Comparison of the use of standard heparin and prostacyclin anticoagulation in spontaneous and pump-driven extracorporeal circuits in patients with combined acute renal and hepatic failure

Protocolized Regional Citrate Anticoagulation during Continuous Renal Replacement Therapy: A Single Center Experience

Background

Regional citrate anticoagulation (RCA) has emerged as a treatment modality that reduces bleeding risk and filter clotting. With initial experience of using RCA with continuous renal replacement therapy (CRRT), we have formulated a working protocol based on published literature.

Objective

The study aimed to evaluate the protocol for routine use of RCA during CRRT requiring anticoagulation and evaluation of filter life.

Methodology

It is a single-center, open-label, prospective, non-randomized, non-interventional, single-arm, observational study conducted at a tertiary care hospital between September 2022 and July 2023. All adult patients with acute kidney injury (AKI) or hyperammonemia requiring CRRT and necessitating the use of anticoagulation were enrolled in the study. The study used Prisma Flex M100 AN 69 dialyzer on Prisma Flex (Baxter) CRRT machines during continuous venovenous hemodiafiltration (CVVHDF). The targeted CRRT dose in all the study patients was 25-30 mL/kg/hour. Based on the published literature, we have developed a working protocol (Appendix 1) for managing patients on CRRT using RCA.

Results

A total of 159 patients were analyzed for the study. The median [interquartile range (IQR)] filter life using RCA was 30 (12-55) hours. Filter clotting was observed in 33.3% of patients. Citrate accumulation was present in 52.25% of patients, but no CRRT was discontinued as citrate accumulation resolved after following the corrective steps in the protocol. None of the patients had citrate toxicity. Chronic liver disease (CLD) (p ≤ 0.001) and those who were post-living donor liver transplant recipients (p = 0.004) had a statistically significant increase in citrate accumulation. Also, patients who had higher lactate at baseline (6 hours post-CRRT initiation), had a higher chance of citrate accumulation.

Conclusion

Our RCA protocol provides a safe approach to regional anticoagulation during CRRT in critically ill patients.

How to cite this article

Pachisia AV, Kumar GP, Harne R, Jagadeesh KN, Patel SJ, Pal D, et al. Protocolized Regional Citrate Anticoagulation during Continuous Renal Replacement Therapy: A Single Center Experience. Indian J Crit Care Med 2024;28(9):859-865.

A Comparison of the Anticoagulation Efficacy and Safety of Epoprostenol to Heparin and Citrate in Children Receiving Continuous Renal Replacement Therapy

INTRODUCTION

Anticoagulants are used in continuous renal replacement therapy (CRRT) to prolong filter life. There are no prior investigations directly comparing epoprostenol to more commonly used forms of anticoagulation in children. Therefore, the primary aim of this study was to assess the efficacy and safety of epoprostenol as compared to heparin and citrate anticoagulation in a pediatric cohort.

METHODS

We performed a retrospective analysis of all patients <18 years of age admitted to an academic quaternary care children's hospital from 2017-2022 who received epoprostenol, heparin, or citrate exclusively for CRRT anticoagulation. Efficacy was evaluated by comparing the hours to the first unintended filter change and the ratio of filters used to CRRT days. Safety was assessed by evaluating changes in platelet count and vasoactive-ionotropic score (VIS).

RESULTS

Of 101 patients, 44 received epoprostenol (43.6%), 38 received heparin (37.6%), and 19 received citrate (18.8%). The first filter change was more commonly planned in patients receiving anticoagulation with epoprostenol (43%) as compared to citrate (11%) or heparin (29%) (p = 0.034). Of those patients where the first filter change was unintended (n = 33), there were greater median hours until the filter was replaced in those receiving epoprostenol (29) when compared to citrate (21) (p = 0.002) or heparin (18) (p = 0.003). There was a smaller median ratio of filters used to days on therapy in the patients that received epoprostenol (0.53) when compared to citrate (1) (p = 0.003) or heparin (0.75) (p = 0.001). For those receiving epoprostenol, there was no significant decrease in platelet count when comparing values prior to CRRT initiation through 7 days of therapy. There was no significant difference in VIS when comparing values prior to CRRT initiation through the first 2 days of CRRT.

CONCLUSIONS

Epoprostenol-based anticoagulation is effective when compared to other anticoagulation strategies used in pediatric CRRT with a favorable side effect profile.

Efficacy of Prostacyclin Anticoagulation in Critically Ill Patients Requiring Extracorporeal Support: A Systematic Review and Meta-Analysis

Extracorporeal support modalities are highly prothrombotic. Anticoagulation is frequently used for patients receiving Continuous Renal Replacement Therapy (CRRT), Molecular Adsorbent Recirculating System (MARS), and Extracorporeal Membrane Oxygenation (ECMO). The objective of this systematic review and meta-analysis is to determine if prostacyclin-based anticoagulation strategies are effective compared to other anticoagulation strategies, in critically ill children and adults who needs extracorporeal support, such as continuous renal replacement therapy. We conducted a systematic review and meta-analysis using multiple electronic databases and included studies from inception to June 1, 2022. Circuit lifespan, proportion of bleeding, thrombotic, and hypotensive events, and mortality were evaluated. Out of 2,078 studies that were screened, 17 studies (1,333 patients) were included. The mean circuit lifespan was 29.7 hours in the patients in the prostacyclin-based anticoagulation series and 27.3 hours in the patients in the heparin- or citrate-based anticoagulation series, with a mean difference of 2.5 hours (95%CI -12.0;16.9, p=0.74, I2=0.99, n=4,003 circuits). Bleeding occurred in 9.5% of the patients in the prostacyclin-based anticoagulation series and in 17.1% of the patients in the control series, which was a statistically significant decrease (LogOR -1.14 (95%CI -1.91;-0.37), p<0.001, I2=0.19, n=470). Thrombotic events occurred in 3.6% of the patients in the prostacyclin-based anticoagulation series and in 2.2% of the patients in the control series, which was not statistically different (LogOR 0.97 (95%CI -1.09;3.04), p=0.35, I2=0.0, n=115). Hypotensive events occurred in 13.4% of the patients in the prostacyclin-based anticoagulation series and in 11.0% of the patients in the control series, which was not statistically different (LogOR -0.56 (95%CI -1.87;0.74), p=0.40, I2=0.35, n=299). The mortality rate was 26.3% in the prostacyclin-based anticoagulation series, and 32.7% in the control series, which was not statistically different (LogOR -0.40 (95%CI -0.87;0.08), p=0.10, I2=0.00, n=390). The overall risk of bias was low to moderate. In this systematic review and meta-analysis of 17 studies, prostacyclin-based anticoagulation was associated with fewer bleeding events, but with similar circuit lifespans, thrombotic events, hypotensive events, and mortality rates. The potential benefits of prostacyclin-based anticoagulation should be explored in large randomized controlled trials.

