Aim: To explore how critical care nurses access, negotiate, and apply knowledge in high-pressure clinical environments, focusing on organisational, cultural, and leadership factors influencing evidence-based practice implementation in acute hospital settings.

Design: A focused ethnographic collective case study conducted across two contrasting critical care units in England.

Methods: Methods included non-participant observation (56 sessions), semi-structured interviews (36 participants), and document review. Spradley’s Developmental Research Sequence guided data generation and analysis. Data were collected over an eight-month (February to September 2022).

Findings: Five major themes were identified: sources of knowledge and acquisition strategies; institutional and hierarchical influences on knowledge use; role of experiential knowledge and clinical intuition; challenges to evidence-based practice implementation; and strategies for integrating knowledge into practice. Organisational structures, leadership engagement, mentorship, and access to updated digital resources were key enablers of evidence-based practice. Barriers included workload pressures, inconsistent guideline dissemination, and hierarchical cultures. Adaptive blending of formal evidence, clinical experience, and intuition characterised effective knowledge negotiation at the bedside.

Conclusion: Knowledge use in critical care nursing is a dynamic, relational process shaped by leadership, organisational culture, and systemic pressures. Availability of evidence alone is insufficient; visible leadership, peer learning, protected educational time, and valuing of experiential knowledge are critical to embedding evidence-based practice into routine practice.

Implications for Patient Care: Strengthening organisational systems, investing in nurse manager development, expanding simulation-based learning, and legitimising experiential knowledge are vital strategies to enhance evidence-based critical care.

Impact: This study provides actionable insights for healthcare leaders, educators, and policymakers seeking to optimise evidence-based practice adoption in high-acuity clinical environments and improve patient outcomes.

Reporting Method: The Consolidated Criteria for Reporting Qualitative Research checklist guided reporting.

No Patient or Public Involvement: Patients and the public were not involved in the design, conduct, reporting, or dissemination of this research.