Excessive argatroban anticoagulation for heparin-induced thrombocytopenia

Thromboprophylaxis with argatroban in critically ill patients with sepsis: a review

During sepsis, an initial prothrombotic shift takes place, in which coagulatory acute-phase proteins are increased, while anticoagulatory factors and platelet count decrease. Further on, the fibrinolytic system becomes impaired, which contributes to disease severity. At a later stage in sepsis, coagulation factors may become depleted, and sepsis patients may shift into a hypo-coagulable state with an increased bleeding risk. During the pro-coagulatory shift, critically ill patients have an increased thrombosis risk that ranges from developing micro-thromboses that impair organ function to life-threatening thromboembolic events. Here, thrombin plays a key role in coagulation as well as in inflammation. For thromboprophylaxis, low molecular weight heparins (LMWH) and unfractionated heparins (UFHs) are recommended. Nevertheless, there are conditions such as heparin resistance or heparin-induced thrombocytopenia (HIT), wherein heparin becomes ineffective or even puts the patient at an increased prothrombotic risk. In these cases, argatroban, a direct thrombin inhibitor (DTI), might be a potential alternative anticoagulatory strategy. Yet, caution is advised with regard to dosing of argatroban especially in sepsis. Therefore, the starting dose of argatroban is recommended to be low and should be titrated to the targeted anticoagulation level and be closely monitored in the further course of treatment. The authors of this review recommend using DTIs such as argatroban as an alternative anticoagulant in critically ill patients suffering from sepsis or COVID-19 with suspected or confirmed HIT, HIT-like conditions, impaired fibrinolysis, in patients on extracorporeal circuits and patients with heparin resistance, when closely monitored.

Argatroban Anticoagulation for Adult Extracorporeal Membrane Oxygenation: A Systematic Review

BACKGROUND

Heparin is the widely used anti-coagulation strategy for patients on extracorporeal membrane oxygenation (ECMO). Nevertheless, heparin-induced thrombocytopenia (HIT) and acquired anti-thrombin (AT) deficiency preclude the use of heparin requiring utilization of an alternative anticoagulant agent. Direct thrombin inhibitors are being proposed as potential alternatives with argatroban as one of the main agents. We aimed to review the evidence with regard to safety and efficacy of argatroban as a potential definitive alternative to heparin in the adult patient population undergoing ECMO support.

METHODS

A web-based systematic literature search was performed in Medline (PubMed) and Embase from inception until June 18, 2020.

RESULTS

The search identified 13 publications relevant to the target (4 cohort studies and 9 case series). Case reports and case series with less than 3 cases were not included in the qualitative synthesis. The aggregate number of argatroban treated patients on ECMO was n = 307. In the majority of studies argatroban was used as a continuous infusion without loading dose. Starting doses on ECMO varied between 0.05 and 2 μg/kg/min and were titrated to achieve the chosen therapeutic target range. The activated partial thormboplastin time (aPTT) was the anticoagulation parameter used for monitoring purposes in most studies, whereas some utilized the activated clotting time (ACT). Optimal therapeutic targets varied between 43-70 and 60-100 seconds for aPTT and between 150-210 and 180-230 seconds for ACT. Bleeding and thromboembolic complication rates were comparable to patients treated with unfractionated heparin (UFH).

CONCLUSIONS

Argatroban infusion rates and anticoagulation target ranges showed substantial variations. The rational for divergent dosing and monitoring approaches are discussed in this paper. Argatroban appears to be a potential alternative to UFH in patients requiring ECMO. To definitively establish its safety, efficacy and ideal dosing strategy, larger prospective studies on well-defined patient populations are warranted.

Evaluation of direct thrombin inhibitors during a critical heparin shortage

A recent heparin shortage related to an outbreak of African Swine Flu in China led to substantial increase in the use of direct thrombin inhibitors (DTI) as an alternative. We evaluated the safety and efficacy of DTIs by assessing the anticoagulation assays within the initial 48 h of therapy comparing before and during shortage. A retrospective evaluation of bivalirudin and argatroban was conducted at a single center before (May 24, 2018 through August 25, 2019) and during heparin shortage (August 26, 2019 through February 20, 2020). The primary outcome was time to first therapeutic activated partial thromboplastin time (aPTT). Secondary outcomes included the percentage of time in therapeutic aPTT range, in-hospital mortality, incidence of recurrent thrombosis, and hemorrhagic events. Of the 204 patients included in the study, 95 patients [bivalirudin (n = 35), argatroban (n = 60)] were included in the pre-shortage cohort and 109 patients [bivalirudin (n = 68), argatroban (n = 41)] were during shortage. No significant difference was observed in the time to first therapeutic aPTT pre- and during shortage (8.9 h ± 10.8 vs 8.8 h ± 10.2, P = 0.62). Compared to pre-shortage cohort, a greater percentage of time was spent in therapeutic aPTT range within the initial 48 h (32% (0-50) vs. 41.6% (0-63), P = 0.04) during shortage without statistically significant differences in the rates of in-hospital mortality, thrombosis, or bleeding. While the optimal DTI protocol is still be determined, the protocols presented in this study allowed for wide-spread utilization of DTIs during a critical heparin shortage without compromising patient safety and effectiveness, likely reflective of the enhancement of DTI protocols, clinician education, and multidisciplinary collaboration and guidance from pharmacy and hematology.

