Blood Transfusions May Impair Endothelium-dependent Vasodilatation in Isolated Left Mammary Arterial Artery Rings and Peripheral Artery Tonometry During Coronary Artery Bypass Surgery

Introduction

Several studies have implicated red blood cell (RBC) transfusion as a risk factor for increased morbidity as well as short- and long-term mortality after coronary artery bypass graft surgery (CABG). Interestingly, this effect is most pronounced among patients undergoing isolated CABG, suggesting that a harmful mechanism of RBC transfusion is not generalizable to all types of surgical procedures but instead may be specific to those patients.

The mechanisms by which blood transfusion may contribute to organ injury, dysfunction and death remain uncertain. Besides the quantity of RBC transfusions, the quality of the product has also been associated with differences in mortality and morbidity.

The use of intraoperative cell salvage and autologous blood transfusion has become an important method of blood conservation. The main aim of autologous transfusion is to reduce the need for allogeneic blood transfusion and its associated complications. However hemolysis and high cell-free hemoglobin (fHb) contents are associated with cell washing devices that collect anticoagulated shed or recovered blood, wash and separate the RBC by centrifugation, and re-infuse the RBC.

fHb is a potent scavenger of nitric oxide (NO), which mediates endothelium-dependent vasodilation, and may therefore be responsible for microvascular perfusion disturbances (arterial spasm). Indeed endothelial dysfunction and persistent microvascular alterations are associated with organ failure and death.