on our simulation data, with the planned increase first to 25 then to 28 critical care beds alone, the new hospital could still cope with the projected increase in admissions.…”

“…There is a valid argument that with increased ICU bed strain, patients are admitted in a worse physiologic status, in turn increasing their LOS ( 8 , 26 ). DES models can be configured to add this element to the simulation; however, for our current model, we could not quantify the unmet need for critical care from the available data ( 9 ). Another limitation of the data was that we only recorded how many days a patient spent at each level of care and we assumed that they move through the system with decreasing level of dependency.…”

Analysis of Benefit of Intensive Care Unit Transfer for Deteriorating Ward Patients

“…To our knowledge, this article is the first to recognize that the effectiveness of ICU care may be modified according to patient characteristics that are unmeasured and those that are measured. 17 , 20 , 21 , 22 We estimate the effectiveness of ICU transfer according to patient age and illness severity alone and combined.…”

Focus on the frail and elderly: who should have a trial of ICU treatment?

“…The trial showed a higher proportion of ICU admissions for elderly patients compared to usual care, but this practice was associated with an increased risk of long-term mortality in the intention-to-treat analysis [1,4]. In contrast, two recent observational studies using causal inference, showed the potential for short-term mortality benefit of ICU admission [7,8] in elderly patients with pneumonia [7]. The two key patient characteristics associated with poor outcomes in these studies were the presence of an underlying malignancy and disability at the time of ICU admission [2].…”