The adequacy of fragmin as a single bolus dose with reused dialyzers

Considerations for Systemic Anticoagulation in ESRD

In the setting of end-stage kidney disease, the incidence and risk for thrombotic events are increased and use of anticoagulants is common. The incidence of bleeding, however, is also a frequent issue and creates additional challenges in the management of anticoagulation therapy. Patients with end-stage renal disease are typically excluded from large clinical trials exploring the use of anticoagulants, which limits our knowledge of optimal management approaches. Furthermore, varying degrees of renal failure in addition to conditions that alter the pharmacokinetics of various anticoagulants or pharmacodynamic response may warrant alternative approaches to dosing. This review will explore systemic chronic anticoagulation therapy in the setting of chronic kidney disease where hemodialysis is required. Agents discussed include vitamin K antagonists, low-molecular-weight heparins, fondaparinux, oral factor Xa antagonists, and direct thrombin inhibitors. Clinical challenges, approaches to dosing regimens, and tools for measuring responses and reversal will be explored.

Systemic anticoagulation considerations in chronic kidney disease

Anticoagulation therapy is commonly required in patients with chronic kidney disease for treatment or prevention of thromboembolic disorders. Anticoagulant management plans can involve use of a single agent, or in some cases, a combination of agents to meet both short- and long-term goals. Systemic anticoagulation in the setting of renal insufficiency poses unique challenges secondary to renal failure-associated hypercoagulable conditions and increased risks for bleeding. Evidence supporting dosing regimens and monitoring approaches in the setting of severe renal impairment or hemodialysis is limited because this population is typically excluded in clinical trials. This review explores concepts of systemic anticoagulation in the chronic kidney disease setting with warfarin, unfractionated heparin, low-molecular-weight heparin, fondaparinux, direct thrombin inhibitors, and anticoagulants in advanced stages of development. Potential strategies for anticoagulant reversal are also briefly described.

Laboratory monitoring of pentasaccharide in a dog model of hemodialysis

Varying dosages of pentasaccharide (400-800 nmol/kg) were compared to a 250-U/kg single bolus dosage of unfractionated heparin (UFH) in a dog model of hemodialysis. Several laboratory assays were used to monitor the effects of pentasaccharide and UFH. The pentasaccharide did not produce any anticoagulant effects as measured by the activated partial thromboplastin time. However, in the anti-Xa chromogenic assay and the Heptest assays, there was a dose-dependent prolongation after pentasaccharide administration. In the group of dogs administered 800 nmol/kg of pentasaccharide, there was a 50% decrease in the thrombin antithrombin (TAT) complex level after 60 minutes on dialysis. In the UFH-treated dogs, wide variations in assays were observed. There was a marked elevation in the activated partial thromboplastin time and Heptest assays up to 6 hours after UFH administration. Both anti-Xa and anti-IIa activity was measured up to 4 hours. In the TAT assay, UFH was found to have a stronger effect in suppressing the formation of TAT in comparison to the pentasaccharide. These results suggest that pentasaccharide can be used as a replacement for UFH in a dog model of hemodialysis to keep the dialysis circuit patent. In addition, the anti-Xa-based assays such as the Heptest and the chromogenic anti-Xa assays can be used to monitor the effects of pentasaccharide in this model.

Efficacy of pentasaccharide in a dog model of hemodialysis

A synthetic heparin pentasaccharide with sole anti-Xa actions has been evaluated for its antithrombotic efficacy in a dog model of hemodialysis. Various dosages of pentasaccharide, 400-800 nmol/kg, were compared with a single bolus dose of unfractionated heparin (250 U/kg). The primary endpoint in these studies was the duration of dialysis time. In addition, dialyzer filter content, venous trap protein, celite and saline ACT and hematocrit measurement. Pentasaccharide at dosages of 600 and 800 nmol/kg produced an extension of dialysis time (> 180 minutes) in contrast to unfractionated heparin at 250 U/kg which only produced antithrombotic effects for periods of up to 150 +/- 42 minutes (n = 5). At a lower dosage of 400 nmol/kg pentasaccharide produced weaker effects and the dialysis circuit was patent for periods of 122 +/- 14.8 (n = 5) minutes. The saline and celite ACT times were not extended at any dosage of pentasaccharide; however, at 250 U/kg, a strong effect was noted with unfractionated heparin (> 800 secs, 647 +/- 211 secs.), respectively. A dose dependent antithrombotic effect was also evident in the studies on the filter clots and venous trap protein content. No difference in the hematocrit was noted in any group. These results clearly suggest that despite the fact that pentasaccharide does not produce any prolongation of the coagulation times, it produces a dose dependent antithrombotic effect in this model of dog hemodialysis. Furthermore, these results also suggest that pentasaccharide at an appropriate dosage can be used as an alternate antithrombotic agent during hemodialysis.

Dalteparin, a Low-Molecular-Weight Heparin: Review of Pharmacology and Pharmacotherapy

Objective:

To review the current literature concerning the use of dalteparin in thromboembolic disease. The chemistry, pharmacokinetics, pharmacodynamics and clinical efficacy for approved and nonapproved uses, and adverse effects are presented.

