Hemostasis during low molecular weight heparin anticoagulation for continuous venovenous hemofiltration: a randomized cross-over trial comparing two hemofiltration rates

Global Scientific Trends in Continuous Renal Replacement Therapy from 2000 to 2023: A Bibliometric and Visual Analysis

INTRODUCTION

Continuous renal replacement therapy (CRRT) is one of the most widely used blood purification and organ support methods in the ICU. However, the development process, the current status, hotspots, and future trends of CRRT remain unclear.

METHOD

The WoSCC database was used to analyze CRRT research evolution and theme trends. VOSviewer was used to construct coauthorship, co-occurrence, co-citation, and network visualizations. CiteSpace is used to detect bursts for co-occurrence items. Several important subtopics were reviewed and discussed in more detail.

RESULTS

Global publications increased from 56 in 2000 to 398 in 2023, a 710.71% increase. Blood Purification published the most manuscripts, followed by the International Journal of Artificial Organs. The USA, the San Bortolo Hospital, and Bellomo were the most productive and impactful institution, country, and author, respectively. Based on co-occurrence cluster analysis, five clusters emerged: (1) clinical applications and management of CRRT; (2) sepsis and CRRT; (3) CRRT anticoagulant management; (4) CRRT and antibiotic pharmacokinetics and pharmacodynamics; and (5) comparison of CRRT and intermittent hemodialysis. COVID-19, initiation, ECOMO, cefepime, guidelines, cardiogenic shock, biomarker, and outcome were the latest high-frequency keywords or strongest bursts, indicating the emerging frontiers of CRRT.

CONCLUSIONS

There has been widespread publication and citation of CRRT research in the past 2 decades. We provide an overview of current trends, global collaboration patterns, basic knowledge, research hotspots, and emerging frontiers.

Timing of kidney replacement therapy initiation for acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a common condition among patients in intensive care units (ICUs) and is associated with high numbers of deaths. Kidney replacement therapy (KRT) is a blood purification technique used to treat the most severe forms of AKI. The optimal time to initiate KRT so as to improve clinical outcomes remains uncertain. This is an update of a review first published in 2018. This review complements another Cochrane review by the same authors: Intensity of continuous renal replacement therapy for acute kidney injury.

OBJECTIVES

To assess the effects of different timing (early and standard) of KRT initiation on death and recovery of kidney function in critically ill patients with AKI.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant's Specialised Register to 4 August 2022 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, EMBASE, conference proceedings, the International Clinical Trials Register, ClinicalTrials and LILACS to 1 August 2022.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs). We included all patients with AKI in the ICU regardless of age, comparing early versus standard KRT initiation. For safety and cost outcomes, we planned to include cohort studies and non-RCTs.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors. The random-effects model was used, and results were reported as risk ratios(RR) for dichotomous outcomes and mean difference(MD) for continuous outcomes, with 95% confidence intervals (CI).

MAIN RESULTS

We included 12 studies enrolling 4880 participants. Overall, most domains were assessed as being at low or unclear risk of bias. Compared to standard treatment, early KRT initiation may have little to no difference on the risk of death at day 30 (12 studies, 4826 participants: RR 0.97,95% CI 0.87 to 1.09; I²= 29%; low certainty evidence), and death after 30 days (7 studies, 4534 participants: RR 0.99, 95% CI 0.92 to 1.07; I² = 6%; moderate certainty evidence). Early KRT initiation may make little or no difference to the risk of death or non-recovery of kidney function at 90 days (6 studies, 4011 participants: RR 0.91, 95% CI 0.74 to 1.11; I² = 66%; low certainty evidence); CIs included both benefits and harms. Low certainty evidence showed early KRT initiation may make little or no difference to the number of patients who were free from KRT (10 studies, 4717 participants: RR 1.07, 95% CI 0.94 to1.22; I² = 55%) and recovery of kidney function among survivors who were free from KRT after day 30 (10 studies, 2510 participants: RR 1.02, 95% CI 0.97 to 1.07; I² = 69%) compared to standard treatment. High certainty evidence showed early KRT initiation increased the risk of hypophosphataemia (1 study, 2927 participants: RR 1.80, 95% CI 1.33 to 2.44), hypotension (5 studies, 3864 participants: RR 1.54, 95% CI 1.29 to 1.85; I² = 0%), cardiac-rhythm disorder (6 studies, 4483 participants: RR 1.35, 95% CI 1.04 to 1.75; I² = 16%), and infection (5 studies, 4252 participants: RR 1.33, 95% CI 1.00 to 1.77; I² = 0%); however, it is uncertain whether early KRT initiation increases or reduces the number of patients who experienced any adverse events (5 studies, 3983 participants: RR 1.23, 95% CI 0.90 to 1.68; I² = 91%; very low certainty evidence). Moderate certainty evidence showed early KRT initiation probably reduces the number of days in hospital (7 studies, 4589 participants: MD-2.45 days, 95% CI -4.75 to -0.14; I² = 10%) and length of stay in ICU (5 studies, 4240 participants: MD -1.01 days, 95% CI -1.60 to -0.42; I² = 0%).

