NoBlood

Jan B. Wade · #1 (**permalink**) 10-13-2005, 06:27 PM

http://www.medscape.com/viewarticle/459236

Red Cell Transfusion "Trigger": A Review

Posted 09/04/2003

Marian Petrides, MD

Abstract and Introduction

Abstract

Despite the publication of several consensus guidelines that set forth recommendations for the transfusion of red cells, actual clinical practice continues to vary widely. Animal data and studies in human volunteers and patients support a red cell transfusion threshold of 7 to 8 g/dl in most patients. However, conflicting data, particularly in cardiac patients and in the elderly, suggest that it may be impossible to define a single red cell "trigger" for all patients. A well-designed, randomized, controlled trial is still needed to establish a safe threshold for red cell transfusion in adults with coronary artery disease.

Introduction

Like any other drug, it is axiomatic that red cells should be administered only when clinically necessary and then in the minimal effective dose. However, because blood components are biologic products, indications for their use and optimal dosing have remained elusive. In the past decade, a number of guidelines have been promulgated for the transfusion of red cells.^[1-6] Although there is general agreement that red cells should be transfused only to improve oxygen-carrying capacity, considerable variability in clinical transfusion practice nonetheless remains.^[7-9] These consensus guidelines suggest that transfusion to a hemoglobin level above 10 g/dl is rarely indicated, that when the hemoglobin falls below 7 to 8 g/dl even healthy young patients may require transfusion, and that normovolemic patients with symptomatic anemia should undergo transfusion regardless of hemoglobin concentration.^[1-6] When the hemoglobin falls to between 7 and 10 g/dl in an asymptomatic patient, however, decision making with regard to whether to transfuse becomes murkier.

The quest to define a minimum threshold hemoglobin concentration at which patients achieve significant (net) benefit from transfusion of red cells is driven by patient safety concerns. First is the desire to minimize exposure to infectious agents, primarily (although not exclusively) transfusion-transmissible viruses. As viral risk is lowered, however, more attention is focused on red cell supply issues and the potential that red cell demand may outpace the supply of units. In addition, there is concern that transfusion-related immunomodulation might result in immunosuppression, increasing the likelihood of infection and/or cancer recurrence in red cell recipients.^{[10, 11]} Another issue to consider is that relatively high hemoglobin levels may in fact be detrimental to the patient, resulting in microcirculatory complications.^[12-14]