COVID-19 and kidney function

AKI is a sudden drop in kidney function, over a few hours to a few days. It commonly occurs with an episode of acute illness and is more likely if the illness is severe or if an individual is at greater risk of the condition. Its severity can range from a minor loss of kidney function to complete kidney failure.

It is essential it is identified and treated quickly, as AKI is associated with about 100,000 deaths a year in the UK, according to Kidney Care UK.

Updated NICE guidance on managing COVID-19 in hospitals lists AKI as one of the acute complications. The guidance says that for people with COVID-19, maintaining optimal fluid status (euvolaemia) is difficult but critical to reducing the incidence of AKI.

Treatments for COVID-19, such as diuretic therapy and non-invasive ventilation, and pre-existing conditions may increase the risk of AKI, and fever and a raised respiratory rate increase insensible fluid loss.

This highlights the complexity of managing unwell patients with the virus while trying to protect their kidney function.

During the first wave, hospitals saw high rates of AKI. Critical care units started to run out of fluid for dialysis machines and NHS England had to issue new guidance on conserving supplies. Almost one in three (29%) of those severely affected by COVID-19 needed dialysis as a result of AKI.

For those with moderate to advanced (stage 3+) chronic kidney disease, the risk of becoming unwell with COVID-19 was increased.

Meanwhile kidney services, including dialysis and transplant, were disrupted by the pandemic, as the NHS focused on treating the critically ill.

Higher risk of death

University Hospital Southampton AKI lead Becky Bonfield says she and her colleagues have seen an increase in the number and severity of AKI cases.

‘Not only have we seen more patients but they are more unwell and more likely to die,’ she says.

In a study published in the journal Nephrology, a third (34%) of those admitted to University Hospital Southampton with COVID-19 in the first wave had an AKI while they were admitted.

Having an AKI at the same time as COVID-19 meant a much higher risk of death – half the patients who also had an AKI died, compared with 21% who did not.

Almost a third of those severely affected by COVID-19 in the first wave of the pandemic needed dialysis

Picture credit: iStock

Causes of acute kidney injury

Most cases of acute kidney injury (AKI) are due to reduced blood flow to the kidneys, usually in a patient already unwell with another health condition.

This reduced blood flow could be caused by:

• » Low blood volume after bleeding, excessive vomiting or diarrhoea, or severe dehydration

• » The heart pumping out less blood than normal as a result of heart failure, liver failure or sepsis

• » Problems with the blood vessels, such as vasculitis – an autoimmune disease that causes inflammation and narrowing of blood vessels

• » Certain medications that can affect the blood supply to the kidney

• » Problems with the kidney itself, such as glomerulonephritis. This may be caused by a reaction to some drugs, infections or the liquid dye used in some types of X-rays

• » A blockage affecting the drainage of the kidneys, such as an enlarged prostate, a tumour in the pelvic area, such as an ovarian or bladder tumour, or kidney stones

Source: NHS – Acute Kidney Injury nhs.uk/conditions/acute-kidney-injury

Ms Bonfield suggests manypeople were affected by AKI in the second wave, as rates of COVID-19 were high, but suspects a greater proportion will have survived compared with the first wave, as understanding of COVID-19 has improved.

With increased rates of AKI during the pandemic, people have experienced renal problems who otherwise would not have done so. Ms Bonfield says she has seen the follow-up clinic for those who have had an AKI in hospital getting busier, and the demographic of patients shifting.

‘Now we have much younger people, in their twenties, thirties and forties, who have had acute AKI and are not getting back to their normal renal baseline,’ she says.

Ms Bonfield says she fears the COVID-19 pandemic could have stored up kidney problems that will gradually reveal themselves. Those who have had an AKI are at higher risk of having it again in future, and of developing chronic kidney disease, which is when kidney function starts to decline.

Ms Bonfield says she has seen patients who have had COVID-19 but did not need intensive care or support for their kidneys at that time but who later presented to hospital with the ongoing effects of long-COVID and AKI.

Long-term effects

Some patients need intensive care therapies to support kidney function on these subsequent admissions, she says. Many were previously well and have no significant underlying conditions.

‘These patients will need their renal function checking regularly for the next two years, and maybe lifelong,’ she says.

‘We are seeing a younger demographic that have had severe AKI. My worry is, if their baseline doesn’t get back to normal, they have a long life ahead of them for their kidney function to deteriorate. Will we have a cohort of people in 20 years’ time who need dialysis or transplants? These patients almost certainly wouldn’t have renal problems if they hadn’t had COVID-19.’

Nurses in primary care and elsewhere need to be alert to signs that kidney function could have declined or be declining, says Ms Bonfield. Kidney decline often has few symptoms initially but can be picked up via blood tests through increased levels of creatinine, a waste product removed by the kidneys.

‘Everyone has a different creatinine baseline,’ Ms Bonfield says. ‘When a nurse is looking at a blood test result, they shouldn’t be thinking about what is ‘normal’, as this is a wide standard. They need to be thinking about what is normal for this patient. Look at older blood tests to see if this creatinine level looks about the same or if it is increasing.’

If there are concerns about a patient’s renal function, referral to a GP is warranted for assessment of the cause, Ms Bonfield says. The GP can then refer to renal services as required. Those at high risk of AKI need to know when to seek help. This can include if they are vomiting or have diarrhoea, which can cause dehydration.

‘Early intervention saves lives with AKI. We don’t want patients staying at home and not seeking medical care,’ Ms Bonfield says.

Risk factors for acute kidney injury

Psychological support

For patients who have been in critical care and are receiving renal treatment, it can be a difficult and overwhelming experience.

Cardiff and Vale University Health Board interim director of nursing for specialist services Claire Main says many patients who had COVID-19 and are coming for renal care are distressed by what they have been through.

‘Are we going to have a cohort of people in 20 years’ time who need dialysis or transplants? These patients almost certainly wouldn’t have renal problems if they hadn’t had COVID-19’

Becky Bonfield, pictured, AKI lead, University Hospital Southampton

‘They have had a difficult journey. They have been acutely unwell and some have ended up on dialysis and with kidney failure,’ says Ms Main, who worked in critical care during the pandemic. ‘We are looking at the psychological and follow-up support those patients need.’

For a full version of this article go to rcni.com/COVID-19-AKI

Find out more

NICE: COVID-19 rapid guideline nice.org.uk/guidance/ng191

Clinical update: detecting AKI and caring for patients rcni.com/detect-AKI