Data Sources:

A MEDLINE search of the English-language literature between 1980 and 1996.

Data Extraction:

The data presented are primarily from controlled studies of dalteparin in humans. Some of the pharmacokinetic/pharmacodynamic and basic pharmacologic data are from animal studies. The majority of the clinical investigations were blind.

Data Synthesis:

Dalteparin sodium is approved for use in the prophylaxis of thromboembolic disease after major abdominal surgery. Dalteparin is a low-molecular-weight heparin (LMWH) with a mean molecular weight of 5,000 Da. It produces its antithrombotic effect through the inhibition of activated factor X and, to a lesser extent, activated factor II.

Conclusions:

Thromboembolic disease may occur in patients such as those over 40 years of age undergoing major surgical procedures lasting longer than 30 minutes. In addition, prolonged bed rest may result in development of thromboembolism due to immobilization and venous stasis. Anticoagulant prophylaxis for deep-vein thrombosis is warranted in these patients. As with other LMWHs, laboratory monitoring of coagulation parameters (e.g., activated partial thromboplastin time and activated coagulation time) is unnecessary. Dalteparin sodium has been demonstrated to be efficacious and safe for the prophylaxis of thromboembolic disease after major abdominal surgery and is a reasonable alternative to unfractionated heparin in these patients. The use of dalteparin for other indications, such as treatment of thromboembolic disease, hemodialysis, and unstable coronary artery disease, also appears to be promising.

Use of low-dose low molecular weight heparin in hemodialysis

We investigated the lowest effective dosage of low molecular weight (LMW) heparin for hemodialysis in comparison to unfractionated (UF) heparin. Initial hemodialysis sessions were undertaken in 10 uremic patients with UF heparin of the dose habitually required for each patient. Four-hour hemodialysis sessions were then undertaken with LMW heparin (nadroparin) in a single bolus (200 anti-Xa unit Institut Choay/kg [aXaU IC/kg], 175 aXaU IC/kg, 150 aXaU IC/kg, or 125 aXaU IC/kg; two sessions for each dosage). Anti-Xa levels and activated partial thromboplastin time (APTT) were monitored hourly during dialysis. Fiber bundle volume of dialyzer was measured before and after dialysis. Urea clearance was determined at the onset and completion of dialysis. There were no episodes of excessive bleeding, clotting of dialyzers, or clots in air traps with UF heparin or LMW heparin. A 35% increase in APTT above baseline was observed in all dialysis sessions 1 hour after LMW heparin bolus, but the APTT decreased rapidly thereafter. The anti-Xa levels exceeded 0.5 U/mL for all sessions using LMW heparin irrespective of the dosage. No significant reduction of urea clearance was found in dialysis with either UF or LMW heparin. No reduction of fiber bundle volume of dialyzer was observed in dialysis with either UF or LMW heparin, although a small reduction (3%) was observed in dialysis with LMW heparin at 125 aXaU IC/kg. We concluded that the use of LMW heparin for hemodialysis is safe and effective as compared with UF heparin. The lowest effective dosage can be reduced to 125 aXaU IC/kg in high-risk patients to reduce hemorrhagic complications.

Regional hemodialysis anticoagulation: hypertonic tri-sodium citrate or anticoagulant citrate dextrose-A

Regional citrate anticoagulation should be a simple process of substituting hypertonic (1.6 mol/L) citrate for heparin and adjusting the infusion to obtain an arterial activated clotting time of 150 to 200 seconds. Serious, documented complications of citrate anticoagulation involve citrate intoxication during isolated ultrafiltration; hyperaluminemia, hyperammonemia, and hypernatremia during sorbent dialysis; and profound alkalosis, paresthesias, arrhythmia, and cardiac arrest during bicarbonate dialysis. We suspected that some of these complications could be avoided by using anticoagulant citrate dextrose-A (ACD) rather than hypertonic tri-sodium citrate (TSC) as the anticoagulant. In a cross-over study with random assignment order eight adults underwent mid-week dialyses with ACD (0.113 mol/L citrate) and TSC (1.6 mol/L citrate) regional citrate anticoagulation. Predialysis to postdialysis changes in Na (mEq/L), Ca (mg/dL), ionized Ca (mg/dL), pH, and HCO3 (mEq/L) are listed below. [Table in journal] Using continuous blood flow and avoiding isolated ultrafiltration and sorbent dialysis should prevent the delivery system complications of regional citrate anticoagulation. During this evaluation isotonic and hypertonic citrate resulted in similar serum sodium changes, and standard dialysate effectively reversed the citrate/calcium interaction of both hypertonic and isotonic citrate infusions to restore homeostasis without a separate calcium infusion. The combination of TSC and bicarbonate dialysate does produce a profound metabolic alkalosis, which is lessened by using ACD. In general, regional citrate anticoagulation is simplified by using standard dialysate with a hypertonic rather than an isotonic citrate infusion, and dangerous complications are further evaded by adjusting the dialysate bicarbonate to 25 to 30 mmol/L or substituting a mixture of citric acid and TSC (ACD) for TSC.