Argatroban for Suspected Heparin-Induced Thrombocytopenia: Contemporary Experience at a Large Teaching Hospital

Heparin-induced thrombocytopenia requires immediate alternative anticoagulation to prevent or treat thromboembolic complications. Argatroban was approved based on multiple-center studies from the 1990s, but subsequent changes in prevailing awareness, diagnostic testing and therapeutic strategies for heparin-induced thrombocytopenia might affect results of argatroban therapy. Charts were retrospectively reviewed from patients administered argatroban for suspected heparin-induced thrombocytopenia over 22 months at a single large university hospital. Twenty-seven patients, most in intensive care units, received a median 0.5 µg/kg/min argatroban over a median 5.5 days. Patients had isolated heparin-induced thrombocytopenia (n = 10), had heparin-induced thrombocytopenia with thrombosis (n = 9), or lacked active heparin-induced thrombocytopenia (n = 8) on final analysis. New thromboses (14.8%), progression of preexisting thromboses (0%), amputation secondary to heparin-induced thrombocytopenia (0%), death (22.2%), bleeding requiring transfusion (3.7%), and any bleeding (22.2%) compared favorably with older multiple-center reports. Deaths occurred mainly with preexisting multiple-organ failure. In contemporary “real world” use, argatroban provides safe and effective anticoagulation, strengthening the mandate to initiate alternative anticoagulation whenever heparin-induced thrombocytopenia appears likely.

Argatroban Therapy for Heparin-Induced Thrombocytopenia in Acutely Ill Patients

Heparin-induced thrombocytopenia (HIT) is a prothrombotic, immune-mediated adverse reaction to heparin therapy. To evaluate clinical outcomes and effects of argatroban therapy in acutely ill HIT patients. Retrospective analysis. Hospital in-patient. Acutely ill patients with clinically diagnosed HIT from previous multicenter, historically controlled studies of argatroban therapy in HIT. Argatroban, adjusted to maintain activated partial thromboplastin times 1.5 to 3 times baseline, or historical control therapy (ie, no direct thrombin inhibition). We identified 488 patients who received argatroban (N = 390; mean dose of 1.9 µg/kg/min for a mean 6 days) or historical control therapy (N = 98) for HIT. The primary all-cause composite endpoint of death, amputation, or new thrombosis within 37 days occurred in 133 (34.1%) argatroban-treated patients and 38 (38.8%) controls ( P = .41). Argatroban, versus control, significantly reduced the primary thrombosis-related composite endpoint of death because of thrombosis, amputation secondary to ischemic complications of HIT, or new thrombosis (17.7% vs 30.6%, P = .007). Significant reductions also occurred in new thrombosis and death because of thrombosis. Major bleeding was similar between groups (7.7% vs 8.2%; P = .84). Adverse outcomes were more likely to occur in patients who were initially diagnosed with HIT and thrombosis, had undergone cardiac surgery, were not white, or had more severe thrombocytopenia. In acutely ill HIT patients, argatroban, versus historical control, provides effective antithrombotic therapy without increasing major bleeding. Patients with more severe thrombocytopenia or HIT-related thrombosis on HIT diagnosis have a poorer prognosis, emphasizing the importance of prompt recognition/ treatment of HIT in acutely ill patients.

Safety and economic considerations of argatroban use in critically ill patients: a retrospective analysis

Background

Heparin-induced thrombocytopenia (HIT) causes thromboembolic complications which threaten life and limb. Heparin is administered to virtually every critically ill patient as a protective measure against thromboembolism. Argatroban is a promising alternative anticoagulant agent. However, a safe dose which still provides effective thromboembolic prophylaxis without major bleeding still needs to be identified.

