Background. The contemporary role of the nurse in managing fluid and hydration in patients is currently ill-defined. Considering the pivotal function nurses have in the delivery of fluid therapies, and the high priority such therapies have in the successful treatment and prevention of secondary brain injury in subarachnoid haemorrhage, the clarification of this role is essential. Aims and objectives. This research aims to clarify the nurse's role in fluid therapies in relation to subarachnoid haemorrhage. The objectives were to determine how nurses presently see their role in relation to fluid management in patients with subarachnoid haemorrhage, to determine the cues to guide their practice, and how this role corresponds to current patient care. A final objective was to identify how the nurse's role can be maximized to provide optimal patient care. Methodological design. This project takes an action research approach to examining the nurse's role in the care of patients with subarachnoid haemorrhage. A combination of focus groups, physiological data, nursing and medical documentation and a review of recent literature were used to meet the aims and objectives of the project. Results. The results illustrate that, while nurses involved in the study are knowledgeable about fluid and hydration in subarachnoid haemorrhage, they have an ambiguity surrounding their role. Improvements can be made in the quality of patient care through educational sessions for staff and clarification of medical and nursing interdisciplinary roles. Conclusion. This action research project has gone a considerable distance towards begin clarifying this role, and has illustrated clearly that the nurse's role is pivotal to the successful implementation of such treatments. With further education and collaboration with the interdisciplinary team the nurses' role can be expanded to provide optimal, and dynamic patient-centred care. Relevance to clinical practice. The results of this study highlight gaps within contemporary nursing and medical approaches to patients with subarachnoid haemorrhage, highlighting areas for improvement. It also begins to clarify the role of the nurse, with evidence of the cues they use to guide their practice.