AUTHORS' CONCLUSIONS

Based on mainly low to moderate certainty of the evidence, early KRT has no beneficial effect on death and may increase the recovery of kidney function. Earlier KRT probably reduces the length of ICU and hospital stay but increases the risk of adverse events. Further adequate-powered RCTs using robust and validated tools that complement clinical judgement are needed to define the optimal time of KRT in critical patients with AKI in order to improve their outcomes. The surgical AKI population should be considered in future research.

Non-pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement therapy

BACKGROUND

Acute kidney injury (AKI) is a common complication amongst people who are critically ill, and it is associated with an increased risk of death. For people with severe AKI, continuous kidney replacement therapy (CKRT), which is delivered over 24 hours, is needed when they become haemodynamically unstable. When CKRT is interrupted due to clotting of the extracorporeal circuit, the delivered dose is decreased and thus leading to undertreatment.

OBJECTIVES

This review assessed the efficacy of non-pharmacological measures to maintain circuit patency in CKRT.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 25 January 2021 which includes records identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) (parallel-group and cross-over studies), cluster RCTs and quasi-RCTs that examined non-pharmacological interventions to prevent clotting of extracorporeal circuits during CKRT.  DATA COLLECTION AND ANALYSIS: Three pairs of review authors independently extracted information including participants, interventions/comparators, outcomes, study methods, and risk of bias. The primary outcomes were circuit lifespan and death due to any cause at day 28. We used a random-effects model to perform quantitative synthesis (meta-analysis). We assessed risk of bias in included studies using the Cochrane Collaboration's tool for assessing risk of bias. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

A total of 20 studies involving 1143 randomised participants were included in the review. The methodological quality of the included studies was low, mainly due to the unclear randomisation process and blinding of the intervention. We found evidence on the following 11 comparisons: (i) continuous venovenous haemodialysis (CVVHD) versus continuous venovenous haemofiltration (CVVH) or continuous venovenous haemodiafiltration (CVVHDF); (ii) CVVHDF versus CVVH; (iii) higher blood flow (≥ 250 mL/minute) versus standard blood flow (< 250 mL/minute); (iv) AN69 membrane (AN69ST) versus other membranes; (v) pre-dilution versus post-dilution; (vi) a longer catheter (> 20 cm) placing the tip targeting the right atrium versus a shorter catheter (≤ 20 cm) placing the tip in the superior vena cava; (vii) surface-modified double-lumen catheter versus standard double-lumen catheter with identical geometry and flow design; (viii) single-site infusion anticoagulation versus double-site infusion anticoagulation; (ix) flat plate filter versus hollow fibre filter of the same membrane type; (x) a filter with a larger membrane surface area versus a smaller one; and (xi) a filter with more and shorter hollow fibre versus a standard filter of the same membrane type. Circuit lifespan was reported in 9 comparisons. Low certainty evidence indicated that CVVHDF (versus CVVH: MD 10.15 hours, 95% CI 5.15 to 15.15; 1 study, 62 circuits), pre-dilution haemofiltration (versus post-dilution haemofiltration: MD 9.34 hours, 95% CI -2.60 to 21.29; 2 studies, 47 circuits; I² = 13%), placing the tip of a longer catheter targeting the right atrium (versus placing a shorter catheter targeting the tip in the superior vena cava: MD 6.50 hours, 95% CI 1.48 to 11.52; 1 study, 420 circuits), and surface-modified double-lumen catheter (versus standard double-lumen catheter: MD 16.00 hours, 95% CI 13.49 to 18.51; 1 study, 262 circuits) may prolong circuit lifespan. However, higher blood flow may not increase circuit lifespan (versus standard blood flow: MD 0.64, 95% CI -3.37 to 4.64; 2 studies, 499 circuits; I² = 70%). More and shorter hollow fibre filters (versus standard filters: MD -5.87 hours, 95% CI -10.18 to -1.56; 1 study, 6 circuits) may reduce circuit lifespan. Death from any cause was reported in four comparisons We are uncertain whether CVVHDF versus CVVH, CVVHD versus CVVH or CVVHDF, longer versus a shorter catheter, or surface-modified double-lumen catheters versus standard double-lumen catheters reduced death due to any cause, in very low certainty evidence. Recovery of kidney function was reported in three comparisons. We are uncertain whether CVVHDF versus CVVH, CVVHDF versus CVVH, or surface-modified double-lumen catheters versus standard double-lumen catheters increased recovery of kidney function. Vascular access complications were reported in two comparisons. Low certainty evidence indicated using a longer catheter (versus a shorter catheter: RR 0.40, 95% CI 0.22 to 0.74) may reduce vascular access complications, however the use of surface-modified double lumen catheters versus standard double-lumen catheters may make little or no difference to vascular access complications.