Methods

Critically ill patients (n = 42) diagnosed with HIT at a tertiary medical center intensive care unit from 2005 to 2010 were included in this retrospective analysis. Patient records were perused for preexisting history of HIT, heparin dosage before HIT, argatroban dosage, number of transfusions required, thromboembolic complications and length of ICU stay (ICU LOS). Patients were allocated to Simplified Acute Physiology Scores above and below 30 (SAPS >30, SAPS <30), respectively. For calculations, patients (n = 19) without previous history of HIT were compared to patients (n = 23) with a history of HIT before initiation of argatroban.

Results

The mean initial argatroban dosage was below 0.4 mcg/kg/min regardless of SAPS score. Maintenance dosage had to be increased in patients with SAPS <30 to 0.54 ± 0.248 mcg/kg/min (p >0.05) to achieve effective anticoagulation. No thromboembolic complications were encountered. Argatroban had to be discontinued temporarily in 16 patients for a total of 57 times due to diagnostic or surgical procedures, supratherapeutic aPTT and bleeding without increasing the number of transfusions. A history of HIT was associated with a shorter ICU LOS and significantly reduced transfusion need when compared to patients with no history of HIT. Cost calculation favour argatroban due to increased transfusion needs during heparin administration and increase ICU LOS.

Conclusion

Argatroban can be used at doses < 0.4 mcg/kg/min without an increase in transfusion requirements and at a reduced overall treatment cost compared to heparin.

[Argatroban, a new antithrombotic treatment for heparin-induced thrombocytopenia application in cardiac surgery and in intensive care]

OBJECTIVES

Although heparin-induced thrombocytopemia (HIT) is uncommon, its thromboembolic complications are potentially life-threatening. The low-molecular weight heparins are less responsible of HIT than unfractionated heparin (UFH) but this latter is still indicated in some circumstances such as cardiac surgery. Argatroban, a selective thrombin inhibitor, recently available, has been indicated in HIT treatment. This review presents the main pharmacological characteristics, its indications and uses in the context of cardiac surgery and in intensive care medicine.

METHODS

Review of the literature in Medline database over the past 15 years using the following keywords: argatroban, cardiac surgery, circulatory assistance, cardiopulmonary bypass.

RESULTS

Despite its short-acting pharmacokinetic, argatroban cannot be recommended during cardiopulmonary bypass. On the contrary, argatroban is indicated in many circumstances in postoperative period of various cardiac surgeries (on-pump, off-pump, circulatory assistance). Nevertheless, after cardiac surgery, doses have to be adapted according to coagulation laboratory testing (ACT), particularly in patients presenting acute organ failure (kidney injury, heart failure, liver failure). This compound has no antagonist and is excluded during severe hepatic failure. The continuous intravenous administration is a drawback.

CONCLUSION

Argatroban is a new direct competitive thrombin inhibitor well evaluated as treatment of HIT after cardiac surgery. In HIT management, argatroban is an interesting alternative to lepirudin that is not anymore available and danaparoid because of supply disturbances.

Argatroban therapy in heparin-induced thrombocytopenia

Argatroban is a direct thrombin inhibitor approved for anticoagulation in heparin-induced thrombocytopenia (HIT; in several countries) and in patients with or at risk of HIT undergoing percutaneous coronary intervention (PCI; in the USA). HIT is a relatively common extreme prothrombotic condition. When HIT is reasonably suspected, an alternative anticoagulant should be promptly initiated. In historical controlled studies, argatroban reduced new thrombosis, mortality from thrombosis and the composite of death, amputation or thrombosis, without increasing bleeding. With intravenous infusion, advantages include short half-life, easy monitoring and elimination primarily by hepatobiliary (rather than renal) means. In patients undergoing PCI, argatroban with or without glycoprotein IIb/IIIa inhibition leads to high rates of procedural success with low bleeding risk. Herein we review argatroban therapy for HIT and for PCI.

Intravenous warfarin and heparin-induced thrombocytopenia: making the diagnosis, management, modern monitoring, and multidisciplinary care

OBJECTIVE

To describe the diagnosis, management, and monitoring of a patient with heparin-induced thrombocytopenia (HIT) with thrombosis and simultaneous bleeding risk treated with argatroban and transitioned to intravenous (IV) warfarin secondary to the inability to administer enteral medications.

CASE SUMMARY

A 71-year-old man was admitted to the surgical intensive care unit (SICU) following aortic valve repair, coronary artery bypass, and ascending aortic aneurysm repair. On postoperative day 9, he was found to have a pulmonary embolism, and therapeutic heparin was started. The following day, his platelet count was found to have dropped precipitously. HIT was diagnosed, heparin was discontinued, and argatroban was initiated. On postoperative day 22, anticoagulation was discontinued because of massive gastrointestinal bleeding. On postoperative day 35, multiple venous thromboses were found, and argatroban was restarted. The patient developed a high-output enterocutaneous fistula, eliminating the option of enteral route of medication administration. The multidisciplinary SICU team transitioned the patient from argatroban to IV warfarin for long-term anticoagulation. The international normalized ratio was monitored and remained therapeutic throughout his admission without further thrombotic complications.

