Transfusion and Skeletal Muscle Tissue Oxygenation

Anaemia is state of decreased blood oxygen carrying capacity . Acute anaemia is associated with increased tissue oxygen extraction . On the other hand, with chronic anaemia human body has time to at least partially adapt to decreased blood oxygen carrying capacity , .

Near-infrared spectroscopy (NIRS) is non-invasive method to assess tissue oxygenation (StO2) and estimate tissue haemoglobin (THb) levels . The investigators have studied skeletal muscle StO2 in critically ill patients with preserved oxygen (i.e., cardiogenic shock) and with impaired oxygen extraction (i.e., septic shock) , , . In addition to measuring resting StO2, the investigators performed vascular occlusion tests to stop arterial blood flow, to estimate oxygen consumption, and at the end of the occlusion, it was also possible to estimate vascular reactivity and maximal reperfusion capability .

Under acute blood loss in trauma patients, the skeletal muscle StO2 measured by NIRS correlates with blood haemoglobin (Hb) and delivery of oxygen, and can easily detect latent stage of haemorrhagic shock . Unexpectedly, chronically anaemic haematology patients with preserved oxygen extraction capability did not show low skeletal StO2 and THb index despite their severe anaemia, which is what would be predicted from normal physiological responses .

It is known that there are structural and functional changes to RBCs during storage. Recent study detected deleterious effects of RBC storage on microvascular responses to transfusion in stable anaemic trauma patients .

The aim of the present study was to re-challenge the current data that anaemia in chronically anaemic haematology patients is not associated with low skeletal muscle StO2, and that the age of RBCs does not influence tissue responses. The investigators investigated these aspects using improved technology NIRS devices, for deeper tissue penetration and removal of the superficial signal from the skin.