The CRIT Study: Anemia and Blood Transfusion in the Critically Ill - Current Clinical Practice in the United States

Howard L. Corwin, MD; Andrew Gettinger, MD; Ronald G. Pearl, MD, PhD; Mitchell P. Fink, MD; Mitchell M. Levy, MD; Edward Abraham, MD; Neil R. MacIntyre, MD; M. Michael Shabot, MD; Mei-Sheng Duh, MPH, ScD; Marc J. Shapiro, MD


Crit Care Med. 2004;32(1) 

In This Article

Abstract and Introduction

Objective: To quantify the incidence of anemia and red blood cell (RBC) transfusion practice in critically ill patients and to examine the relationship of anemia and RBC transfusion to clinical outcomes.
Design: Prospective, multiple center, observational cohort study of intensive care unit (ICU) patients in the United States. Enrollment period was from August 2000 to April 2001. Patients were enrolled within 48 hrs of ICU admission. Patient follow-up was for 30 days, hospital discharge, or death, whichever occurred first.
Setting: A total of 284 ICUs (medical, surgical, or medical-surgical) in 213 hospitals participated in the study.
Patients: A total of 4,892 patients were enrolled in the study.
Measurements and Main Results: The mean hemoglobin level at baseline was 11.0 ± 2.4 g/dL. Hemoglobin level decreased throughout the duration of the study. Overall, 44% of patients received one or more RBC units while in the ICU (mean, 4.6 ± 4.9 units). The mean pretransfusion hemoglobin was 8.6 ± 1.7 g/dL. The mean time to first ICU transfusion was 2.3 ± 3.7 days. More RBC transfusions were given in study week 1; however, in subsequent weeks, subjects received one to two RBC units per week while in the ICU. The number of RBC transfusions a patient received during the study was independently associated with longer ICU and hospital lengths of stay and an increase in mortality. Patients who received transfusions also had more total complications and were more likely to experience a complication. Baseline hemoglobin was related to the number of RBC transfusions, but it was not an independent predictor of length of stay or mortality. However, a nadir hemoglobin level of <9 g/dL was a predictor of increased mortality and length of stay.
Conclusions: Anemia is common in the critically ill and results in a large number of RBC transfusions. Transfusion practice has changed little during the past decade. The number of RBC units transfused is an independent predictor of worse clinical outcome.

The value of red blood cell (RBC) transfusion in clinical practice was unchallenged through most of this century.[1] However, in the early 1980s, transfusion practice began to come under systematic scrutiny.[2,3,4] Initially, the primary concerns related to the risks of transfusion-related infections, particularly human immunodeficiency virus and hepatitis. However, the issues are now much more complex. The examination and debate over RBC transfusion risks during the last two decades has led to a more critical examination of transfusion benefits. Further complicating these issues has been the growing shortage of RBCs available for transfusion.

The issues surrounding RBC transfusion are particularly important in the critically ill. Anemia is very common in the critically ill; almost 95% of patients admitted to the intensive care unit (ICU) have a hemoglobin level below normal by ICU day 3.[5] As a consequence of this anemia, critically ill patients receive a large number of RBC transfusions. More than 50% of patients admitted to the ICU receive RBC transfusions during their ICU stay.[6,7] In those patients with an ICU length of stay (LOS) of >1 wk, the proportion of patients transfused increases to 85%.[6] In a survey of ICUs across the United States conducted a decade ago, 14% of ICU patients on the day of the survey received at least one unit of transfused RBCs.[8]

Recent data suggest that many critically ill patients can tolerate hemoglobin levels as low as 7 g/dL and that a "liberal" RBC transfusion strategy may in fact lead to worse clinical outcomes.[9] However, a hemoglobin level of 7 g/dL represents a threshold or "trigger" for transfusion that is much lower than the level generally regarded as standard practice.[6,7] The impact of the scrutiny of transfusion practice during the last decade on current clinical practice is not known. The present study was undertaken to determine current transfusion practice in ICUs in the United States and to examine the impact of anemia and RBC transfusion on the clinical outcomes of critically ill patients.