Positive fluid balance is associated with earlier acute kidney injury in COVID-19 patients

Introduction: Managing fluid balance in COVID-19 patients can be challenging, particularly if acute kidney injury (AKI) develops.
Aim of the study: We study the relationship between fluid net input and output (FNIO) in COVID-19 patients with development of AKI, time to development of AKI, in-hospital length of stay (LOS), and in-hospital mortality.
Material and Methods: Retrospective study of 403 patients with COVID-19. Data for FNIO were from day 1 through day 10 or earlier if AKI occurred.
Results: AKI occurred in 22.8%, in-hospital mortality occurred in 26.3%, mean days to AKI were 7.7 (SD=6.3), and mean LOS was 11.5 (SD=13.2) days. In the multivariate logistic regression analyses, increased FNIO mean was significantly associated with slightly increased odds for mortality (OR=1.001, 95% CI:1.0001, 1.0011, p=0.02) but was not significantly associated with AKI. In the multivariate linear regression analyses, increased FNIO mean was significantly associated with lesser days to AKI (B=-6.63*10-5, SE=<0.001, p=0.003) in the whole sample, greater days to AKI in the subset of those with ICU treatment (B=<0.001, SE=<0.001, p<0.001), while FNIO mean was not significantly associated with LOS.
Conclusions: Positive fluid balance was associated with faster onset of AKI and increased mortality. Fluid administration in patients with COVID-19 should be guided by routinely measuring FNIO. A restrictive fluid management regimen rather than usual care should be practiced.