Anticoagulation in patients with acute kidney injury undergoing kidney replacement therapy

Kidney replacement therapy (KRT) is used to provide supportive therapy for critically ill patients with severe acute kidney injury and various other non-renal indications. Modalities of KRT include continuous KRT (CKRT), intermittent hemodialysis (HD), and sustained low efficiency daily dialysis (SLED). However, circuit clotting is a major complication that has been investigated extensively. Extracorporeal circuit clotting can cause reduction in solute clearances and can cause blood loss, leading to an upsurge in treatment costs and a rise in workload intensity. In this educational review, we discuss the pathophysiology of the clotting cascade within an extracorporeal circuit and the use of various types of anticoagulant methods in various pediatric KRT modalities.

Continuous renal replacement therapy under special conditions like sepsis, burn, cardiac failure, neurotrauma, and liver failure

Continuous renal replacement therapy (CRRT) in sepsis does have a role in removing excessive fluid, and also role in removal of mediators although not proven today, and to allow fluid space in order to feed. In these conditions, continuous renal replacement therapy can improve morbidity but never mortality so far. Regarding sepsis, timing has become a more important issue after decades and is currently more discussed than dosing. Rationale of blood purification has evolved a lot in the last years regarding sepsis with the discovery of many types of sorbent allowing ideas from science fiction to become reality in 2021. Undoubtedly, COVID-19 has reactivated the interest of blood purification in sepsis but also in COVID-19. Burn is even more dependent about removal of excessive fluid as compared to sepsis. Regarding cardiac failure, ultrafiltration can improve the quality of life and morbidity when diuretics are becoming inefficient but can never improve mortality. Regarding brain injury, CRRTs have several advantages as compared to intermittent hemodialysis. In liver failure, there have been no randomized controlled trials to examine whether single-pass albumin dialysis offers advantages over standard supportive care, and there is always the cost of albumin.

Do anti-platelet drugs improve duration of continuous renal replacement therapy? A retrospective cohort study in cardiac ICU patients

OBJECTIVE

The objective of this study was to investigate the impact of anti-platelet drug/s on duration of continuous renal replacement therapy (CRRT) in those patients where anti-coagulants were not used due to certain contraindications and in cases where patients were on anti-platelet drugs and were given anti-coagulant during CRRT.

METHOD

This single-center, retrospective cohort study was conducted using the medical records patients treated with CRRT in the cardiac ICU of the inpatient urban facility, located in North India. Data was collected from only those patients who received CRRT for the duration of at least 12 h. Patient's in NAC group were not on any anti-platelet/s and did not receive anti-coagulant during CRRT. AC and AP group patients received anti-coagulant alone or were already on anti-platelet/s and did not receive anti-coagulant respectively while ACAP group patients were on anti-platelet drug/s and also received anti-coagulant during CRRT.

RESULT

Patients in AC, AP, or ACAP group showed significantly (p < 0.001) higher CRRT filter life compared to NAC group. The median CRRT filter life was significantly higher in the ACAP group compared to AC (p < 0.05) and AP (p < 0.001) groups.

CONCLUSION

This study indicates that systemic anti-platelet therapy can provide additional support in critical patients undergoing CRRT even with or without anti-coagulant therapy. However, the increase in CRRT filter life was more profound in patients who were on anti-platelet/s and also received anti-coagulant drug/s during CRRT.

Prostacyclin as an Anticoagulant for Continuous Renal Replacement Therapy in Children

Effective delivery of continuous renal replacement therapy (CRRT) depends on the longevity of the filter and circuit used in the CRRT machine. Safe and effective anticoagulation is crucial for maintaining the patency of these circuits. In children, heparin and citrate are the commonly used anticoagulants but they are limited by serious side effects and thus calls for meticulous monitoring. In conditions where neither of these can be used, prostacyclin can be an effective alternative. Prostacyclin is a platelet inhibitor that can be safely used as an efficient anticoagulant in CRRT. When combined with heparin, it induces a heparin-sparing effect, which can reduce the dosage and side effects of heparin. Furthermore, there is no need for performing time-consuming monitoring tests. Although prostacyclin seems to be an attractive option, there is scanty evidence about its use as an anticoagulant in CRRT in children. We review the evidence and practicalities, and propose a guideline for the use of prostacyclin as an anticoagulant in children requiring CRRT.

We Use Heparin as the Anticoagulant for CRRT

Continuous Renal Replacement Therapy (CRRT) usually requires anticoagulation to prevent clotting of the extracorporeal circuit. Interruptions due to filter clotting significantly reduce total therapy time and CRRT efficacy. Although heparin has traditionally been the most common anticoagulant used for CRRT, increasing evidence suggests that heparin is less effective than regional citrate in prolonging circuit life and considerably increases patient bleeding risk. Advantages of regional citrate anticoagulation (RCA) include less bleeding, increased circuit life, and less blood transfusion requirement. RCA should be the anticoagulant of choice for CRRT.

