Background: Ambulance paramedics play a critical role expediting patient access to emergency treatments. Standardised handover communication frameworks have led to improvements in accuracy and speed of information transfer but their impact upon time-critical scenarios is unclear. Patient outcomes might be improved by paramedics staying for a limited time after handover to assist with shared patient care. We aimed to categorize and synthesise data from studies describing development/extension of the ambulance-based paramedic role during and after handover for time-critical conditions (trauma, stroke and myocardial infarction). Methods: We conducted an electronic search of published literature (Jan 1990 to Sep 2016) by applying a structured strategy to eight bibliographic databases. Two reviewers independently assessed eligible studies of paramedics, emergency medical (or ambulance) technicians that reported on the development, evaluation or implementation of (i) generic or specific structured handovers applied to trauma, stroke or myocardial infarction (MI) patients; or (ii) paramedic-initiated care processes at handover or post-handover clinical activity directly related to patient care in secondary care for trauma, stroke and MI. Eligible studies had to report changes in health outcomes. Results: We did not identify any studies that evaluated the health impact of an emergency ambulance paramedic intervention following arrival at hospital. A narrative review was undertaken of 36 studies shortlisted at the full text stage which reported data relevant to time-critical clinical scenarios on structured handover tools/protocols; protocols/enhanced paramedic skills to improve handover; or protocols/enhanced paramedic skills leading to a change in in-hospital transfer location. These studies reported that (i) enhanced paramedic skills (diagnosis, clinical decision making and administration of treatment) might supplement handover information; (ii) structured handover tools and feedback on handover performance can impact positively on paramedic behaviour during clinical communication; and (iii) additional roles of paramedics after arrival at hospital was limited to 'direct transportation' of patients to imaging/specialist care facilities. Conclusions: There is insufficient published evidence to make a recommendation regarding condition-specific handovers or extending the ambulance paramedic role across the secondary/tertiary care threshold to improve health outcomes. However, previous studies have reported non-clinical outcomes which suggest that structured handovers and enhanced paramedic actions after hospital arrival might be beneficial for time-critical conditions and further investigation is required.