Aims To explore patients' fundamental care needs, to which extent they are met and to assess how the care activities of Registered Nurses and assistant nurses are accomplished. A further aim is to investigate their associations with contextual factors in an emergency department setting.

Design Quantitative exploratory observational study with data collected through structured observations.

Methods Seventy-five patients, 30 registered nurses, and 20 assistant nurses were recruited from one emergency department. Structured observation protocols, spot checks, and follow-up dialogues were used. Descriptive and analytical statistics were calculated.

Results A total of 812 fundamental care needs were observed: physical (45%), psychosocial (38%), and relational (14%). The prevalence of missed nursing care was 20% and was more prevalent among older patients, those receiving care in shared spaces, and during crowding. In total, 3797 care activities were observed. Medical/technical activities were implemented at a higher rate than integration of care activities; unlike the latter, higher rates were significantly associated with crowding, the surgical section, and registered nurses compared to assistant nurses.

Conclusion Missed nursing care was more prevalent among older patients and those in shared spaces or during crowding. The increased rate of medical/technical care activities was associated with crowding, whereas the integration of care activities remained unchanged.

Implications for the Profession and Patient Care Fast-track solutions robust to crowding could reduce missed nursing care among older patients. Staff and management should critically assess physical layout in relation to crowding and missed nursing care. Crowding is a system-level phenomenon representing a significant driver of missed nursing care in the emergency department, and responsibility for addressing this decline in care quality must be acknowledged at system and policy levels.

Impact This study provides evidence of how organizational conditions shape nursing care delivery in emergency departments and will inform interventions to improve care quality and safety.