Hemodynamic tolerance of intermittent hemodialysis in critically ill patients: usefulness of practice guidelines

Focus on oliguria during renal replacement therapy

Oliguria is a clinical symptom characterized by decreased urine output, which can occur at any stage of acute kidney injury and also during renal replacement therapy. In some cases, oliguria may resolve with adjustment of blood purification dose or fluid management, while in others, it may suggest a need for further evaluation and intervention. It is important to determine the underlying cause of oliguria during renal replacement therapy and to develop an appropriate treatment plan. This review looks into the mechanisms of urine production to investigate the mechanism of oliguria during renal replacement therapy from two aspects: diminished glomerular filtration rate and tubular abnormalities. The above conditions all implying a renal oxygen supply-demand imbalance, which is the signal of worsening kidney injury. It also proposes a viable clinical pathway for the treatment and management of patients with acute kidney injury receiving renal replacement therapy.

Impact of the first 24 h of continuous kidney replacement therapy on hemodynamics, ventilation, and analgo-sedation in critically ill children

BACKGROUND

In a group of children admitted to the paediatric intensive care unit (PICU) receiving continuous kidney replacement therapy (CKRT), we aim to evaluate the data about their hemodynamic, ventilation and analgo-sedation profile in the first 24 h of treatment and possible associations with mortality.

METHODS

Retrospective cohort study of children admitted to the PICU of the University Hospital of Padova undergoing CKRT between January 2011 and March 2021. Data was collected at baseline (T0), after 1 h (T1) and 24 h (T24) of CKRT treatment. The differences in outcome measures were compared between these time points, and between survivors and non-survivors.

RESULTS

Sixty-nine patients received CKRT, of whom 38 (55%) died during the PICU stay. Overall, the vasoactive inotropic score and the adrenaline dose increased at T1 compared to T0 (p = 0.012 and p = 0.022, respectively). Compared to T0, at T24 patients showed an improvement in the following ventilatory parameters: Oxygenation Index (p = 0.005), Oxygenation Saturation Index (p = 0.013) PaO2/FiO2 ratio (p = 0.005), SpO2/FiO2 ratio (p = 0.002) and Mean Airway Pressure (p = 0.016). These improvements remained significant in survivors (p = 0.01, p = 0.027, p = 0.01 and p = 0.015, respectively) but not in non-survivors. No changes in analgo-sedative drugs have been described.

CONCLUSIONS

CKRT showed a significant impact on hemodynamics and ventilation in the first 24 h of treatment. We observed a significant rise in the inotropic/vasoactive support required after 1 h of treatment in the overall population, and an improvement in the ventilation parameters at 24 h only in survivors.

Initiation of continuous renal replacement therapy versus intermittent hemodialysis in critically ill patients with severe acute kidney injury: a secondary analysis of STARRT-AKI trial

BACKGROUND

There is controversy regarding the optimal renal-replacement therapy (RRT) modality for critically ill patients with acute kidney injury (AKI).

METHODS

We conducted a secondary analysis of the STandard versus Accelerated Renal Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial to compare outcomes among patients who initiated RRT with either continuous renal replacement therapy (CRRT) or intermittent hemodialysis (IHD). We generated a propensity score for the likelihood of receiving CRRT and used inverse probability of treatment with overlap-weighting to address baseline inter-group differences. The primary outcome was a composite of death or RRT dependence at 90-days after randomization.

RESULTS

We identified 1590 trial participants who initially received CRRT and 606 who initially received IHD. The composite outcome of death or RRT dependence at 90-days occurred in 823 (51.8%) patients who commenced CRRT and 329 (54.3%) patients who commenced IHD (unadjusted odds ratio (OR) 0.90; 95% confidence interval (CI) 0.75-1.09). After balancing baseline characteristics with overlap weighting, initial receipt of CRRT was associated with a lower risk of death or RRT dependence at 90-days compared with initial receipt of IHD (OR 0.81; 95% CI 0.66-0.99). This association was predominantly driven by a lower risk of RRT dependence at 90-days (OR 0.61; 95% CI 0.39-0.94).

CONCLUSIONS

In critically ill patients with severe AKI, initiation of CRRT, as compared to IHD, was associated with a significant reduction in the composite outcome of death or RRT dependence at 90-days.

Management of renal replacement therapy among adults in French intensive care units: A bedside practice evaluation

Background

This study aimed to investigate renal replacement therapy (RRT) practices in a representative nationwide sample of French intensive care units (ICUs).

Methods

From July 1 to October 5 2021, 67 French ICUs provided data regarding their ICU and RRT implementation. We used an online questionnaire to record general data about each participating ICU, including the type of hospital, number of beds, staff ratios, and RRT implementation. Each center then prospectively recorded RRT parameters from 5 consecutive acute kidney injury (AKI) patients, namely the indication, type of dialysis catheter used, type of catheter lock used, type of RRT (continuous or intermittent), the RRT parameters initially prescribed (dose, blood flow, and duration), and the anticoagulant agent used for the circuit.

Results

A total of 303 patients from 67 ICUs were analyzed. Main indications for RRT were oligo-anuria (57.4%), metabolic acidosis (52.1%), and increased plasma urea levels (47.9%). The commonest insertion site was the right internal jugular (45.2%). In 71.0% of cases, the dialysis catheter was inserted by a resident. Ultrasound guidance was used in 97.0% and isovolumic connection in 90.1%. Citrate, unfractionated heparin, and saline were used as catheter locks in 46.9%, 24.1%, and 21.1% of cases, respectively.

Conclusions

Practices in French ICUs are largely compliant with current national guidelines and international literature. The findings should be interpreted in light of the limitations inherent to this type of study.

An update review on hemodynamic instability in renal replacement therapy patients

BACKGROUND

Hemodynamic instability in patients undergoing kidney replacement therapy (KRT) is one of the most common and essential factors influencing mortality, morbidity, and the quality of life in this patient population.

METHOD

Decreased cardiac preload, reduced systemic vascular resistance, redistribution of fluids, fluid overload, inflammatory factors, and changes in plasma osmolality have all been implicated in the pathophysiology of hemodynamic instability associated with KRT.

RESULT

A cascade of these detrimental mechanisms may ultimately cause intra-dialytic hypotension, reduced tissue perfusion, and impaired kidney rehabilitation. Multiple parameters, including dialysate composition, temperature, posture during dialysis sessions, physical activity, fluid administrations, dialysis timing, and specific pharmacologic agents, have been studied as possible management modalities. Nevertheless, a clear consensus is not reached.

CONCLUSION

This review includes a thorough investigation of the literature on hemodynamic instability in KRT patients, providing insight on interventions that may potentially minimize factors leading to hemodynamic instability.

Management of Intermittent Hemodialysis in the Critically Ill Patient

Intermittent hemodialysis remains a cornerstone of extracorporeal KRT in the intensive care unit, either as a first-line therapy for AKI or a second-line therapy when patients transition from a continuous or prolonged intermittent therapy. Intermittent hemodialysis is usually provided 3 days per week in this setting on the basis that no clinical benefits have been demonstrated with more frequent hemodialysis. This should not detract from the importance of continually assessing and refining the hemodialysis prescription (including the need for extra treatments) according to dynamic changes in extracellular volume and other parameters, and ensuring that an adequate dose of hemodialysis is being delivered to the patient. Compared with other KRT modalities, the cardinal challenge encountered during intermittent hemodialysis is hemodynamic instability. This phenomenon occurs when reductions in intravascular volume, as a consequence of ultrafiltration and/or osmotic shifts, outpace compensatory plasma refilling from the extravascular space. Myocardial stunning, triggered by intermittent hemodialysis, and independent of ultrafiltration, may also contribute. The hemodynamic effect of intermittent hemodialysis is likely magnified in patients who are critically ill due to an inability to mount sufficient compensatory physiologic responses in the context of multiorgan dysfunction. Of the many interventions that have undergone testing to mitigate hemodynamic instability related to KRT, the best evidence exists for cooling the dialysate and raising the dialysate sodium concentration. Unfortunately, the evidence supporting routine use of these and other interventions is weak owing to poor study quality and limited sample sizes. Intermittent hemodialysis will continue to be an important and commonly used KRT modality for AKI in patients with critical illness, especially in jurisdictions where resources are limited. There is an urgent need to harmonize the definition of hemodynamic instability related to KRT in clinical trials and robustly test strategies to combat it in this vulnerable patient population.

