4 Artificial oxygen carriers

Intravenous (i.v.) artificial oxygen carriers are intended to ensure adequate tissue oxygenation in critical anaemia (haemorrhagic shock, profound normovolaemic haemodilution). As regards their efficacy, both synthetic haemoglobin solutions and perfluorocarbon (PFC) emulsions, are suited to preserve tissue oxygenation after nearly complete blood exchange in various experimental models. Safety aspects, however, have so far limited the administration of artificial oxygen carriers. While pharmacological properties of synthetic haemoglobin solutions facilitate their administration as ‘resuscitation fluids’ in haemorrhagic shock (possible 1:1 replacement of shed blood), PFC emulsions can only be infused in low doses to avoid overload of the reticuloendothelial system. Therefore PFC are unsuitable for volume resuscitation in shock. Low-dose i.v. PFC can be used to increase the margin of safety for tissue oxygenation in haemodiluted patients, experiencing intraoperative blood loss. ‘Bridging’ the bleeding period by allowing severe normovolaemic haemodilution in the presence of i.v. PFC, together with the possibility of replacing the temporarily restricted oxygen transport capacity of i.v. PFC emulsions with autologous red blood cells, might become part of an allogeneic blood transfusion sparing concept in elective surgery.