Factors affecting circuit life during continuous renal replacement therapy in children with liver failure

Despite abnormal clotting, circuits clot during continuous renal replacement therapy (CRRT) in children with acute liver failure (ALF). We report our experience. All children with ALF needing CRRT were studied over 2 years. Patient and circuit factors associated with circuit use were evaluated. Thirty-one children in liver failure (median age 7.4 years) underwent CRRT, of which 17 (54.8%) died. A total of 98 filtration episodes were used. The smallest access catheter was 6.5 Fr, while the largest was 13.5 Fr. The most common filter used was HFO7 (63%). Mean duration (SD) of circuit use was 33.13(30.83) hours. Of the 98 filtration episodes, circuits blocked in 25, whereas the access catheter blocked in 25. Fifty-two circuits were changed electively for a variety of reasons. Prostacyclin was the anticoagulant in 62 filtration episodes. The remaining filtration episodes had either no anticoagulation or heparin. The mean (SD) "downtime" was 5.13 (9.15) hours. We found a significant association between fresh frozen plasma (FFP) use with circuit blockade. Neither the duration of CRRT nor the "downtime" influenced mortality. The CRRT circuits blocked in children despite deranged clotting in liver disease. Circuits are changed for a variety of reasons other than clotting. The use of FFP reduces circuit life.

No sustained impact of intermittent extracorporeal liver support on thrombocyte time course in a randomized controlled albumin dialysis trial

Reduction of platelets is a common finding in patients with liver disease and can be aggravated by extracorporeal therapies, e.g. artificial liver support. The impact of extracorporeal albumin dialysis on the time count and time course of platelets in liver failure patients was evaluated in a randomized controlled clinical trial. Mean thrombocyte reduction during a single extracorporeal liver support therapy was -15.1% [95%CI: -17.7; -12.5]. No differences were found between treatments of patients with a more reduced platelet count (<100 GPT/L: -15.6% [-19.5; -11.7%]; n = 43) compared to patients with normal or slightly decreased thrombocytes (-14.6% [-18.3%; -11.0%]; n = 43; P = 0.719). The variation of platelet count within 24 h after onset of extracorporeal therapy treatment was less, albeit significant (-3.5% [-6.3%; -0.7%], P < 0.016). Absolute thrombocyte variability was comparable between both groups (with extracorporeal therapy -5.6 GPT/L [-9.7; -1.4], without extracorporeal therapy -1.3 GPT/L [-7.3; 4.7]; P = 0.243), whereas relative decrease of thrombocytes within a 24-h period of extracorporeal therapy was greater than the changes in patients without extracorporeal therapy (-3.5% [-6.3%; -0.7%] vs. 2.0% [-2.0%; 5.9%]; P = 0.026]. Within a period of two weeks after enrollment, no significant differences of platelet count were observed either between the two groups or in the time course (P(group) = 0.337, P(time) = 0.277). Reduction of platelets during intermittent extracorporeal liver support was less pronounced within a 24-h period as before and after a single treatment and was comparable to variations in the control group without extracorporeal therapy.

Enhanced platelet apoptosis in chronic uremic patients

BACKGROUND

There is a paucity of research on platelet apoptosis and its contribution to platelet dysfunction in uremic patients. The present study sought to analyze platelets apoptosis in uremic patients who underwent different dialysis modalities.

METHODS

Sixteen chronic uremic patients (5 on hemodialysis, 6 on peritoneal dialysis and 5 on non-dialysis) and 16 controls were studied. Platelet-rich plasma was detected for apoptotic events including depolarization of mitochondrial inner membrane potential (ΔΨm), phosphatidylserine (PS) exposure, activation of caspases-3 and Bcl-2 family proteins variations by Flow Cytometry or by Western-Blot. Washed normal platelets were incubated with normal or uremic platelet poor plasma and then were detected apoptotic events. Platelets function was assessed by ristocetin induced aggregative function test.

RESULTS

Compared to controls, uremic platelets demonstrated greater apoptosis for the ΔΨm depolarization (43.48 ± 9.58 vs. 52.76 ± 15.36, p = 0.005) as well as PS exposure (1.36 ± 0.51 vs. 0.99 ± 0.27, p < 0.001). There was no significant difference among different treatment groups (for the ΔΨm depolarization f = 0.16, p = 0.85; for the PS exposure f = 1.06, p = 0.36). Western Blot analyses showed caspase-3 activation and pro-apoptotic Bcl-2 family proteins expression. Platelets exposed to uremic plasma exhibited distinct apoptosis phenomena. Ristocetin induced platelet aggregation was markedly diminished in uremic patients and treated platelets.

CONCLUSIONS

These findings indicate that platelets are incurred apoptosis in uremia patients. Uremic plasma accelerates apoptosis of normal platelets, resulting in a dysfunctional pattern of platelets in uremia. Uremic platelets apoptosis has no relationship with dialysis modality.

Artificial Placenta - Lung Assist Devices for Term and Preterm Newborns with Respiratory Failure

Respiratory insufficiency is a major cause of neonatal mortality and long-term morbidity, especially in very low birth weight infants. Today, non-invasive and mechanical ventilation are commonly accepted procedures to provide respiratory support to newborns, but they can reach their limit of efficacy. To overcome this technological plateau and further reduce mortality rates, the technology of an “artificial placenta”, which is a pumpless lung assist device connected to the umbilical vessels, would serve to expand the therapeutic spectrum when mechanical ventilation becomes inadequate to treat neonates with severe respiratory insufficiency.

The first attempts to create such an artificial placenta took place more than 60 years ago. However, there has been a recent renaissance of this concept, including developments of its major components like the oxygenator, vascular access via umbilical vessels, flow control, as well as methods to achieve hemocompatibility in extracorporeal circuits. This paper gives a review of past and current development, animal experiments and human case studies of artificial placenta technology.

