Evaluation of RBC Transfusion Practice in Adult ICUs and the Effect of Restrictive Transfusion Protocols on Routine Care

Abstract

Objective: Research supports the efficacy and safety of restrictive transfusion protocols to reduce avoidable RBC transfusions, but evidence of their effectiveness in practice is limited. This study assessed whether admission to an ICU with an restrictive transfusion protocol reduces the likelihood of transfusion for adult patients.

Design: Observational study using data from the multicenter, cohort Critical Illness Outcomes Study. Patient-level analyses were conducted with RBC transfusion on day of enrollment as the outcome and admission to an ICU with a restrictive transfusion protocol as the exposure of interest. Covariates included demographics, hospital course (e.g., lowest hematocrit, blood loss), severity of illness (e.g., Sequential Organ Failure Assessment score), interventions (e.g., sedation/analgesia), and ICU characteristics (e.g., size). Multivariable logistic regression modeling assessed the independent effects of restrictive transfusion protocols on transfusions.

Setting: Fifty-nine U.S. ICUs.

Patients: A total of 6,027 adult ICU patients.

Interventions: None.

Measurements and main results: Of the 59 study ICUs, 24 had an restrictive transfusion protocol; 2,510 patients (41.6%) were in an ICU with an restrictive transfusion protocol. The frequency of RBC transfusion among patients with severe (hematocrit, < 21%), moderate (hematocrit, 21-30%), and mild (hematocrit, > 30%) anemia in restrictive transfusion protocol ICUs was 67%, 19%, and 4%, respectively, compared with 60%, 14%, and 2% for those in ICUs without an restrictive transfusion protocol. Only 27% of transfusions were associated with a hematocrit less than 21%. Adjusting for confounding factors, restrictive transfusion protocols independently reduced the odds of transfusion in moderate anemia with an odds ratio of 0.59 (95% CI, 0.36-0.96) while demonstrating no effect in mild (p = 0.93) or severe (p = 0.52) anemia.

Conclusions: In this sample of ICU patients, transfusions often occurred outside evidence-based guidelines, but admission to an ICU with an restrictive transfusion protocol did reduce the risk of transfusion in moderately anemic patients controlling for patient and ICU factors. This study supports the effectiveness of restrictive transfusion protocols for influencing transfusions in clinical practice.

Figure 1

Study flow chart.

Figure 2

Unadjusted frequency of RBC transfusion by hematocrit, comparing subjects in ICUs with Restrictive Transfusion Protocols vs. ICUs without. Hematocrits (Hct) of subjects are rounded to nearest 2%. Error bars represent the Standard Error of Proportions. Vertical reference lines mark standard hematocrit transfusion thresholds of 21 and 30%, demarcating three categories of mild (Hct≥30%, n=2,770) moderate (21%≤Hct<30%, n=3,053) and severe (Hct<21%, n=331) anemia.

Figure 3

Final adjusted model for RBC transfusion by hematocrit comparing exposure to a Restrictive Transfusion Protocol(RTP) vs. not exposed, adjusting for covariates with (A) hematocrit as categorical variable and the effect of an RTP as independent in each category and (B) hematocrit as a continuous variable with spline knots at hematocrits of 21 and 30% and RTP effects assessed in each range relative to spline knots. Predicted adjusted outcomes were calculated for a patient with mean values for all other covariates. Gray band indicates 95% confidence interval for adjusted odds ratio of transfusion for an RTP. On the study day, 228 (63%) patients with a Hct <21% were transfused, 239 (32%) with Hct 21–23.9%, 152 (13.9%) with Hct 24–26.9%, 82 (7.4%) with Hct 27–29.9%, and 70 (2.6%) with Hct >30%.