The approach to anticoagulation in patients treated with extracorporeal therapy in the intensive care unit

Risk of incident bleeding after acute kidney injury: A retrospective cohort study

PURPOSE

End-stage kidney disease (ESKD) causes bleeding diathesis; however, whether these findings are extrapolable to acute kidney injury (AKI) remains uncertain. We assessed whether AKI is associated with an increased risk of bleeding.

METHODS

Single-center retrospective cohort study, excluding readmissions, admissions <24 h, ESKD or kidney transplants. The primary outcome was the development of incident bleeding analyzed by multivariate time-dependent Cox models.

RESULTS

In 1001 patients, bleeding occurred in 48% of AKI and 57% of non-AKI patients (p = .007). To identify predictors of incident bleeding, we excluded patients who bled before ICU (n = 488). In bleeding-free patients (n = 513), we observed a trend toward higher risks of bleeding in AKI (22% vs. 16%, p = .06), and a higher risk of bleeding in AKI-requiring dialysis (38% vs. 17%, p = .01). Cirrhosis, AKI-requiring dialysis, anticoagulation, and coronary artery disease were associated with bleeding (HR 3.67, 95%CI:1.33-10.25; HR 2.82, 95%CI:1.26-6.32; HR 2.34, 95%CI:1.45-3.80; and HR 1.84, 95%CI:1.06-3.20, respectively), while SOFA score and sepsis had a protective association (HR 0.92 95%CI:0.84-0.99 and HR 0.55, 95%CI:0.34-0.91, respectively). Incident bleeding was not associated with mortality.

CONCLUSIONS

AKI-requiring dialysis was associated with incident bleeding, independent of anticoagulant administration. Studies are needed to better understand how AKI affects coagulation and clinical outcomes.

Citrate Anticoagulation during CVVH in High Risk Bleeding Patients

Background

Regional citrate anticoagulation (RCA) is an effective form of anticoagulation for continuous renal replacement therapy (CRRT) in patients with contraindications to heparin. Its use has been very limited, possibly because of the need for special infusion solutions and difficult monitoring of the metabolic effects.

Objective

To investigate the safety and the feasibility of an RCA method for continuous veno-venous hemofiltration (CVVH) using commercially available replacement fluid.

Methods

We evaluated 11 patients at high risk of bleeding, requiring CVVH. RCA was performed using commercially available replacement fluid solutions to maintain adequate acid-base balance. We adjusted the rate of citrate infusion to achieve a post-filter ionized calcium concentration [iCa] <0.4 mmol/L when blood flow was <250 ml/min, or <0.6 mmol/L when blood flow was >250 ml/min. When needed, we infused calcium gluconate to maintain systemic plasma [iCa] within the normal range.

Results

Twenty-nine filters ran for a total of 965.5 h. Average filter life was 33.6±20.5 h. Asymptomatic hypocalcemia was detected in 6.9% of all samples. No [iCa] values <0.9 mmol/L were observed. Hypercalcemia (1.39±0.05 mmol/L) occurred in 2.5% of all samples. We observed hypernatremia (threshold 153 mmol/L) and alkalosis (threshold 7.51) in only 9.3% and 9.4% respectively of all samples, mostly concomitantly. No patient showed any signs of citrate toxicity. Conclusions: We developed a protocol for RCA during CVVH using commercially available replacement fluid that proved safe, flexible and applicable in an Intensive Care Unit (ICU) setting.

Management of regional citrate anticoagulation in pediatric high-flux dialysis: activated coagulation time versus post-filter ionized calcium

