A pragmatic implementation and outcomes evaluation of the older persons emergency network acute outreach service (OPEN AOS) model utilising the integrated PRISM and RE-AIM framework: the OPEN AOS study protocol

Globally, the population aged 65 years and over is increasing and with this growth comes a rising risk of chronic diseases that often require emergency care. Older adults living in Residential Aged Care Facilities (RACFs) have increased healthcare utilisation including visits to Emergency Departments (EDs). EDs are busy, noisy environments poorly suited to meeting the care needs of older adults. Older adults attending EDs often receive delayed and fragmented care, unnecessary procedures and tests and are at greater risk of iatrogenic complications. The Older Person’s Emergency Network Acute Outreach Service (OPEN AOS) based in Queensland, Australia, is a nurse-led, physician-supported model that provides ED substitution care to older adults living in RACFs. This paper outlines the OPEN AOS study protocol, which comprises three components and uses the integrated Practical, Robust, Implementation, and Sustainability Model (PRISM) and Reach, Effectiveness, Adoption, Implementation and Maintenance (RE-AIM) framework to guide a comprehensive evaluation. The study comprises a pragmatic multi-methods design, consisting of three discrete yet related components. Component 1 is a retrospective, quasi-experimental design comparing outcomes for patients seen in the RACF by the OPEN AOS clinical team (intervention group) to standard ambulance attendance in the RACF resulting in transport to ED care (control group) between 1 July 2022 and 30 June 2023. Component 2 is a retrospective economic evaluation of the OPEN AOS model measuring the incremental cost per patient of OPEN AOS care compared to standard ambulance attendance resulting in transport to ED care. Component 3 adopts a prospective qualitative approach to explore and understand the contextual factors influencing implementation with the aim of informing effective delivery and supporting the potential scale and spread of the OPEN AOS model. The OPEN AOS model aims to deliver ED-substitution care in RACFs for older adults. This study will adopt a pragmatic approach to assess both outcomes and implementation processes, utilizing the integrated PRISM and RE-AIM frameworks for comprehensive evaluation. Findings will inform the design of similar models and guide health system decision-making for adopting approaches like the OPEN AOS model.