BackgroundWhilst pre-alerts have been shown to improve outcomes for some patients requiring immediate time-critical treatment (e.g. stroke), little is known about their usefulness for other patients and what processes are used by Emergency Department (EDs) to respond to them. In the current context of high demand, it is important to understand how pre-alerts affect EDs.MethodsWe undertook non-participation observation (162 hours, 143 pre-alerts) and semi-structured interviews (40 staff) within six UK Emergency Departments (EDs), between August 2022-April 2023. Interview transcripts and observation notes were imported into NVivo™ and analysed using a thematic approach.ResultsPre-alert calls involved significant time and resources for ED staff but enabled staff to prepare for patient’s arrival both practically and psychologically, particularly when demand was high. High demand created additional pre-alerts due to advice or ‘heads up’ calls from ambulance clinicians concerned about handover delay. Despite some pre-alert fatigue regarding patients who did not always require a special response (e.g. sepsis), ED clinicians prioritised and valued pre-alerts, perceiving higher risks from under-alerting than over-alerting. Variation in ED processes for a) senior clinical review of pre-alerted patients not brought into resus and b) receiving, documenting and informing others of pre-alerts resulted in inconsistent response to ambulance clinicians. ED response (where the patient should be taken) largely reflected resources available (beds, staffing, acuity of other patients) rather than appropriateness of the pre-alert.ImplicationsIn the context of high demand, much variation in response to pre-alerts is outside ED staff’s control. There is potential for EDs to increase consistency in reviewing how pre-alert calls are answered, what information is documented and how this is communicated to others, including when they are not accepted into resus. Improved communication between ambulance and ED services may help avoid tension caused by different perceptions or understandings of pre-alerts.What is known on this topic?Ambulance pre-alerts can help Emergency Department staff to prepare for a patient’s arrival and can lead to improved outcomes for patients requiring immediate senior review upon arrival.Research about pre-alert practice focuses on outcomes for patients who have been pre-alerted but there is a lack of evidence about the effect of pre-alerts on ED staff and ED patient management.What this study addsVariation in ED processes, layout and capacity led to different ED responses to pre-alert calls, particularly for patients who were not brought into resus.ED response is primarily dependent upon resources available at the time of the call and assessment of the need for active treatment. Pre-alerted patients who may be suitable for a resus bay may be seen in another area of the ED when the ED is crowded or has higher priority patientsPre-alerts used ED resources but were valued in terms of enabling both practical and psychological preparedness.How this study might affect research, practice or policyStandardisation of processes for improving flow and assessing high risk patients may help reduce variation in ED management and provide more consistent support for ambulance cliniciansUnderstanding that EDs may not be able to provide an expected or consistent response to pre-alert calls is important for ambulance clinicians assessing their own pre-alert practice.