Renal mitochondrial dysfunction in ovine experimental sepsis-associated acute kidney injury.

Sheep develop sepsis-associated acute kidney injury (SA-AKI) during experimental sepsis despite normal to increased renal oxygen delivery. A disturbed relation between oxygen consumption (V̇o2) and renal Na+ transport has been demonstrated in sheep and in clinical studies of AKI, which could be explained by mitochondrial dysfunction. We investigated the function of isolated renal mitochondria compared with renal oxygen handling in an ovine hyperdynamic model of SA-AKI. Anesthetized sheep were randomized to either an infusion of live Escherichia coli with resuscitative measures (sepsis group; n = 13 animals) or served as controls (n = 8 animals) for 28 h. Renal V̇o2 and Na+ transport were repeatedly measured. Live cortical mitochondria were isolated at baseline and at the end of the experiment and assessed in vitro with high-resolution respirometry. Sepsis markedly reduced creatinine clearance, and the relation between Na+ transport and renal V̇o2 was decreased in septic sheep compared with control sheep. Cortical mitochondrial function was altered in septic sheep with a reduced respiratory control ratio (6.0 ± 1.5 vs. 8.2 ± 1.6, P = 0.006) and increased complex II-to-complex I ratio during state 3 (1.6 ± 0.2 vs. 1.3 ± 0.1, P = 0.0014) mainly due to decreased complex I-dependent state 3 respiration (P = 0.016). However, no differences in renal mitochondrial efficiency or mitochondrial uncoupling were found. In conclusion, renal mitochondrial dysfunction composed of a reduction of the respiratory control ratio and an increased complex II/complex I relation in state 3 was demonstrated in an ovine model of SA-AKI. However, the disturbed relation between renal V̇o2 and renal Na+ transport could not be explained by a change in renal cortical mitochondrial efficiency or uncoupling.NEW & NOTEWORTHY We studied the function of renal cortical mitochondria in relation to oxygen consumption in an ovine model of sepsis with acute kidney injury. We demonstrated changes in the electron transport chain induced by sepsis consisting of a reduced respiratory control ratio mainly by a reduced complex I-mediated respiration. Neither an increase in mitochondrial uncoupling nor a reduction in mitochondrial efficiency was demonstrated and cannot explain why oxygen consumption was unaffected despite reduced tubular transport.

Decreased renal perfusion during acute kidney injury in critical COVID-19 assessed by magnetic resonance imaging: a prospective case control study.

BACKGROUND: Renal hypoperfusion has been suggested to contribute to the development of acute kidney injury (AKI) in critical COVID-19. However, limited data exist to support this. We aim to investigate the differences in renal perfusion, oxygenation and water diffusion using multiparametric magnetic resonance imaging in critically ill COVID-19 patients with and without AKI. METHODS: A prospective case-control study where patients without prior kidney disease treated in intensive care for respiratory failure due to COVID-19 were examined. Kidney Disease: Improving Global Outcomes Creatinine criteria were used for group allocation. Main comparisons were tested using Mann-Whitney U test. RESULTS: Nineteen patients were examined, ten with AKI and nine without AKI. Patients with AKI were examined in median 1 [0-2] day after criteria fulfillment. Age and baseline Plasma-Creatinine were similar in both groups. Total renal blood flow was lower in patients with AKI compared with patients without (median 645 quartile range [423-753] vs. 859 [746-920] ml/min, p = 0.037). Regional perfusion was reduced in both cortex (76 [51-112] vs. 146 [123-169] ml/100 g/min, p = 0.015) and medulla (28 [18-47] vs. 47 [38-73] ml/100 g/min, p = 0.03). Renal venous saturation was similar in both groups (72% [64-75] vs. 72% [63-84], ns.), as was regional oxygenation (R2*) in cortex (17 [16-19] vs. 17 [16-18] 1/s, ns.) and medulla (29 [24-39] vs. 27 [23-29] 1/s, ns.). CONCLUSIONS: In critically ill COVID-19 patients with AKI, the total, cortical and medullary renal blood flows were reduced compared with similar patients without AKI, whereas no differences in renal oxygenation were demonstrable in this setting. Trial registration ClinicalTrials ID: NCT02765191 , registered May 6 2014 and updated May 7 2020.

Evolution of NETosis markers and DAMPs have prognostic value in critically ill COVID-19 patients.

