The clinical significance of postoperative anaemia
Inflammatory cytokines after surgery and trauma invoke a response characterized by, among other effects, decreased iron uptake from the gastrointestinal tract and iron sequestration in macrophages, along with a diminished erythroid response to erythropoietin and decreased erythropoietin production.
Other contributory causes to postoperative anaemia include pre-existing preoperative anaemia and traumatic and surgical blood loss. Added to these is an element of haemodilution occurring as a result of fluid replacement before, during, and after surgery. Normovolaemic haemodilution is well tolerated due to compensatory mechanisms that maintain an adequate myocardial and peripheral tissue oxygenation. On the other hand, hypovolaemic anaemia must be avoided, as the cardiovascular compensatory mechanisms required to maintain oxygen transport in the setting of anaemia are severely compromised.