Critically ill patients are frequently transfused with red blood cell (RBC) units with the predominant intention to increase arterial oxygen content and thus oxygen delivery to the tissues.

To date, RBC transfusions have been proven effective in patients with profound anaemia or circulatory shock. However, the impact of the storage process and the so-called storage lesion on oxygen-carrying properties and, hence, the efficacy of RBC transfusion regarding tissue oxygenation are much debated at present. Alterations of RBC physiology have been comprehensively described ex vivo. Reduced deformability, increased adhesiveness and aggregability of stored RBC impair their rheological properties; anaerobic cellular metabolism with reduced contents of 2,3 bisphosphoglycerate and adenosine triphosphate (ATP) increases oxygen affinity and impairs oxygen release to the tissues.

This study aims to monitor the effect RBC transfusion has on the regional cerebral oxygen saturation (rSO2) of critically ill patients. rSO2 will be measured indirectly, using near infrared spectroscopy (NIRS) . Patients will be monitored once it looms that they might require RBC transfusion. The monitoring is continued for the time of transfusion and the hours afterwards.

Inclusion Criteria:

• expected requirement of RBC transfusion
• 18 yrs and older

Exclusion Criteria:

• severe traumatic brain injury (Glasgow coma scale < 9), subarachnoid hemorrhage (Hunt and Hess scale ≥ 3) or intracranial hemorrhage
• cerebral ischaemia
• active bleeding
• patients necessitating ongoing resuscitation
• deficient signal of rSO2 impeding its proper valuation

Critically ill patients requiring haemotherapy