AUTHORS' CONCLUSIONS

The use of CVVHDF as compared with CVVH, pre-dilution haemofiltration, a longer catheter, and surface-modified double-lumen catheter may be useful in prolonging the circuit lifespan, while higher blood flow and more and shorter hollow fibre filter may reduce circuit life. The Overall, the certainty of evidence was assessed to be low to very low due to the small sample size of the included studies. Data from future rigorous and transparent research are much needed in order to fully understand the effects of non-pharmacological interventions in preventing circuit coagulation amongst people with AKI receiving CKRT.

Thrombin Generation and Platelet Function in ICU Patients Undergoing CVVHD Using Regional Citrate Anticoagulation

Background: To investigate pro- and anticoagulant alterations in uremic critically ill patients prior to and during continuous renal replacement therapy. In addition to the conventional thrombin generation assay (TGA), we performed a thrombomodulin-modified variant to better elucidate procoagulant imbalances. Platelet function was determined via multiple electrode aggregometry (MEA) to round off hemostatic analysis.

Methods: We prospectively enrolled patients at surgical intensive care units (ICU) with acute kidney injury undergoing continuous veno-venous hemodialysis using regional citrate anticoagulation. TGA and platelet function testing were performed at baseline (≤ 12 h prior to continuous renal replacement therapy) and on 3 consecutive days (day A–C) of extracorporeal therapy.

Results: We did not observe significant changes in thrombin generation after start or during renal replacement therapy. Ratios of endogenous thrombin potential in patients were significantly increased (p < 0.001) compared to standardized plasma of healthy donors confirming the assumed procoagulant alterations in ICU patients. Test results of the conventional TGA differed significantly (p < 0.05) from those of the thrombomodulin-modified assay. The area under the curve remained below MEA reference values during the entire observation period, indicating a persistent reduction in platelet function.

Conclusion: In summary, in-depth analysis using standard and modified TGA, as well as calculation of endogenous thrombin potential (ETP) ratios, revealed no further aggravation of the procoagulatory shift in the critically ill patient during CVVHD using regional citrate anticoagulation. MEA ruled out the potential impact of platelets.

Clinical Trial Registration: German Clinical Trials Register (DRKS00004336), 29 August 2012; www.drks.de.

Influence of recombinant human-soluble thrombomodulin on extracorporeal circuit clotting in septic patients undergoing blood purification: a propensity-matched cohort study

