IntroductionAcute Kidney Injury (AKI) is common in critical ill populations and its association with high short-term mortality is well established. However, long-term risks of death and renal dysfunction are poorly understood and few studies exclude patients with pre-existing renal disease, meaning outcome for de novo AKI has been difficult to elicit. We aimed to compare the long-term risk of Chronic Kidney Disease (CKD), End Stage Renal Disease (ESRD) and mortality in critically ill patients with and without severe de novo AKI.MethodThis cohort study was conducted between 2005 and 2011 in Swedish intensive care units (ICU). Data from 130134 adult patients listed on the Swedish intensive care register-database was linked with other national registries. Patients with pre-existing CKD (4192) and ESRD (1389) were excluded, as were cases (26771) with incomplete data. Patients were classified according to AKI exposure during ICU admission. Outcome in the de novo AKI group was compared to the non-exposed (no-AKI) intensive care control group. Primary outcome was all-cause mortality. Follow-up ranged from one to seven years (median 2.1 years). Secondary outcomes were incidence of CKD and ESRD and median follow-up was 1.3 years.ResultsOf 97 782 patients, 5273 (5.4%) had de novo AKI. These patients had significantly higher crude mortality at one (48.4% vs. 24.6%) and five years (61.8% vs. 39.1%) compared to the control group. The first 30% of deaths in AKI patients occurred within 11 days of ICU admission whilst the 30-centile in the no-AKI group died by 748 days. CKD was significantly more common in AKI survivors at one year (6.0% vs. 0.44%) than in no-AKI group (adjusted incidence rate ratio (IRR) 7.6). AKI patients also had significantly higher rates of ESRD at one (2.0% vs. 0.08%) and at five years (3.9% vs. 0.3%) than those in the comparison group (adjusted IRR 22.5).ConclusionThis large cohort study demonstrated that de novo AKI is associated with increased short and long-term risk of death. AKI is independently associated with increased risk of CKD and ESRD as compared to an ICU control population. Severe de novo AKI survivors should be routinely followed-up and their renal function monitored.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-0920-y) contains supplementary material, which is available to authorized users.

IntroductionPrevalence of chronic kidney disease (CKD) amongst intensive care unit (ICU) admissions is rising. How mortality and risk of end-stage renal disease (ESRD) differs between those with and without CKD and with acute kidney injury (AKI) is unclear. Determining factors that increase the risk of ESRD is essential to optimise treatment, identify patients requiring nephrological surveillance and for quantification of dialysis provision.MethodThis cohort study used the Swedish intensive care register 2005–2011 consisting of 130,134 adult patients. Incomplete cases were excluded (26,771). Patients were classified (using diagnostic and intervention codes as well as admission creatinine values) into the following groups: ESRD, CKD, AKI, acute-on-chronic disease (AoC) or no renal dysfunction (control). Primary outcome was all-cause mortality. Secondary outcome was ESRD incidence.ResultsOf 103,363 patients 4,192 had pre-existing CKD; 1389 had ESRD; 5273 developed AKI and 998 CKD patients developed AoC. One-year mortality was greatest in AoC patients (54 %) followed by AKI (48.7 %), CKD (47.6 %) and ESRD (40.3 %) (P < 0.001). Five-year mortality was highest for the CKD and AoC groups (71.3 % and 68.2 %, respectively) followed by AKI (61.8 %) and ESRD (62.9 %) (P < 0.001). ESRD incidence was greatest in the AoC and CKD groups (adjusted incidence rate ratio (IRR) 259 (95 % confidence interval (CI) 156.9–429.1) and 96.4, (95 % CI 59.7–155.6) respectively) and elevated in AKI patients compared with controls (adjusted IRR 24 (95 % CI 3.9–42.0); P < 0.001). Risk factors independently associated with ESRD in 1-year survivors were, according to relative risk ratio, AoC (356; 95 % CI 69.9–1811), CKD (267; 95 % CI 55.1–1280), AKI (30; 95 % CI 5.98–154) and presence of elevated admission serum potassium (4.6; 95 % CI 1.30–16.40) (P < 0.001).ConclusionsPre-ICU renal disease significantly increases risk of death compared with controls. Subjects with AoC disease had extreme risk of developing ESRD. All patients with CKD who survive critical care should receive a nephrology referral.Trial registrationClinical trials registration number: NCT02424747 April 20th 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-1101-8) contains supplementary material, which is available to authorized users.

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Background Outcome for critically ill patients with COVID-19 treated with continuous renal replacement therapy (CRRT) is largely unknown. We describe mortality and renal outcome in this group. Methods This observational study was conducted at a university hospital in Sweden. We studied critically ill adult COVID-19 patients with Acute Kidney injury (AKI) who received CRRT. Results In 451 patients, AKI incidence was 43.7%. 18.2% received CRRT. Median age of CRRT patients was 60 years (IQR 54–65), 90% were male, median BMI was 29 (IQR 25–32), 23.2% had Diabetes, 37.8% hypertension and 6.1% chronic kidney disease prior to admission. 100% required mechanical ventilation. 8.5% received Extra Corporeal Membrane Oxygenation. Median length of stay was 23 days (IQR 15–26). ICU mortality was 39% and 90-day mortality was 45.1%. Age, baseline creatinine values and body weight change were associated with 60 days mortality. Of the survivors, no patients required dialysis at hospital discharge, 73.8% recovered renal function and a median 10.5% of body weight was lost during admission. Conclusions Critically ill COVID-19 patients with AKI who received CRRT had a 90-day mortality of 45.1%. At follow-up, three quarters of survivors had recovered renal function. This information is important in the clinical management of COVID-19.

