Intensive Care Unit Admission and Survival among Older Patients with Chronic Obstructive Pulmonary Disease, Heart Failure, or Myocardial Infarction

Abstract

Rationale: Admission to an intensive care unit (ICU) may be beneficial to patients with pneumonia with uncertain ICU needs; however, evidence regarding the association between ICU admission and mortality for other common conditions is largely unknown.

Objectives: To estimate the relationship between ICU admission and outcomes for hospitalized patients with exacerbation of chronic obstructive pulmonary disease (COPD), exacerbation of heart failure (HF), or acute myocardial infarction (AMI).

Methods: We performed a retrospective cohort study of all acute care hospitalizations from 2010 to 2012 for U.S. fee-for-service Medicare beneficiaries aged 65 years and older admitted with COPD exacerbation, HF exacerbation, or AMI. We used multivariable adjustment and instrumental variable analysis to assess each condition separately. The instrumental variable analysis used differential distance to a high ICU use hospital (defined separately for each condition) as an instrument for ICU admission to examine marginal patients whose likelihood of ICU admission depended on the hospital to which they were admitted. The primary outcome was 30-day mortality. Secondary outcomes included hospital costs.

Results: Among 1,555,798 Medicare beneficiaries with COPD exacerbation, HF exacerbation, or AMI, 486,272 (31%) were admitted to an ICU. The instrumental variable analysis found that ICU admission was not associated with significant differences in 30-day mortality for any condition. ICU admission was associated with significantly greater hospital costs for HF ($11,793 vs. $9,185, P < 0.001; absolute increase, $2,608 [95% confidence interval, $1,377-$3,840]) and AMI ($19,513 vs. $14,590, P < 0.001; absolute increase, $4,922 [95% confidence interval, $2,665-$7,180]), but not for COPD.

Conclusions: ICU admission did not confer a survival benefit for patients with uncertain ICU needs hospitalized with COPD exacerbation, HF exacerbation, or AMI. These findings suggest that the ICU may be overused for some patients with these conditions. Identifying patients most likely to benefit from ICU admission may improve health care efficiency while reducing costs.

Keywords: chronic obstructive pulmonary disease; heart failure; instrumental variable; intensive care; myocardial infarction.

Figure 1.

Estimation of the marginal patient population. For each condition, the marginal patient population was estimated by the method of Newhouse and McClellan (40). Marginal patients were admitted to the intensive care unit (ICU) solely because they lived proximally to a high-ICU-use hospital. After stratifying patients by each condition’s median differential distance, patients who were admitted to the general ward, despite living close to a high-ICU-use hospital, were considered patients who would always be admitted to the general ward, regardless of hospital. Patients who were admitted to the ICU, despite living far from a high-ICU-use hospital, were considered patients who would always be admitted to the ICU, regardless of hospital. The difference between these two groups provides the estimated marginal patient population, those who might be admitted to the ICU or to the general ward depending on the hospital. AMI = acute myocardial infarction; COPD = chronic obstructive pulmonary disease; HF = heart failure.