Kidney disease tied to high death rates in COVID patients

COVID-19 patients who have chronic kidney disease (CKD) or develop coronavirus-related kidney injury in the intensive care unit (ICU) face higher odds of death than their otherwise-healthy peers, according to a study published late last week in Anaesthesia.

Led by researchers at Imperial College London, the retrospective study involved 372 adult COVID-19 patients in four ICUs in the United Kingdom from Mar 10 to Jul 31. Of the 372 patients, 216 (58%) had kidney impairment, 22% of which was CKD (48 patients) and 78% of which developed during hospitalization (168 patients).

Degree of injury, need for dialysis

In total, 139 of 372 patients (37%) died. Of the 156 patients with healthy kidneys, 32 (21%) died in the hospital, in contrast with 81 of 168 patients (48%) with newly developed kidney injury and 11 of 22 (50%) with CKD stage 1 through 4.

Among the other 26 patients who had CKD, 9 of 19 patients (47%) with end-stage renal failure (ESRF), who had already required routine outpatient dialysis, died. The death rate was highest in CKD patients who had undergone kidney transplant (6 of 7 [86%]).

Death rates rose along with worsening kidney injury classified by Kidney Disease: Improving Global Outcomes (KDIGO) classification; of 157 patients with stage 0 (least) injury, 33 (21%) died, compared with those with more serious stages 1 to 3 injury (91/186 [49%]).

Those who died were more likely to have needed dialysis than survivors (64/139 [46%] vs 57/233 [24%]). But once dialysis was started, death rates were not significantly different between survivors and non-survivors in patients with new kidney injury (39/82 [48%] vs 43/82 [52%]) or non–end-stage CKD (8/17 [47%] vs 9/17 [53%]).

Among 216 patients with kidney impairment, 121 (56%) needed dialysis in the hospital, and 9 of the 48 survivors who required dialysis for the first time in the ICU (19%) continued to need it after they were released, suggesting that COVID-19 may lead to long-term kidney impairment. Most patients (337 of 372 [91%] required mechanical ventilation. Median Acute Physiology and Chronic Health Evaluation (APACHE) II score was 15, with 0 the least likely to die in the ICU and 71 the most likely.

Vigilance, intensive care

The authors said that were surprised that the death rate in patients with ESRF and on dialysis, who usually have poorer outcomes in many other illnesses, wasn't significantly higher than in those with less-serious CKD and coronavirus-related kidney injury. The finding, they noted, suggests that COVID-19 patients receiving dialysis—including those with ESRF—have a similar chance for survival as those with less severe disease or injury and thus should be considered for ICU care.

But the researchers caution that their results may have been subject to selection bias, in which some patients with ESRF who were too sick for admission to the ICU may not have been included in the study during the peak of the last UK COVID-19 surge.

Patients were, on average, about 60 years old, 72% of them were men, and 76% were black or Asian.

The authors said that they don't know exactly why patients with impaired kidneys are more likely than others to die of COVID-19 but theorize that it could be because the virus causes inflammation of the kidney blood vessels, similar to how it inflames the lungs; the enhanced immune response ("cytokine storm") triggered by the virus injures the kidneys; or multiorgan failure leads to kidney tissue death.

"Our data demonstrate that renal impairment in patients admitted to intensive care with COVID‐19 is common and is associated with a high mortality and requirement for on‐going renal support after discharge from critical care," the authors wrote. "Attention needs to be paid to patients with COVID‐19 with any form of renal impairment and every effort made to prevent progression of renal injury in order to reduce mortality."

The researchers also remarked that patients who require dialysis in the hospital have a much lower survival rate than those who don't, which could have implications for resource allocation. "The impact on resource utilisation is considerable, especially in a pandemic situation where resources may have to be rationed," they wrote.

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