Early COVID-related acute kidney injury recovery may course with hydroelectrolytic disorders in patients with high risk of insensible fluid loss

Acute Kidney Injury (AKI) may occur in more than 30% of COVID hospitalized patients, and renal recovery is poorly described.

Aim: We aimed to evaluate the renal short-term recovery profile of COVID-related AKI (COV+) compared to COVID-unrelated AKI (COV-).

Design: case-control retrospective single-center study.

Methods: All patients admitted to the Hospital das Clínicas, University of São Paulo, who recovered AKI from April to June of 2020 (COV+, n=98) and from August to October of 2019 (COV-, n=50) were analyzed. Recovery was defined by spontaneous serum creatinine drop or withdrawal of dialysis. Serum electrolytes were analyzed during the first five days of recovery.

Results: Among 333 COV+ patients, 98 recovered from AKI  (29.4%), while 50 of 177 COV- patients recovered (28.2%). The COV- group presented higher prevalence of chronic morbidities, while the COV+ group had a worse acute clinical course requiring vasoactive drugs (VAD), mechanical ventilation (MV) and dialysis. COVID-19 diagnosis was associated with need of mechanical ventilation, dialysis, presence of fever, and higher use of any diuretic drug during first days of recovery. The presence of fever and mechanical ventilation were the predictors associated with intravascular volume depletion surrogates (daily progressive rising in sodium levels and elevation in serum urea: creatinine ratio). Neither COVID-19 nor diuretics use seem to be independent risk factors for this

Conclusions: Intravascular volume depletion surrogates are more common in short-term AKI-recovery of patients presenting fever and mechanical ventilation, commons features in SARS-CoV2 infection