Anaemia, Iron-Deficiency and Reducing Transfusion in Cardiac Surgery and A Novel Method for the Measurement of Total Haemoglobin Mass

Abstract

Anaemia and iron-deficiency are common in cardiac surgical patients and are associated with poor surgical and patient-centred outcomes. Pre-operative anaemia is increasingly being treated with intravenous iron despite a lack of high-quality evidence of its effectiveness. This thesis explores these topics with a literature review exploring anaemia, iron-deficiency, and transfusion in cardiac surgery, and further review on transfusion risk-prediction models, and treatment of pre-operative anaemia with intravenous iron. The first methodological chapter describes the development of a new risk-scoring system to predict those who are likely to require peri-operative red blood cell transfusion in cardiac surgical patients in the UK. This risk scoring system was then modified and recalibrated using an Australian database to create an alternative score applicable to that population, described in the subsequent chapter. The use of intravenous iron has increased significantly since the introduction of new iron-preparations and is now recommended in many treatment pathways and guidelines. This has occurred in advance of high-quality evidence that it can effectively treat anaemia in the pre-operative period and have any meaningful effect on patient outcomes. Chapter 5 describes a UK-wide multicentre trial that demonstrated that IV iron can significantly increase haemoglobin concentration in cardiac surgical patients in the pre-operative period. Challenges in the recruitment for larger studies of anaemic cardiac surgical patients led to an exploration of the recent trends in anaemia-rates over the last 5-7 years, which is described in Chapter 6. This demonstrates that anaemia rates in certain areas have decreased significantly over that period and there has been concomitant exponential increase in the use of intravenous iron preparations in various medical settings. The final methodological chapter describes a novel method for measuring total haemoglobin mass, which may be a more appropriate method of assessing anaemia in various disease states. Previous methods have been difficult to establish and complicated to undertake. This chapter describes a new method using a modification of an existing respiratory function test which is demonstrated to be a simple method of estimating total haemoglobin mass and plasma volume.