Early initiation of treatment and fine-tuning of the RRT technique may improve outcome. Consensus regarding AKI definitions, renal function measurement and standardised follow-up regimens are required. Further long-term studies are needed.

Background The Doppler-derived renal resistive index (RRI) is emerging as a promising bedside tool for assessing renal perfusion and risk of developing acute kidney injury in critically ill patients. It is not known what level of ultrasonography competence is needed to obtain reliable RRI values. Objective The aim of this study was to evaluate the feasibility of RRI measurements by an intermediate and novice sonographer in a volunteer population. Methods After a focused teaching session, an intermediate (resident), novice (medical student) and expert sonographer performed RRI measurements in 23 volunteers consecutively and blinded to the results of one another. Intraclass correlation coefficients and Bland–Altman plots were used to evaluate interobserver reliability, bias and precision. Results Both non-experts were able to obtain RRI values in all volunteers. Median RRI in the population measured by the expert was 0.58 (interquartile range 0.52–0.62). The intraclass correlation coefficient was 0.96 (95% confidence interval 0.90–0.98) for the intermediate and expert, and 0.85 (95% confidence interval 0.69–0.94) for the novice and expert. In relation to the measurements of the expert, both non-experts showed negligible bias (mean difference 0.002 [95% confidence interval − 0.005 to 0.009, p = 0.597] between intermediate and expert, mean difference 0.002 [95% confidence interval − 0.011 to 0.015, p = 0.752] between novice and expert) and clinically acceptable precision (95% limits of agreement − 0.031 to 0.035 for the intermediate, 95% limits of agreement − 0.056 to 0.060 for the novice). Conclusions RRI measurements by both an intermediate and novice sonographer in a volunteer population were reliable, accurate and precise after a brief course. RRI is easy to learn and feasible within the scope of point-of-care ultrasound.

Background Renal dysfunction after acute kidney injury (AKI) is common, potentially modifiable, but poorly understood. Acute kidney disease (AKD) describes renal dysfunction 7 to 90 days after AKI and is determined by percentage change in creatinine from baseline. Chronic kidney disease (CKD) is defined as the estimated glomerular filtration rate (eGFR) less than 60 ml/min/1.73 m2 persisting for more than 90 days. We compared CKD incidence using both creatinine- and cystatin C-based GFR with AKD incidence at 90 days in AKI survivors. Methods A prospective cohort study was conducted in a Swedish intensive care unit (ICU) between 2008 and 2010. We included AKI patients alive at 90 days. We excluded patients <18 and >100 years, death before follow-up, CKD prior to admission, and follow-up before 60 days or beyond 270 days. Creatinine and cystatin C were measured at 90 days and converted to eGFR (mL/min/1.73 m2). Results We included 274 patients. At 90-day follow-up, the median creatinine eGFR (MDRD) was 81.6 (IQR 58.6–106.8) and median cystatin C eGFR was 51.5 (IQR 35.8–70.7). The incidence of CKD (eGFR < 60) was 25.8% based on creatinine but 63.7% using cystatin C estimates. AKD was present in 47 patients (18.9%). Age, discharge cystatin C, creatinine at discharge, and female gender predicted creatinine-defined CKD at follow-up. Age, discharge cystatin C, CRRT on ICU, and diabetes were associated with cystatin C-based CKD. Conclusions In AKI survivors followed up at 3 months, CKD criteria were met in a quarter of patients using creatinine and in two-thirds using cystatin C eGFR. Less than one-fifth of patients fulfilled AKD criteria. The application of AKD criteria may underestimate renal dysfunction in AKI survivors.

Background Renal resistive index (RRI) is a promising tool for the assessment of acute kidney injury (AKI) in critically ill patients in general, but its role and association to AKI among patients with Coronavirus disease 2019 (COVID-19) is not known. Objective The aim of this study was to describe the pattern of RRI in relation to AKI in patients with COVID-19 treated in the intensive care unit. Methods In this observational cohort study, RRI was measured in COVID-19 patients in six intensive care units at two sites of a Swedish University Hospital. AKI was defined by the creatinine criteria in the Kidney Disease Improving Global Outcomes classification. We investigated the association between RRI and AKI diagnosis, different AKI stages and urine output. Results RRI was measured in 51 patients, of which 23 patients (45%) had AKI at the time of measurement. Median RRI in patients with AKI was 0.80 (IQR 0.71–0.85) compared to 0.72 (IQR 0.67–0.78) in patients without AKI (p = 0.004). Compared to patients without AKI, RRI was higher in patients with AKI stage 3 (median 0.83, IQR 0.71–0.85, p = 0.006) but not in patients with AKI stage 1 (median 0.76, IQR 0.71–0.83, p = 0.347) or AKI stage 2 (median 0.79, min/max 0.79/0.80, n = 2, p = 0.134). RRI was higher in patients with an ongoing AKI episode compared to patients who never developed AKI (median 0.72, IQR 0.69–0.78, p = 0.015) or patients who developed AKI but had recovered at the time of measurement (median 0.68, IQR 0.67–0.81, p = 0.021). Oliguric patients had higher RRI (median 0.84, IQR 0.83–0.85) compared to non-oliguric patients (median 0.74, IQR 0.69–0.81) (p = 0.009). After multivariable adjustment, RRI was independently associated with AKI (OR for 0.01 increments of RRI 1.22, 95% CI 1.07–1.41). Conclusions Critically ill COVID-19 patients with AKI have higher RRI compared to those without AKI, and elevated RRI may have a role in identifying severe and oliguric AKI at the bedside in these patients.