Hospital Volume-Outcome Relationships Among Medical Admissions to ICUs

doi:10.1378/chest.128.3.1682

Chest

Volume 128, Issue 3, September 2005, Pages 1682-1689

https://doi.org/10.1378/chest.128.3.1682 Get rights and content

Background

Positive relationships between hospital volume and outcomes have been demonstrated for several surgeries and medical conditions. However, little is known about the volume-outcome relationship in patients admitted to medical ICUs.

Objective

To determine the relationship between hospital volume and risk-adjusted in-hospital mortality for patients admitted to ICUs with respiratory, neurologic, and GI disorders.

Design

Retrospective cohort study.

Setting

Twenty-nine hospitals in a single metropolitan area.

Patients

Adult ICU admissions from 1991 through 1997.

Methods

Using Cox proportional hazards models, we compared in-hospital mortality between tertiles of hospital volume (high, medium, and low) for respiratory (n = 16,949), neurologic (n = 13,805), and GI (n = 12,881) diseases after adjusting for age, gender, admission severity of illness, admitting diagnosis, and source. Severity of illness was measured using the APACHE (acute physiology and chronic health evaluation) III methodology.

Results

Among respiratory and neurologic ICU admissions, hazard ratios were similar (p ≥ 0.05) in patients in low-, medium-, and high-volume hospitals. However, among GI diagnoses, risk of mortality was lower in high-volume hospitals, relative to low-volume hospitals (hazard ratio, 0.68; 95% confidence interval [CI], 0.54 to 0.85; p < 0.001), and was somewhat lower in medium-volume hospitals (hazard ratio, 0.83; 95% CI, 0.68 to 1.01; p = 0.06). Among subgroups based on severity of illness, high-volume hospitals had lower mortality, relative to low-volume hospitals, among sicker patients (APACHE III score > 57) in the respiratory cohort (hazard ratio, 0.77; 95% CI, 0.59 to 0.99) and the GI cohort (hazard ratio, 0.67; 95% CI, 0.53 to 0.85).

Conclusions

Associations between ICU volume and risk-adjusted mortality were significant for patients with GI diagnoses and for sicker patients with respiratory diagnoses. However, associations were not significant for patients with neurologic diagnoses. The lack of a consistent volume-outcome relationship may reflect unmeasured patient complexity in higher-volume hospitals, relative standardization of care across ICUs, or lack of efficacy of some accepted ICU processes of care.

Section snippets

Materials and Methods

The current study represented a secondary analysis of data that was originally collected through Cleveland Health Quality Choice, a regional initiative to measure hospital performance in 29 hospitals in Northeast Ohio. Within these hospitals, data were collected on 196,097 consecutive admissions to 44 medical, mixed medical and surgical, surgical, and neurosurgical ICUs during the period March 1991 to March 1997. Exclusion criteria have been previously described¹⁸ and included patients < 16

Results

The demographic characteristics of patients in the three cohorts are shown in Table 1. The mean age of patients was generally lower among patients in high-volume hospitals for all three diagnoses. Gender distributions differed only for patients with GI diagnoses. Patients in high-volume hospitals were less likely to be admitted from the emergency department (ED) and were more likely to be admitted from other acute-care hospitals or from other hospital floors. Mean APACHE III scores were highest

Discussion

This is the first study to our knowledge to examine the relationship between hospital volume and outcome among medical admissions to adult ICUs. After adjusting for admission severity of illness using a robust physiologic-based measure, the study yielded mixed results. While there were no significant overall differences in mortality for patients with pulmonary and neurologic diagnoses, we did find lower mortality in high-volume hospitals for patients with GI diagnoses. Moreover, mortality was

References (31)

