Clinical characteristics and outcome of critically ill COVID-19 patients with acute kidney injury: a single centre cohort study

Abstract

Background: Acute kidney injury (AKI) is a common manifestation among patients critically ill with SARS-CoV-2 infection (Coronavirus 2019) and is associated with significant morbidity and mortality. The pathophysiology of renal failure in this context is not fully understood, but likely to be multifactorial. The intensive care unit outcomes of patients following COVID-19 acute critical illness with associated AKI have not been fully explored. We conducted a cohort study to investigate the risk factors for acute kidney injury in patients admitted to and intensive care unit with COVID-19, its incidence and associated outcomes.

Methods: We reviewed the medical records of all patients admitted to our adult intensive care unit suffering from SARS-CoV-2 infection from 14th March 2020 until 12th May 2020. Acute kidney injury was defined using the Kidney Disease Improving Global Outcome (KDIGO) criteria. The outcome analysis was assessed up to date as 3rd of September 2020.

Results: A total of 81 patients admitted during this period. All patients had acute hypoxic respiratory failure and needed either noninvasive or invasive mechanical ventilatory support. Thirty-six patients (44%) had evidence of AKI (Stage I-33%, Stage II-22%, Renal Replacement Therapy (RRT)-44%). All patients with AKI stage III had RRT. Age, diabetes mellitus, immunosuppression, lymphopenia, high D-Dimer levels, increased APACHE II and SOFA scores, invasive mechanical ventilation and use of inotropic or vasopressor support were significantly associated with AKI. The peak AKI was at day 4 and mean duration of RRT was 12.5 days. The mortality was 25% for the AKI group compared to 6.7% in those without AKI. Among those received RRT and survived their illness, the renal function recovery is complete and back to baseline in all patients.

Conclusion: Acute kidney injury and renal replacement therapy is common in critically ill patients presenting with COVID-19. It is associated with increased severity of illness on admission to ICU, increased mortality and prolonged ICU and hospital length of stay. Recovery of renal function was complete in all survived patients.

Keywords: Acute kidney injury; COVID-19; Intensive care.

Fig. 1

COVID-19 patient flow diagram. AKI, Acute Kidney Injury; RRT, Renal Replacement Therapy. The Acute Kidney Injury is defied according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria

Fig. 2

The lymphocyte counts (10⁹/l) and D-Dimer levels for Day 1 (a: lymphocyte, b: d-Dimer) and over the 7 days of Intensive Care Unit admission (c: lymphocyte counts, d; D-Dimer) for both groups with and without acute kidney injury. The 2A and 2B are presented as Box and Whiskers plots with median and maximum and minimum values. 2C and 2D shows scatter plots and the lines represent median values. ^*The comparison between AKI vs No AKI group for that particular time point by Mann-Whitney U test and P < 0.05

Fig. 3

Daily cumulative fluid balance for patients with and without AKI for the first 10 days of ICU admission. Data is presented as median and interquatile ranges. ^*The comparison between AKI vs No AKI group for that particular time point by Mann-Whitney U test and P < 0.05

Fig. 4

The recovery of acute kidney injury across all stages of AKI as defined by the Kidney Disease Improving Global Outcomes (KDIGO) criteria over time during the intensive care unit stay. The RRT group recovery is defined as normalisation of renal function off renal replacement therapy. AKI, Acute kidney injury; ICU, Intensive Care Unit; RRT, Renal Replacement Therapy