OBJECTIVE This paper is a report of an investigation of the development, implementation and outcomes of a clinical guideline for nurse-led early extubation of adult coronary artery bypass graft patients. BACKGROUND Healthcare knowledge translation and utilization is an emerging but under-developed research area. The complex context for guideline development and use is methodologically challenging for robust and rigorous evaluation. This study contributes one such evaluation. METHODS This was a mixed methods evaluation, with a dominant quantitative study with a secondary qualitative study in a single UK cardiac surgery centre. An interrupted time series study (N = 567 elective coronary artery bypass graft patients) with concurrent within person controls was used to measure the impact of the guideline on the primary outcome: time to extubation. Semi-structured interviews with 11 clinical staff, informed by applied practitioner ethnography, explored the process of guideline development and implementation. The data were collected between January 2001 and January 2003. RESULTS There was no change in the interrupted time series study primary outcome as a consequence of the guideline implementation. The qualitative study identified three themes: context, process and tensions highlighting that the guideline did not require clinicians to change their practice, although it may have helped maintain practice through its educative role. CONCLUSIONS Further investigation and development of appropriate methods to capture the dynamism in healthcare contexts and its impact on guideline implementation seems warranted. Multi-site mixed methods investigations and programmes of research exploring knowledge translation and utilization initiatives, such as guideline implementation, are needed.