But despite an hour without power, including in the intensive care ward, no patients at Karolinska University Hospital in Huddinge, south of Stockholm, were harmed.
At around 4pm the hospital reopened its accident and emergency ward, which had been forced to turn away ambulances when the power was lost.
“One operation was postponed for a couple of hours but it’s underway now. It’s a kidney transplant,” said Svante Baehrendtz, the hospital’s chief surgeon.
According to analysis carried out on Saturday afternoon, the fault appeared to lie in the hospital’s own power distribution network, possibly as a result of old cables.
Karolinska hospital has around 1,600 beds and was almost full when the power cut happened.
The problem was solved with a temporary rewiring, but the effects were still being felt late on Saturday. One consequence was that the hospital’s computer systems had not yet come back online.
“For the moment there are no safety risks to patients. But it was a serious situation during the hour in which we had no power,” said Baehrendtz.
The battery units which take over from the hospitals main reserve supply – for powering drip monitors, respirators and pumps in the intensive care ward – only kept the machines going for a short while. When they ran out, staff were forced to ventilate intensive care patients by hand, Baehrendtz explained.
Tommy Hoff, the managing director of Locum – the county council’s subsidiary which has responsibility for the power supply – said he took what happened extremely seriously.
“We have different backup systems to stop this from happening. Now we obviously need to analyse what went wrong and immediately put it right,” he said.
The reserve supply is tested every month and every hospital with an emergency ward has a similar system.
“The technical solutions can vary a bit, but the principle is the same,” said Hoff.
Stockholm county council is to demand a report on the incident from Locum, according to press officer Anders Fridell.
“Naturally it’s not acceptable that a hospital is affected in this way, irrespective of the cause,” said Fridell.