Recent years has seen an increasing use of regional citrate anticoagulation in pediatric dialysis. Several approaches have been described for monitoring anticoagulation in the extracorporeal circuit, such as serum citrate levels, post-filter ionized calcium (iCa), and activated coagulation time (ACT). However, no standard recommendations have yet been established for applying any of these parameters, especially for iCa. The objective of this retrospective analysis was to establish adequate coagulation management using post-filter iCa values. Normal values for ACTester-based ACT were established using a group of 64 children who were divided into two subgroups, with one subgroup comprising children without chronic kidney disease or coagulation disorder (age 1.2-17.5 years, median 9.7 years) and one consisting of 32 uremic patients (age 0.6-17.5 years, median 13.7 years). In a second group of 13 patients (aged 7-17 years), all of whom were undergoing high-flux dialysis (HD) with regional citrate anticoagulation (RCA), we assessed 73 post-filter blood samples for ionized calcium and ACT. A receiver operating characteristic graph was used to identify the iCa threshold needed to achieve adequate anticoagulation. Normal values for ACT were 90 s [2 standard deviations (SD) 72-109] in healthy children and 94 s (2 SD 75-113) in the uremic children. There was no statistically significant difference between the groups. In the children undergoing HD with RCA, the post-filter iCa level correlated with ACT (r = -0.94, p < 0.001). A post-filter iCa level of < or = 0.30 mmol/l reliably predicted an ACT >120 s. Our citrate protocol [citrate 3% rate (ml/h) approximately blood flow rate (ml/min) x 2] meets the established criteria with a high sensitivity. Based on these results, we conclude that the post-filter iCa level can be reliably used for the management of extracorporeal anticoagulation with citrate in pediatric HD. We recommend the application of our citrate prescription protocol in the setting of pediatric intermittent hemodialysis.

In vitro and in vivo evaluation of enoxaparin removal by continuous renal replacement therapies with acrylonitrile and polysulfone membranes

BACKGROUND

Enoxaparin is a low-molecular-weight heparin for which the degree of elimination through hemofilters during continuous renal replacement therapy (CRRT) is not well established.

OBJECTIVE

The elimination of enoxaparin by CRRT, using acrylonitrile (AN69) or polysulfone (PS) membranes, was studied in vitro and among critically ill patients.

METHODS

In vitro procedures were carried out using Ringer's lactate, bovine albumin-containing Ringer's lactate, or fresh human plasma as enoxaparin vehicle, using AN69 or PS membranes, and following continuous veno-venous hemofiltration (CVVH) or continuous veno-venous hemodialysis (CVVHD). Prefilter and ultrafiltrate samples were collected over 60 minutes. All procedures were carried out in triplicate. Patients undergoing CRRT entered the in vivo study. Enoxaparin was administered subcutaneously once daily. The sieving coefficient (Sc) and saturation coefficient (Sa) were calculated as the relation between anti-factor Xa activity in simultaneously collected dialysate/ultrafiltrate samples and plasma samples.

RESULTS

Mean Sc (for CVVH) or Sa (for CVVHD) values in the in vitro procedures ranged from 0.16 to 0.57. Sc values during CVVH were significantly higher than Sa values during CVVHD in the Ringer's lactate procedures for both membranes (AN69 membrane, P = 0.014; PS membrane, P < 0.001) and in the plasma procedures with the PS membrane (P < 0.001). Six male and 2 female patients (all white) participated in the in vivo study. Their mean body weight ranged from 55 to 80 kg, and their age ranged from 71 to 82 years. In patients, Sc or Sa achieved values between 0.26 and 0.67. No significant differences were found in vivo in the permeability of the 2 membranes to enoxaparin.

CONCLUSIONS

In these studies, the Sc and Sa values suggested that enoxaparin passed through AN69 and PS membranes during CRRT. Further pharmacokinetic and clinical studies are needed to determine whether a dose adjustment for enoxaparin is needed for patients undergoing CRRT.

[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.

Regional Citrate Anticoagulation during Hemodialysis

BACKGROUND

Regional citrate anticoagulation during hemodialysis is promising, but its clinical implementation is routinely cumbersome because a continuous adjustment of calcium infusion at the dialyzer outlet is needed. Duocart biofiltration (DCB) is a new hemodialysis method using a calcium and magnesium-free dialysate containing only sodium chloride and bicarbonate combined with the infusion into the venous line of a solution containing the ionic complement (K, Ca, Mg) and glucose. Since the dialysate is calcium- and magnesium-free and infusion rate of the solution containing calcium is automatically determined by the dialysis delivery system according to the on-line measured value of ionic dialysance, DCB seems a technique especially suitable for citrate anticoagulation procedure.

