Role of storage time of red blood cells on microcirculation and tissue oxygenation in critically ill patients.

Purpose Of Review: To review the current literature on the role of storage time of transfused red blood cells on microcirculation and tissue oxygenation in critically ill patients.

Recent Findings: The actual target of transfusion of red blood cells is the maintenance of adequate tissue oxygenation. Recent studies suggest that, besides hemoglobin concentration, mixed or central venous oxygen saturation may also be used as surrogate markers for the estimation of transfusion requirement. However, variables reflecting the concrete target of transfusion, that is tissue oxygenation, appear to be more suitable in this regard. In addition, there is an increasing body of evidence on adverse effects of transfusion of--primarily older--red blood cells on tissue oxygenation and microcirculation. This might be explained, at least in part, by so-called storage lesions, which commence immediately after donation of blood and aggravate over time.

Summary: Large-scale prospective randomized trials are needed to explicitly clarify the role of new transfusion triggers, such as tissue oxygenation, and the impact of storage lesions of packed red blood cells on tissue oxygenation and--more important--on clinical outcomes in different patient populations.