Debate: Intermittent Hemodialysis versus Continuous Kidney Replacement Therapy in the Critically Ill Patient: The Choice Should Be Evidence Based

Kidney replacement therapy (KRT) plays a major role in the treatment of severe AKI. Intermittent hemodialysis (HD) and continuous KRT (CKRT) are the main modalities in critically ill patients with AKI. CKRT is the preferred modality in many countries because of its alleged superiority on both hemodynamic tolerance and on kidney function recovery. In fact, randomized controlled trials (RCTs) comparing the two modalities have not shown any actual benefit of one technique over the other on mortality, hemodynamics, or kidney function recovery. Those RCTs were conducted more than 15 years ago. Major progress was eventually made leading to much lower mortality rates in recent studies than in previous studies. In addition, those RCTs included a noticeable proportion of patients who could have recovered without ever receiving KRT, as demonstrated by several recent studies. In the absence of evidence of clinical superiority of one KRT modality, the choice must be addressed not only regarding clinical outcome but also resources and logistics. Conclusions of health technology assessments and study reports were heterogeneous and conflicting concerning cost-effectiveness of intermittent HD versus CKRT. All these considerations justify a reevaluation of the issue in new RCTs that take into account recent knowledge on KRT initiation and management. Pending results of such study, the choice should be guided mainly by organizational considerations in each unit and without condemning any modality in the absence of proof.

Comprehensive Management of Blood Pressure in Patients with Septic AKI

Acute kidney injury (AKI) is one of the serious complications of sepsis in clinical practice, and is an important cause of prolonged hospitalization, death, increased medical costs, and a huge medical burden to society. The pathogenesis of AKI associated with sepsis is relatively complex and includes hemodynamic abnormalities due to inflammatory response, oxidative stress, and shock, which subsequently cause a decrease in renal perfusion pressure and eventually lead to ischemia and hypoxia in renal tissue. Active clinical correction of hypotension can effectively improve renal microcirculatory disorders and promote the recovery of renal function. Furthermore, it has been found that in patients with a previous history of hypertension, small changes in blood pressure may be even more deleterious for kidney function. Therefore, the management of blood pressure in patients with sepsis-related AKI will directly affect the short-term and long-term renal function prognosis. This review summarizes the pathophysiological mechanisms of microcirculatory disorders affecting renal function, fluid management, vasopressor, the clinical blood pressure target, and kidney replacement therapy to provide a reference for the clinical management of sepsis-related AKI, thereby promoting the recovery of renal function for the purpose of improving patient prognosis.

Sodium flux during hemodialysis and hemodiafiltration treatment of acute kidney injury: Effects of dialysate and infusate sodium concentration at 140 and 145 mmol/L

BACKGROUND

A higher sodium (Na) dialysate concentration is recommended during renal replacement therapy (RRT) of acute kidney injury (AKI) to improve intradialytic hemodynamic tolerance, but it may lead to Na loading to the patient. We aimed to evaluate Na flux according to Na dialysate and infusate concentrations at 140 and 145 mmol/L during hemodialysis (HD) and hemodiafiltration (HDF).

METHODS

Fourteen AKI patients that underwent consecutive HD or HDF sessions with Na dialysate/infusate at 140 and 145 mmol/L were included. Per-dialytic flux of Na was estimated using mean sodium logarithmic concentration including diffusive and convective influx. We compared the flux of sodium between HD140 and 145, and between HDF140 and 145.

RESULTS

Nine HD140, ten HDF140, nine HD145, and 11 HDF145 sessions were analyzed. A Na gradient from the dialysate/replacement fluid to the patient was observed with dialysate/infusate Na at 145 mmol/L in both HD and HDF (p = 0.01). The comparison of HD145 to HD140 showed that higher Na dialysate induced a diffusive Na gradient to the patient (163 mmol vs. -25 mmol, p = 0.004) and that of HDF145 to -140 (211 vs. 36 mmol, p = 0.03) as well. Intradialytic hemodynamic tolerance was similar across all RRT sessions.

CONCLUSIONS

During both HD and HDF, a substantial Na loading occurred with a Na dialysate and infusate at 145 mmol/L. This Na loading is smaller in HDF with Na dialysate and infusate concentration at 140 mmol/L and inversed with HD140. Clinical and intradialytic hemodynamic tolerance was fair regardless of Na dialysate and infusate.

Association of Intradialytic Hypotension and Ultrafiltration with AKI-D Outcomes in the Outpatient Dialysis Setting

Identifying modifiable predictors of outcomes for cases of acute kidney injury requiring hemodialysis (AKI-D) will allow better care of patients with AKI-D. All patients with AKI-D discharged to University of Virginia (UVA) outpatient HD units between 1 January 2017 to 31 December 2019 (n = 273) were followed- for up to six months. Dialysis-related parameters were measured during the first 4 weeks of outpatient HD to test the hypothesis that modifiable factors during dialysis are associated with AKI-D outcomes of recovery, End Stage Kidney Disease (ESKD), or death. Patients were 42% female, 67% Caucasian, with mean age 62.8 ± 15.4 years. Median number of dialysis sessions was 11 (6–15), lasting 3.6 ± 0.6 h. At 90 days after starting outpatient HD, 45% recovered, 45% were declared ESKD and 9.9% died, with no significant changes noted between three and six months. Patients who recovered, died or were declared ESKD experienced an average of 9, 10 and 16 intradialytic hypotensive (IDH) episodes, respectively. More frequent IDH episodes were associated with increased risk of ESKD (p = 0.01). A one liter increment in net ultrafiltration was associated with 54% increased ratio of ESKD (p = 0.048). Optimizing dialysis prescription to decrease frequency of IDH episodes and minimize UF, and close monitoring of outpatient dialysis for patients with AKI-D, are crucial and may improve outcomes for these patients.

Continuous renal replacement therapy versus intermittent hemodialysis as first modality for renal replacement therapy in severe acute kidney injury: a secondary analysis of AKIKI and IDEAL-ICU studies

Background

Intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT) are the two main RRT modalities in patients with severe acute kidney injury (AKI). Meta-analyses conducted more than 10 years ago did not show survival difference between these two modalities. As the quality of RRT delivery has improved since then, we aimed to reassess whether the choice of IHD or CRRT as first modality affects survival of patients with severe AKI.

Methods

This is a secondary analysis of two multicenter randomized controlled trials (AKIKI and IDEAL-ICU) that compared an early RRT initiation strategy with a delayed one. We included patients allocated to the early strategy in order to emulate a trial where patients would have been randomized to receive either IHD or CRRT within twelve hours after the documentation of severe AKI. We determined each patient’s modality group as the first RRT modality they received. The primary outcome was 60-day overall survival. We used two propensity score methods to balance the differences in baseline characteristics between groups and the primary analysis relied on inverse probability of treatment weighting.

Results

A total of 543 patients were included. Continuous RRT was the first modality in 269 patients and IHD in 274. Patients receiving CRRT had higher cardiovascular and total-SOFA scores. Inverse probability weighting allowed to adequately balance groups on all predefined confounders. The weighted Kaplan–Meier death rate at day 60 was 54·4% in the CRRT group and 46·5% in the IHD group (weighted HR 1·26, 95% CI 1·01–1·60). In a complementary analysis of less severely ill patients (SOFA score: 3–10), receiving IHD was associated with better day 60 survival compared to CRRT (weighted HR 1.82, 95% CI 1·01–3·28; p < 0.01). We found no evidence of a survival difference between the two RRT modalities in more severe patients.