Hemostasis in patients with acute kidney injury secondary to acute liver failure

Acute kidney injury (AKI) occurs in over half of patients with acute liver failure. Despite prolonged prothrombin times and thrombocytopenia, continuous renal replacement therapy circuits frequently develop clots during patient treatment. Here we assessed factors contributing to this by measuring coagulation parameters (standard coagulation tests, pro- and anticoagulant factors, thromboelastography, and thrombin generation) in 20 consecutive patients with acute liver failure; mean age 42 years. Within 48 h, 10 had developed stage 3 AKI and 9 required continuous renal replacement therapy, of whom 2 had frequent circuit clots. The patients with stage 3 AKI were found to have significantly lower platelet counts and levels of factor V and the natural anticoagulants antithrombin, Protein C and Protein S, but increased extrinsic pathway activation and von Willebrand factor levels. Tissue factor levels were greater in those with stage 3 AKI, as was microparticle activity. Although patients with acute liver failure and advanced AKI requiring continuous renal replacement therapy have an even more marked thrombocytopenia and more prolonged extrinsic pathway activation, this was not associated with increased bleeding. Thus, more frequent circuit clots during continuous renal replacement therapy appear to be due to a combination of increased tissue factor and microparticle release, endothelial activation, and reduction in natural anticoagulants.

Optimization of heparin anticoagulation for hemodialysis

Unfractionated heparin remains the most commonly used anticoagulant for extracorporeal therapies worldwide due to cost, years of clinical experience showing effectiveness and safety for outpatient hemodialysis. Most centers administer unfractionated heparin as an initial bolus followed by a constant infusion, which is then stopped prior to the end of the dialysis session. Although the anticoagulant effect of heparin can be monitored at the bedside, most centers take a pragmatic stance for routine outpatient hemodialysis, and adjust bolus doses and infusion rates based on visual inspection of the dialyzer header and venous air detector chamber for clots, and stop the heparin infusion based on the time taken for needle puncture sites to stop bleeding at the end of the hemodialysis session. Heparin is negatively charged and can bind to plasma proteins, leukocytes, and plastic. As such, it is important to achieve adequate mixing of heparin with blood to optimize anticoagulation within the extracorporeal circuit, by administering an intravenous bolus a few minutes prior to connecting the patient to the circuit and ensuring thorough mixing of the heparin infusion.

Clinical review: use of renal replacement therapies in special groups of ICU patients

Acute kidney injury (AKI) in ICU patients is typically associated with other severe conditions that require special attention when renal replacement therapy (RRT) is performed. RRT includes a wide range of techniques, each with specific characteristics and implications for use in ICU patients. In the present review we discuss a wide range of conditions that can occur in ICU patients who have AKI, and the implications this has for RRT. Patients at increased risk for bleeding should be treated without anticoagulation or with regional citrate anticoagulation. In patients who are haemodynamically unstable, continuous therapies are most often employed. These therapies allow slow removal of volume and guarantee a stable blood pH. In patients with cerebral oedema, continuous therapy is recommended in order to prevent decreased cerebral blood flow, which will lead to cerebral ischemia. Continuous therapy will also prevent sudden change in serum osmolality with aggravation of cerebral oedema. Patients with hyponatraemia, as in liver failure or decompensated heart failure, require extra attention because a rapid increase of serum sodium concentration can lead to irreversible brain damage through osmotic myelinolysis. Finally, in patients with severe lactic acidosis, RRT can be used as a bridging therapy, awaiting correction of the underlying cause. Especially in ICU patients who have severe AKI, treatment with RRT requires balancing the pros and cons of different options and modalities. Exact and specific guidelines for RRT in these patients are not available for most clinical situations. In the present article we provide an update on the existing evidence.

Regional citrate anticoagulation in predilution continuous venovenous hemofiltration using prismocitrate 10/2 solution

Regional citrate anticoagulation (RCA) for continuous renal replacement therapy (CRRT) is associated with a longer filter life and fewer bleeding events. Complexity of the regimen is the major hurdle preventing widespread application. This study describes a simple predilution continuous venovenous hemofiltration (CVVH) protocol utilizing a commercially prepared replacement solution containing citrate (Prismocitrate 10/2). Ten patients with acute renal failure were evaluated. The Prismaflex system was used for predilution CVVH, with Prismocitrate 10/2 running at 2500 mL/h as the main predilution replacement. An 8.4% sodium bicarbonate solution was infused at 50 mL/h in the first 2 h followed by 30 mL/h; 10% calcium gluconate was given to achieve an ionized calcium (iCa) level of 1-1.2 mmol/L. The circuit was run for 72 h unless there was filter clotting, transportation was required, or the patient did not require further CRRT. Total treatment duration was 504.5 h. The post-dilution equivalent ultrafiltration rate was 32.9 mL/kg/h (interquartile range [IQR] 31.6-38.2) and the median circuit life was 50.3 h (IQR 25.5-72.0). None of the circuit was changed due to circuit clotting. The median systemic iCa was 0.98 mmol/L (IQR 0.91-1.08). The total calcium-to-iCa ratio was 2.33 (IQR 2.21-2.45). None of the patients developed hypernatremia (Na ≥ 150 mmol/L) or citrate toxicity (total Ca-to-iCa ratio > 2.5 plus increasing metabolic acidosis), and metabolic alkalosis (pH ≥ 7.5) occurred in one patient. This simple RCA CVVH protocol using commercially-prepared solution could be a feasible, relatively safe, and effective alternative to the conventional regimen for patients with a body weight up to 80 kg.

Transfusion requirements and clinical outcome in intensive care patients receiving continuous renal replacement therapy: comparison of prostacyclin vs. heparin prefilter administration

Prostacyclin (PGI(2)) analogous are potent antithrombotics recommended as prefilter infusion during renal replacement therapy (RRT) when heparin is contraindicated. It is debated whether PGI(2) administration during RRT affects transfusion requirements and outcome. Retrospective cohort study of all patients at a general intensive care unit (ICU) receiving continuous RRT (CRRT) in a 14-month period. Patients were stratified according to the used anticoagulant, that is prefilter PGI(2) group (n=24) and prefilter heparin group (n=70). The ICU stay of the patients was divided into three time periods: before, during and after CRRT. For each time period, laboratory values were analysed as changes/day and blood transfusion requirements as absolute values. Organ failures during the ICU stay and 1 year all-cause mortality were registered. During CRRT the PGI(2) group had a higher incidence of disseminated intravascular coagulation (DIC) (P=0.006), severe thrombocytopenia (P=0.03), higher maximum Sequential Organ Failure Assessment score (P<0.001) and higher rate of blood transfusions (P=0.006) compared to the heparin group. However, patients in the PGI(2) group tended to have lower mortality rates compared to those in the heparin group (30 days, 21 vs. 39%, P=0.12; 90 days, 34 vs. 53%, P=0.10 and 365 days, 38 vs. 57%, P=0.09). Patients receiving prefilter PGI(2) during CRRT were more severely ill and required more blood transfusions. Despite this, a trend towards lower mortality was observed in the PGI(2) group suggesting beneficial effects of PGI(2) administration in ICU patients undergoing CRRT.

