Medicine (St Vincent's) - Theses
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ItemThe role of cardiac output and fluid responsive measurements in improving outcomes after major abdominal surgery in adults( 2021)Adequate delivery of oxygen to tissues is essential to tissue healing and preserving organ function following major surgery which is characterised by an increased oxygen demand. Cardiac output (CO), the flow out of the heart, can now be measured with monitors using technology that allows them to be used safely during the perioperative period. This thesis explores the monitors used to target CO, the effect of targeting CO, goal-directed therapy (GDT), and haemodynamic differences between restrictive and liberal fluid therapy. The CO technology of focus in this thesis is the oesophageal Doppler with arterial pressure waveform devices and plethysmography also assessed for their ability for agreement to clinical events. Two prospective observational studies assessed the ability of the monitors to track the clinical events of fluid and vasopressor administration. Compared to each other, the Doppler monitor and arterial pressure waveform monitor had reduced concordance to track CO changes following fluid boluses with even poorer concordance to vasopressor administration. Compared to the reference standard of thermodilution, both technologies displayed reduced precision but the Doppler tracked fluid boluses more consistently. A randomised control trial was conducted with patients having colorectal resection surgery targeting an optimal CO using fluid bolus therapy. Importantly, it was conducted within a contemporary enhanced recovery after surgery (ERAS) framework to demonstrate whether GDT can have a benefit in addition to optimal perioperative care. There was no difference in hospital length of stay or proportion of patients with major complications. A meta-analysis of other studies shows that the benefit to GDT with a Doppler technology device is effective in reducing complications but the results are less applicable with lower perioperative risk, such as patients within an ERAS framework. Finally, the haemodynamic effect of a restrictive fluid therapy compared to a modestly liberal fluid therapy was observed with CO monitoring and fluid responsive parameters. Fluid restriction resulted in a reduced CO and stroke volume which may explain a finding of increased kidney injury and surgical site infection observed in this group. In summary, targeting an increased CO in major abdominal surgery may show reductions in complications but this is not seen in low-risk patients. A Doppler CO monitor has a better ability to detect changes after a fluid bolus but measurement of CO clinically is still challenging with reduced precision observed. The demonstration of reduced CO with fluid restriction supports the importance of avoiding the harmful effects of hypovolaemia and the utility of the measurement and targeting of CO.
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ItemContext for improving access to care for children and youth with diabetes in less-resourced countries( 2020)There are major deficits in knowledge related to the epidemiology and care of the various types of diabetes in young people in less-resourced countries. Multiple barriers exist at individual, community, health system, national, and international levels that must be overcome to lessen the gap in outcomes between advantaged and disadvantaged regions. This thesis presents 11 published papers by the candidate addressing this gap in knowledge. Type 1 diabetes (T1D) incidence data is presented for three countries with no previous data (Fiji, Bolivia and Azerbaijan), showing differing rates in each country, and in Fiji differing rates in the two main ethnic populations. Novel information on the types of diabetes is presented for Azerbaijan (along with the incidence data aforementioned), Pakistan and Bangladesh. Results in Azerbaijan were similar to those seen in European populations. In Pakistan and Bangladesh, it is common to see atypical forms that clinically present like T1D cases but do not have low C-peptide values or diabetes autoantibodies. Five papers examine costs and access to care. In a survey of 71 countries, availability of nearly all key components of care was greatly reduced in lower-income countries. A study of costs to families in 15 countries demonstrated that the cost of core supplies is prohibitively expensive for many families. A comprehensive review of issues surrounding access to supplies for self-monitoring of blood glucose presents new information on the global market and makes numerous practical recommendations. Progress towards Universal Health Coverage for provision of insulin and blood glucose test strips was evaluated in 44 countries, showing that there was greater progress for insulin than for test strips. A novel framework for describing T1D care levels (Basic, Intermediate and Comprehensive) provides a way of identifying the steps required to improve care in a particular situation, and the data presented from Bolivia shows that Intermediate Care can achieve outcomes similar to those in some highly-resourced countries. The final paper, using robust, novel and replicable methodology, demonstrates the efficacy of traditional evaporative cooling devices used for insulin storage where refrigerators are not available. In conclusion, efforts to improve care for young people with diabetes in less-resourced countries must take into account wide differences in incidence and the types of diabetes that occur between countries. Furthermore, for care to improve, many components of care need to be addressed. The concept of ‘Intermediate Care’ provides an achievable level of care that can result in reasonable outcomes even in poorly resourced health systems.