Association of Intensive Care Unit Patient-to-Clinician Ratios with Mortality Across Two U.S. Health Systems

Rationale The association of interprofessional team member workload with intensive care unit (ICU) outcomes is understudied. Objectives To evaluate the association of patient-to-intensivist ratio (PIR), patient-to-respiratory therapist ratio (PRTR), and patient–to–clinical pharmacist ratio (PpharmR) with hospital mortality. Methods We conducted a retrospective study of adults admitted from the emergency department to an ICU with acute respiratory failure or sepsis within two U.S. healthcare systems (2013–2018). Our primary exposures were patient-to-clinician ratios (PIR, PRTR, and PpharmR) averaged over the ICU stay; our primary outcome was hospital mortality. We used multivariable mixed-effects regression, with patient-to-clinician ratios modeled as restricted cubic splines (four knots). We primarily considered each exposure separately, then included all ratios together. Results Our cohort included 45,036 patients (mean age, 66.0 [standard deviation, 16.6] years; 23,420 [52.0%] men) across 27 ICUs within 24 hospitals. Of these, 29,326 (65.1%) had acute respiratory failure, 32,434 (72.0%) had sepsis, and 9,675 (21.5%) died in the hospital. The average PIR was 9.3 (standard deviation, 3.6), and the average PRTR was 7.9 (standard deviation, 3.2); the average PpharmR was 15.0 (standard deviation, 5.5) among patients (n = 8,950 of 45,036) in ICUs with clinical pharmacists (n = 8 of 27). We found no significant association between average daily PIR (Wald test for all spline terms: P = 0.24) or PRTR (P = 0.18) and hospital mortality in the full cohort; similarly, among patients in ICUs with pharmacists, no significant association of PpharmR with mortality was observed (P = 0.08). Models including ratios together yielded similar null results. Conclusions We did not identify an association of any average daily patient-to-clinician ratio with hospital mortality for U.S. ICU patients with sepsis or respiratory failure.