Albumin dialysis without anticoagulation in high-risk patients: an observational study

Severe liver failure causes coagulopathy and high bleeding risk. Albumin dialysis with Molecular Adsorbent Recirculating System (MARS) (Gambro, Lund, Sweden) is useful for treatment. However, anticoagulation during its use is of uncertain value. We omitted heparin-saline priming and intradialytic heparin and examined its effects. Albumin dialysis was performed in critically ill patients with intermittent circuit saline flushes (2664 ± 2420 mL per treatment). A total of 12 patients (M : F = 10:2; age 49 ± 9 years) were thus treated: 6 for fulminant hepatic failure and 6 for acute-on-chronic liver failure. The overall hospitalization duration was 31 ± 30 days. A total of 44 treatment sessions were performed (average 8 ± 7 sessions per patient). Prescribed versus achieved MARS duration were 13 ± 3 versus 11 ± 4 h, P < 0.05. Twenty-three percent (10/44) of MARS sessions clotted, 11% (5/44) of treatments were electively terminated, and 2% (1/44) developed vascular catheter occlusion. Spontaneous bleeding occurred in 9% (4/44). Pre- versus post-MARS systemic and blood circuit transmembrane pressures (mm Hg), and albumin dialysate afferent and efferent pressures were all stable. Coagulation indices were (pre- vs. post-MARS): (i) prothrombin time (seconds): 36 ± 30 versus 42 ± 33, P = 0.143; (ii) activated partial thromboplastin time (seconds): 78 ± 43 versus 88 ± 45, P = 0.117; and (iii) platelet count (×10(3) /µL): 87 ± 40 versus 76 ± 48, P = 0.004. Systemic blood solute concentrations pre- versus post-MARS were: (i) serum urea (mg/dL): 22.4 ± 19.6 versus 14.0 ± 8.4, P < 0.05; (ii) serum creatinine (mg/dL): 2.8 ± 2.3 versus 1.9 ± 1.5, P < 0.05; (iii) total bilirubin (mg/dL): 29.5 ± 8.8 versus 20.5 ± 5.1, P < 0.05; and (iv) plasma ammonia (µg/dL): 186 ± 85 versus 129 ± 66, P < 0.05. Anticoagulant-free albumin dialysis remained effective despite frequent circuit clotting. This led to significant exacerbation of thrombocytopenia although bleeding risk remained low.

Continuous renal replacement therapy for liver disease

Continuous renal replacement therapy (CRRT) is becoming the treatment of choice for critically ill patients with acute renal failure around the world. In particular, CRRT is used for patients with combined liver and acute renal failure, because they are often hemodynamically unstable. The question arises as to whether the use of CRRT should be extended to those patients with acute and chronic liver failure who do not have dialysis-dependent renal failure. CRRT could potentially allow some detoxification by removing water-soluble toxins and also allow regulation of intravascular volume and correction of sodium and other electrolyte and acid-base imbalances. By providing homeostatic control, CCRT could potentially help support patients by bridging to liver transplantation and managing those who eventually recover with hepatic regeneration.

Continuous renal replacement therapy (CRRT) in patients with liver disease: is circuit life different?

BACKGROUND/AIMS

Clotting of haemofiltration circuits is a major complication of continuous renal replacement therapies (CRRT), yet systemic anticoagulation risks haemorrhage. Traditionally, patients with liver failure are managed with no or minimal anticoagulation, because of abnormal clotting tests and the perceived, increased bleeding risk.

METHODS

We retrospectively reviewed CRRT circuit life in 50 patients; 3 groups of liver failure patients treated with CRRT (acute liver failure (ALF), acute on chronic liver disease (ACLD) and post-elective liver transplantation (LTx)), with two control groups; systemic sepsis (SS) and haematological malignancy (Haem).

RESULTS

CCRT circuit life was significantly greater in the Haem group, compared to the others; 24.3+/-23.9h, vs. 11+/-10.5 ALF, 11.6+/-6.6 ACLF, 7.4+/-5.1 LTx and 9.2+/-6.5 SS, p<0.05, with Haem group requiring fewest new CCRT circuits within 48h; 2.4+/-1.0 vs. 4.3+/-1.3 ALF, 4.2+/-2.1 ACLF, 5.3+/-1.5 LTx and 4.6+/-1.5 SS, p<0.05 and least blood transfusions; 1.2+/-1.3 vs. 4.8+/-4.2 ALF, 4.2+/-4.1 ACLF, 2.2+/-2.1 LTx and 3.0+/-1.5 SS. Transmembrane pressures were higher in those CCRT circuits with haemofilter/dialyzer clotting, compared to other causes, such as access dysfunction (123+/-74 vs. 71.8+/-29.3 mm Hg, p=0.009). In those patients in whom anticoagulation was started due to repeated filter clotting, circuit life improved from 5.6+/-3.4 to 19+/-12.7h, p<0.01.

CONCLUSION

Despite abnormal laboratory coagulation tests and thrombocytopenia, CCRT circuits clot frequently in liver failure patients. Anticoagulation did improve CRRT circuit survival without an obvious increase in bleeding or blood transfusion requirement. Thus anticoagulation should be considered in these patients with repeated circuit clotting.