Blood purification has been widely performed for critically ill patients, even in cases without renal failure. Effective anticoagulation of the extracorporeal circuit is necessary to prevent circuit clotting. We hypothesized that administration of recombinant human-soluble thrombomodulin (rhsTM) to septic patients undergoing blood purification may prevent circuit clotting, because this agent regulates coagulation. We performed a retrospective, single-center, propensity-matched cohort study in the intensive care unit of Nishichita General Hospital. We included septic patients admitted to the intensive care unit from May 2015 to August 2020 who underwent blood purification. Patients who received rhsTM during intensive care unit admission to the end of the first blood purification (rhsTM group) were matched 1:1 with other patients (control group). The primary outcome was the occurrence of circuit clotting during the first blood purification. A total of 138 patients were included in the study [43 patients (31%) in the rhsTM group and 95 patients (69%) in the control group]. After propensity score matching, 42 pairs of patients were selected, and patients in the rhsTM group had a lower incidence of circuit clotting (21 vs. 55%, P = 0.003). One case of major bleeding occurred in the rhsTM group, but there was no difference in the incidence of major bleeding between groups (2 vs. 0%, P = 1.0). In conclusion, this propensity-matched cohort study indicated that the administration of rhsTM to septic patients undergoing blood purification may prevent extracorporeal circuit clotting.

Pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement therapy

BACKGROUND

Acute kidney injury (AKI) is a major comorbidity in hospitalised patients. Patients with severe AKI require continuous renal replacement therapy (CRRT) when they are haemodynamically unstable. CRRT is prescribed assuming it is delivered over 24 hours. However, it is interrupted when the extracorporeal circuits clot and the replacement is required. The interruption may impair the solute clearance as it causes under dosing of CRRT. To prevent the circuit clotting, anticoagulation drugs are frequently used.

OBJECTIVES

To assess the benefits and harms of pharmacological interventions for preventing clotting in the extracorporeal circuits during CRRT.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 September 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs or cluster RCTs) and quasi-RCTs of pharmacological interventions to prevent clotting of extracorporeal circuits during CRRT.

DATA COLLECTION AND ANALYSIS

Data were abstracted and assessed independently by two authors. Dichotomous outcomes were calculated as risk ratio (RR) with 95% confidence intervals (CI). The primary review outcomes were major bleeding, successful prevention of clotting (no need of circuit change in the first 24 hours for any reason), and death. Evidence certainty was determined using the Grading of Recommendation Assessment, Development, and Evaluation (GRADE) approach.

MAIN RESULTS

A total of 34 completed studies (1960 participants) were included in this review. We identified seven ongoing studies which we plan to assess in a future update of this review. No included studies were free from risk of bias. We rated 30 studies for performance bias and detection bias as high risk of bias. We rated 18 studies for random sequence generation,ààsix studies for the allocation concealment, three studies for performance bias, three studies for detection bias,à nine studies for attrition bias,à14 studies for selective reporting and nine studies for the other potential source of bias, as having low risk of bias. We identified eight studies (581 participants) that compared citrate with unfractionated heparin (UFH). Compared to UFH, citrate probably reduces major bleeding (RR 0.22, 95% CI 0.08 to 0.62; moderate certainty evidence) and probably increases successful prevention of clotting (RR 1.44, 95% CI 1.10 to 1.87; moderate certainty evidence). Citrate may have little or no effect on death at 28 days (RR 1.06, 95% CI 0.86 to 1.30, moderate certainty evidence). Citrate versus UFH may reduce the number of participants who drop out of treatment due to adverse events (RR 0.47, 95% CI 0.15 to 1.49; low certainty evidence). Compared to UFH, citrate may make little or no difference to the recovery of kidney function (RR 1.04, 95% CI 0.89 to 1.21; low certainty evidence). Compared to UFH, citrate may reduceàthrombocytopenia (RR 0.39, 95% CI 0.14 to 1.03; low certainty evidence). It was uncertain whether citrate reduces a cost to health care services because of inadequate data. For low molecular weight heparin (LMWH) versus UFH, six studies (250 participants) were identified. Compared to LMWH, UFH may reduce major bleeding (0.58, 95% CI 0.13 to 2.58; low certainty evidence). It is uncertain whether UFH versus LMWH reduces death at 28 days or leads to successful prevention of clotting. Compared to LMWH, UFH may reduce the number of patient dropouts from adverse events (RR 0.29, 95% CI 0.02 to 3.53; low certainty evidence). It was uncertain whether UFH versus LMWH leads to the recovery of kidney function because no included studies reported this outcome. It was uncertain whether UFH versus LMWH leads to thrombocytopenia. It was uncertain whether UFH reduces a cost to health care services because of inadequate data. For the comparison of UFH to no anticoagulation, one study (10 participants) was identified. It is uncertain whether UFH compare to no anticoagulation leads to more major bleeding. It is uncertain whether UFH improves successful prevention of clotting in the first 24 hours, death at 28 days, the number of patient dropouts due to adverse events, recovery of kidney function, thrombocytopenia, or cost to health care services because no study reported these outcomes. For the comparison ofàcitrate to no anticoagulation,àno completed study was identified.

