Background: Family members of critically ill patients face considerable uncertainty and distress during their close other's intensive care unit (ICU) stay, with about 20-60% of family members experiencing post-traumatic distress post-ICU. Guidelines recommend structured family inclusion, communication, and support, but the existing evidence base around protocolized family support interventions is modest and requires substantiation.

Methods: To test the clinical effectiveness and explore the implementation of a multicomponent, nurse-led family support intervention in ICUs, the investigators will undertake a parallel, cluster-randomized, controlled, multicenter superiority hybrid-type 1 trial. The trial will include eight clusters (ICUs) per study arm, with a projected total sample size of 896 family members of adult, critically ill patients treated in the German-speaking part of Switzerland. The trial targets family members of critically ill patients with an expected ICU stay of 48 hours or longer. Families in the control arm will receive usual care. Families in the intervention arm, in addition to usual care, will receive a family support intervention consisting of specialist nurse support along the patient pathway at defined time-points, including follow-up care, and nurse-coordinated liaison and structured, interprofessional communication by the ICU team. The primary study endpoint is quality of family care, operationalized as family members' satisfaction with ICU care at discharge. Secondary endpoints include quality of communication and nurse support, family management of critical illness (functioning, resilience), and family members' mental health (well-being, psychological distress) measured at admission, discharge, and after three, six, and twelve months. Data of all participants, regardless of protocol adherence, will be analyzed using linear mixed-effects models, with the individual participant as the unit of inference.

Discussion: The FICUS trial will establish the effectiveness of the family support intervention and generate knowledge of its implementability. Both types of evidence are necessary to determine whether the intervention works as intended in clinical practice and whether an effective intervention could be scaled-up to other ICUs. The study findings will make a significant contribution to the current body of knowledge on effective ICU care that promotes family participation and well-being.

Background: Family members are important to the well-being and recovery of critically ill persons, yet are themselves profoundly affected by the critical illness. During a close other's treatment in an intensive care unit (ICU), families experience high levels of stress and uncertainty, particularly in the event of surrogate decision-making and loss. Poor communication, insufficient shared decision-making, and inadequate emotional and practical support by intensive care staff have been found to add to families' burden. Poor-quality care has been associated with adverse mental health outcomes, which is reported by 20-60% of family members. A lack of engagement and support, coupled with acute stress, not only increases family suffering, but affects family members' functioning in everyday life, and limits their ability to engage in caregiving activities needed by the survivor of critical illness or cope with their loss.

Rationale: To increase the quality of family care and prevent adverse mental health outcomes, ICU guidelines recommend family engagement, communication, and support as well as the use of specific roles, but the evidence base for these recommendations is weak to date. Only a few studies have investigated family support interventions that consist of structured communication and / or specific family nursing roles. Promising effects have been found on family members' communication and support experience. However, findings on psychological distress remain inconclusive whereas insights on family management ability are virtually absent. Moreover, best practice around family engagement in ICU is often not implemented consistently in routine care. Hence, real-world evidence generated by randomized controlled designs is necessary to establish the effect of such multi-component interventions on quality of family care and their potential in supporting family management of critical illness and in reducing adverse mental health outcomes.

Aims: The study aims to determine the effect of a guideline-based, nurse-led, interprofessional family support intervention on quality of family care, family management, and individual mental health compared to usual care provided to family members. The study also aims to identify implementation barriers/enablers in the real-world context in which the study intervention is implemented to discern determinants and strategies of implementation success.

Methodology: The trial is designed as a multi-center, parallel cluster randomized superiority hybrid-type 1 trial with 8 clusters per study arm and a projected sample size of 896 family members of adult, critically ill patients treated in acute care hospitals in the German-speaking part of Switzerland. It will target family members with great needs, such as those of patients with more complex and longer-lasting critical illness, those of patients admitted with a life-threatening condition, and those who are required to make surrogate decisions. Family members of patients requiring short-lasting peri-operative or peri-interventional ICU treatment will be excluded. In addition to usual care, families in the intervention group will receive (1) specialist nurse support along the patient pathway at defined time-points, from admission to discharge with subsequent follow-up care, and (2) nurse-coordinated liaison and structured, interprofessional communication by the ICU team. Family members in the control group will receive usual care. The primary study endpoint is quality of family care, operationalized as family members' satisfaction with ICU care at discharge. Secondary endpoints include quality of communication and nurse support, family management of critical illness (functioning, resilience), and index family members' mental health (well-being, psychological distress) obtained upon admission, discharge, and after 3, 6, and 12 months. Data of all participants, regardless of protocol adherence, will be analyzed using linear mixed-effects models, with the individual participant as the unit of inference. A mixed-method study will be used to examine implementation barriers / facilitators and successful strategies at intervention units.

Expected outcomes and impact: The FICUS trial will establish the effectiveness of the family support intervention and generate knowledge on effective implementation processes. Both types of evidence are necessary to determine whether the intervention works as intended, but also to explore how it works in clinical practice, so that an effective intervention could be scaled-up to other ICUs. The study findings will make a significant contribution to the current body of knowledge on effective ICU care that promotes family participation and well-being. They will also promote evidence-based family care in ICU.

Potential participants are family members of critically ill persons admitted to a study ICU. A family member is defined as a close other from the patient's perspective, as noted in the clinical record or in advanced directives, or as indicated by the legally defined surrogate decision-maker.

Inclusion criteria regarding patients (one or several):

• Expected length of stay in ICU ≥48 hours, as predicted by the intaking ICU clinician (physician or nurse) at admission.
• Life-threatening condition with a high risk of death or long-lasting functional impairment.
• High risk of prolonged mechanical ventilation (>24 hours).

Inclusion criteria regarding family members (all must apply):

• Primary support person of the patient.
• Able to complete family-reported outcome measures (questionnaires) in German language.
• Age ≥18 years.
• Signed informed consent form.

Exclusion criteria regarding patients (one leads to exclusion):

• Preexisting declined general consent.
• ICU stay <24 hours.

Exclusion criteria regarding family members (one leads to exclusion):

• Prior inclusion in FICUS trial on another study ICU.
• Cognitive inability to understand the study or complete the questionnaire as appraised by clinicians and / or study recruitment staff.
• Inability to complete baseline data collection within the required timeframe after admission / study enrollment (Calvert et al., 2018).