Association of Intensive Care Unit Admission With Mortality Among Older Patients With Pneumonia

Abstract

Importance: Among patients whose need for intensive care is uncertain, the relationship of intensive care unit (ICU) admission with mortality and costs is unknown.

Objective: To estimate the relationship between ICU admission and outcomes for elderly patients with pneumonia.

Design, setting, and patients: Retrospective cohort study of Medicare beneficiaries (aged >64 years) admitted to 2988 acute care hospitals in the United States with pneumonia from 2010 to 2012.

Exposures: ICU admission vs general ward admission.

Main outcomes and measures: Primary outcome was 30-day all-cause mortality. Secondary outcomes included Medicare spending and hospital costs. Patient and hospital characteristics were adjusted to account for differences between patients with and without ICU admission. To account for unmeasured confounding, an instrumental variable was used-the differential distance to a hospital with high ICU admission (defined as any hospital in the upper 2 quintiles of ICU use).

Results: Among 1,112,394 Medicare beneficiaries with pneumonia, 328,404 (30%) were admitted to the ICU. In unadjusted analyses, patients admitted to the ICU had significantly higher 30-day mortality, Medicare spending, and hospital costs than patients admitted to a general hospital ward. Patients (n = 553,597) living closer than the median differential distance (<3.3 miles) to a hospital with high ICU admission were significantly more likely to be admitted to the ICU than patients living farther away (n = 558,797) (36% for patients living closer vs 23% for patients living farther, P < .001). In adjusted analyses, for the 13% of patients whose ICU admission decision appeared to be discretionary (dependent only on distance), ICU admission was associated with a significantly lower adjusted 30-day mortality (14.8% for ICU admission vs 20.5% for general ward admission, P = .02; absolute decrease, -5.7% [95% CI, -10.6%, -0.9%]), yet there were no significant differences in Medicare spending or hospital costs for the hospitalization.

Conclusions and relevance: Among Medicare beneficiaries hospitalized with pneumonia, ICU admission of patients for whom the decision appeared to be discretionary was associated with improved survival and no significant difference in costs. A randomized trial may be warranted to assess whether more liberal ICU admission policies improve mortality for patients with pneumonia.

Figure

Instrumental Variable Subgroup and Sensitivity Analyses for 30-Day Mortality Among Elderly Patients With Pneumonia Admitted to the ICU vs General Ward ICU indicates intensive care unit; ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification. With exception of the inverse probability weighting estimate, all models used an instrumental variable to adjust for all variables in Table 1 and Table 2 in addition to all 29 individual Elixhauser comorbidities and clustering of patients within hospitals. The regression models excluded 11 703 patients (1%) due to missing differential distance (n = 5166), admission source (n = 4053), urban/rural (n = 2430), pneumonia volume (n = 107). The Angus organ failure score identifies severity of illness by patient organ failures derived from the administrative record with a maximum score of 6. Higher scores indicate more organ failures. Details of the inverse probability weighting estimate can be found in eAppendix 2 in the Supplement. The severely ill subgroup excluded individuals with shock (ICD-9-CM: 458, 785.5–785.59, 958.4, 998.0), cardiac or respiratory arrest (ICD-9-CM: 427.5, 799.1), cardiopulmonary resuscitation (ICD-9-CM: 99.60, 99.63), or invasive or noninvasive mechanical ventilation (ICD-9-CM: 96.7, 96.70, 96.71, 96.72, 93.90). Error bars represent 95%CIs for absolute mortality differences (ICU vs general ward) for all models.