Critically ill COVID-19 patients with acute kidney injury more likely to die than those with pre-existing chronic kidney disease

New research being presented at Euroanaesthesia, the annual meeting of the European Society of Anaesthesiology and Intensive Care (ESAIC), held online this year, suggests that among COVID-19 patients admitted to the intensive care unit (ICU), those who have an abrupt decline in kidney function are more likely to die during hospitalisation than those with pre-existing kidney diseases. Moreover, renal replacement therapy (such as dialysis) does little to improve their chances of survival.

A sudden loss of kidney function—a condition known as acute kidney injury (AKI)—affects over a quarter of patients hospitalised with COVID-19 [1]. Previous studies suggest that kidney injury is linked with higher risk of death in COVID-19 patients. But outcomes of patients hospitalised with COVID-19 and AKI are not well understood. When AKI is severe, kidney function may be replaced by dialysis that removes toxins and excess fluid and salts that accumulate in the bloodstream.

To investigate whether AKI in COVID-19 patients without prior kidney disease correlates with a higher mortality, and whether this risk can be reduced by dialysis, Austrian researchers retrospectively studied all 129 patients who were admitted with confirmed COVID-19 to two intensive care units at a major teaching hospital in Vienna between September 1^st, 2020 and February 15^th, 2021. The median age of the patients was 66.5 years and two-thirds were male.

Patients were divided into three groups: those with a history of kidney disease at admission (33 patients); previously healthy kidney patients who developed acute kidney injury on day five of their ICU stay (those with an estimated glomerular filtration [eGFR] rate of <90 mL/min; 26 patients); and those with normal kidney function both before admission and on day five of their ICU stay (eGFR ≥90 mL/min; 70 patents). All patients were followed until the end of their ICU stay. In total, 32 patients needed renal replacement therapy.
 

The researchers found that 55% (18 of 33) of patients with a history of kidney disease, 46% (12 of 26) of patients with AKI, and 83% (58 of 70) of patients with normal kidney function survived their ICU stay—showing a highly significant difference in survival between the three groups.

In the two groups with kidney dysfunction, the likelihood of survival was significantly below average, indicating a higher risk of dying compared to normal kidney function. The results suggest that neither the earlier initiation of dialysis or the number of days on dialysis had a significant impact on survival.

“Our findings confirm that kidney dysfunction is a key risk factor for COVID-19-related death in intensive care patients. But, more importantly, they suggest that COVID-19 patients who develop acute kidney injury face a higher risk of dying in the ICU than those with pre-exisiting chronic kidney disease”, says lead author  Katharina Oberneder from Sigmund-Freud-Private University, Vienna, Austria. “Ultimately, what is most important is focusing on the early diagnosis of acute kidney dysfunction and how we can use these results to improve the care of critically ill COVID-19 patients.”

The researchers hope to do further research to better understand how different factors impact outcomes in this population and develop further insights about how to best to treat this high-risk population.

The authors note that their findings are observational and are limited to a small number of patients in one hospital in Vienna and that their data may be limited by its retrospective nature.