Hospitals are having to conserve life-saving dialysis fluid in the coming days because of national shortages, as it has been revealed that 28% of coronavirus patients in intensive care who need significant help to breathe also need kidney support.

According to the Intensive Care National Audit & Research Centre, more than one in four critically ill coronavirus patients on advanced respiratory support need dialysis for an average time of four days to keep them alive.

The shortages have forced NHS England to send out emergency guidance to trusts telling them to conserve supplies and lend fluids to each other where needed.

The guidance advises a new strategy, including limiting trusts to four days’ supply and advising equipment to connect the patient to dialysis machines can be used for longer than previous guidance stated.

The letter said: “The revised strategy should be to conserve both fluids and sets [equipment used to connect the patient to a dialysis machine] used in CVVH [a form of dialysis] and it is recommended that the following actions are taken. In contrast to previous guidance, sets should be used for 24-48 hours. If the supply of machines allows, the use of the set may continue longer up to the recommended time permitted,” said James Palmer, the national medical director of specialised services at NHS England, in a letter.

It continued: “To further conserve fluid stocks, CVVH is preferred to CVVHD [a type of dialysis that uses more fluid], but individualised case by case. During the current clinical scenario, the addition dialysis (CVVHD mode) should be rarely needed.”

Another letter said that providers should be limited to ordering four days of supply. It added: “On Monday 27 April the supply chain constraints will be reviewed so further ordering frequency can be defined aiming to move to weekly orders as soon as stocks allow.”

The letter said: “With units who have less than four days supply in stock from 22 April, based upon recent usage, should place new orders for four days clinical requirements only (Thursday 23 April through to Sunday 26 April).”

It advised trusts to work together to support each other seeking “a mutual aid solution supported by the critical care and renal networks”.

It said: “The networks should actively contact all the constituent providers to identify available stock. If a network solution is determined escalation is required to the regional incident team to determine whether a cross network solution is possible.”

Dialysis is a procedure to remove waste products and excess fluid from the blood when the kidneys stop working properly. It often involves diverting blood to a machine to be cleaned.

Continuous veno-venous hemodialysis (CVVHD) uses fluids to draw out the byproducts of metabolism when the kidneys are failing to pass it out. Continuous Veno-Venous Hemofiltration (CVVH) uses pressure, and less fluids that CVVHD, to filter out the byproducts of metabolism. It is a temporary treatment for patients with acute renal failure who are unstable. With CVVH, a dialysis catheter is placed in one of the main veins of the body. Different forms of dialysis use differing amounts of fluids.

A doctor who works with coronavirus patients, speaking anonymously, said: “There is clearly a concern about the nation’s ability to provide renal replacement therapy during the pandemic. Renal failure is often a complicating development in patients that are critically ill. If supplies of fluid and sets run low enough, then difficult decisions will have to be made about who receives renal replacement therapy and who doesn’t.”

He added: “It seems that [the person who wrote the letter] is worried our capacity to provide renal replacement will run dry without proper management of fluids and consumables.”

“One of the issues had with covid is around the fact that more patients need support for kidneys than previously,” said the vice-dean of the Faculty of Intensive Care Medicine, Dr Daniele Bryden.

“For example, in China about 15% of patients in intensive care needed kidney support and we are noticing a higher number in the UK. In London some areas are reporting 25% patients needing some degree of support with kidneys.”

Bryden said it was unclear why this was. “No one knows why that is but one thing it may be is that we are not seeing the same population being affected, we may have a higher population in the UK of more people at risk of kidney failure.”

She added: “Those with high blood pressure and diabetes are more at risk of ending up in intensive care with covid … [They are] also groups of people with low level risk getting kidney issues when they become unwell.”

“Nationally we are looking to support each other and make sure kidney support is provided so we are giving it in a different way or using support from dialysis facilities in hospital or locally if you have got them.”

An NHS spokesperson said: “There is significant global pressure on the supplies of the particular types of renal replacement therapies being used to treat Covid-19 patients who develop kidney problems, and the NHS is working with government and our partners to ensure supplies are maintained.”