Conclusion

Compared to IHD, CRRT as first modality seemed to convey no benefit in terms of survival or of kidney recovery and might even have been associated with less favorable outcome in patients with lesser severity of disease. A prospective randomized non-inferiority trial should be implemented to solve the persistent conundrum of the optimal RRT technique.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03955-9.

Hemodynamic and Metabolic Tolerance of Acetate-Free Biofiltration in Mechanically Ventilated Critically Ill Patients: A Real-Life Study

Intradialytic hypotension can lead to superimposed organ hypoperfusion and ultimately worsens long-term kidney outcomes in critically ill patients requiring kidney replacement therapy. Acetate-free biofiltration (AFB), an alternative technique to bicarbonate-based hemodialysis (B-IHD) that does not require dialysate acidification, may improve hemodynamic and metabolic tolerance of dialysis. In this study, we included 49 mechanically ventilated patients requiring 4 h dialysis (AFB sessions n = 66; B-IHD sessions n = 62). Whereas more AFB sessions were performed in patients at risk of hemodynamic intolerance, episodes of intradialytic hypotension were significantly less frequent during AFB compared to B-IHD, whatever the classification used (decrease in mean blood pressure ≥ 10 mmHg; systolic blood pressure decrease >20 mmHg or absolute value below 95 mmHg) and after adjustment on the use of vasoactive agent. Diastolic blood pressure readily increased throughout the dialysis session. The use of a bicarbonate zero dialysate allowed the removal of 113 ± 25 mL/min of CO₂ by the hemofilter. After bicarbonate reinjection, the global CO₂ load induced by AFB was +25 ± 6 compared to +80 ± 12 mL/min with B-IHD (p = 0.0002). Thus, notwithstanding the non-controlled design of this study, hemodynamic tolerance of AFB appears superior to B-IHD in mechanically ventilated patients. Its use as a platform for CO₂ removal also warrants further research.

Renal Replacement Therapy for Acute Kidney Injury in French Intensive Care Units: A Nationwide Survey of Practices

BACKGROUND

The frequency of acute kidney injury (AKI) can be as high as 50% in the intensive care unit (ICU). Despite the publication of national guidelines in France in 2015 for the use of RRT, there are no data describing the implementation of these recommendations in real-life.

METHODS

We performed a nationwide survey of practices from November 15, 2019, to January 24, 2020, in France. An electronic questionnaire based on the items recommended in the national guidelines was sent using an online survey platform, to the chiefs of all ICUs in France. The questionnaire comprised a section for the Department Chief about local organization and facilities, and a second section destined for individual physicians about their personal practices.

RESULTS

We contacted the Department Chief in 356 eligible ICUs, of whom 88 (24.7%) responded regarding their ICU organization. From these 88 ICUs, 232/285 physicians (82%) completed the questionnaire regarding individual practices. The practices reported by respondent physicians were as follows: intermittent RRT was first-line choice in >75% in a patient with single organ (kidney) failure at the acute phase, whereas continuous RRT was predominant (>75%) in patients with septic shock or multi-organ failure. Blood and dialysate flow for intermittent RRT were 200-300 mL/min and 400-600 mL/min, respectively. The dose of dialysis for continuous RRT was 25-35 mL/kg/h (65%). Insertion of the dialysis catheter was mainly performed by the resident under echographic guidance, in the right internal jugular vein. The most commonly used catheter lock was citrate (53%). The most frequently cited criterion for weaning from RRT was diuresis, followed by a drop in urinary markers (urea and creatinine).

CONCLUSION

This study shows a satisfactory level of reported compliance with French guidelines and recent scientific evidence among ICU physicians regarding initiation of RRT for AKI in the ICU.

Renal replacement therapy in extra-corporeal membrane oxygenation patients: A survey of practices and new insights for future studies

BACKGROUND

Patients under extra-corporeal membrane oxygenation (ECMO) are at high risk of developing acute kidney injury and renal replacement therapy (RRT) is frequently needed. The aim of this study was to explore RRT use in ECMO patients, as no recommendations exist in this setting.

METHODS

An online questionnaire about RRT management in ECMO patients was sent to the members of the ARCOTHOVA (Anesthésie-Réanimation Coeur-Thorax-Vaisseaux) association and to the GFRUP (Groupe Francophone de Réanimation et Urgences Pédiatriques).

RESULTS

Ninety intensivists from adult ICU and twenty from paediatric ICU responded to the questionnaire. RRT use was common as 67% respondents reported that more than 25% of their ECMO patients needed RRT. RRT indications were similar between centres, with persistent anuria (83%), metabolic acidosis (80%), fluid overload (78%) and hyperkalaemia (80%) being the more prevalent. Continuous renal replacement therapy was the preferred technique (97%). Continuous veno-venous haemofiltration was predominant (64%) over continuous veno-venous haemodiafiltration (21%). Unfractionated heparin was employed as first line choice anticoagulation in 61% and regional citrate anticoagulation in 16%. Integration of RRT device directly into the ECMO circuit was the preferred configuration (40%) while parallel systems with separate catheter were used in 30%. When the integrated approach was chosen, RRT device was most frequently connected with inlet and outlet lines after the ECMO pump (58%) and pressure alarms were encountered for 60% of participants.

CONCLUSIONS

Our results highlight the high variability of practice between centres. They suggest the need to compare the integrated and parallel configurations of combining RRT and ECMO.

Prevalence and risk factors of hemodynamic instability associated with preload-dependence during continuous renal replacement therapy in a prospective observational cohort of critically ill patients

Background

Hemodynamic instability is a frequent complication of continuous renal replacement therapy (CRRT). Postural tests (i.e., passive leg raising in the supine position or Trendelenburg maneuver in the prone position) combined with measurement of cardiac output are highly reliable to identify preload-dependence and may provide new insights into the mechanisms involved in hemodynamic instability related to CRRT (HIRRT). We aimed to assess the prevalence and risk factors of HIRRT associated with preload-dependence in ICU patients.

We conducted a single-center prospective observational cohort study in ICU patients with acute kidney injury KDIGO 3, started on CRRT in the last 24 h, and monitored with a PiCCO® device. The primary endpoint was the rate of HIRRT episodes associated with preload-dependence during the first 7 days after inclusion. HIRRT was defined as the occurrence of a mean arterial pressure below 65 mmHg requiring therapeutic intervention. Preload-dependence was assessed by postural tests every 4 h, and during each HIRRT episode. Data are expressed in median [1st quartile–3rd quartile], unless stated otherwise.

Results

42 patients (62% male, age 69 [59–77] year, SAPS-2 65 [49–76]) were included 6 [1–16] h after CRRT initiation and studied continuously for 121 [60–147] h. A median of 5 [3–8] HIRRT episodes occurred per patient, for a pooled total of 243 episodes. 131 episodes (54% [CI_95% 48–60%]) were associated with preload-dependence, 108 (44%, [CI_95% 38–51%]) without preload-dependence, and 4 were unclassified. Multivariate analysis (using variables collected prior to HIRRT) identified the following variables as risk factors for the occurrence of HIRRT associated with preload-dependence: preload-dependence before HIRRT [odds ratio (OR) = 3.82, p < 0.001], delay since last HIRRT episode > 8 h (OR = 0.56, p < 0.05), lactate (OR = 1.21 per 1-mmol L⁻¹ increase, p < 0.05), cardiac index (OR = 0.47 per 1-L min⁻¹ m⁻² increase, p < 0.001) and SOFA at ICU admission (OR = 0.91 per 1-point increase, p < 0.001). None of the CRRT settings was identified as risk factor for HIRRT.

Conclusions

In this single-center study, HIRRT associated with preload-dependence was slightly more frequent than HIRRT without preload-dependence in ICU patients undergoing CRRT. Testing for preload-dependence could help avoiding unnecessary decrease of fluid removal in preload-independent HIRRT during CRRT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00883-9.

