Hospital managers are to clean wards to cover for 200 domestic staff who are striking in a dispute over pay.
South Tyneside Hospital chiefs said managers were stepping in to cover for 24 hours on Thursday to ensure that no operations or clinics are cancelled.
Unison said cleaners felt "undervalued" and wanted a pay rise. Hospital bosses said patients would not be affected.
The staff are already operating a work to rule and overtime ban and a further strike is planned for 27 July.
The strike has gone ahead after talks between the hospital trust, cleaners and the conciliation service, Acas, broke down.
Important job
Liz Twist, Unison's regional head of health, said: "The workers are angry at the trust's refusal to agree job descriptions which they believe would give them more pay and a higher future earning potential.
"Strike action is always a last resort but our members feel that they have been unfairly treated and are being undervalued by their employer.
"They are not asking for something for nothing - just the right job description, the right grade and the right pay for the important job they do."
Ian Frame, spokesman for South Tyneside Foundation Trust, said the move would cost £400,000 a year which the trust could not afford.
He said: "It would cost a lot a money to re-grade staff - the cost of running about half a ward a year.
"I know of only one other trust that has re-graded staff and I can't understand why we should be any different to other trusts in the UK."