When and in whom to initiate continuous renal replacement therapy (CRRT) for acute kidney injury (AKI) remains a highly controversial topic with large practice variation around the world. Even within countries, practice variation exists and recommendations for clinical practice are not specific. In this article, we report the consensus recommendations for timing and patient selection for CRRT - the results of the 2016 Acute Disease Quality Initiative XVII conference on ‘precision CRRT'. We suggest that these recommendations could serve to develop the best clinical practice and standards of care for use of CRRT in patients with AKI. Finally, we identify and highlight the areas of ongoing uncertainty and propose an agenda for future research.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901 .

This article reports the conclusions of the second part of a consensus expert conference on the nomenclature of renal replacement therapy (RRT) techniques currently utilized to manage acute kidney injury and other organ dysfunction syndromes in critically ill patients. A multidisciplinary approach was taken to achieve harmonization of definitions, components, techniques, and operations of the extracorporeal therapies. The article describes the RRT techniques in detail with the relevant technology, procedures, and phases of treatment and key aspects of volume management/fluid balance in critically ill patients. In addition, the article describes recent developments in other extracorporeal therapies, including therapeutic plasma exchange, multiple organ support therapy, liver support, lung support, and blood purification in sepsis. This is a consensus report on nomenclature harmonization in extracorporeal blood purification therapies, such as hemofiltration, plasma exchange, multiple organ support therapies, and blood purification in sepsis.

Cardiac surgery is a leading cause of acute kidney injury (AKI). Such AKI patients may develop progressive chronic kidney disease (CKD). Others, who appear to have sustained no permanent loss of function (normal serum creatinine), may still lose renal functional reserve (RFR). We extended the follow-up in the observational ‘Preoperative RFR Predicts Risk of AKI after Cardiac Surgery’ study from hospital discharge to 3 months after surgery for 86 (78.2%) patients with normal baseline estimated glomerular filtration rate (eGFR), and re-measured RFR with a high oral protein load. The primary study endpoint was change in RFR. Study registration at clinicaltrials.gov Identifier: NCT03092947, ISRCTN Registry: ISRCTN16109759. At 3 months, three patients developed new CKD. All remaining patients continued to have a normal eGFR (93.3 ± 15.1 mL/min/1.73 m²). However, when stratified by post-operative AKI and cell cycle arrest (CCA) biomarkers, AKI patients displayed a significant decrease in RFR {from 14.4 [interquartile range (IQR) 9.5 − 24.3] to 9.1 (IQR 7.1 − 12.5) mL/min/1.73 m²; P < 0.001} and patients without AKI but with positive post-operative CCA biomarkers also experienced a similar decrease of RFR [from 26.7 (IQR 22.9 − 31.5) to 19.7 (IQR 15.8 − 22.8) mL/min/1.73 m²; P < 0.001]. In contrast, patients with neither clinical AKI nor positive biomarkers had no such decrease of RFR. Finally, of the three patients who developed new CKD, two sustained AKI and one had positive CCA biomarkers but without AKI. Among elective cardiac surgery patients, AKI or elevated post-operative CCA biomarkers were associated with decreased RFR at 3 months despite normalization of serum creatinine. Larger prospective studies to validate the use of RFR to assess renal recovery in combination with biochemical biomarkers are warranted.

Studies have demonstrated a positive correlation between fluid overload (FO) and adverse outcomes in critically ill patients. The present study aims at defining the impact of hyperhydration on the Intensive Care Unit (ICU) mortality risk, comparing Bioelectrical Impedance Vector Analysis (BIVA) assessment with cumulative fluid balance (CFB) recording. We performed a prospective, dual-centre, clinician-blinded, observational study of consecutive patients admitted to ICU with an expected length of ICU stay of at least 72 hours. During observational period (72–120 hours), CFB was recorded and cumulative FO was calculated. At the admission and daily during the observational period, BIVA was performed. We considered FO between 5 % and 9.99 % as moderate and a FO ≥10 % as severe. According to BIVA hydration scale of lean body mass, patients were classified as normohydrated (>72.7 %–74.3 %), mild (>71 %–72.7 %), moderate (>69 %–71 %) and severe (≤69 %) dehydrated and mild (>74.3 %–81 %), moderate (>81 %–87 %) and severe (>87 %) hyperhydrated. Two multivariate logistic regression models were performed: the ICU mortality was the response variable, while the predictor variables were hyperhydration, measured by BIVA (BIVA model), and FO (FO model). A p-value <0.05 was considered to indicate statistical significance. One hundred and twenty-five patients were enrolled (mean age 64.8 ± 16.0 years, 65.6 % male). Five hundred and fifteen BIVA measurements were performed. The mean CFB recorded at the end of the observational period was 2.7 ± 4.1 L, while the maximum hydration of lean body mass estimated by BIVA was 83.67 ± 6.39 %. Severe hyperhydration measured by BIVA was the only variable found to be significantly associated with ICU mortality (OR 22.91; 95 % CI 2.38–220.07; p < 0.01). The hydration status measured by BIVA seems to predict mortality risk in ICU patients better than the conventional method of fluid balance recording. Moreover, it appears to be safe, easy to use and adequate for bedside evaluation. Randomized clinical trials with an adequate sample size are needed to validate the diagnostic properties of BIVA in the goal-directed fluid management of critically ill patients in ICU.