Aetiology of preoperative anaemia in patients undergoing elective cardiac surgery-the challenge of pillar one of Patient Blood Management.

Preoperative anaemia is common in patients undergoing cardiac surgery. Whilst there is a strong association with increased morbidity and mortality, it is currently unclear whether treatment of anaemia leads to patient benefit. This retrospective study aimed to determine the aetiology of preoperative anaemia in a cohort of patients undergoing elective cardiac surgery over two years at a tertiary hospital. Laboratory data obtained at the preoperative assessment clinic visit were assessed to stratify patients into four groups-iron deficiency anaemia (IDA), possible IDA, anaemia of chronic disease (ACD) and non-anaemic patients with low ferritin according to the 'Preoperative haemoglobin assessment and optimisation template' of the Australian Patient Blood Management (PBM) Guidelines. Of patients with preoperative anaemia, 23.1% had IDA, 6.6% had possible IDA and 70.3% had possible ACD. Of the patients with possible ACD, 30% had a ferritin <100 µg/l, representing limited iron stores or coexisting absolute iron deficiency in the setting of chronic disease. In addition, 46.2% of those with possible ACD had iron studies indicative of functional iron deficiency. Time between assessment and surgery was as little as one day in a third of patients and in only 7% was it more than seven days. Our findings indicate that about one-third of our patients with preoperative anaemia had evidence of iron deficiency, a potentially reversible cause of anaemia. In addition, a significant number had either limited iron stores that may render them iron deficient by surgery, or a functional iron deficiency.