Nurses and midwives walked off the job for four hours for the second time in a month at Lake Macquarie Private Hospital on Thursday in a bid for better pay and conditions.
They also want their meal and toilet breaks, which they often don't have time to take.
They held signs saying "ask me how long I hold my pee" and "safe staffing saves lives".
The four-hour strike followed 72 per cent of staff across Ramsay Health Care hospitals in NSW rejecting the company's revised pay offer.
Ramsay initially offered the workers an 11 per cent pay rise over three years, but the workers are seeking 18 per cent and improved conditions for parental and personal leave.
After the first strike, Ramsay upped its offer to 12.5 per cent.
The action involved members of the NSW Nurses and Midwives' Association (NSWNMA) rallying along the Pacific Highway, outside the hospital at Gateshead.
Kate Briggs, a delegate of the Lake Macquarie Private branch, said the pay offer was "pretty insulting".
"We feel undervalued, underpaid and overworked," Mrs Briggs said.
Nurses and midwives sought "pay in line with CPI at minimum".
"With the cost of living crisis, we all know that everything is going up except our wages," she said.
"There's a lot of pressure on staff to provide the best possible care, but we don't have enough staff to do that.
"I work in the operating theatre. We often go without toilet and meal breaks. It's very hard for us to keep going.
"We're supposed to get two paid 10-minute breaks or one 20-minute break, and a half-hour lunch or dinner break across an eight-hour shift."
She said nurses "often don't drink much water during our shift".
"If we don't get other staff to relieve us for a break, then we're not able to get off the floor as there's no one to cover us should anything potentially go wrong.
"We don't want to leave doctors and patients without nursing support."
The protected action included bans on working overtime and led the hospital to cancel surgeries.
The union said members had "vowed to fight on and escalate industrial action against the country's largest private hospital operator".
It would do so until Ramsay "comes to the table with a respectful and reasonable pay offer".
"Ramsay also continues to refuse calls to introduce nurse/midwife to patient ratios."
A Ramsay Health Care spokesperson said "we respect the decision of our nurses and midwives, who voted not to accept the proposed new enterprise agreement".
"A yes vote would have ensured a new agreement and a 6 per cent increase next year.
"We will take some time to carefully consider the outcome of the ballot and determine next steps."
The spokesperson added that it was "disappointed that this action has now negatively impacted patients", with several surgeries cancelled.
Patient safety was its "highest priority" and it would not do procedures "without the appropriate staff available".
"We have communicated directly with impacted patients and will endeavour to have their health-care journey back on track as soon as possible."
