Implementation lessons learnt when evaluating palliative care interventions in the intensive care unit: relationships between implementation determinants, strategies, and models of delivery.

Background
Palliative and end-of-life care have important roles in intensive care units (ICUs) given symptom burden and rate of mortality in ICUs. However, we do not know how ICU-based palliative care interventions should be implemented. This systematic review aims to identify and synthesise knowledge on how ICU-based palliative care interventions have been implemented and provide critical recommendations for successful implementation.

Methods
Systematic review methods following PRISMA reporting guidelines. Search strategy combined palliative care, intensive care, and implementation terms. Searches up to December 2022 of MEDLINE, Embase, Cochrane, CINAHL, and PsycINFO. Components from an adapted Smith’s Implementation Research Logic Model were used to develop themes for reporting intervention characteristics, implementation determinants (barriers and facilitators), implementation strategies, mechanisms, and outcomes, and to synthesise relationships between these components.

Results
79 included studies: 8 process evaluations, and 71 effectiveness studies. Published evidence on ICU-based palliative care interventions is wide-reaching, but reporting on implementation factors (determinants, strategies, mechanisms) is variable and often lacking. In particular, patient and family-related determinants, and any mechanisms, were not reported. Main facilitators are adequate resources and a symbiotic relationship between palliative care and ICU teams. Main barriers are ICU team reluctance toward palliative care involvement, lack of skills and familiarity, and high ICU acuity. Main implementation strategies were utilising champions, providing education and resources, involving stakeholders, creating adaptable interventions, and building relationships between palliative care and ICU teams. Mechanisms most commonly worked by facilitating collaborative working.

Conclusion
Most research into ICU-based palliative care interventions does not report on how the intervention is implemented into practice. Patient and family perspectives on implementation are rarely sought. Even with strong effectiveness evidence for an intervention, improvements in care will not be achieved without consideration of context-specific implementation strategies. We provide actionable recommendations to address this and identify the relevant research gaps.