AUTHORS' CONCLUSIONS

Currently,àavailable evidence does not support the overall superiority of any anticoagulant to another. Compared to UFH, citrate probably reduces major bleeding and prevents clotting and probably has little or no effect on death at 28 days. For other pharmacological anticoagulation methods, there is no available data showing overall superiority to citrate or no pharmacological anticoagulation. Further studies are needed to identify patient populations in which CRRT should commence with no pharmacological anticoagulation or with citrate.

Anticoagulation strategies in extracorporeal circulatory devices in adult populations

Extracorporeal circulatory devices such as hemodialysis and extracorporeal membrane oxygenation can be lifesaving; however, they are also prone to pathologic events including device failure, venous and arterial thrombosis, hemorrhage, and an accelerated risk for atherosclerotic disease due to interactions between blood components and device surfaces of varying biocompatibility. While extracorporeal devices may be used acutely for limited periods of time (eg, extracorporeal membrane oxygenation, continuous venovenous hemofiltration, therapeutic apheresis), some patients require chronic use of these technologies (eg, intermittent hemodialysis and left ventricular assist devices). Given the substantial thrombotic risks associated with extracorporeal devices, multiple antiplatelet and anticoagulation strategies-including unfractionated heparin, low-molecular-weight heparin, citrate, direct thrombin inhibitors, and direct oral anticoagulants, have been used to mitigate the thrombotic milieu within the patient and device. In the following manuscript, we outline the current data on anticoagulation strategies for commonly used extracorporeal circulatory devices, highlighting the potential benefits and complications involved with each.

Pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement therapy

BACKGROUND

Acute kidney injury (AKI) is a major comorbidity in hospitalised patients. Patients with severe AKI require continuous renal replacement therapy (CRRT) when they are haemodynamically unstable. CRRT is prescribed assuming it is delivered over 24 hours. However, it is interrupted when the extracorporeal circuits clot and the replacement is required. The interruption may impair the solute clearance as it causes under dosing of CRRT. To prevent the circuit clotting, anticoagulation drugs are frequently used.

OBJECTIVES

To assess the benefits and harms of pharmacological interventions for preventing clotting in the extracorporeal circuits during CRRT.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 September 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs or cluster RCTs) and quasi-RCTs of pharmacological interventions to prevent clotting of extracorporeal circuits during CRRT.

DATA COLLECTION AND ANALYSIS

Data were abstracted and assessed independently by two authors. Dichotomous outcomes were calculated as risk ratio (RR) with 95% confidence intervals (CI). The primary review outcomes were major bleeding, successful prevention of clotting (no need of circuit change in the first 24 hours for any reason), and death. Evidence certainty was determined using the Grading of Recommendation Assessment, Development, and Evaluation (GRADE) approach.