METHODS

Thirty DCB sessions were performed in 10 patients with increased risk of bleeding. A commercially available mixture of trisodium citrate, citric acid and glucose was infused into the arterial line at a rate equal to 3% of dialyzer blood flow. The ionic complement (K: 48 mM, Ca: 42 mM, Mg: 14 mM, glucose: 110 mM) was infused at a rate equal to 1/24 ionic dialysance value automatically determined each 15 min by the dialysis monitor. DCB sessions were compared to 21 conventional bicarbonate hemodialysis (BHD) sessions with low-molecular-weight heparin anticoagulation.

RESULTS

Whole blood activated clotting time (WBACT) measured in the venous line (before infusion of ionic complement) was 200% of the WBACT value in the arterial line. Clotting and citrate-related adverse events were not observed. Postdialysis compression time of the arteriovenous access is significantly (p<0.001) shorter after DCB sessions (3.9+/-1.1 min) compared with BHD sessions (8.7+/-4.6 min).

CONCLUSION

Citrate anticoagulation during Duocart biofiltration is effective, safe and suitable for routine use because calcium infusion rate is automatically adjusted without the need of monitoring degree of anticoagulation and level of ionized calcium.

Reviews: The Current State of Nonuremic Applications for Extracorporeal Blood Purification

Despite the commonly accepted indications for hemodialysis and extracorporeal depuritive techniques, some clinicians have come to rely on blood purification for clinical states where the targeted substance for removal differs from uremic waste products. Over the last decade, a number of studies have emerged to help define the application of extracorporeal blood purification (ECBP) to these "nonuremic" indications. This review describes the application of extracorporeal blood purification in clinical states including sepsis, rhabdomyolysis, congestive heart failure, hepatic failure, tumor lysis syndrome, adult respiratory distress syndrome, intravenous contrast exposure, and lactic acidosis. Additional comments are provided to review existing literature on thermoregulation and osmoregulation, including acute brain injury.

The Acute Dialysis Quality Initiative--part VI: access and anticoagulation in CRRT

Both the choice of vascular access and anticoagulant regimen for continuous renal replacement therapy (CRRT) are a major determinant of not only circuit life span but also affect solute clearance. This evidence-based review critically examines the published rature on different vascular access sites, access types, and anticoagulation regimens, to provide clinical guidelines for good working practices and to direct future studies.

Dialysis modalities in the intensive care unit

Acute renal failure in the ICU is a clinically diverse entity. Consequently, the indications for initiation of dialysis therapy are varied. In general, the indications are solute control, volume control, or both. A variety of dialysis modalities are available; however, there is no consensus as to the optimal modality for any particular group of patients. A careful understanding of the particular benefits, limitations, and potential complications of each modality coupled with a thorough assessment of the individual patient's need formulate the basis for dialysis modality selection. In certain circumstances, the more conventional intermittent therapies are sufficient, whereas in other settings, CRRT techniques are advantageous. The impact of modality selection on outcome remains an area of significant controversy. Future studies in which more uniformity within specific subgroups of patients with ARF is sought may shed light on the optimal modality for a particular patient group. Newer therapies aimed at more optimal and more specific blood purification may prove promising in the management of complex critically ill patients with ARF and other comorbid conditions.

Citrate anticoagulation in a piglet model of pediatric continuous renal replacement therapy

OBJECTIVE

To develop pediatric guidelines for the use of citrate as a regional anticoagulant for continuous renal replacement therapy (CRRT) using a neonatal piglet model.

DESIGN

Prospective observational study.

SETTING

Animal laboratory in the research center of a tertiary-level children's hospital.

SUBJECTS

Ten neonatal piglets.

INTERVENTIONS AND MEASUREMENTS

Using a venovenous CRRT circuit and filter, we randomly altered the filter blood flow rate, replacement flow rate, and citrate flow rate over conventional pediatric ranges. Measured end points were prefilter serum ionized calcium and citrate levels.

MAIN RESULTS

A prefilter serum citrate concentration of 6 mmol/L is required to maintain the prefilter ionized calcium < or =0.4 mmol/L. Using multiple regression analysis on collected data, we derived a formula to predict prefilter serum citrate for combinations of replacement flow rate, blood flow rate, and citrate flow rate.

