摘要: Transfusion rates vary widely between [1–4], and probably also within [5, 6] clinical centres, for procedures that might reasonably be expected to have similar transfusion demands or rates. The local practice may defined by a number of factors, such as the consensus on postoperative haemoglobin level platelet level, preferences opinion leaders in community [7], availability committee with an authoritative surveillance system, variations supply regional risks public perceptions those risks.