MAIN RESULTS

A total of 34 completed studies (1960 participants) were included in this review. We identified seven ongoing studies which we plan to assess in a future update of this review. No included studies were free from risk of bias. We rated 30 studies for performance bias and detection bias as high risk of bias. We rated 18 studies for random sequence generation,  six studies for the allocation concealment, three studies for performance bias, three studies for detection bias,  nine studies for attrition bias, 14 studies for selective reporting and nine studies for the other potential source of bias, as having low risk of bias. We identified eight studies (581 participants) that compared citrate with unfractionated heparin (UFH). Compared to UFH, citrate probably reduces major bleeding (RR 0.22, 95% CI 0.08 to 0.62; moderate certainty evidence). Citrate may have little or no effect on death at 28 days (RR 1.06, 95% CI 0.86 to 1.30, moderate certainty evidence), while citrate versus UFH may have little or no effect on successful prevention of clotting (RR 1.01, 95% CI 0.77 to 1.32; moderate certainty evidence). Citrate versus UFH may reduce the number of participants who drop out of treatment due to adverse events (RR 0.47, 95% CI 0.15 to 1.49; low certainty evidence). Compared to UFH, citrate may make little or no difference to the recovery of kidney function (RR 0.95, 95% CI 0.66 to 1.36; low certainty evidence). Compared to UFH, citrate may reduce thrombocytopenia (RR 0.39, 95% CI 0.14 to 1.03; low certainty evidence). It was uncertain whether citrate reduces a cost to health care services because of inadequate data. For low molecular weight heparin (LMWH) versus UFH, six studies (250 participants) were identified. Compared to LMWH, UFH may reduce major bleeding (0.58, 95% CI 0.13 to 2.58; low certainty evidence). It is uncertain whether UFH versus LMWH reduces death at 28 days or leads to successful prevention of clotting. Compared to LMWH, UFH may reduce the number of patient dropouts from adverse events (RR 0.29, 95% CI 0.02 to 3.53; low certainty evidence). It was uncertain whether UFH versus LMWH leads to the recovery of kidney function because no included studies reported this outcome. It was uncertain whether UFH versus LMWH leads to thrombocytopenia. It was uncertain whether UFH reduces a cost to health care services because of inadequate data. For the comparison of UFH to no anticoagulation, one study (10 participants) was identified. It is uncertain whether UFH compare to no anticoagulation leads to more major bleeding. It is uncertain whether UFH improves successful prevention of clotting in the first 24 hours, death at 28 days, the number of patient dropouts due to adverse events, recovery of kidney function, thrombocytopenia, or cost to health care services because no study reported these outcomes. For the comparison of citrate to no anticoagulation, no completed study was identified.

AUTHORS' CONCLUSIONS

Currently, available evidence does not support the overall superiority of any anticoagulant to another. Compared to UFH, citrate probably reduces major bleeding and probably has little or no effect on preventing clotting or death at 28 days. For other pharmacological anticoagulation methods, there is no available data showing overall superiority to citrate or no pharmacological anticoagulation. Further studies are needed to identify patient populations in which CRRT should commence with no pharmacological anticoagulation or with citrate.

Timing of renal replacement therapy initiation for acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a common condition among patients in intensive care units (ICUs), and is associated with high death. Renal replacement therapy (RRT) is a blood purification technique used to treat the most severe forms of AKI. The optimal time to initiate RRT so as to improve clinical outcomes remains uncertain.This review complements another Cochrane review by the same authors: Intensity of continuous renal replacement therapy for acute kidney injury.

OBJECTIVES

To assess the effects of different timing (early and standard) of RRT initiation on death and recovery of kidney function in critically ill patients with AKI.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant's Specialised Register to 23 August 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov. We also searched LILACS to 11 September 2017.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs). We included all patients with AKI in ICU regardless of age, comparing early versus standard RRT initiation. For safety and cost outcomes we planned to include cohort studies and non-RCTs.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors. The random-effects model was used and results were reported as risk ratios (RR) for dichotomous outcomes and mean differences (MD) for continuous outcomes, with 95% confidence intervals (CI).

MAIN RESULTS

We included five studies enrolling 1084 participants. Overall, most domains were assessed as being at low or unclear risk of bias. Compared to standard treatment, early initiation may reduce the risk of death at day 30, although the 95% CI does not rule out an increased risk (5 studies, 1084 participants: RR 0.83, 95% CI 0.61 to 1.13; I2 = 52%; low certainty evidence); and probably reduces the death after 30 days post randomisation (4 studies, 1056 participants: RR 0.92, 95% CI 0.76 to 1.10; I2= 29%; moderate certainty evidence); however in both results the CIs included a reduction and an increase of death. Earlier start may reduce the risk of death or non-recovery kidney function (5 studies, 1076 participants: RR 0.83, 95% CI 0.66 to 1.05; I2= 54%; low certainty evidence). Early strategy may increase the number of patients who were free of RRT after RRT discontinuation (5 studies, 1084 participants: RR 1.13, 95% CI 0.91 to 1.40; I2= 58%; low certainty evidence) and probably slightly increases the recovery of kidney function among survivors who discontinued RRT after day 30 (5 studies, 572 participants: RR 1.03, 95% CI 1.00 to 1.06; I2= 0%; moderate certainty evidence) compared to standard; however the lower limit of CI includes the null effect. Early RRT initiation increased the number of patients who experienced adverse events (4 studies, 899 participants: RR 1.10, 95% CI 1.03 to 1.16; I2 = 0%; high certainty evidence). Compared to standard, earlier RRT start may reduce the number of days in ICU (4 studies, 1056 participants: MD -1.78 days, 95% CI -3.70 to 0.13; I2 = 90%; low certainty evidence), but the CI included benefit and harm.