Ultrafiltration in critically ill patients treated with kidney replacement therapy

Management of fluid overload is one of the most challenging problems in the care of critically ill patients with oliguric acute kidney injury. Various clinical practice guidelines support fluid removal using ultrafiltration during kidney replacement therapy. However, ultrafiltration is associated with considerable risks. Emerging evidence from observational studies suggests that both slow and fast rates of net fluid removal (that is, net ultrafiltration (UFNET)) during continuous kidney replacement therapy are associated with increased mortality compared with moderate UFNET rates. In addition, fast UFNET rates are associated with an increased risk of cardiac arrhythmias. Experimental studies in patients with kidney failure who were treated with intermittent haemodialysis suggest that fast UFNET rates are also associated with ischaemic injury to the heart, brain, kidney and gut. The UFNET rate should be prescribed based on patient body weight in millilitres per kilogramme per hour with close monitoring of patient haemodynamics and fluid balance. Dialysate cooling and sodium modelling may prevent haemodynamic instability and facilitate large volumes of fluid removal in patients with kidney failure who are treated with intermittent haemodialysis, but the effects of this strategy on organ injury are less well studied in critically ill patients treated with continuous kidney replacement therapy. Randomized trials are required to examine whether moderate UFNET rates are associated with a reduced risk of haemodynamic instability, organ injury and improved outcomes in critically ill patients.

Kidney Replacement Therapy for Fluid Management

Emerging evidence from observational studies suggests that both slower and faster net ultrafiltration rates during kidney replacement therapy are associated with increased mortality in critically ill patients with acute kidney injury and fluid overload. Faster rates are associated with ischemic organ injury. The net ultrafiltration rate should be prescribed based on patient body weight in milliliters per kilogram per hour, with close monitoring of patient hemodynamics and fluid balance. Randomized trials are required to examine whether moderate net ultrafiltration rates compared with slower and faster rates are associated with reduced risk of hemodynamic instability, organ injury, and improved outcomes.

Comparison between regional citrate anticoagulation and heparin for intermittent hemodialysis in ICU patients: a propensity score-matched cohort study

BACKGROUND

Regional citrate anticoagulation (RCA) is the gold standard of anticoagulation for continuous renal replacement therapy but is rarely used for intermittent hemodialysis (IHD) in ICU. Few studies assessed the safety and efficacy of RCA during IHD in ICU; however, no data are available comparing RCA to heparin anticoagulation, which are commonly used for IHD. The aim of this study was to assess the efficacy and safety of RCA compared to heparin anticoagulation during IHD.

METHODS

This retrospective single-center cohort study included consecutive ICU patients treated with either heparin anticoagulation (unfractionated or low-molecular-weight heparin) or RCA for IHD from July to September in 2015 and 2017. RCA was performed with citrate infusion according to blood flow and calcium infusion by diffusive influx from dialysate. Using a propensity score analysis, as the primary endpoint we assessed whether RCA improved efficacy, quantified with Kt/V from the ionic dialysance, compared to heparin anticoagulation. The secondary endpoint was safety. Exploratory analyses were performed on the changes in efficacy and safety between the implementation period (2015) and at long term (2017).

RESULTS

In total, 208 IHD sessions were performed in 56 patients and were compared (124 RCA and 84 heparin coagulation). There was no difference in Kt/V between RCA and heparin (0.95 ± 0.38 vs. 0.89 ± 0.32; p = 0.98). A higher number of circuit clotting (12.9% vs. 2.4%; p = 0.02) and premature interruption resulting from acute high transmembrane pressure (21% vs. 7%; p = 0.02) occurred in the RCA sessions compared to the heparin sessions. In the propensity score-matching analysis, RCA was associated with an increased risk of circuit clotting (absolute differences = 0.10, 95% CI [0.03-0.18]; p = 0.008). There was no difference in efficacy and safety between the two time periods (2015 and 2017).

CONCLUSION

RCA with calcium infusion by diffusive influx from dialysate for IHD was easy to implement with stable long-term efficacy and safety but did not improve efficacy and could be associated with an increased risk of circuit clotting compared to heparin anticoagulation in non-selected ICU patients. Randomized trials to determine the best anticoagulation for IHD in ICU patients should be conducted in a variety of settings.

A randomized trial of albumin infusion to prevent intradialytic hypotension in hospitalized hypoalbuminemic patients

BACKGROUND

Intradialytic hypotension (IDH) is a frequent complication of intermittent hemodialysis (IHD), occurring from 15 to 50% of ambulatory sessions, and is more frequent among hospitalized patients with hypoalbuminemia. IDH limits adequate fluid removal and increases the risk for vascular access thrombosis, early hemodialysis (HD) termination, and mortality. Albumin infusion before and during therapy has been used for treating IDH with the varying results. We evaluated the efficacy of albumin infusion in preventing IDH during IHD in hypoalbuminemic inpatients.

METHODS

A randomized, crossover trial was performed in 65 AKI or ESKD patients with hypoalbuminemia (albumin < 3 g/dl) who required HD during hospitalization. Patients were randomized to receive 100 ml of either 0.9%sodium chloride or 25% albumin intravenously at the initiation of each dialysis. These two solutions were alternated for up to six sessions. Patients' vital signs and ultrafiltration removal rate were recorded every 15 to 30 min during dialysis. IDH was assessed by different definitions reported in the literature. All symptoms associated with a noted hypotensive event as well as interventions during the dialysis were recorded.

RESULTS

Sixty-five patients were submitted to 249 sessions; the mean age was 58 ([Formula: see text] 12), and 46 (70%) were male with a mean weight of 76 ([Formula: see text] 18) kg. The presence of IDH was lower during albumin sessions based on all definitions. The hypotension risk was significantly decreased based on the Kidney Disease Outcomes Quality Initiative definition; (15% with NS vs. 7% with albumin, p = 0.002). The lowest intradialytic SBP was significantly worse in patients who received 0.9% sodium chloride than albumin (NS 83 vs. albumin 90 mmHg, p = 0.035). Overall ultrafiltration rate was significantly higher in the albumin therapies [NS - 8.25 ml/kg/h (- 11.18 5.80) vs. 8.27 ml/kg/h (- 12.22 to 5.53) with albumin, p = 0.011].

CONCLUSION

In hypoalbuminemic patients who need HD, albumin administration before the dialysis results in fewer episodes of hypotension and improves fluid removal. Albumin infusion may be of benefit to improve the safety of HD and achievement of fluid balance in these high-risk patients. ClinicalTrials.gov Identifier: NCT04522635.

Acute cardiorenal syndrome in acute heart failure: focus on renal replacement therapy

Almost half of hospitalised patients with acute heart failure develop acute cardiorenal syndrome. Treatment consists of optimisation of fluid status and haemodynamics, targeted therapy for the underlying cardiac disease, optimisation of heart failure treatment and preventive measures such as avoidance of nephrotoxic agents. Renal replacement therapy may be temporarily needed to support kidney function, mostly in case of diuretic resistant fluid overload or severe metabolic derangement. The best timing to initiate renal replacement therapy and the best modality in acute heart failure are still under debate. Several modalities are available such as intermittent and continuous renal replacement therapy as well as hybrid techniques, based on two main principles: haemofiltration and haemodialysis. Although continuous techniques have been associated with less haemodynamic instability and a greater chance of renal recovery, cohort data are conflicting and randomised controlled trials have not shown a difference in recovery or mortality. In the presence of diuretic resistance, isolated ultrafiltration with individualisation of ultrafiltration rates is a valid option for decongestion in acute heart failure patients. Practical tools to optimise the use of renal replacement therapy in acute heart failure-related acute cardiorenal syndrome were discussed.

Bedside prediction of intradialytic hemodynamic instability in critically ill patients: the SOCRATE study

BACKGROUND

Despite improvements in intermittent hemodialysis management, intradialytic hemodynamic instability (IHI) remains a common issue that could account for increased mortality and delayed renal recovery. However, predictive factors of IHI remain poorly explored. The objective of this study was to evaluate the relationship between baseline macrohemodynamic, tissue hypoperfusion parameters and IHI occurrence.

METHODS

Prospective observational study conducted in a 18-bed medical ICU of a tertiary teaching hospital. Cardiovascular SOFA score, index capillary refill time (CRT) and lactate level were measured just before (T0) consecutive intermittent hemodialysis sessions performed for AKI. The occurrence of IHI requiring a therapeutic intervention was recorded.