Continuous renal replacement therapies in patients with liver disease

Patients with acute and chronic liver disease are prone to hypotension, and mortality increases when acute kidney injury supervenes. Hypotension during renal replacement therapy compromises cerebral perfusion, which can exacerbate cerebral edema in cases of fulminant hepatic failure and those with encephalopathy due to chronic liver failure. As such, any renal replacement therapy utilized should have minimal adverse effects on cardiovascular and cerebrovascular stability. Continuous modes of renal replacement therapy have been shown to cause less cardiovascular and cerebrovascular instability compared to other modalities, and as such are the treatments of choice for this group of critically ill patients.

Role of citrate and other methods of anticoagulation in patients with severe liver failure requiring continuous renal replacement therapy

Anticoagulation is required during continuous renal replacement therapy to prevent filter clotting and optimize filter performance. However, anticoagulation may also be associated with serious bleeding complications. Patients with liver failure often suffer from underlying coagulopathy and are especially prone to anticoagulation complications. The aim of this review is to present the unique features of patients with hepatic injury in terms of anticoagulation disorders and to analyze data on safety and efficacy of the different anticoagulation methods for liver failure patients undergoing continuous renal replacement therapy.

Iloprost for additional anticoagulation in continuous renal replacement therapy--a pilot study

PURPOSE

The aim of this pilot study was to compare the effect of heparin anticoagulation with and without iloprost administration during continuous renal replacement therapy (CRRT) in critically ill patients.

MATERIAL AND METHODS

In a prospective, randomized, controlled pilot study at an intensive care unit at a university hospital, 20 patients requiring CRRT were investigated. Patients were allocated into two groups: group 1, the heparin group; and group 2, the heparin plus 1 ng/kg/min iloprost. In both groups, activated partial thromboplastin time (aPTT) was adjusted to 40-50 sec. Observation time was a maximum of 7 days.

RESULTS

Median filter run time was significantly prolonged by iloprost administration to a median of 14 h (13-26 h) compared to 10 h (4-12 h) in the heparin group (p = 0.004). A decrease in platelet count was attenuated by iloprost administration (p = 0.012). There were no bleeding complications in either group. Hemofiltration efficiency did not differ significantly between the groups.

CONCLUSION

Additional administration of iloprost prolonged the filter run time of continuous veno-venous hemofiltration (CVVH) in this setting and attenuated the fall in platelet count during CRRT.

Clinical review: Patency of the circuit in continuous renal replacement therapy

Premature circuit clotting is a major problem in daily practice of continuous renal replacement therapy (CRRT), increasing blood loss, workload, and costs. Early clotting is related to bioincompatibility, critical illness, vascular access, CRRT circuit, and modality. This review discusses non-anticoagulant and anticoagulant measures to prevent circuit failure. These measures include optimization of the catheter (inner diameter, pattern of flow, and position), the settings of CRRT (partial predilution and individualized control of filtration fraction), and the training of nurses. In addition, anticoagulation is generally required. Systemic anticoagulation interferes with plasmatic coagulation, platelet activation, or both and should be kept at a low dose to mitigate bleeding complications. Regional anticoagulation with citrate emerges as the most promising method.

Continuous venovenous haemofiltration using a citrate buffered substitution fluid

Different methods of regional anticoagulation using citrate in continuous renal replacement therapy have been described in the past. However, these procedures were usually very complex or did not reach modem requirements for effective continuous renal replacement therapy. Furthermore, little is known about long-term acid-base stability and citrate levels during the treatment. We describe a system in which citrate is used both as anticoagulant and as the sole buffer substance in continuous venovenous haemofiltration. Our citrate-containing, calcium-free substitution fluid was used in predilution mode with a constant ratio between blood flow (120 to 150 ml/min) and substitution flow (2400 to 3000 ml/hour). Anticoagulation was limited to the extracorporeal circuit. Twenty patients with acute renal failure on mechanical ventilation were treated, four for eight hours, four for 24 hours and 12 as long they needed continuous renal replacement therapy (9.6 +/- 5.0 days, range 4.0 to 39.3 days). We achieved stable acid-base and electrolyte balance in all patients. We observed no bleeding complications (patient activated clotting time 112.4 +/- 17.1 s, post-filter circuit activated clotting time 270.5 +/- 80.3 s) and achieved appropriate filter life times (48.6 +/- 13.2 h). Predilution, citrate-based substitution fluid provides both anticoagulation within the extracorporeal circuit and control of acid-base balance in critically ill patients at risk of bleeding in acute renal failure. It is easy to apply and safe. Clearance can be varied as long as a constant ratio between blood and substitution flow is maintained.

Hypercoagulation and thrombophilia in liver disease

A complex balance exists between endogenous procoagulants and the anticoagulant system in liver disease patients. Hypercoagulable events occur in cirrhosis patients despite the well-known bleeding diathesis of liver disease. These events may be clinically evident, such as in portal vein thrombosis or pulmonary embolism, but these conditions may also be a silent contributor to certain disease states, such as portopulmonary hypertension or parenchymal extinction with liver atrophy as well as thrombosis of extracorporeal circuits in dialysis or liver assist devices. Moreover, liver disease-related hypercoagulability may contribute to vascular disease in the increasingly common condition of non-alcoholic fatty liver disease. Despite the incidence of these problems, there are few widely accessible and practical laboratory tests to evaluate the risk of a hypercoagulable event in cirrhosis patients. Furthermore, there is little research on the use of commonly accepted anticoagulants in patients with liver disease. This article is a result of an international symposium on coagulation disorders in liver disease and addresses several areas of specific interest in hypercoagulation in liver disease. Critical areas lacking clinical information are highlighted and future areas of research interest are defined with an aim to foster clinical research in this field.