DISCUSSION

HIT occurs when antibodies develop to heparin-platelet factor 4 complexes, causing simultaneous hypercoagulability and thrombocytopenia. It is diagnosed based on both clinical factors and laboratory testing. Treatment includes discontinuation of all forms of heparin; initiation of a nonheparin anticoagulant, such as argatroban; and transition to warfarin.

CONCLUSIONS

IV warfarin is a therapeutic option for patients with malabsorption issues. A multidisciplinary team in an intensive care setting optimizes cost-effective, patient-centered, and safe care.

Safety and Efficacy of Argatroban in the Management of Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a life-threatening adverse reaction to heparin therapy that is characterized by thrombocytopenia and an increased risk of venous and arterial thrombosis. According to guidelines, in patients with strongly suspected or confirmed HIT all sources of heparin have to be discontinued and an alternative, nonheparin anticoagulant for HIT treatment must immediately be started. For both the prophylaxis of thrombembolic events in HIT and the treatment of HIT with thrombosis the direct thrombin inhibitor argatroban is approved in the United States. The objective of this review is to describe the mechanism of action and the pharmacokinetic profile of argatroban, to characterize argatroban regarding its safety and therapeutic efficacy and to discuss its place in therapy in HIT.

Argatroban in the management of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an immunoglobulin-mediated serious complication of heparin therapy characterized by thrombocytopenia and high risk for venous and arterial thrombosis: HIT and thrombosis syndrome (HITTS). Argatroban, a direct thrombin inhibitor, is indicated as the anticoagulant for the treatment and prophylaxis of thrombosis in patients with HIT and in patients undergoing percutaneous coronary intervention (PCI) who have HIT. The aim of this review is to examine the pharmacological characteristics and the clinical efficacy and safety of this drug in adults with HIT, including those undergoing PCI. Briefly, 2 prospective multicenter, nonrandomized, open-label studies evaluated the efficacy and safety of argatroban as an anticoagulant in patients with HIT or HITTS. Both studies showed that the incidence of the primary efficacy end point, a composite of all-cause death, all-cause amputation, or new thrombosis, was reduced in argatroban-treated patients vs control subjects with HIT or HITTS. In both studies, bleeding rates were similar between the groups. Argatroban was evaluated as the anticoagulant therapy in 3 prospective, multicenter, open-label studies in HIT patients who underwent PCI. The studies were similar in design with respect to patient inclusion and exclusion criteria, the argatroban dosing regimen, and primary efficacy outcomes. The investigators performed a pooled analysis of these studies, which showed that most (≥95%) patients achieved a satisfactory outcome from the procedure and adequate anticoagulation (coprimary end points).

Argatroban therapy for heparin-induced thrombocytopenia in ICU patients with multiple organ dysfunction syndrome: a retrospective study

Introduction

Heparin-induced thrombocytopenia (HIT) is a serious, prothrombotic, immune-mediated adverse reaction triggered by heparin therapy. When HIT is diagnosed or suspected, heparins should be discontinued, and an alternative, fast-acting, parenteral, nonheparin anticoagulation such as argatroban should be initiated. Limited and inconsistent data exist about dosing of argatroban in intensive care unit (ICU) patients with critical illnesses.

Methods

Retrospective analysis of 12 ICU patients with multiple organ dysfunction syndrome (MODS) treated with argatroban for suspected or diagnosed HIT.

Results

The 12 ICU patients with a mean platelet count of 46,000 ± 30,310 had a mean APACHE II score of 26.7 ± 7.8 on ICU admission and a mean SAPS II score of 61.5 ± 16.3 on the first day of argatroban administration. A mean argatroban starting dose of 0.32 ± 0.25 μg/kg/min (min, 0.04; max, 0.83) was used to achieve activated partial thromboplastin times (aPTTs) >60 sec or aPTTs of 1.5 to 3 times the baseline aPTT. Adjustment to aPTT required dose reduction in six (50%) patients. Patients were treated for a mean of 5.5 ± 3.3 days. The final mean dose in these critically ill patients was 0.24 ± 0.16 μg/kg/min, which is about one eighth of the usually recommended dose and even markedly lower than the previously suggested dose for critically ill ICU patients. In all patients, desired levels of anticoagulation were achieved. The mean argatroban dose was significantly lower in patients with hepatic insufficiency compared with patients without hepatic impairment (0.10 ± 0.06 μg/kg/min versus 0.31 ± 0.14 μg/kg/min; P = 0.026). The mean argatroban dose was significantly correlated with serum bilirubin (r = -0.739; P = 0.006).

