Representatives from both the Public Service Association and the New Zealand Nurses Organisation have written "please explain" letters to regional chief executive Brian Rousseau over Mrs Samuel's appointment.
They have no issue with Mrs Samuel's abilities, but are concerned at the lack of consultation on the issue.
Mr Rousseau has indicated he does not wish to comment further on the matter before responding to the unions.
Mrs Samuel, who was the nursing leader at the Southland District Health Board, was appointed to the new role by Mr Rousseau following the resignation of Otago's chief nursing officer, Teresa Bradfield, and took up the job earlier this month.
This week, there has been further concern expressed at the lack of discussion with unions around the advertising for an Otago District Health Board deputy for Mrs Samuel. Applications for the job close on February 27.
NZNO Otago organiser Lorraine Lobb said it was not clear to her what the status of the new deputy was and how it compared with the position held by Mrs Bradfield.
She was looking forward to meeting Mrs Samuel soon to discuss concerns.
PSA organiser Julie Morton said she had been frustrated at the lack of consultation because it had the potential to affect good relationships which had been building between board management and the union in the last year.
Mrs Samuel said Mrs Bradfield had always had an assistant in her Dunedin role, but she wanted to rework that so that it aligned more with her new position.
She felt the role should add strength to the nursing workforce, supporting the work already done by nurse directors.
Mrs Samuel's appointment means nurses will have one representative on the regional executive, rather than the two, one from each board which had been suggested following consultation last year.
Mr Rousseau had originally proposed the chief nursing officers of each board fill the position by rotation, but concerns raised about that, including lack of continuity, meant it was dropped.
Mrs Samuel said under the old arrangements she and Mrs Bradfield had worked closely and she did not consider the nurses' voice at that level would be diminished.
The nursing matters being addressed at regional executive level were not unique to Otago; they would apply to nurses from the Waitaki south.
Teams in both Southland and Otago would be reporting to her and there were already groups interacting across both regions.
