Do Blood Transfusions Increase ARDS Risk?

Early transfusion of more than five units of packed red blood cells (PRBCs) may be an independent predictor of ARDS in trauma patients, according to researchers in the February Anesthesiology.

“Indiscriminate use of blood products adds significant risk to the patient,” corresponding author John D. Lang Jr, MD, Associate Professor of Anesthesiology and Pulmonary and Critical Care Medicine at the University of Washington School of Medicine in Seattle, told Pulmonary Reviews. “Systems should be implemented to facilitate and oversee evidence-based transfusion practices, if at all possible.”

A DOSE-DEPENDENT RELATIONSHIP

In a retrospective analysis, Dr. Lang—along with Onuma Chaiwat, MD, also from the University of Washington School of Medicine, and colleagues—ascertained how many units of PRBCs (ie, none, one to five, six to 10, or > 10) were used in transfusions of trauma patients within 24 hours of hospital admission and assessed ARDS outcome. The investigators used data from the National Study on Costs and Outcomes of Trauma in conjunction with the Harborview Injury Prevention and Research Center. Patients were included on the basis of age (18 to 84) and trauma severity (ie, at least one injury with Abbreviated Injury Scale score ≥ 3).

Consistent with the American-European Consensus Conference, patients were diagnosed with ARDS if they had a PaO₂/FiO₂ of less than 200 mm Hg, bilateral infiltrates on their frontal chest radiograph, and pulmonary wedge pressure of 18 mm Hg or lower, or lack of clinical evidence of left atrial hypertension. Patients were deemed to have pneumonia if they had radiologic and clinical evidence of the disease, as well as bacteriologic confirmation, all within three days of presentation.

In 14,070 trauma patients whose data was included in this analysis, 521 (4.6%) developed ARDS, of which 331 (63.5) received early PRBCs transfusion. “Patients who developed ARDS received significantly greater quantities of PRBCs during the first 24 hours after admission” than patients who did not develop ARDS (6.0 vs 1.1 units, respectively), the investigators observed. Independent predictors for ARDS were mean new injury severity score, thoracic injury, polytrauma, pneumonia, receiving more than five units of fresh frozen plasma, and receiving six to 10 units of PRBCs.

Multivariate analysis showed that compared with patients who did not receive PRBCs, patients who received six to 10 units of PRBCs and those who received more than 10 units were at a higher risk of ARDS (adjusted odds ratio [OR], 2.48 and 2.62, respectively). After adjustment for covariates, transfusion of PRBCs within 24 hours of hospitalization remained significant for ARDS (adjusted OR, 1.06).

“Each unit of PRBCs transfused early after admission increased the risk of ARDS by 6%,” the researchers pointed out. “Conservative transfusion strategies that decrease PRBC exposure by even one unit may be warranted to reduce the risk of ARDS in injured patients.”

In-hospital mortality rates were higher for patients with higher early PRBC transfusion rates: specifically, 15.1% for patients who received more than 10 units, 11.6% for those with six to 10 units, 7.3% for those with one to five units, and 3.8% for patients who did not undergo PRBC transfusion. After adjustment, a multivariate analysis revealed a significant association between the number of units of PRBCs and hospital mortality (OR, 1.05).

WEIGHING THE RISKS OF TRANSFUSION THERAPY

The lack of data on the timing of ARDS onset beyond the diagnosis that occurred during hospitalization was a limitation of their study, the authors noted. “Consequently, we cannot separate cases of transfusion-related acute lung injury from ARDS using the consensus definition and determine the association between early transfusion and late onset of ARDS.” Other limiting factors included the lack of data available on the timing of the onset of pneumonia, the inability to extrapolate results to other age-groups, and lack of donor blood information.

“Our publication is not definitive,” Dr. Lang asserted, “but what we hope is that it serves as a cautionary note—each decision to transfuse blood products brings with it tangible risks to an already high-risk patient.” In the meantime, he urged clinicians to be driven by data when considering PRBC transfusions in trauma patients at risk. “Most health care systems involved in caring for polytrauma patients have become very efficient in turning around tests that serve as transfusion triggers, such as complete blood counts and coagulation profiles,” he acknowledged.

“In light of inconsistent improvement in tissue oxygenation demonstrated with transfused PRBCs and the unproven benefit of using fresh frozen plasma to correct coagulation tests, all critical care clinicians should have a compelling physiologic reason to transfuse each individual unit of PRBCs or fresh frozen plasma to critically ill patients, especially if ARDS risk factors are present,” commented Alexander B. Benson, MD, and Marc Moss, MD, both from the Division of Pulmonary Sciences and Critical Care Medicine at the University of Colorado Denver and Health Sciences Center in Aurora, in an accompanying editorial.

“Future randomized clinical trials will be necessary to confirm the important results of [this study] so that the use of less blood products during the initial resuscitation of trauma victims actually decreases the risk of developing ARDS,” they concluded.

—Frederique H. Theuvenin

Suggested Reading
Benson AB, Moss M. Trauma and acute respiratory distress syndrome: weighing the risks and benefits of blood transfusions. Anesthesiology. 2009;110(2):216-217.
Chaiwat O, Lang JD, Vavilala MS, et al. Early packed red blood cell transfusion and acute respiratory distress syndrome after trauma. Anesthesiology. 2009;110(2):351-360.

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