Table 4 Assessment variables for acceptability and feasibility

Relative to the study design

(1) Caregiver and patient recruitment

• Primary indicator: obtaining consent from at least 75% of the caregivers approached to participate in the study

• Recruitment time

• Percentage of eligible people who were included in the study

• Effectiveness of recruitment strategies

• Caregiver reasons for refusal to participate in the study

• Number of potential participants

• Difficulties in obtaining patient consent

(2) Randomization

• Reasons for patient refusal to participate after the delirium episode

• Number of non-eligible participants randomized

(3) Participant retention

• Reasons for withdrawal from the study

(4) Data collection

• Rate of completion of questionnaires

• Percentage of outcome measures collected

• Reasons for non-completion of questionnaires

• Time required for completion of outcome measure tools

• Respect of the data collection plan

• Validity of cerebral oximetry as an indicator of delirium

(5) Between-group contamination

• Rate of participants in the control group exposed to the intervention (overlapping time for the intervention and usual care, e.g., because of prolonged hospital stay)

• Attendance rate of caregivers at the bedside

• Moments of the day for which caregivers were present

• Number of family members, other than the caregiver, who visited the patient

• Relationships between visitors and the patient

• Total time spent at the bedside by the caregiver

• Total time spent at the bedside by other visitors

Relative to the intervention

(1) Satisfaction of primary caregivers with the intervention

• The scores on the Treatment Acceptability and Preference Questionnaire (TAP) [42], completed on day 4 after delirium onset will help assess caregivers appreciation of the intervention. This questionnaire contains 5 items on which appreciation is scored using Likert scales, the higher the scores the more appreciation. The reported α is ≥0.80.

Intervention group only

(2) Availability necessary to provide the intervention

• Total amount of time allocated to each contacts provided through the intervention

• Duration of the presence of the intervention

• Duration of the presence of the primary caregivers for the intervention

• Moments of the day which took place at the bedside visits on T1, T2, and T3

Intervention group only

(3) Material resources

• Costs relative to printed documents and electrodes used to measure cerebral oximetry

(4) Fidelity to the components and structure of the intervention

• Number of encounters received/planned

• Modalities of intervention planned versus received

• Reasons for encounters not received

Intervention group only

Intervention group only

(5) Selection and use of delirium management behaviors

• Number of suggested behaviors in comparison to adopted behaviors by the primary caregivers

• Clinical condition of the patient at each visit

Intervention group only

• Number and type of behavior adopted by the intervention provider at each visit on T1, T2, and T3

• Number and type of behavior adopted by the primary caregiver at each visit on T1, T2, and T3

Intervention group only