Association Of A Novel Index Of Hospital Capacity Strain With Admission To Intensive Care Units

Abstract [from journal]

Rationale: Prior approaches to measuring healthcare capacity strain have been constrained by using individual care units, limited metrics of strain, or general, rather than disease-specific, populations.

Objectives: We sought to develop a novel composite strain index and measure its association with ICU admission decisions and hospital outcomes.

Methods: Using more than 9.2 million acute care encounters from 27 Kaiser Permanente Northern California and Penn Medicine hospitals from 2013 to 2018, we deployed multivariable ridge logistic regression to develop a composite strain index based on hourly measurements of 22 capacity strain metrics across emergency departments, wards, step-down units, and ICUs. We measured the association of this strain index with ICU admission and clinical outcomes using multivariable logistic and quantile regression.

Results: Among high-acuity patients with sepsis (n = 90,150) and acute respiratory failure (n = 45,339) not requiring mechanical ventilation or vasopressors, strain at the time of emergency department disposition decision was inversely associated with the probability of ICU admission (sepsis: adjusted probability 29.0% [95% confidence interval 28.0-30.0%] at the lowest to 9.3% [8.7-9.9%] at the highest strain index decile; acute respiratory failure: 47.2% [45.6-48.9%] at the lowest to 12.1% [11.0-13.2%] at the highest decile; p < 0.001 at all levels). Among subgroups of patients who almost always or never went to the ICU, strain was not associated with hospital length of stay, mortality, or discharge disposition (all p ≥ 0.13). Strain was also not meaningfully associated with patient characteristics.

Conclusions: Hospital strain, measured by a novel composite strain index, is strongly associated with ICU admission among patients with sepsis and/or acute respiratory failure. This strain index fulfills the assumptions of a strong within-hospital instrumental variable for quantifying the net benefit of admission to the ICU for patients with sepsis and/or acute respiratory failure.