Conclusions

ICU Patients with MODS and HIT can be effectively treated with argatroban. A decrease in the initial dosage is mandatory in this patient population. Further studies are needed to investigate argatroban elimination and dosage adjustments for critically ill patients.

Prolonged elevation of plasma argatroban in a cardiac transplant patient with a suspected history of heparin-induced thrombocytopenia with thrombosis

BACKGROUND

Direct thrombin inhibitors (DTIs) provide an alternative method of anticoagulation for patients with a history of heparin-induced thrombocytopenia (HIT) or HIT with thrombosis (HITT) undergoing cardiopulmonary bypass (CPB). In the following report, a 65-year-old critically ill patient with a suspected history of HITT was administered argatroban for anticoagulation on bypass during heart transplantation. The patient required massive transfusion support (55 units of red blood cells, 42 units of fresh-frozen plasma, 40 units of cryoprecipitate, 40 units of platelets, and three doses of recombinant Factor VIIa) for severe intraoperative and postoperative bleeding.

STUDY DESIGN AND METHODS

Plasma samples from before and after CPB were analyzed postoperatively for argatroban concentration using a modified ecarin clotting time (ECT) assay.

RESULTS

Unexpectedly high concentrations of argatroban were measured in these samples (range, 0-32 microg/mL), and a prolonged plasma argatroban half life (t(1/2)) of 514 minutes was observed (published elimination t(1/2) is 39-51 minutes [< or = 181 minutes with hepatic impairment]).

CONCLUSIONS

Correlation of plasma argatroban concentration versus the patient's coagulation variables and clinical course suggest that prolonged elevated levels of plasma argatroban may have contributed to the patient's extended coagulopathy. Because DTIs do not have reversal agents, surgical teams and transfusion services should remain aware of the possibility of massive transfusion events during anticoagulation with these agents. This is the first report to measure plasma argatroban concentration in the context of CPB and extended coagulopathy.

Argatroban: a review of its use in the management of heparin-induced thrombocytopenia

Argatroban, a highly selective direct thrombin inhibitor, is indicated for use as an anticoagulant for the treatment and prophylaxis of thrombosis in patients with heparin-induced thrombocytopenia (HIT), and in patients undergoing percutaneous coronary intervention (PCI) who have, or are at risk for, HIT. Intravenous argatroban improved clinical outcomes and was generally well tolerated in adults with HIT or HIT with thrombosis syndrome (HITTS). In two pivotal, open-label, historically controlled studies in adults with HIT, the incidence of the primary composite endpoint (all-cause death, all-cause amputation, or new thrombosis) was significantly lower in argatroban recipients than in historical controls, and more argatroban recipients than historical controls stayed event-free during the study according to a Kaplan-Meier analysis. In adults with HITTS in these trials, although the incidence of the primary composite endpoint did not differ significantly between argatroban recipients and historical controls, a Kaplan-Meier analysis showed that more patients receiving argatroban than historical controls remained event-free during the study. Major and minor bleeding rates in argatroban recipients were generally similar to those in historical controls in these studies. Argatroban was also an effective anticoagulant in patients with HIT undergoing PCI in three small, uncontrolled trials, pooled data from which showed that most (>or=95%) patients achieved a satisfactory outcome of the PCI procedure and adequate anticoagulation (coprimary endpoints). It was generally well tolerated in these patients, with the incidence of major bleeding being <or=1.1%. The efficacy and safety of argatroban in pediatric patients has not been established. However, a small uncontrolled, preliminary study suggests that it may be useful in seriously ill pediatric patients requiring nonheparin anticoagulation.

Anticoagulation with argatroban in a parturient with heparin-induced thrombocytopenia

Unfractionated heparin and low-molecular-weight heparin are currently the anticoagulants of choice for the prevention of recurrent thromboembolic disease during pregnancy. However, heparin-induced thrombocytopenia contraindicates the use of unfractionated heparin and low-molecular-weight heparin. We describe a patient who was admitted to our hospital with deep vein thrombosis at 18 weeks of gestation and who developed heparin-induced thrombocytopenia during her antenatal care. Therapeutic anticoagulation was initially achieved with argatroban, then changed to fondaparinux. During early labor, fondaparinux was discontinued and intravenous argatroban was substituted. Argatroban was discontinued during transition to active labor. After return of a normal partial thromboplastin time, combined spinal-epidural analgesia was induced for routine completion of labor and vaginal delivery. We discuss the decisions made in the maintenance of this patient's anticoagulation during the peripartum period as well as timing of her neuraxial labor analgesia.

