0706 GMT November 29, 2020
CKD is a type of kidney disease in which kidney function declines over a period of months to years, and is more common in older people. There are five stages of the disease, ranging from early stages (one and two) in which people initially have no symptoms, through to the more serious stages three to five, which can be associated with complications such as high blood pressure, type 2 diabetes and heart disease. CKD stage five is termed end stage kidney failure which must be treated with either dialysis (at home or in hospital), involving complex filtering machinery that takes over the blood-cleaning functions of the kidneys, or with a kidney transplant, medicalxpress.com reported.
AKI is an abrupt loss of kidney function that takes place over seven days or less, and can have several causes, including the damage and inflammation caused by the COVID-19 virus itself, loss of blood flow to the kidneys, damage from pharmaceutical drugs or other ingested/injected substances, or by anything obstructing the flow of urine in the urinary tract.
This new study, led by Dr. Sanooj Soni from Imperial College London, UK, and colleagues, examined the association between AKI and CKD with clinical outcomes in 372 patients with COVID-19 admitted to four regional intensive care units (ICUs) in the UK between March 10 to July 23, 2020 (Hammersmith Hospital, London; St Mary's Hospital, London; Charing Cross Hospital, London; and Queen Elizabeth Hospital, Birmingham).
The average age of the patients was around 60 years, and 72% of them were male. Also of note was the fact that the majority of patients were of Black, Asian of Ethnic Minority (BAME) background (281 patients, 76%).
A total of 216 (58%) patients had some form of kidney impairment (45% developed AKI during their ICU stay, while 13% had pre-existing CKD), while 42% had no CKD or AKI. The patients who developed AKI had no history of serious kidney disease before their ICU admission (known from blood tests either at admission to hospital or from their medical records), suggesting that the AKI was directly related to their COVID-19 infection.
The authors found that patients with no kidney injury or disease had a mortality of 21% (32/156 patients). Those with new onset AKI caused by the COVID-19 virus had a mortality of 48% (81/168), whilst for those with pre-existing CKD (stages 1-4) mortality was 50% (11 /22). In those patients with end-stage kidney failure (i.e. CKD stage five), where they already required regular out-patient dialysis, mortality was 47% (9 of 19 patients). Mortality was greatest in those patients with kidney transplants, with six out of seven patients (86%) dying, highlighting that these patients are an extremely vulnerable group.
The investigators also examined the rates of renal replacement therapy, a form of hospital dialysis, due to COVID-19 in these ICU patients with kidney injury. Out of 216 patients with any form of kidney impairment, 121 (56%) patients required renal replacement therapy. Of the 48 survivors who needed dialysis for the first time during their ICU stay, nine patients (19%) had to continue with dialysis after discharge from ICU, suggesting COVID-19 may lead to chronic kidney problems.
"To the best of our knowledge, this is the first comprehensive analysis of outcomes in critically unwell COVID-19 patients in the UK with kidney failure, particularly in patients with pre-existing chronic kidney disease," said the authors.
The authors noted their surprise that mortality in patients with end-stage kidney failure and on dialysis, who normally have worse outcomes in many other diseases, was similar to that in patients with less severe kidney disease and COVID-19 associated AKI. This finding may suggest that such patients benefit equally from ICU admission and thus the threshold for admission should be calibrated accordingly in any future COVID-19 surge. Put another way, these results suggest that patients on dialysis with COVID-19 appear as likely to survive as patients with less serious CKD or AKI and can be considered for admission to an ICU bed.
However, the authors recommend caution interpreting these results due to selection bias — meaning that in this study only patients who were cared for in ICU during the peak of the last surge were included and other patients with end stage kidney failure, who may have been too unwell for admission to ICU, were not. This may have contributed to these findings of similar mortality in patients with end-stage kidney failure compared to those with less serious forms of CKD and AKI.