AUTHORS' CONCLUSIONS

Based mainly on low quality of evidence identified, early RRT may reduce the risk of death and may improve the recovery of kidney function in critically patients with AKI, however the 95% CI indicates that early RRT might worsen these outcomes. There was an increased risk of adverse events with early RRT. Further adequate-powered RCTs using appropriate criteria to define the optimal time of RRT are needed to reduce the imprecision of the results.

Renal replacement therapy and anticoagulation

Today, up to 20% of all intensive care unit patients require renal replacement therapy (RRT), and continuous renal replacement therapies (CRRT) are the preferred technique. In CRRT, effective anticoagulation of the extracorporeal circuit is mandatory to prevent clotting of the circuit or filter and to maintain filter performance. At present, a variety of systemic and regional anticoagulation modes for CRRT are available. Worldwide, unfractionated heparin is the most widely used anticoagulant. All systemic techniques are associated with significant adverse effects. Most important are bleeding complications and heparin-induced thrombocytopenia (HIT-II). Regional citrate anticoagulation (RCA) is a safe and effective technique. Compared to systemic anticoagulation, RCA prolongs filter running times, reduces bleeding complications, allows effective control of acid-base status, and reduces adverse events like HIT-II. In this review, we will discuss systemic and regional anticoagulation techniques for CRRT including anticoagulation for patients with HIT-II. Today, RCA can be recommended as the therapy of choice for the majority of critically ill patients requiring CRRT.

Non anti-coagulant factors associated with filter life in continuous renal replacement therapy (CRRT): a systematic review and meta-analysis

BACKGROUND

Optimising filter life and performance efficiency in continuous renal replacement therapy has been a focus of considerable recent research. Larger high quality studies have predominantly focussed on optimal anticoagulation however CRRT is complex and filter life is also affected by vascular access, circuit and management factors. We performed a systematic search of the literature to identify and quantify the effect of vascular access, circuit and patient factors that affect filter life and presented the results as a meta-analysis.

METHODS

A systematic review and meta-analysis was performed by searching Pubmed (MEDLINE) and Ovid EMBASE libraries from inception to 29th February 2016 for all studies with a comparator or independent variable relating to CRRT circuits and reporting filter life. Included studies documented filter life in hours with a comparator other than anti-coagulation intervention. All studies comparing anticoagulation interventions were searched for regression or hazard models pertaining to other sources of variation in filter life.

RESULTS

Eight hundred nineteen abstracts were identified of which 364 were selected for full text analysis. 24 presented data on patient modifiers of circuit life, 14 on vascular access modifiers and 34 on circuit related factors. Risk of bias was high and findings are hypothesis generating. Ranking of vascular access site by filter longevity favours: tunnelled semi-permanent catheters, femoral, internal jugular and subclavian last. There is inconsistency in the difference reported between femoral and jugular catheters. Amongst published literature, modality of CRRT consistently favoured continuous veno-venous haemodiafiltration (CVVHD-F) with an associated 44% lower failure rate compared to CVVH. There was a trend favouring higher blood flow rates. There is insufficient data to determine advantages of haemofilter membranes. Patient factors associated with a statistically significant worsening of filter life included mechanical ventilation, elevated SOFA or LOD score, elevations in ionized calcium, elevated platelet count, red cell transfusion, platelet factor 4 (PF-4) antibodies, and elevated fibrinogen. Majority of studies are observational or report circuit factors in sub-analysis. Risk of bias is high and findings require targeted investigations to confirm.

CONCLUSION

The interaction of patient, pathology, anticoagulation, vascular access, circuit and staff factors contribute to CRRT filter life. There remains an ambiguity from published data as to which site and side should be the first choice for vascular access placement and what interaction this has with patient factors and timing. Early consideration of tunnelled semi-permanent access may provide optimal filter life if longer periods of CRRT are anticipated. There remains an absence of robust evidence outside of anti-coagulation strategies despite over 20 years of therapy delivery however trends favour CVVHD-F over CVVH.

