Health care in England's National Health Service (NHS) were facing for "exceptionally low" staffing on Sunday as nurses staged a 28-hour strike over pay.
The strike, ending just before midnight on Monday, comes after a High Court judge ruled it would be unlawful for the industrial action to continue into Tuesday as originally planned.
Measures were in place to keep patients safe after concerns were raised on the impact of the strike action on emergency services, Royal College of Nursing (RCN) general secretary Pat Cullen said on Sunday.
The union initially said it would not agree to derogations – broad areas of care where staffing is guaranteed despite industrial action – but granted some exemptions on Friday in an apparent U-turn.
London's Great Ormond Street Hospital (GOSH) is among organisations where nurses have agreed to derogations after it voiced "serious concerns" about patient safety during the walkout.
The hospital said it was "incredibly grateful" to RCN members for offering assurances but took the decision not to stand down a "business continuity incident" until it was confident it could staff services during the strike.
NHS England warned that staffing levels in some areas of the country will be "exceptionally low, lower than on previous strike days".
It added the number of rescheduled appointments due to strike action is set to hit half a million next week.
Health Secretary Steve Barclay has said the 28-hour nursing strike is "premature" and "disrespectful" to other unions.
The comments come ahead of a meeting of the NHS Staff Council, made up of health unions, employers and Government representatives, which will discuss the Government's 5% pay offer.