RESULTS

Two hundred eleven sessions, corresponding to 72 (34%) first sessions and 139 (66%) later sessions, were included. As IHI mostly occurred during first sessions (43% vs 12%, P < 0.0001), following analyses were performed on the 72 first sessions. At T0, cardiovascular SOFA score ≥1 (87% vs 51%, P = 0.0021) was more frequent before IHI sessions, as well as index CRT ≥ 3 s (55% vs 15%, P = 0.0004), and hyperlactatemia > 2 mmol/L (68% vs 29%, P = 0.0018). Moreover, the occurrence of IHI increased with the number of macrohemodynamic and tissue perfusion impaired parameters, named SOCRATE score (cardiovascular SOFA, index CRT and lactATE): 10% (95% CI [3%, 30%]), 33% (95% CI [15%, 58%]), 55% (95% CI [35%, 73%]) and 80% (95% CI [55%, 93%]) for 0, 1, 2 and 3 parameters, respectively (AUC = 0.79 [0.69-0.89], P < 0.0001). These results were confirmed by analyzing the 139 later sessions included in the study.

CONCLUSIONS

The SOCRATE score based on 3 easy-to-use bedside parameters correlates with the risk of IHI. By improving risk stratification of IHI, this score could help clinicians to manage intermittent hemodialysis initiation in critically ill AKI patients.

Timing of Renal Replacement Therapy for Severe Acute Kidney Injury in Critically Ill Patients

Acute kidney injury (AKI) affects many ICU patients and is responsible for increased morbidity and mortality. Although lifesaving in many situations, renal replacement therapy (RRT) may be associated with complications, and the appropriate timing of its initiation is still the subject of intense debate. An early initiation strategy can prevent some metabolic complications, whereas a delayed one may allow for renal function recovery in some patients without need for this costly and potentially dangerous technique. For years, most of the knowledge on this issue stemmed from observational studies or small randomized controlled trials. Recent randomized controlled trials have indicated that a watchful waiting strategy (in the absence of life-threatening conditions such as severe hyperkalemia or pulmonary edema) during severe AKI allowed many patients to escape RRT and did not seem to adversely affect survival compared with a strategy of immediate RRT. In addition, data suggest that a delayed strategy may reduce the rate of complications (such as catheter infection) and favor renal function recovery. Ongoing studies will have to both confirm these conclusions and clarify to what extent the delay in initiating RRT can be prolonged. Pending those results, the bulk of evidence suggests that, in the absence of potential severe complications of AKI, delaying RRT is a valid and safe strategy that may also allow for considerable cost savings.

Ultrasound-based clinical profiles for predicting the risk of intradialytic hypotension in critically ill patients on intermittent dialysis: a prospective observational study

BACKGROUND

Intradialytic hypotension, a complication of intermittent hemodialysis, decreases the efficacy of dialysis and increases long-term mortality. This study was aimed to determine whether different predialysis ultrasound cardiopulmonary profiles could predict intradialytic hypotension.

METHODS

This prospective observational single-center study was performed in 248 critically ill patients with acute kidney injury undergoing intermittent hemodialysis. Immediately before hemodialysis, vena cava collapsibility was measured by vena cava ultrasound and pulmonary congestion by lung ultrasound. Factors predicting intradialytic hypotension were identified by multiple logistic regression analysis.

RESULTS

Intradialytic hypotension was observed in 31.9% (n = 79) of the patients, interruption of dialysis because of intradialytic hypotension occurred in 6.8% (n = 31) of the sessions, and overall 28-day mortality was 20.1% (n = 50). Patients were classified in four ultrasound profiles: (A) 108 with B lines > 14 and vena cava collapsibility > 11.5 mm m^-2, (B) 38 with B lines < 14 and vena cava collapsibility ≤ 11.5 mm m^-2, (C) 36 with B lines > 14 and vena cava collapsibility Di ≤ 11.5 mm m^-2, and (D) 66 with B lines < 14 and vena cava collapsibility > 11.5 mm m^-2. There was an increased risk of intradialytic hypotension in patients receiving norepinephrine (odds ratios = 15, p = 0.001) and with profiles B (odds ratios = 12, p = 0.001) and C (odds ratios = 17, p = 0.001).

CONCLUSION

In critically ill patients on intermittent hemodialysis, the absence of hypervolemia as assessed by lung and vena cava ultrasound predisposes to intradialytic hypotension and suggests alternative techniques of hemodialysis to provide better hemodynamic stability.

Mechanisms for hemodynamic instability related to renal replacement therapy: a narrative review

Hemodynamic instability related to renal replacement therapy (HIRRT) is a frequent complication of all renal replacement therapy (RRT) modalities commonly used in the intensive care unit. HIRRT is associated with increased mortality and may impair kidney recovery. Our current understanding of the physiologic basis for HIRRT comes primarily from studies of end-stage kidney disease patients on maintenance hemodialysis in whom HIRRT is referred to as ‘intradialytic hypotension’. Nonetheless, there are many studies that provide additional insights into the underlying mechanisms for HIRRT specifically in critically ill patients. In particular, recent evidence challenges the notion that HIRRT is almost entirely related to excessive ultrafiltration. Although excessive ultrafiltration is a key mechanism, multiple other RRT-related mechanisms may precipitate HIRRT and this could have implications for how HIRRT should be managed (e.g., the appropriate response might not always be to reduce ultrafiltration, particularly in the context of significant fluid overload). This review briefly summarizes the incidence and adverse effects of HIRRT and reviews what is currently known regarding the mechanisms underpinning it. This includes consideration of the evidence that exists for various RRT-related interventions to prevent or limit HIRRT. An enhanced understanding of the mechanisms that underlie HIRRT, beyond just excessive ultrafiltration, may lead to more effective RRT-related interventions to mitigate its occurrence and consequences.

[Renal replacement therapy for acute kidney injury in the intensive care unit]

Renal replacement therapy for acute kidney injury has been used for more than 60 years. Except when life-threatening metabolic complications such as severe hyperkalaemia are present, renal replacement therapy initiation criteria are the subject of intense debate. Significant progress has been made with the publication of the AKIKI multicenter trial, which showed that a delayed renal replacement therapy initiation strategy (in the absence of life-threatening metabolic complications) was not associated with a difference in mortality compared to an early renal replacement therapy initiation strategy. In addition, this delayed strategy obviated the need for renal replacement therapy in almost 50% of cases was associated with a more rapid renal function recovery and with a lower incidence of catheter-bloodstream related infections. Research on renal replacement therapy modalities (continuous vs. intermittent renal replacement therapy, citrate vs. heparin anticoagulation, jugular vs. femoral catheterization) did not show any obvious superiority of one modality over another. Thus, the choice depends mainly on local considerations (patient recruitment, availability of modalities, staff experience). The criteria for renal replacement therapy discontinuation are still unclear due to difficulties in assessing renal function recovery. Urine output remains the main criteria in the decision to wean from renal replacement therapy. Pending the confirmation of AKIKI trial by similar studies in progress, it seems reasonable to choose a delayed renal replacement therapy initiation strategy under watchful surveillance in case of severe acute kidney injury in the absence of life-threatening metabolic complications.

Interventions to prevent hemodynamic instability during renal replacement therapy in critically ill patients: a systematic review

Background

Hemodynamic instability related to renal replacement therapy (HIRRT) may increase the risk of death and limit renal recovery. Studies in end-stage renal disease populations on maintenance hemodialysis suggest that some renal replacement therapy (RRT)-related interventions (e.g., cool dialysate) may reduce the occurrence of HIRRT, but less is known about interventions to prevent HIRRT in critically ill patients receiving RRT for acute kidney injury (AKI). We sought to evaluate the effectiveness of RRT-related interventions for reducing HIRRT in such patients across RRT modalities.