Clinical experience with argatroban for heparin-induced thrombocytopenia in a large teaching hospital

BACKGROUND

Argatroban is a direct thrombin inhibitor approved for the prophylaxis or treatment of thrombosis in patients with heparin-induced thrombocytopenia (HIT). The product monograph does not guide clinicians beyond specifying the initial dose of 2 μg/kg per minute (or 0.5 μg/kg per minute for patients with hepatic impairment). Some authors have suggested that in the intensive care unit (ICU) and for patients with acute cardiac disease and those with renal or hepatic dysfunction, this dose may result in a supratherapeutic activated partial thromboplastin time (aPTT).

OBJECTIVES

To evaluate the efficacy and safety of argatroban in adult patients with suspected HIT in a large teaching hospital, and to review dosing for patients in the ICU, patients with acute cardiac disease, and patients with renal or hepatic dysfunction.

METHODS

Charts of patients with suspected HIT who had received argatroban for at least 24 h between October 1, 2005, and October 1, 2007, at the Foothills Medical Centre, Calgary, Alberta, were examined retrospectively.

RESULTS

Thirty patients met the inclusion criteria, with charts available for review. Of these, 21 (70%) patients had an initial argatroban dose of 2 μg/kg per minute and 4 (13%) had an initial dose of 0.5 μg/kg per minute. The median duration of therapy was 6 days, and the mean dose was 2.14 μg/kg per minute. There were 122 dosage adjustments, the most common change being 0.5 μg/kg per minute, followed by adjustments of 1 and 0.1 μg/kg per minute. Six patients had supratherapeutic aPTT values (above 100 s), and none experienced major bleeding.

CONCLUSIONS

The results of this study suggest that an initial argatroban dose of 2 μg/kg per minute is appropriate for patients with no hepatic dysfunction. Patients with acute cardiac disease and critically ill patients may require lower doses of argatroban; however no dosage adjustments are required for patients with renal dysfunction.

Reducing harm associated with anticoagulation: practical considerations of argatroban therapy in heparin-induced thrombocytopenia

Argatroban is a hepatically metabolized, direct thrombin inhibitor used for prophylaxis or treatment of thrombosis in heparin-induced thrombocytopenia (HIT) and for patients with or at risk of HIT undergoing percutaneous coronary intervention (PCI). The objective of this review is to summarize practical considerations of argatroban therapy in HIT. The US FDA-recommended argatroban dose in HIT is 2 microg/kg/min (reduced in patients with hepatic impairment and in paediatric patients), adjusted to achieve activated partial thromboplastin times (aPTTs) 1.5-3 times baseline (not >100 seconds). Contemporary experiences indicate that reduced doses are also needed in patients with conditions associated with hepatic hypoperfusion, e.g. heart failure, yet are unnecessary for renal dysfunction, adult age, sex, race/ethnicity or obesity. Argatroban 0.5-1.2 microg/kg/min typically supports therapeutic aPTTs. The FDA-recommended dose during PCI is 25 microg/kg/min (350 microg/kg initial bolus), adjusted to achieve activated clotting times (ACTs) of 300-450 sec. For PCI, argatroban has not been investigated in hepatically impaired patients; dose adjustment is unnecessary for adult age, sex, race/ethnicity or obesity, and lesser doses may be adequate with concurrent glycoprotein IIb/IIIa inhibition. Argatroban prolongs the International Normalized Ratio, and published approaches for monitoring the argatroban-to-warfarin transition should be followed. Major bleeding with argatroban is 0-10% in the non-interventional setting and 0-5.8% periprocedurally. Argatroban has no specific antidote, and if excessive anticoagulation occurs, argatroban infusion should be stopped or reduced. Improved familiarity of healthcare professionals with argatroban therapy in HIT, including in special populations and during PCI, may facilitate reduction of harm associated with HIT (e.g. fewer thromboses) or its treatment (e.g. fewer argatroban medication errors).