CONCLUSIONS

The available literature and our past experience indicate that a prefilter ionized calcium < or =0.4 mmol/L is required to anticoagulate a CRRT circuit; a prefilter serum citrate concentration of 6 mmol/L is required to achieve this. Our multiple regression analysis can be expressed graphically to allow easy calculation of the required citrate flow rate, given the knowledge of the replacement flow rate and blood flow rate. Our results provide the first guidelines for the use of citrate as a regional anticoagulant in a pediatric-size model of CRRT.

Drugs used to limit blood surface interactions

Since the days of the triumvirate of aspirin, heparin, and warfarin, health care practitioners have attempted to blunt the response of the coagulation system. Use of CPB has enhanced our awareness of the effects that a foreign surface has on blood in general. Success in correcting or preventing life-threatening conditions caused by thromboembolic disease depends on having the ability to correct the condition as well as the ability to limit the body's response to the intervention. Knowing how the body responds to foreign surfaces is crucial, as is awareness of current methods to limit these responses. This approach will help ensure procedural success with fewer side effects and better overall patient outcomes.

Anticoagulation for continuous renal replacement therapy

Anticoagulation during continuous renal replacement therapy should aim for an optimal filter performance allowing the delivery of an adequate dose of renal replacement therapy. On the other hand, the patient's safety should not be endangered. Although numerous options have been proposed, none of them appears to be ideal. Unfractionated heparin is still the most widely used anticoagulant. Reported experience with low-molecular-weight heparin is limited and does not confirm the anticipated increased safety. Regional citrate anticoagulation has been shown to reduce bleeding complications during continuous haemodialysis. A recent report demonstrates the feasibility and safety of citrate anticoagulation during continuous predilution haemofiltration. However, its use is labour intensive and the prevention of side-effects requires meticulous monitoring. Hirudin, a selective thrombin inhibitor, appears to be a suitable, although not completely safe, alternative in patients with heparin-induced thrombocytopenia. Continuous renal replacement therapy without anticoagulation may result in acceptable filter lives in patients with reduced coagulatory potential or an increased risk of bleeding. Although receiving little attention in the literature, the adequate selection of treatment characteristics may also contribute to an improved filter performance.

Renal replacement therapy in the patient with acute brain injury

The patient with an acute brain injury requiring renal replacement therapy presents a major problem in that conventional intermittent hemodialysis may exacerbate the injury by compromising cerebral perfusion pressure, either after a reduction in cerebral perfusion or because of increased cerebral edema. Compared with standard intermittent hemodialysis, the continuous forms of renal replacement therapy (CRRT) provide an effective therapy in terms of solute clearance, coupled with improved cardiovascular and intracranial stability. The disadvantage of CRRT is that anticoagulation may be required, and anticoagulants with systemic effects may provoke intracerebral hemorrhage, either at the site of damage or around the intracranial pressure monitoring device. Although peritoneal dialysis does not require anticoagulation, the clearances achieved are often less than those of CRRT, and sudden changes in intraperitoneal volume may provoke cardiovascular and thus intracranial instability.

Local anticoagulation of the extracorporeal circuit with heparin and subsequent neutralization with protamine during immunoadsorption

A regimen of local anticoagulation of an immunoadsorption device was studied. The extracorporeal circuit was anticoagulated with citrate (5.5%) and a continuous infusion of heparin (2,000 U/h or 1,500 U/h), which was neutralized by a continuous infusion of protamine chloride (75% of the heparin dose) before reinfusion in 23 patients treated with low-density lipoprotein or immunoglobulin apheresis. Sufficient anticoagulation of the extracorporeal circuit was obtained (activated partial thromboplastin time [APTT] > 180 seconds; thrombin time [TT] > 120 seconds; anti-Xa activity, 1.05 +/- 0.21 U/mL) during the entire treatment of 190 minutes, whereas coagulation parameters in the patients' blood stayed within the normal range. In a control group without heparin neutralization, full systemic anticoagulation of the patients occurred (APTT, 157.8 +/- 30.6 seconds; TT, 119.8 +/- 0.4 seconds; anti-Xa activity, 0.88 +/- 0.21 U/mL). No side effects or clotting of the system were observed. Our data show that this regimen of local anticoagulation is a safe protocol for extracorporeal circulation without exposing the patients to anticoagulants.