Critical Care - Theses
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ItemDecarbonising Healthcare( 2021)At COP26, thirty-six countries committed to develop low-carbon health systems, with a further fourteen countries setting a target of net-zero healthcare by 2050. There is currently little information available, however, on the carbon footprint of most healthcare activities, nor is there any recognised way for carbon emissions to be included in the clinical decision-making process. This research explores how healthcare can rapidly reduce its carbon footprint while not adversely effecting patient health. It does so in three parts: methodology, measurement, and mitigation. Methodology explores how to incorporate carbon footprints, calculated from environmental life cycle assessment (LCA), into health technology assessments (HTAs) including cost-effectiveness analysis and cost-benefit analysis, or as one criterion in a multi-criteria decision analysis. There are no technical impediments to stop the incorporation of carbon emissions into HTAs. Rather, the main barrier is that unlike other sectors of the economy, currently few LCAs have been undertaken in healthcare to quantify carbon emissions. Measurement examined the consequential and attributional life cycle carbon emissions of pathology blood tests (full blood examination, coagulation profile, urea and electrolytes, C-reactive protein, and arterial blood gases); the attributional life cycle carbon emissions of urinalysis; and the consequential and attributional life cycle carbon emissions of diagnostic imaging (magnetic resonance imaging (MRI), computerised tomography (CT), chest X-ray (CXR), mobile chest X-ray (MCXR), and ultrasound(US)). The consequential LCA of pathology testing showed the greatest source of carbon emissions originated from phlebotomy, which can be reduced by only ordering tests when necessary. The attributional LCA additionally showed the impacts of standby power usage, which can be reduced by moving to renewable energy and ensuring analysers are highly utilised. For diagnostic imaging for both attributional and consequential analysis, X-rays and US have lesser carbon emissions compared to MRI and CT, and therefore should be preferentially used wherever possible. The attributional LCA showed that MRIs and CTs have a carbon footprint similar to the known carbon hotspot of anaesthesia. These carbon emissions can be similarly reduced by moving to renewable energy and ensuring the high utilisation rates of scanners. Mitigation shows how an intervention to reduce unnecessary pathology testing by the Department of Medicine at St George Hospital, Sydney, led to 10% reduction in pathology tests over the six-month intervention period. The reduction resulted in a saving of 132kg carbon dioxide equivalent (CO2e) and A$53,573, with no change in adverse patient outcomes. The second part of Mitigation investigated the prevalence of unnecessary routine preoperative testing at Western Health. It found virtually no unnecessary testing, with the odds of potentially receiving an unnecessary preoperative test being 0.017. This thesis highlights that there are large research areas to be undertaken for healthcare to decarbonise, especially in performing LCAs of healthcare consumables, devices, and interventions. Additionally, the thesis shows that low-value care, such as the overutilisation of testing, should be an initial focus towards healthcare’s decarbonisation, as reducing low-value care reduces carbon emissions while not adversely effecting patient health.
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ItemNon-anaemic iron deficiency: validity as a therapeutic target in the peri-operative setting( 2020)Given the known associations between iron deficiency anaemia (an advanced form of iron deficiency) and poor outcomes after major surgery, it is biologically plausible that early, or non-anaemic iron deficiency (NAID) may also be associated with worse outcomes. Accordingly, Australian guidelines recommend NAID be corrected routinely pre-operatively. However, evidence supporting independent associations between NAID and poor postoperative outcomes, and for postoperative outcomes to be improved if pre-operative NAID is treated, is limited. Additional evidence is required to answer the primary research question for this thesis: how should clinicians identify and manage NAID prior to major surgery? I have further divided this central question into four subsidiary research questions, which the various chapters in this thesis attempt to answer. Firstly, what are the associations between NAID and outcome following major surgery? In two retrospective observational studies presented in Chapters 2 and 3, I found a signal between iron deficient states and worse postoperative outcomes in non-anemic patients undergoing cardiac surgery and surgery for colorectal cancer. However, confounding associations were also found between NAID and other health conditions. The protocols for two currently running prospective observational studies in the same populations are presented which will provide more definitive evidence for these hypothesised associations. Secondly, are the current World Health Organization definitions of anaemia and non-anaemia an accurate reflection of peri-operative risk, especially when considering the inherent bias of biological sex? In Chapter 4, I present a study that examined the haemoglobin thresholds of anaemic (and by extension, non-anaemia) in women and men presenting for major abdominal surgery. My findings suggest that women with ‘borderline’ anaemia (a haemoglobin concentration of 120 – 129 g/L), despite being considered ‘normal’ under current guidelines have worse postoperative outcomes suggesting the threshold for pre-operative diagnosis of anaemia (and thus intervention) should be 130 g/L for women and men. Thirdly, what are the associations between the response of iron status to inflammation and outcomes after major surgery? This question is partially answered by a retrospective study presented in Chapter 5, where I explore a new, variant iron status termed inflammatory hyperferritinaemia and outline its associations between various negative biological markers and poor outcomes following major abdominal surgery. Finally, if one assumes that NAID is associated with poorer postoperative outcomes, the fourth logical question to be asked is whether administering iron intravenously to patients with pre-operative iron deficiency improves said outcomes? A Cochrane systematic review and meta-analysis examining intravenous iron for the treatment of adults with NAID is presented in Chapter 6, highlighting the paucity of evidence supporting this practice. Additionally, the results of a pilot and feasibility study in patients with NAID undergoing colorectal cancer surgery comparing intravenous iron with placebo are presented in Chapter 7. This latter study experienced considerable difficulty in recruitment; however, I discuss several important lessons for the design of subsequent clinical trials. Understanding how NAID influences postoperative outcomes and whether such outcomes can be modified is essential to guide clinicians in identifying and managing this common peri-operative condition. This thesis provides preliminary evidence that examines this problem and outlines a roadmap for future research.