Anticoagulation Minimization Is Safe and Effective in Albumin Liver Dialysis Using the Molecular Adsorbent Recirculating System

The molecular adsorbent recirculating system (MARS) is a blood purification device with renal and hepatic dialytic effects. This study examined the use of low-dose unfractionated heparin in MARS. This was a prospective, observational study of 15 MARS treatment sessions (mean duration per treatment cycle = 12.2 +/- 4.5 h) in four patients with severe acute decompensation of chronic liver disease (n = 3) and fulminant hepatic failure (n = 1) treated with intermittent MARS. All patients were critically ill (APACHE II 24.8 +/- 3.3). Renal dialysis was with continuous hemofiltration and/or slow low-efficiency dialysis. One MARS session was terminated because of vascular access occlusion (1/15; 6.7%). Bleeding was noted in two sessions (2/15; 13%). Twelve MARS sessions were heparin-free and three treatments were with mean heparin dose of 833 +/- 382 IU. Serum biochemical parameters pre- and post-MARS were total bilirubin (micromol/L): 409.4 +/- 141.6 versus 282.9 +/- 90, P < 0.05; plasma ammonia (micromol/L): 44.3 +/- 21.2 versus 28.8 +/- 20.2, P = 0.002; urea (mmol/L): 15.9 +/- 11.8 versus 7.9 +/- 6.6, P = 0.002; creatinine (micromol/L): 252.4 +/- 151.9 versus 150.1 +/- 96.6, P = 0.003. Pre-MARS versus post-MARS systolic (SBPs) and diastolic (DBPs) blood pressures (mm Hg) were SBP = 129.2 +/- 27.7 versus 124 +/- 25, P = 0.838; and DBP = 60.7 +/- 15.3 versus 56 +/- 13, P = 0.595. Prothrombin time (PT), activated partial thromboplastin time (aPTT) and platelet count (Plt) pre- and post-MARS were PT(s): 22 +/- 7.9 versus 23.8 +/- 10.2, P = 0.116; aPTT (s): 64.5 +/- 40.9 versus 85.5 +/- 50.6, P = 0.092; and Plt (x10(3)/mm(3)): 87 +/- 67.6 versus 68.8 +/- 39, P = 0.098. MARS priming with heparin saline was safe. Heparin-minimized MARS did not compromise circuit function and longevity in extended intermittent MARS.

Anticoagulation in CRRT: Agents and strategies in Australian ICUs

BACKGROUND

Continuous Renal Replacement Therapy (CRRT) should ideally operate with as little interruption as possible. The majority of circuit terminations occur due to clotting. The Longevity of CRRT is able to be improved when the extracorporeal circuit is anticoagulated.

AIMS

This article willt focus attention on anticoagulant agents used in Australian intensive care units (ICU) to prevent clotting in the CRRT circuit.

DISCUSSION

Anticoagulants reviewed include unfractionated or standard heparin, regional heparinisation, low-molecular weight heparins and heparinoids, regional citrate, platelet-inhibiting agents (prostacyclin), thrombin antagonists (recombinant hirudin) and therapy with no anticoagulant use. Each type of anticoagulant was reviewed for mode of action, the method of delivery and how the effect is monitored. Circuit life and the incidence of bleeding were considered as the principle end points in selecting therapy, as well as side-effects with administration such as metabolic disturbances, contraindications to use including allergy and ease of use in the clinical environment.

CONCLUSION

No approach to anticoagulation has yet been reported to be as successful in extending circuit life, whilst remaining inexpensive, easy to manage and easy to reverse, as unfractionated heparin. Certain patient conditions may preclude the use of heparin, such as heparin-induced thrombocytopenia (HIT); then heparinoids, thrombin antagonists and sodium citrate are suggested as alternatives. Regional citrate reduces haemorrhagic complications in patients who have coagulation disorders or are at risk of bleeding. Clinical experience with various agents and strategies should also influence choice. The option of no anticoagulant may be appropriate in selected patients rather than more expensive and less familiar drugs.

[Use of isolated epoprostenol or associated to heparin for the maintenance of the patency of the continuous renal replacement technical circuits]

OBJECTIVE

At present, there is no consensus on the best anticoagulant regimen for the maintenance of extrarenal clearance circuits (RRTC). We present our experience with the isolated use of epoprostenol in patients at risk of bleeding or associated to non-fractionated heparin (nFH) in patients with problems of early coagulation of the filters.

DESIGN

Prospective study of cohorts on all the RRTC filters used in our service since 1994.

SCOPE

Forty-two-bed polyvalent ICU in a tertiary hospital.

INTERVENTIONS

Anticoagulation was administered in prefilter perfusion, at doses of 5-7 U/kg/hour for nFH or 4-5 ng/kg/min for epoprostenol. The combined use was done with equal doses of epoprostenol and nFH at 2,5 U/kg/hour. VARIABLES OF MAIN INTEREST: We analyzed the duration of each filter, reason for removing the filter, existence of coagulopathy, platelet count, appearance of bleeding, anticoagulant used and dose.

RESULTS

We analyzed the use of 2,322 filters (66,957 hours) in 389 patients, 54% of whom had a clot. nFH was used in 74% of the filters for a median of 39 hours (interquartile range: 19-75), epoprostenol in 6% for 32 hours (interquartile range: 17-48) and combined therapy in 4% for 27 hours (interquartile range: 19-41). In the epoprostenol group, we detected a decrease in blood pressure in only two filters that became normal when the dose was decreased. The filters that were initially anticoagulated with nFH had a 14-hour survival as a median versus 27 hours in combined therapy (p < 0.001). In absence of coagulopathy or thrombopenia, we observed mild bleeding in 8%, moderate in 1% and serious in 1% in the 1,170 filters treated with nFH. We only observed mild bleeding in 3% in 66 filters with epoprostenol.

CONCLUSIONS

Isolated epoprostenol in patients at risk of bleeding provided a similar duration of the filters to nFH, decreasing the risk of bleeding. The use of epoprostenol plus low dose nFH significantly increases their duration in patients with early coagulation.