Methods

A systematic review of publications was undertaken using MEDLINE, MEDLINE in Process, EMBASE, and Cochrane’s Central Registry for Randomized Controlled Trials (RCTs). Studies that assessed any intervention’s effect on HIRRT (the primary outcome) in critically ill patients with AKI were included. HIRRT was variably defined according to each study’s definition. Two reviewers independently screened abstracts, identified articles for inclusion, extracted data, and evaluated study quality using validated assessment tools.

Results

Five RCTs and four observational studies were included (n = 9; 623 patients in total). Studies were small, and the quality was mostly low. Interventions included dialysate sodium modeling (n = 3), ultrafiltration profiling (n = 2), blood volume (n = 2) and temperature control (n = 3), duration of RRT (n = 1), and slow blood flow rate at initiation (n = 1). Some studies applied more than one strategy simultaneously (n = 5). Interventions shown to reduce HIRRT from three studies (two RCTs and one observational study) included higher dialysate sodium concentration, lower dialysate temperature, variable ultrafiltration rates, or a combination of strategies. Interventions not found to have an effect included blood volume and temperature control, extended duration of intermittent RRT, and slower blood flow rates during continuous RRT initiation. How HIRRT was defined and its frequency of occurrence varied widely across studies, including those involving the same RRT modality. Pooled analysis was not possible due to study heterogeneity.

Conclusions

Small clinical studies suggest that higher dialysate sodium, lower temperature, individualized ultrafiltration rates, or a combination of these strategies may reduce the risk of HIRRT. Overall, for all RRT modalities, there is a paucity of high-quality data regarding interventions to reduce the occurrence of HIRRT in critically ill patients.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-1965-5) contains supplementary material, which is available to authorized users.

Volume Management by Renal Replacement Therapy in Acute Kidney Injury

Management of fluid balance is one of the basic but vital tasks in the care of critically ill patients. Hypovolemia results in a decrease in cardiac output and tissue perfusion and may lead to progressive multiple organ dysfunction, including the development of acute renal injury (AKI). However, in an effort to reverse pre-renal oliguria, it is not uncommon for patients with established oliguric acute renal failure, particularly when associated with sepsis, to receive excessive fluid resuscitation, leading to fluid overload. In patients with established oliguria, renal replacement therapy may be required to treat hypervolemia. Safe prescription of fluid loss during RRT requires intimate knowledge of the patient's underlying condition, understanding of the process of ultrafiltration and close monitoring of the patient's cardiovascular response to fluid removal. To preserve tissue perfusion in patients with AKI, it is important that RRT be prescribed in a way that optimizes fluid balance by removing fluid without compromising the effective circulating fluid volume. In patients who are clinically fluid overloaded, it is equally important that the amount of fluid removed be as exact as possible. Fluid balance errors can occur as a result of inappropriate prescription, operator error or machine error. Some CRRT machines have potential for significant fluid errors if alarms can be overridden. Threshold values for fluid balance error have been developed which can be used to predict the severity of harm. It is important that RRT education programs emphasize the risk associated with fluid balance errors and with overriding machine alarms.

The Importance of Dialysate Sodium Concentration in Determining Interdialytic Weight Gains in Chronic Hemodialysis Patients: The PanThames Renal Audit

Background and Objectives

There is controversy as to the optimum dialysate sodium to be used for hemodialysis patients, with reports of hypertension and increased interdialytic weight gains with high sodium dialysates and intradialytic hypotension and cramps with low sodium dialysates.

Methods

We analyzed the effect of different dialysate sodium concentrations during a one-week period in an audit of 2187 established patients regularly receiving dialysis three times a week. Patients were given general dietary advice to restrict dietary sodium intake, but no systematic assessment of dietary sodium intake was undertaken.

Results

The prescription of a dialysate sodium concentration of 140 mmol/L and >140 mmol/L, was associated with greater interdialytic weight gains, 3.5% and 4.1% respectively, compared to 2.8% and 2.7% for those using dialysate sodium concentrations of 137 and 136 mmol/L, respectively (p<0.05). The mean pulse pressure was greater patients dialyzing using a sodium of 140 mmol/L, compared to 136 mmol/L, 70 (13) vs 63 (15) mmHg (p<0.011). In addition, 13.5% of patients using the highest sodium dialysate suffered symptomatic intradialytic hypotension requiring intravenous fluid resuscitation, compared to 2.7% who used the lowest sodium concentrate (p<0.05).

Conclusions

This analysis would support the use of lower dialysate sodium concentrations to aid in reducing interdialytic weight gains and subsequent intradialytic hypotension.

Fluids for Prevention and Management of Acute Kidney Injury

Fluids are the only known method of attenuating renal injury. Furthermore, whether for hydration, resuscitation or renal replacement therapy, fluid prescriptions must be tailored to the fluid and electrolyte, cardiovascular status and residual renal function of the patient. Different fluids have significantly different effects both on volume expansion as well as on the electrolyte and acid-base balance; while controversial, different fluids may even influence renal function differently. This systematic review focuses on fluids for prevention and management of acute kidney injury. We have reviewed the available evidence and have made recommendations for clinical practice and future studies.

Pragmatic studies for acute kidney injury: Consensus report of the Acute Disease Quality Initiative (ADQI) 19 Workgroup

PURPOSE

Acute kidney injury (AKI) has become a major medical and financial burden in China along with the rest of the world. There have been considerable advances in the understanding of the epidemiology and pathogenesis of AKI. However, there is no consensus regarding the optimal care for patients. The Acute Disease Quality Initiative (ADQI) 19 meeting focused on identifying and designing relevant and achievable AKI-related studies in China.

MATERIALS & METHODS

The working group developed a list of preliminary questions and objectives and performed analysis of the existing literature. Relevant studies were identified through a literature search using the MEDLINE database and bibliographies of relevant research and review articles. We then used a two-step Delphi process to prioritize a research agenda and proposed specific study designs to address unmet needs.

RESULTS

Important gaps in existing knowledge were identified and pragmatic studies were proposed in three distinct areas: care bundles for AKI prevention, renal replacement therapy (RRT) for AKI, and fluid management. In addition, the use of biomarkers to guide clinical trials was discussed.

CONCLUSIONS

Consensus was reached on a research agenda for AKI with a specific focus on pragmatic trials in China.

Risk of serous retinal detachment in patients with end-stage renal disease on dialysis

The aim of this retrospective, nationwide, matched cohort study was to investigate the association of serous retinal detachment with having end-stage renal disease (ESRD) while on dialysis. The cohort study included 94,024 patients with ESRD on dialysis registered between January 2000 to December 2009 in the Taiwan National Health Insurance Research Database. An age- and sex-matched control group comprised 94,024 patients selected from the Taiwan Longitudinal Health Insurance Database 2000. Information for each patient was collected from the index date until December 2011. Twenty-seven ESRD patients and 11 controls developed serous retinal detachment (P < 0.001) during follow-up, demonstrating a significantly increased risk of serous retinal detachment in patients with ESRD on dialysis compared with controls (incidence rate ratio = 3.39, 95% confidence interval [CI] = 1.68–6.83). After adjustment for potential confounders, patients were 3.86 times more likely to develop serous retinal detachment than the full cohort (adjusted HR = 3.86, 95% CI = 1.15–12.96). In conclusion, patients with ESRD on dialysis demonstrate an increased risk of serous retinal detachment. Interdisciplinary collaboration between nephrologists and ophthalmologists is important to deal with serous retinal detachment in patients with ESRD on dialysis and prevent impairments of visual acuity.