Argatroban anticoagulation in intensive care patients: effects of heart failure and multiple organ system failure

We retrospectively evaluated argatroban dosing patterns, clinical outcomes, and the effects of heart failure and multiple organ system failure on dosing requirements in 65 adult, intensive care patients administered argatroban anticoagulation for clinically suspected heparin-induced thrombocytopenia (n=56) or history of heparin-induced thrombocytopenia (n=9). Argatroban was initiated then titrated to achieve target activated partial thromboplastin times 1.5 to 3 times normal control (ie, 42-84 seconds). Overall, argatroban was initiated at 1.14+/-0.62 microg/kg/min (mean+/-SD) and administered for 11.4+/-9.5 days, with comparable dosing patterns between patients with suspected, versus previous, heparin-induced thrombocytopenia. Sixty-four (98.5%) patients achieved target activated partial thromboplastin times, typically following no or one dose adjustment. Therapeutic doses were lower in patients with, versus without, heart failure (0.58+/-0.28 vs 0.97+/-0.6 microg/kg/min, P= .042) and decreased as the number of failed organ systems increased from 1 to 2 to =3 (1.10+/-0.67 vs 0.87+/-0.47 vs 0.58+/-0.47 microg/kg/min, P= .008). From argatroban initiation until patient discharge or death, 11 (16.9%) patients (3 off argatroban) developed thromboembolic complications; 14 (21.5%) died (11 off argatroban, 7 from multiple organ system failure); and 1 (1.5%) required amputation. Nine patients (13.8%) experienced bleeding, none fatal. This experience suggests that argatroban administered at approximately 1 micro/kg/min provides adequate levels of anticoagulation in many intensive care unit patients with suspected or previous heparin-induced thrombocytopenia. Reduced doses are needed when heart failure or multiple organ system failure is present.

[Direct thrombin inhibitors: pharmacology and application in cardiovascular anesthesia]

The options for drug-controlled anticoagulation are becoming noticeably more manifold. In the area of anaesthesiology and intensive care, there are furthermore special disease patterns, such as heparin-induced thrombocytopenia (HIT) to be known, diagnosed and treated. This article gives a review of the substance groups of the direct thrombin inhibitors (DTI) as alternative anticoagulants for HIT in combination with cardiovascular diseases. For the administration of DTIs, experience and the correct dose are the keys to success and are the deciding factors for the two sides of haemostasis: thrombosis and haemorrhage.

Weight-based argatroban dosing nomogram for treatment of heparin-induced thrombocytopenia

BACKGROUND

Manufacturer recommendations for argatroban use in the setting of heparin-induced thrombocytopenia (HIT) state that the dosage should be titrated to a goal activated partial thromboplastin time (aPTT) of 1.5-3 times the baseline aPTT. The lack of a clear dosing strategy with argatroban may result in delayed stabilization of aPTT. There are no published nomograms to guide the dosing of argatroban.

OBJECTIVE

To study the anticoagulant effect and incidence of bleeding and thrombotic events in patients receiving argatroban, with doses determined using a weight-based nomogram.

METHODS

Patients with suspected or documented HIT at an 800-bed teaching community hospital were prospectively treated, in a nonrandomized, nonblinded manner, with argatroban; dosage adjustments were made according to 1 of 2 variations of a dosing nomogram: standard or hepatic/critically ill. The primary outcomes were time to aPTT stabilization and percentage of patients whose aPTTs were within the therapeutic range of 45-90 seconds at 6, 12, 24, 48, 72, and 96 hours. Secondary outcomes were the percentage of patients whose aPTTs were subtherapeutic, supratherapeutic, or above the therapeutic threshold of 45 seconds at each time interval; incidence of thrombotic events; number of dosage adjustments to achieve stabilization; and number of major bleeding events.

RESULTS

Fifty-one patients were prospectively treated using the standard (n = 34) and hepatic/critically ill (n = 17) nomograms. Mean time to aPTT stabilization was 16.25 hours with the standard nomogram and 27.05 hours with the hepatic/critically ill nomogram. The percentages of patients with aPTTs within the therapeutic range at each time interval were 82.4%, 82.4%, 88.2%, 96.4%, 100%, and 100% with the standard nomogram and 58.8%, 82.4%, 76.5%, 93.3%, 100%, and 90.9% with the hepatic/critically ill nomogram. There were no thrombotic events after the initiation of argatroban. Three cases of major bleeding occurred.

CONCLUSIONS

The nomogram is an effective dosing tool for achieving and maintaining therapeutic levels of anticoagulation.

Review: Recent Advances in Argatroban-Warfarin Transition in Patients With Heparin-induced Thrombocytopenia

Heparin-induced thrombocytopenia is a devastating, life-threatening, immune-mediated complication of therapy with unfractionated heparin, and less frequently, with low molecular weight heparin. Direct thrombin inhibitors are now standard therapy for the prevention of thrombosis in heparin-induced thrombocytopenia. Argatroban, a small synthetic molecule that inhibits thrombin at its active site, is increasingly used as the direct thrombin inhibitors of choice. Transition to longer term oral anticoagulation needs to be instituted after the platelet count has risen, because of the persistent risk of thrombosis. Although guidelines available in the literature outline the management of heparin-induced thrombocytopenia, they are not presented in a concise and comprehensive manner easily followed by physicians. This article reviews current recommendations, relevant studies, and clinical management trials carried out on patients with heparin-induced thrombocytopenia and provides updated, detailed guidelines for treatment of heparin-induced thrombocytopenia with emphasis on a key part of the management, the argatroban—warfarin transition.

