Resuscitation from hemorrhagic shock via transfusion of anaerobically stored RBCs improves outcomes

Transfusion of red blood cells (RBCs) stored anaerobically – in the absence of oxygen – is a promising technique to improve resuscitation from hemorrhagic shock, according to animal studies reported in SHOCK^®: Injury, Inflammation, and Sepsis: Laboratory and Clinical Approaches, Official Journal of the Shock Society. The journal is published in the Lippincott portfolio by Wolters Kluwer.

Resuscitation from hemorrhagic shock via transfusion of anaerobically stored RBCs recovered cardiac function, restored hemodynamic stability, and improved outcomes."

Pedro Cabrales, PhD, of University of California, San Diego, and colleagues

But more research is needed to determine whether the improved recovery seen with anaerobically stored RBCs in rats will translate into benefits for patients in hemorrhagic shock after trauma.

Current RBC 'expiration date' doesn't reflect functional outcomes

Hemorrhagic shock causes roughly half of deaths in trauma patients. Reduced oxygenation due to blood loss can rapidly lead to cardiovascular collapse, organ failure, and death. Patients in hemorrhagic shock need transfusion of large volumes of RBCs to recover blood flow, oxygenation, and hemodynamic stability.

During conventional storage – ie, refrigeration – RBCs are subject to certain types of cellular damage, called "storage lesions." Currently, the US Food and Drug Administration limits RBC storage time to 42 days, in approved solutions. That regulation is based on survival of transfused RBCs after 24 hours in healthy volunteers.

Researchers are looking at new approaches to decrease storage lesions in RBCs. "Anaerobic storage of blood has been proposed to improve the quality and uniformity of RBC units by decreasing oxidative changes occurring during storage," according to the authors.

In the experiments, rats were subjected to hemorrhagic shock and then transfused with conventionally or anaerobically stored RBCs. A third group of animals received RBCs stored anaerobically with a small amount of carbon dioxide (anaerobic/hypercapnic storage). Transfusion focused on restoring and maintaining normal blood pressure – similar to the target used in treating hemorrhagic shock in trauma patients.

Several measures of recovery improved in rats receiving anaerobically stored RBCs, compared to those receiving conventionally stored RBCs. The anaerobically stored RBCs restored blood pressure faster, at a lower volume of transfusion. Rats in the conventional storage group required transfusion of about 60 percent of normal blood volume to restore blood pressure, compared to about 30 percent in the anaerobic storage groups.

Anaerobically restored RBCs also led to better recovery of cardiac function and restoration of normal blood chemistry levels, including blood oxygenation. There were also fewer signs of organ and tissue damage in animals receiving anaerobically stored RBCs. The improvements with anerobic storage were similar with or without carbon dioxide.

Red blood cell recovery 24 hours after transfusion – the FDA-approved measure for determining RBC storage times – was similar among the three techniques. Dr. Cabrales and coauthors write, "From a functional standpoint, defining 'expiration dates' for stored RBCs in additive solutions based on 24-hour recovery is inappropriate, especially as RBC units age at different rates and 24-hour recovery does not correlate with other markers."

The researchers conclude: "These data suggest that storing RBCs anaerobically could result in better transfusion recipient outcomes." However, they emphasize the need for clinical trials to assess the effects of anaerobically stored RBC transfusion in trauma patients with hemorrhagic shock – including long-term follow-up to assess neurological function and other outcomes.