Coronavirus disease 19 (COVID-19) presents with disease severities of varying degree. In its most severe form, infection may lead to respiratory failure and multi-organ dysfunction. Here we study the levels and evolution of the damage associated molecular patterns (DAMPS) cell free DNA (cfDNA), extracellular histone H3 (H3) and neutrophil elastase (NE), and the immune modulators GAS6 and AXL in relation to clinical parameters, ICU scoring systems and mortality in patients (n = 100) with severe COVID-19. cfDNA, H3, NE, GAS6 and AXL were increased in COVID-19 patients compared to controls. These measures associated with occurrence of clinical events and intensive care unit acquired weakness (ICUAW). cfDNA and GAS6 decreased in time in patients surviving to 30 days post ICU admission. A decrease of 27.2 ng/mL cfDNA during ICU stay associated with patient survival, whereas levels of GAS6 decreasing more than 4.0 ng/mL associated with survival. The presence of H3 in plasma was a common feature of COVID-19 patients, detected in 38% of the patients at ICU admission. NETosis markers cfDNA, H3 and NE correlated well with parameters of tissue damage and neutrophil counts. Furthermore, cfDNA correlated with lowest p/f ratio and a lowering in cfDNA was observed in patients with ventilator-free days.

COVID-19 patients in intensive care develop predominantly oliguric acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) is a syndrome of reduced glomerular filtration rate and/or reduced urine flow associated with mortality in corona virus disease 2019 (COVID-19). AKI is often associated with renal tissue damage, which may lead to chronic kidney disease. Biomarkers of tissue damage may identify patients of particular risk. METHODS: In a prospective observational study of 57 patients admitted to intensive care, AKI incidence and characteristics was evaluated according to KDIGO criteria and related to days after admission. Urinary albumin, Neutrophil Gelatinase-Associated Lipocalin (NGAL), Kidney Injury Molecule 1 (KIM-1) and Plasma Tissue Inhibitor of MetalloProteinase 2 (TIMP-2) were analysed in 52 patients at admission. The majority (n = 51, 89%) of patients developed AKI, and 27 (47%) patients had predominantly oliguric AKI where oliguria was more severe than plasma Creatinine increase. Severe oliguria within first 2 days after admission was common (n = 37, 65%), whereas stage 2 and 3 AKI due to Creatinine occurred later than day 2 in 67% (12/18) of cases. Renal replacement therapy was started in 9 (16%) patients, and 30-day mortality was 28%. Urinary biomarkers were increased in a majority of patients, but did not robustly predict KDIGO stage. Most patients had microalbuminuria, and severe albuminuria (albumin Creatinine ratio > 30 mg/mmol) was found in n = 9 (17%) patients. CONCLUSIONS: A majority of patients with COVID-19 admitted to the ICU develop AKI. The functional deficit is often low urinary volume, and initial levels of biomarkers are generally increased without clear relation to final AKI stage.

Increased levels of plasma cytokines and correlations to organ failure and 30-day mortality in critically ill Covid-19 patients.

BACKGROUND: The infection caused by SARS CoV-2 has been postulated to induce a cytokine storm syndrome that results in organ failure and even death in a considerable number of patients. However, the inflammatory response in Corona virus disease-19 (Covid-19) and its potential to cause collateral organ damage has not been fully elucidated to date. This study aims to characterize the acute cytokine response in a cohort of critically ill Covid-19 patients. METHOD: 24 adults with PCR-confirmed Covid-19 were included at time of admission to intensive care a median of eleven days after initial symptoms. Eleven adult patients admitted for elective abdominal surgery with preoperative plasma samples served as controls. All patients were included after informed consent was obtained. 27 cytokines were quantified in plasma. The expression of inflammatory mediators was then related to routine inflammatory markers, SAPS3, SOFA score, organ failure and 30-day mortality. RESULTS: A general increase in cytokine expression was observed in all Covid-19 patients. A strong correlation between respiratory failure and IL-1ra, IL-4, IL-6, IL-8 and IP-10 expression was observed. Acute kidney injury development correlated well with increased levels of IL-1ra, IL-6, IL-8, IL-17a, IP-10 and MCP-1. Generally, the cohort demonstrated weaker correlations between cytokine expression and 30-day mortality out of which IL-8 showed the strongest signal in terms of mortality. CONCLUSION: The present study found that respiratory failure, acute kidney injury and 30-day mortality in critically ill Covid-19 patients are associated with moderate increases of a broad range of inflammatory mediators at time of admission.