HEMATOLOGY: ISSUES IN THE DIALYSIS PATIENT: Anticoagulation and Continuous Renal Replacement Therapy

More than half of patients with acute renal failure in the intensive care unit require dialysis, and the majority of them have significant hemodynamic instability. Continuous renal replacement therapy (CRRT) is often the preferred dialysis modality in these patients. One requirement for CRRT is anticoagulation, which can expose patients to the risk of bleeding. However, absence of effective anticoagulation may result in clotting of the CRRT circuit and subsequently less effective treatment. While heparins are widely used for anticoagulation, because of potential side effects such as bleeding and heparin-induced thrombocytopenia, alternative anticoagulation protocols should be considered. Citrate anticoagulation, regional heparin/protamine, predilution, r-hirudin, prostacyclin, and nafamostat are among these methods.

Effect of regional citrate anticoagulation on thrombogenicity and biocompatibility during CVVHDF

This study was designed to assess the principal markers of thrombogenicity and biocompatibility during continuous veno-venous hemodiafiltration (CVVHDF) using regional citrate anticoagulation (RCA). In a prospective study, 11 procedures with a polysulfone membrane were performed in nine critically ill patients with acute renal failure and impaired hemostasis. Blood samples were taken before and during CVVHDF at diafilter outlet--before calcium-induced reversal of the effect of citrate--at 15, 60, 360, and 1440 minutes. In four patients, 10 CVVHDF sessions were performed with systemic heparin anticoagulation (HA) using a polyacrylonitrile membrane. During RCA, blood thrombocyte count, plasma thrombin-antithrombin III complexes, beta-thromboglobulin, and von Willebrand factor levels did not differ significantly from baseline. Plasma D dimer levels rose significantly at 360 minutes; however, the difference between diafilter inlet and outlet levels was nonsignificant. There was a significant increase in plasma C5a concentrations and a decline in blood leukocyte count in the early phase of CVVHDF. Just as in RCA, no increase in plasma thrombogenicity indices was observed during HA. However, clotting times in blood entering patients' circulation were significantly prolonged. Plasma C5a concentrations increased significantly at the beginning of CVVHDF. RCA can effectively inhibit the thrombogenic effect of the extracorporeal circuit in CVVHDF. The effect of HA may be similar, however, at the expense of systemic anticoagulation and risk of bleeding. RCA, performed in a way that overcomes thrombogenicity, does not completely eliminate complement activation and/or transient leukopenia during CVVHDF.

Anticoagulation strategies in continuous renal replacement therapy: can the choice be evidence based?

OBJECTIVES

Critical illness increases the tendency to both coagulation and bleeding, complicating anticoagulation for continuous renal replacement therapy (CRRT). We analyzed strategies for anticoagulation in CRRT concerning implementation, efficacy and safety to provide evidence-based recommendations for clinical practice.

METHODS

We carried out a systematic review of the literature published before June 2005. Studies were rated at five levels to create recommendation grades from A to E, A being the highest. Grades are labeled with minus if the study design was limited by size or comparability of groups. Data extracted were those on implementation, efficacy (circuit survival), safety (bleeding) and monitoring of anticoagulation.

RESULTS

Due to the quality of the studies recommendation grades are low. If bleeding risk is not increased, unfractionated heparin (activated partial thromboplastin time, APTT, 1-1.4 times normal) or low molecular weight heparin (anti-Xa 0.25-0.35 IU/l) are recommended (grade E). If facilities are adequate, regional anticoagulation with citrate may be preferred (grade C). If bleeding risk is increased, anticoagulation with citrate is recommended (grade D(-)). CRRT without anticoagulation can be considered when coagulopathy is present (grade D(-)). If clotting tendency is increased predilution or the addition of prostaglandins to heparin may be helpful (grade C(-)).

CONCLUSION

Anticoagulation for CRRT must be tailored to patient characteristics and local facilities. The implementation of regional anticoagulation with citrate is worthwhile to reduce bleeding risk. Future trials should be randomized and should have sufficient power and well defined endpoints to compensate for the complexity of critical illness-related pro- and anticoagulant forces. An international consensus to define clinical endpoints is advocated.

Prostacyclin versus citrate in continuous haemodiafiltration: an observational study in patients with high risk of bleeding

BACKGROUND

The efficacy and safety of prostacyclin (PGI2) and citrate (ACD) anticoagulation were observed and compared during continuous haemodiafiltration.

METHODS

Mechanically ventilated patients received either the PGI2 analogue epoprostenol (group A, n = 17) in escalating doses of 4.5-10.0 ng.kg(-1).min(-1) in combination with heparin (6 IU.kg(-1).h(-1)) or 2.2% ACD (group B, n = 15). Blood flow was set to match the circuit-filling volume per unit time equal to the intravascular half-life of PGI2.

RESULTS

Median filter lifetimes were 26 h (interquartile range 16-37) in group A (39 filters) and 36.5 h (interquartile range 23-50) in group B (56 filters; p < 0.01). In group A, 4 patients (23.5%, p < 0.05) had the dose reduced due to hypotension. The final mean dose of PGI2 was 8.7 +/- 2.4 ng.kg(-1).min(-1). Four patients in group A (23.5%, p < 0.05) were switched to ACD due to a decrease in platelet count. No bleeding episodes, decrease in platelet count or adverse haemodynamic effects were encountered in group B. The cost of epoprostenol plus low dose heparin (EUR 204.73 +/- 53.04) was significantly higher than the cost of ACD-based anticoagulation (EUR 93.92 +/- 45.2, p < 0.05).

CONCLUSION

ACD offers longer filter survival, has no impact on platelet count and is less expensive. Increasing the dose of PGI2 up to the average of 8.7 ng.kg(-1).min(-1) did not increase the haemodynamic side effects.

Renal replacement therapy in the intensive care unit

Acute renal failure is a common complication in the intensive care unit (ICU). Over the last 25 years, there have been significant technological advances in the delivery of renal replacement therapy, particularly as it pertains to the critically ill patient population. Despite these advances, acute renal failure in critically ill patients continues to carry a poor prognosis. In this article, we review the current literature about timing and initiation of renal replacement therapy in the ICU as well as practical considerations regarding the prescription and delivery of dialysis.