Mc GrathPD et al.
Operator volume and outcomes in 12,998 percutaneous coronary interventions: Northern New England Cardiovascular Disease Study Group
J Am Coll Cardiol
(1998)
SirioCA et al.
Community-wide assessment of intensive care outcomes using a physiologically based prognostic measure: implications for critical care delivery from Cleveland Health Quality Choice
Chest
(1999)
KnausWA et al.
The APACHE III prognostic system: risk prediction of hospital mortality for critically ill hospitalized adults
Chest
(1991)
VincentJL
Need for intensivists in intensive care units
Lancet
(2000)
Interpreting the volume-outcome relationship in the context of health care quality: workshop summary.2000 Institute of...
MahadevaR et al.
Clinical outcome in relation to care in centers specializing in cystic fibrosis: cross sectional study
BMJ
(1998)
LuftHS et al.
Should operations be regionalized? The empirical relation between surgical volume and mortality
N Engl J Med
(1979)
FloodAB et al.
Does practice make perfect? Part I: The relation between hospital volume and outcomes for selected diagnostic categories
Med Care
(1984)
HannanEL et al.
Coronary angioplasty volume-outcome relationships for hospitals and cardiologists
JAMA
(1997)
JollisJG et al.
Relationship between physician and hospital coronary angioplasty volume and outcome in elderly patients
Circulation
(1997)

HoggRS et al.

Relation between hospital HIV/AIDS caseload and mortality among persons with HIV/AIDS in Canada

Clin Invest Med

(1998)

StoneVE et al.

The relation between hospital experience and mortality for patients with AIDS

JAMA

(1992)

BennettCL et al.

The relation between hospital experience and in-hospital mortality for patients with AIDS-related PCP

JAMA

(1989)

BirkmeyerJD et al.

Hospital volume and surgical mortality in the United States

N Engl J Med

(2002)

DrussBG et al.

The volume-quality relationship of mental health care: does practice make perfect?

Am J Psychiatry

(2004)

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Citation Excerpt :
This variation of the volume-outcome relationship may be related to the complexity of diagnosis and management in these conditions. Durairaj et al15 found that in comparison with a nonselected population of patients who were mechanically ventilated, only the most severe (ie, with an APACHE [Acute Physiology and Chronic Health Evaluation] III score > 57) benefited from high-volume hospitals. Glance et al18 showed that only critically ill patients with a Simplified Acute Physiology Score (SAPS) 2 ≥ 30 benefited from a high-volume center.
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Overall, 29 of the studies (63%) reported a statistically significant association between higher admission volume and improved outcomes. The magnitude of the association (mortality OR between the lowest vs highest stratum of volume centers), as well as the thresholds used to characterize high volume, varied across clinical conditions. Critically ill patients with cardiovascular (n = 7, OR = 1.49 [1.11-2.00]), respiratory (n = 12, OR = 1.20 [1.04-1.38]), severe sepsis (n = 4, OR = 1.17 [1.03-1.33]), hepato-GI (n = 3, OR = 1.30 [1.08-1.78]), neurologic (n = 3, OR = 1.38 [1.22-1.57]), and postoperative admission diagnoses (n = 3, OR = 2.95 [1.05-8.30]) were more likely to benefit from admission to higher-volume centers compared with lower-volume centers. Studies that controlled for ICU or hospital organizational factors were less likely to find a significant volume-outcome relationship than studies that did not control for these factors.
Critically ill patients generally benefit from care in high-volume centers, with more substantial benefits in selected high-risk conditions. This relationship may in part be mediated by specific ICU and hospital organizational factors.

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Chest

Clinical Investigations in Critical CareHospital Volume-Outcome Relationships Among Medical Admissions to ICUs

Background

Objective

Design

Setting

Patients

Methods

Results

Conclusions

Section snippets

Materials and Methods

Results

Discussion

J Am Coll Cardiol

Chest

Chest

Lancet

Clinical outcome in relation to care in centers specializing in cystic fibrosis: cross sectional study

BMJ

Should operations be regionalized? The empirical relation between surgical volume and mortality

N Engl J Med

Does practice make perfect? Part I: The relation between hospital volume and outcomes for selected diagnostic categories

Med Care

Coronary angioplasty volume-outcome relationships for hospitals and cardiologists

JAMA

Relationship between physician and hospital coronary angioplasty volume and outcome in elderly patients

Circulation

Relation between hospital HIV/AIDS caseload and mortality among persons with HIV/AIDS in Canada

Clin Invest Med

The relation between hospital experience and mortality for patients with AIDS

JAMA

The relation between hospital experience and in-hospital mortality for patients with AIDS-related PCP

JAMA

Hospital volume and surgical mortality in the United States

N Engl J Med

The volume-quality relationship of mental health care: does practice make perfect?

Am J Psychiatry

Clinical Investigations in Critical Care
Hospital Volume-Outcome Relationships Among Medical Admissions to ICUs