Acute kidney injury in the ICU: from injury to recovery: reports from the 5th Paris International Conference

The French Intensive Care Society organized its yearly Paris International Conference in intensive care on June 18-19, 2015. The main purpose of this meeting is to gather the best experts in the field in order to provide the highest quality update on a chosen topic. In 2015, the selected theme was: "Acute Renal Failure in the ICU: from injury to recovery." The conference program covered multiple aspects of renal failure, including epidemiology, diagnosis, treatment and kidney support system, prognosis and recovery together with acute renal failure in specific settings. The present report provides a summary of every presentation including the key message and references and is structured in eight sections: (a) diagnosis and evaluation, (b) old and new diagnosis tools,

Acute kidney injury in the ICU: from injury to recovery: reports from the 5th Paris International Conference

The French Intensive Care Society organized its yearly Paris International Conference in intensive care on June 18-19, 2015. The main purpose of this meeting is to gather the best experts in the field in order to provide the highest quality update on a chosen topic. In 2015, the selected theme was: "Acute Renal Failure in the ICU: from injury to recovery." The conference program covered multiple aspects of renal failure, including epidemiology, diagnosis, treatment and kidney support system, prognosis and recovery together with acute renal failure in specific settings. The present report provides a summary of every presentation including the key message and references and is structured in eight sections: (a) diagnosis and evaluation, (b) old and new diagnosis tools,

[Renal replacement therapy in acute kidney injury]

Acute kidney injury is still a common complication in intensive care units and is associated with a significantly increased risk for morbidity and mortality. Various treatment concepts, like continuous renal replacement therapy (RRT) or (modified) intermittent procedures, as well as different methods of anticoagulation and the general decision of when and if to initiate RRT have to be considered by the treating physician. While giving vital input on when to initiate RRT, the German ELAIN (Early versus late initiation of renal replacement therapy in critically ill patients) trial and the French AKIKI (The artificial kidney initiation in kidney injury) trial raised many more questions. Currently in its recruiting phase, the STARRT-AKI (Standard versus accelerated initiation of renal replacement therapy in acute kidney injury) trial is designed to hopefully give a definitive statement. Due to a planned recruiting phase until 2019, results are expected in 2020 at the earliest. Regarding the termination of RRT, recurring diuresis of more than 450 ml/24 h is a good indicator for recovery of renal function.

The intensive care medicine agenda on acute kidney injury

Acute kidney injury (AKI) is a common complication in the critically ill. Current standard of care mainly relies on identification of patients at risk, haemodynamic optimization, avoidance of nephrotoxicity and the use of renal replacement therapy (RRT) in established AKI. The detection of early biomarkers of renal tissue damage is a recent development that allows amending the late and insensitive diagnosis with current AKI criteria. Increasing evidence suggests that the consequences of an episode of AKI extend long beyond the acute hospitalization. Citrate has been established as the anticoagulant of choice for continuous RRT. Conflicting results have been published on the optimal timing of RRT and on the renoprotective effect of remote ischaemic preconditioning. Recent research has contradicted that acute tubular necrosis is the common pathology in AKI, that septic AKI is due to global kidney hypoperfusion, that aggressive fluid therapy benefits the kidney, that vasopressor therapy harms the kidney and that high doses of RRT improve outcome. Remaining uncertainties include the impact of aetiology and clinical context on pathophysiology, therapy and prognosis, the clinical benefit of biomarker-driven interventions, the optimal mode of RRT to improve short- and long-term patient and kidney outcomes, the contribution of AKI to failure of other organs and the optimal approach for assessing and promoting renal recovery. Based on the established gaps in current knowledge the trials that must have priority in the coming 10 years are proposed together with the definition of appropriate clinical endpoints.

Hypotension and hypovolemia during hemodialysis: is the usual suspect innocent?

Hypotension during intermittent hemodialysis is common, and has been attributed to acute volume shifts, shifts in osmolarity, electrolyte imbalance, temperature changes, altered vasoregulation, and sheer hypovolemia. Although hypovolemia may intuitively seem a likely cause for hypotension in intensive care patients, its role in the pathogenesis of intradialytic hypotension may be overestimated.

Continuous renal replacement therapy versus intermittent hemodialysis in intensive care patients: impact on mortality and renal recovery

PURPOSE

The best renal replacement therapy (RRT) modality remains controversial. We compared mortality and short- and long-term renal recovery between patients treated with continuous RRT and intermittent hemodialysis.

METHODS

Patients of the prospective observational multicenter cohort database OUTCOMEREA™ were included if they underwent at least one RRT session between 2004 and 2014. Differences in patients' baseline and daily characteristics between treatment groups were taken into account by using a marginal structural Cox model, allowing one to substantially reduce the bias resulting from confounding factors in observational longitudinal data analysis. The composite primary endpoint was 30-day mortality and dialysis dependency.

RESULTS

Among 1360 included patients with RRT, 544 (40.0 %) and 816 (60.0 %) were initially treated by continuous RRT and intermittent hemodialysis, respectively. At day 30, 39.6 % patients were dead. Among survivors, 23.8 % still required RRT. There was no difference between groups for the primary endpoint in global population (HR 1.00, 95 % CI 0.77-1.29; p = 0.97). In patients with higher weight gain at RRT initiation, mortality and dialysis dependency were significantly lower with continuous RRT (HR 0.54, 95 % CI 0.29-0.99; p = 0.05). Conversely, this technique appeared to be deleterious in patients without shock (HR 2.24, 95 % CI 1.24-4.04; p = 0.01). Six-month mortality and persistent renal dysfunction were not influenced by the RRT modality in patients with dialysis dependence at ICU discharge.

CONCLUSION

Continuous RRT did not appear to improve 30-day and 6-month patient outcomes. It seems beneficial for patients with fluid overload, but might be deleterious in the absence of hemodynamic failure.

Evaluation of Intermittent Hemodialysis in Critically Ill Cancer Patients with Acute Kidney Injury Using Single-Pass Batch Equipment

BACKGROUND

Data on renal replacement therapy (RRT) in cancer patients with acute kidney injury (AKI) in the intensive care unit (ICU) is scarce. The aim of this study was to assess the safety and the adequacy of intermittent hemodialysis (IHD) in critically ill cancer patients with AKI.

METHODS AND FINDINGS

In this observational prospective cohort study, 149 ICU cancer patients with AKI were treated with 448 single-pass batch IHD procedures and evaluated from June 2010 to June 2012. Primary outcomes were IHD complications (hypotension and clotting) and adequacy. A multiple logistic regression was performed in order to identify factors associated with IHD complications (hypotension and clotting). Patients were 62.2 ± 14.3 years old, 86.6% had a solid cancer, sepsis was the main AKI cause (51%) and in-hospital mortality was 59.7%. RRT session time was 240 (180-300) min, blood/dialysate flow was 250 (200-300) mL/min and UF was 1000 (0-2000) ml. Hypotension occurred in 25% of the sessions. Independent risk factors (RF) for hypotension were dialysate conductivity (each ms/cm, OR 0.81, CI 0.69-0.95), initial mean arterial pressure (each 10 mmHg, OR 0.49, CI 0.40-0.61) and SOFA score (OR 1.16, CI 1.03-1.30). Clotting and malfunctioning catheters (MC) occurred in 23.8% and 29.2% of the procedures, respectively. Independent RF for clotting were heparin use (OR 0.57, CI 0.33-0.99), MC (OR 3.59, CI 2.24-5.77) and RRT system pressure increase over 25% (OR 2.15, CI 1.61-4.17). Post RRT blood tests were urea 71 (49-104) mg/dL, creatinine 2.71 (2.10-3.8) mg/dL, bicarbonate 24.1 (22.5-25.5) mEq/L and K 3.8 (3.5-4.1) mEq/L.

CONCLUSION

IHD for critically ill patients with cancer and AKI offered acceptable hemodynamic stability and provided adequate metabolic control.

Prevalence and risk factors of hypotension associated with preload-dependence during intermittent hemodialysis in critically ill patients

BACKGROUND

Hypotension is a frequent complication of intermittent hemodialysis (IHD) performed in intensive care units (ICUs). Passive leg raising (PLR) combined with continuous measurement of cardiac output is highly reliable to identify preload dependence, and may provide new insights into the mechanisms involved in IHD-related hypotension. The aim of this study was to assess prevalence and risk factors of preload dependence-related hypotension during IHD in the ICU.

METHODS

A single-center prospective observational study performed on ICU patients undergoing IHD for acute kidney injury and monitored with a PiCCO® device. Primary end points were the prevalence of hypotension (defined as a mean arterial pressure below 65 mm Hg) and hypotension associated with preload dependence. Preload dependence was assessed by the passive leg raising test, and considered present if the systolic ejection volume increased by at least 10% during the test, as assessed continuously by the PiCCO® device.

