Background: Over 25,000 cardiac surgery operations are performed in Australia each year, with up to 10% of patients suffering clinically significant bleeding and, therefore poorer outcomes. Treatment of bleeding invariably requires transfusion of blood products; however, blood product transfusion may contribute to perioperative sequelae, incrementally increasing adverse outcomes including length of intensive care and hospital stay, mortality, and cost. There is a significant body of evidence including clinical practice guidelines to support clinician decision making regarding appropriate therapies and strategies to manage bleeding. Applying evidence-based bleeding management therapies could assist with minimising risk, but international literature demonstrates compliance is not high and contributing factors are not well understood. Managing bleeding in the cardiac surgical operating environment is technically complex, requiring the effective and efficient collaboration of multiple disciplines, employing multiple therapies over various timepoints during the perioperative period. Improvements in compliance through effective implementation activities are likely to be challenged by context, complexity, and process within the cardiac surgical and larger healthcare environment. At the outset of this doctoral thesis, the extent of current compliance with evidence-based bleeding management in Australia, the context in which clinicians provide this care, and any difficulties clinicians faced to implement practice improvement were unknown. Aim: The aim of this study was to understand the extent and context of the implementation of evidence-based bleeding management in Australian cardiac surgery units. Design/Methods: This research employed a pragmatic, multi-phase, mixed methods study design inclusive of three phases, underpinned by three theoretical approaches including the Knowledge to Action Framework (KTA), Theoretical Domains Framework (TDF), and the Capability, Opportunity, Motivation, Behaviour Model (COM–B). Phase One: The objective of Phase One was to develop an understanding of bleeding management implementation activity occurring at a local level. Factors influencing the success of a previously implemented single-centre quality improvement initiative to enhance bleeding management in adult cardiac surgery were explored using explanatory case study methods, with the KTA framework as an underpinning theoretical approach. Results of this study informed the development of a survey tool for Phase Two. Phase Two: A national cross-sectional survey was conducted to quantify bleeding management practices at a national level. Perspectives were sought from cardiac surgeons, cardiac anaesthetists, and perfusionists. Thirty-nine close-ended questions focused on routine bleeding management practices to address pre- and intra-operative care. An open-ended question asked about what factors clinicians perceived would improve their bleeding management practice. Quantitative data were analysed with SPSS and the qualitative data were thematically analysed, underpinned by the TDF and COM–B. Results from the Phase Two quantitative survey informed the interview guide in Phase Three. Phase Three: Perspectives of bleeding management of front-line providers from across Australia were investigated during semi-structured interviews, underpinned by the TDF and COM–B. Interviews explored key stakeholders’ beliefs about barriers and facilitators, their experiences, concerns, and successes when implementing evidence-based bleeding management strategies. Results: Phase One findings provided context on the milieu of variables impacting implementation. Keys to the success of the quality initiative were: 1. an appropriately skilled project manager to facilitate the implementation process; 2. tools to support changes in workflow and decision making including a bleeding management treatment algorithm with point-of-care coagulation testing; 3. strong clinical leadership from the multidisciplinary team; and 4. the evolution of the project manager position into a perpetual clinical position to support sustainability. The Phase Two study revealed wide variation (3% to 86%) in compliance to the queried evidence-based bleeding management recommendations among surgeons, anaesthetists, and perfusionists in Australian cardiac surgery units. Conceptualising factors believed necessary to improve practice were a standardised approach including: point-of-care diagnostic assays; a bleeding management algorithm; access to concentrated coagulation factors; cardiac surgery-specific bleeding management education; multidisciplinary team agreement; dedicated blood management clinicians; and an overarching national approach. The Phase Three semi-structured interview findings identified that barriers experienced by clinicians included: a lack of confidence with change management skills; variability with non-technical skills; lack of cross-discipline education specific to cardiac surgery bleeding management; complicated institutional processes; lack of dedicated blood management clinicians; incongruent goals; and disparities between public and private healthcare services. Key messages for enabling successful implementation were: increasing ‘capability’ through standardisation of bleeding management practice; monitoring, auditing, and feedback of data; and ‘opportunity’ through efficient, supportive processes to allowing clinicians to navigate unfamiliar business and financial models of healthcare. No one strategy could improve the implementation of evidence-based practice; rather, success was dependent on mixing and matching improvements of technical and non-technical skills, and procedural and organisational measures, in conjunction with commitment to overarching shared goals. Integrated Results and Meta-Inferences: Data from all study phases were integrated and analysed with the TDF and COM–B model revealing wide variation in reported evidence-based bleeding management, primarily as a result of factors impacting clinicians’ ‘capability’ and ‘opportunity’ to implement practice improvements. Motivation to change practice was not revealed as a barrier. The integrated findings confirmed clinicians’ capability to shape change could be achieved with standardisation of practice and behavioural regulation using contextually relevant evidence and locally tailored tools. Cross-discipline, cardiac surgery-specific education and training were identified as an effective means to improve communication, particularly where variability in non-technical skills were present. A lack of change management skills was found to adversely impact the ability of clinicians to access opportunities needed to implement practice improvements. The opportunity to successfully shape change is negatively affected by complex organisational process, and disparities in multidisciplinary partnerships and shared goals. Finally, dedicated blood management nursing roles add value and enhance capacity for practice improvements by functioning as intermediaries, enabling relationships and networks, and adapting and facilitating the transfer of knowledge. Conclusion: This study has demonstrated that despite numerous evidence-based guidelines for managing bleeding in cardiac surgery, there is wide variation in compliance and thus a pressing need to implement practice improvements. Findings from this PhD research has provided a strong platform for clinicians, organisations, and researchers to work from to translate knowledge and implement change. There is a high level of engagement from front-line Australian clinicians to advance bleeding management practice. Organisations and governance bodies need to ‘tap’ into this human resource and support clinicians as they coalesce ‘knowledge’ and ‘translation’ with accountability, mismatched clinical goals, rambling organisational structures, fragmented governance, and fiscal responsibility. This series of studies revealed the use of theory-based investigation on the context of evidence–practice gaps can articulate elements of practice improvement requiring discussion and debate that may otherwise be rendered acceptable or largely invisible. This research has extended current evidence and generated new and novel evidence on the implementation of bleeding management in Australian cardiac surgery units. We now understand what factors are associated with implementing successful bleeding management practice improvements, where compliance to evidence-based bleeding management needs to improve, and what needs to be done to support clinicians to implement change and close the evidence–practice gap. The next step is to formulate opportunities to make it happen.