Low-molecular weight heparin infusion as anticoagulation for haemodialysis

Background

Low-molecular weight heparin (LMWH) is commonly used as an anticoagulant for haemodialysis by a single-bolus injection. However, its application in extended haemodialysis has been infrequently studied. In particular, for nocturnal home haemodialysis patients sleeping throughout treatment, the need for additional intradialytic bolus might render the use of LMWH impractical. To overcome this limitation, we changed traditional bolus injections to continuous infusion. We first tested our method among in-centre 4-h haemodialysis patients to establish a feasible and safe infusion regimen before utilizing it in extended dialyses at home.

Methods

Recruited patients were given nadroparin (standardized at 65 IU/kg) as an anticoagulant for haemodialysis. They were first randomized to receive nadroparin either by bolus injection or infusion. Afterwards, the patients underwent crossover to receive the alternate method of LMWH anticoagulation. The degrees of anticoagulation and bleeding complications were compared.

Results

Sixteen haemodialysis patients were recruited. After nadroparin administration, anti-Xa levels at the first hour were significantly higher by the bolus than the infusion methods (0.68 ± 0.10 versus 0.49 ± 0.10 IU/mL, P < 0.001) and were similar by the second hour (0.56 ± 0.10 versus 0.55 ± 0.11 IU/mL, P = 0.64). At the sixth hour, anti-Xa levels by the infusion method were significantly higher (0.35 ± 0.13 versus 0.25 ± 0.10 IU/mL, P < 0.001), suggesting the infusion approach required a dosage reduction. There were no bleeding events reported in either method.

Conclusions

LMWH infusion is feasible and safe. The method avoids early excessive anticoagulation caused by bolus injection and reduces the LMWH dose. Future studies should be conducted to evaluate LMWH infusion in extended haemodialysis treatment.

Low concentrations of citrate reduce complement and granulocyte activation in vitro in human blood

Background

The use of acetate in haemodialysis fluids may induce negative effects in patients including nausea and increased inflammation. Therefore, haemodialysis fluids where acetate is substituted with citrate have recently been developed. In this study, we investigated the biocompatibility of citrate employing concentrations used in haemodialysis.

Methods

The effects of citrate and acetate were investigated in human whole blood in vitro under conditions promoting biomaterial-induced activation. Complement activation was measured as generation of C3a, C5a and the sC5b-9 complex, and granulocyte activation as up-regulation of CD11b expression. For the experimental set-up, a mathematical model was created to calculate the concentrations of acetate and citrate attained during haemodialysis.

Results

Citrate reduced granulocyte activation and did not induce higher complement activation compared with acetate at concentrations attained during haemodialysis. Investigating different citrate concentrations clearly showed that citrate is a potent complement inhibitor already at low concentrations, i.e. 0.25 mM, which is comparable with concentrations detected in the blood of patients during dialysis with citrate-containing fluids. Increased citrate concentration up to 6 mM further reduced the activation of C3a, C5a and sC5b-9, as well as the expression of CD11b.

Conclusions

Our results suggest that citrate is a promising substitute for acetate for a more biocompatible dialysis, most likely resulting in less adverse effects for the patients.

Clinical review: anticoagulation for continuous renal replacement therapy--heparin or citrate?

Heparin is the most commonly prescribed anticoagulant for continuous renal replacement therapy. There is, however, increasing evidence questioning its safety, particularly in the critically ill. Heparin mainly confers its anticoagulant effect by binding to antithrombin. Heparin binds to numerous other proteins and cells as well, however, compromising its efficacy and safety. Owing to antithrombin consumption and degradation, and to the binding of heparin to acute phase proteins, and to apoptotic and necrotic cells, critical illness confers heparin resistance. The nonspecific binding of heparin further leads to an unpredictable interference with inflammation pathways, microcirculation and phagocytotic clearance of dead cells, with possible deleterious consequences for patients with sepsis and systemic inflammation. Regional anticoagulation with citrate does not increase the patient's risk of bleeding. The benefits of citrate further include a longer or similar circuit life, and possibly better patient and kidney survival. This needs to be confirmed in larger randomized controlled multicenter trials. The use of citrate might be associated with less inflammation and has useful bio-energetic implications. Citrate can, however, with inadequate use cause metabolic derangements. Full advantages of citrate can only be realized if its risks are well controlled. These observations suggest a greater role for citrate.