Acute normovolaemic haemodilution and autotransfusion in neurosurgical patients.

Sir,

The use of acute normovolaemic haemodilution and autotransfusion in neurosurgical patients is an interesting topic for discussion.[1] Naqash et al. concluded that “Acute Normovolemic Hemodilution with Autotransfusion is a safe and feasible technique to reduce intraoperative blood loss and the need for homologous blood transfusion in patients”.[1] Based on this interesting study with rather few subjects, the conclusion might imply that the technique is acceptable. However, the technique is time-consuming and results in complication.[2] In addition, its reducing the need for homologous blood is small.[2] The alternative, hypervolaemic haemodilution, should be further comparatively evaluated.[2] In fact, there are conflicting evidences regarding both these techniques (normovolaemic versus hypervolaemic haemodilution) to reduce intraoperative blood loss and the need for homologous transfusion. Each method has its own merit and demerit. Although the observations of Entholzner and colleagues highlight the demerits of acute normovolaemic haemodilution, Singbarti and colleagues[3] felt that hypervolaemic haemodilution cannot replace normovolaemic haemodilution to reduce homologous transfusions, although for blood losses <40% of blood volume the hypervolaemic haemodilution appeared to be superior. Moreover, Naqash et al. evaluated only the feasibility of acute normovolaemic haemodilution in patients undergoing excision of intracranial meningioma. Blood loss in these patients may sometimes exceed more than 40% of the blood volume. Hence, it is still required for further good systematic comparative study to conclude on the effectiveness of both techniques.