RESULTS

Forty-seven patients totaling 107 IHD sessions were included. Hypotension was observed in 61 IHD sessions (57%, CI95%: 47-66%) and was independently associated with inotrope administration, higher SOFA score, lower time lag between ICU admission and IHD session, and lower MAP at IHD session onset. Hypotension associated with preload dependence was observed in 19% (CI95%: 10-31%) of sessions with hypotension, and was associated with mechanical ventilation, lower SAPS II, higher pulmonary vascular permeability index (PVPI) and dialysate sodium concentration at IHD session onset. ROC curve analysis identified PVPI and mechanical ventilation as the only variables with significant diagnostic performance to predict hypotension associated with preload dependence (respective AUC: 0.68 (CI95%: 0.53-0.83) and 0.69 (CI95%: 0.54-0.85). A PVPI ≥ 1.6 at IHD session onset predicted occurrence of hypotension associated with preload dependence during IHD with a sensitivity of 91% (CI95%: 59-100%), and a specificity of 53% (CI95%: 42-63%).

CONCLUSIONS

The majority of hypotensive episodes occurring during intermittent hemodialysis are unrelated to preload dependence and should not necessarily lead to reduction of fluid removal by hemodialysis. However, high PVPI at IHD session onset and mechanical ventilation are risk factors of preload dependence-related hypotension, and should prompt reduction of planned fluid removal during the session, and/or an increase in session duration.

Daily urinary urea excretion to guide intermittent hemodialysis weaning in critically ill patients

Background

There are no easily available markers of renal recovery to guide intermittent hemodialysis (IHD) weaning. The aim of this study was to identify markers for IHD weaning in critically ill patients with acute kidney injury (AKI).

Methods

We performed a retrospective single-center cohort study of patients treated with IHD for at least 7 days and four dialysis sessions for AKI between 2006 and 2011 in an intensive care unit (ICU) of a French university hospital. Blood and urinary markers were recorded on the day of the last IHD in the ICU for unweaned patients and 2 days after the last IHD for weaned patients. Factors associated with IHD weaning were identified by multiple logistic regression. The areas under the receiver operating characteristic curve (AUROC) and the characteristics of the best diagnostic thresholds were compared.

Results

Sixty-seven patients were analyzed, including thirty-seven IHD-weaned patients. Urine output [odds ratio (OR) 1.59, 95 % confidence interval (CI) 1.20–2.10 (per ml/kg/24 h increase); P = 0.01] and urinary urea concentration [OR 1.29, 95 % CI 1.01–1.64 (per 10 mmol/L increase); P = 0.04] were both associated with IHD weaning. The optimal diagnostic thresholds for IHD weaning were urine output greater than 8.5 ml/kg/24 h, urinary urea concentration greater than 148 mmol/L, and daily urea excretion greater than 1.35 mmol/kg/24 h, with accuracy of 82.1 %, 76.1 %, and 92.5 % (P = 0.03), respectively. The AUROC of daily urinary urea excretion (0.96) was greater than the AUROC of urine output (0.86) or the AUROC of urinary urea concentration (0.83) (P < 0.001).

Conclusions

A daily urinary urea excretion greater than 1.35 mmol/kg/24 h was found to be the best marker for weaning ICU patients with AKI from IHD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1225-5) contains supplementary material, which is available to authorized users.

Renal Replacement Therapy

During the last few years, due to medical and surgical evolution, patients with increasingly severe diseases causing multiorgan dysfunction are frequently admitted to intensive care units. Therapeutic options, when organ failure occurs, are frequently nonspecific and mostly directed towards supporting vital function. In these scenarios, the kidneys are almost always involved and, therefore, renal replacement therapies have become a common routine practice in critically ill patients with acute kidney injury. Recent technological improvement has led to the production of safe, versatile and efficient dialysis machines. In addition, emerging evidence may allow better individualization of treatment with tailored prescription depending on the patients' clinical picture (e.g. sepsis, fluid overload, pediatric). The aim of the present review is to give a general overview of current practice in renal replacement therapies for critically ill patients. The main clinical aspects, including dose prescription, modality of dialysis delivery, anticoagulation strategies and timing will be addressed. In addition, some technical issues on physical principles governing blood purification, filters characteristics, and vascular access, will be covered. Finally, a section on current standard nomenclature of renal replacement therapy is devoted to clarify the "Tower of Babel" of critical care nephrology.

Renal replacement therapy in adult and pediatric intensive care : Recommendations by an expert panel from the French Intensive Care Society (SRLF) with the French Society of Anesthesia Intensive Care (SFAR) French Group for Pediatric Intensive Care Emergencies (GFRUP) the French Dialysis Society (SFD)

Acute renal failure (ARF) in critically ill patients is currently very frequent and requires renal replacement therapy (RRT) in many patients. During the last 15 years, several studies have considered important issues regarding the use of RRT in ARF, like the time to initiate the therapy, the dialysis dose, the types of catheter, the choice of technique, and anticoagulation. However, despite an abundant literature, conflicting results do not provide evidence on RRT implementation. We present herein recommendations for the use of RRT in adult and pediatric intensive care developed with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system by an expert group of French Intensive Care Society (SRLF), with the participation of the French Society of Anesthesia and Intensive Care (SFAR), the French Group for Pediatric Intensive Care and Emergencies (GFRUP), and the French Dialysis Society (SFD). The recommendations cover 4 fields: criteria for RRT initiation, technical aspects (access routes, membranes, anticoagulation, reverse osmosis water), practical aspects (choice of the method, peritoneal dialysis, dialysis dose, adjustments), and safety (procedures and training, dialysis catheter management, extracorporeal circuit set-up). These recommendations have been designed on a practical point of view to provide guidance for intensivists in their daily practice.

Comparison of two strategies for initiating renal replacement therapy in the intensive care unit: study protocol for a randomized controlled trial (AKIKI)

BACKGROUND

There is currently no validated strategy for the timing of renal replacement therapy (RRT) for acute kidney injury (AKI) in the intensive care unit (ICU) when short-term life-threatening metabolic abnormalities are absent. No adequately powered prospective randomized study has addressed this issue to date. As a result, significant practice heterogeneity exists and may expose patients to either unnecessary hazardous procedures or undue delay in RRT.

METHODS/DESIGN

This is a multicenter, prospective, randomized, open-label parallel-group clinical trial that compares the effect of two RRT initiation strategies on overall survival of critically ill patients receiving intravenous catecholamines or invasive mechanical ventilation and presenting with AKI classification stage 3 (KDIGO 2012). In the 'early' strategy, RRT is initiated immediately. In the 'delayed' strategy, clinical and metabolic conditions are closely monitored and RRT is initiated only when one or more events (severity criteria) occur, including: oliguria or anuria for more than 72 hours after randomization, serum urea concentration >40 mmol/l, serum potassium concentration >6 mmol/l, serum potassium concentration >5.5 mmol/l persisting despite medical treatment, arterial blood pH <7.15 in a context of pure metabolic acidosis (PaCO2 < 35 mmHg) or in a context of mixed acidosis with a PaCO2 ≥ 50 mmHg without possibility of increasing alveolar ventilation, acute pulmonary edema due to fluid overload despite diuretic therapy leading to severe hypoxemia requiring oxygen flow rate >5 l/min to maintain SpO2 > 95% or FiO2 > 50% under invasive or noninvasive mechanical ventilation. The primary outcome measure is overall survival, measured from randomization (D0) until death, regardless of the cause. The minimum follow-up duration for each patient will be 60 days. Two interim analyses are planned, blinded to group allocation. It is expected that there will be 620 subjects in all.

DISCUSSION

The AKIKI study will be one of the very few large randomized controlled trials evaluating mortality according to the timing of RRT in critically ill patients with AKI classification stage 3 (KDIGO 2012). Results should help clinicians decide when to initiate RRT.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01932190.