Research

Anemia, transfusions and hospital outcomes among critically ill patients on prolonged acute mechanical ventilation: a retrospective cohort study

Marya D Zilberberg¹ , Lee S Stern² , Daniel P Wiederkehr² , John J Doyle² and Andrew F Shorr³

¹School of Public Health and Health Sciences, University of Massachusetts, North Pleasant Street, Amherst, Massachusetts 01003, USA

²Analytica International, Park Avenue South, New York, New York 10016, USA

³Division of Pulmonary and Critical Care Medicine, Washington Hospital Center, Irving Street Northwest, Washington, District of Columbia 20010, USA

author email corresponding author email

Critical Care 2008, 12:R60doi:10.1186/cc6885

Published:	28 April 2008

Abstract

Introduction

Patients requiring prolonged acute mechanical ventilation (PAMV) represent one-third of those who need mechanical ventilation, but they utilize two-thirds of hospital resources devoted to mechanical ventilation. Measures are needed to optimize the efficiency of care in this population. Both duration of intensive care unit stay and mechanical ventilation are associated with anemia and increased rates of packed red blood cell (pRBC) transfusion. We hypothesized that transfusions among patients receiving PAMV are common and associated with worsened clinical and economic outcomes.

Methods

A retrospective analysis of a large integrated claims database covering a 5-year period (January 2000 to December 2005) was conducted in adult patients receiving PAMV (mechanical ventilation for ≥ 96 hours). The incidence of pRBC transfusions was examined as the main exposure variable, and hospital mortality served as the primary outome, with hospital length of stay and costs being secondary outcomes.

Results

The study cohort included 4,344 hospitalized patients receiving PAMV (55% male, mean age 61.5 ± 16.4 years). Although hemoglobin level upon admission was above 10 g/dl in 75% of patients, 67% (n = 2,912) received at least one transfusion, with a mean of 9.1 ± 12.0 units of pRBCs transfused per patient over the course of hospitalization. In regression models adjusting for confounders, exposure to pRBCs was associated with a 21% increase in the risk for hospital death (95% confidence interval [CI] = 1.00 to 1.48), and marginal increases in length of stay (6.3 days, 95% CI = 5.1 to 7.6) and cost ($48,972, 95% CI = $45,581 to $52,478).

Conclusion

Patients receiving PAMV are at high likelihood of being transfused with multiple units of blood at relatively high hemoglobin levels. Transfusions independently contribute to increased risk for hospital death, length of stay, and costs. Reducing exposure of PAMV patients to blood may represent an attractive target for efforts to improve quality and efficiency of health care delivery in this population.