Treatment and prevention of heparin-induced thrombocytopenia: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about the recognition, treatment, and prevention of heparin-induced thrombocytopenia (HIT) is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patient values may lead to different choices. Among the key recommendations in this chapter are the following: For patients receiving heparin in whom the clinician considers the risk of HIT to be > 1.0%, we recommend platelet count monitoring over no platelet count monitoring (Grade 1C). For patients who are receiving heparin or have received heparin within the previous 2 weeks, we recommend investigating for a diagnosis of HIT if the platelet count falls by >/= 50%, and/or a thrombotic event occurs, between days 5 and 14 (inclusive) following initiation of heparin, even if the patient is no longer receiving heparin therapy when thrombosis or thrombocytopenia has occurred (Grade 1C). For patients with strongly suspected (or confirmed) HIT, whether or not complicated by thrombosis, we recommend use of an alternative, nonheparin anticoagulant (danaparoid [Grade 1B], lepirudin [Grade 1C], argatroban [Grade 1C], fondaparinux [Grade 2C], or bivalirudin [Grade 2C]) over the further use of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) therapy or initiation/continuation of vitamin K antagonists (VKAs) [Grade 1B]. The guidelines include specific recommendations for nonheparin anticoagulant dosing that differ from the package inserts. For patients with strongly suspected or confirmed HIT, we recommend against the use of vitamin K antagonist (VKA) [coumarin] therapy until after the platelet count has substantially recovered (usually, to at least 150 x 10(9)/L) over starting VKA therapy at a lower platelet count (Grade 1B); that VKA therapy be started only with low maintenance doses (maximum, 5 mg of warfarin or 6 mg of phenprocoumon) over higher initial doses (Grade 1B); and that the nonheparin anticoagulant (eg, lepirudin, argatroban, danaparoid) be continued until the platelet count has reached a stable plateau, the international normalized ratio (INR) has reached the intended target range, and after a minimum overlap of at least 5 days between nonheparin anticoagulation and VKA therapy rather than a shorter overlap (Grade 1B). For patients receiving VKAs at the time of diagnosis of HIT, we recommend use of vitamin K (10 mg po or 5 to 10 mg IV) [Grade 1C].

Reduced Argatroban Doses After Coronary Artery Bypass Graft Surgery

Background:

The Food and Drug Administration–approved argatroban dose for heparin-induced thrombocytopenia (HIT) is 2 μg/kg/min (0.5 μg/kg/min in hepatic impairment), adjusted to achieve activated partial thromboplastin time (aPTT) 1.5–3 times baseline. Recent data suggest that reduced doses are required after cardiovascular surgery.

Objective:

To characterize dosing requirements, aPTTs, factors affecting dosage, and clinical outcomes in patients administered argatroban after coronary artery bypass graft (CABG) surgery.

Methods:

Charts of 39 patients who underwent CABG surgery and were administered argatroban postoperatively for laboratory-confirmed HIT (n = 25), antibody-negative suspected HIT (n = 10), or previous HIT requiring anticoagulation (n = 4) were retrospectively reviewed. Patient characteristics, argatroban dosing information, aPTTs (target range 45–90 sec), and outcomes were summarized. Regression analyses explored potential effectors of dosage.

Results:

Patient features, argatroban dosing patterns, and aPTTs were similar among groups. Many patients had laboratory evidence of some hepatic and/or renal dysfunction (median [range] bilirubin 1.0 [0.3–8.0] mg/dL, creatinine clearance 47 [18–287] mL/min). Overall, median argatroban doses were 0.5 μg/kg/min initially and 0.6 μg/kg/min during therapy (median duration 5.3 days). After argatroban initiation, aPTTs were greater than 90 seconds at first assessment in 4 patients (3 with abnormal hepatic function test results) initially administered 0.5, 1, 2, and 2 μg/kg/min, respectively. Within approximately 16 hours of therapy, 33 (85%) patients achieved consecutive therapeutic aPTTs. No association was detected between mean dose during therapy and preoperative ejection fraction, routine hepatic or renal function test results (other than blood urea nitrogen [BUN]), or surgery type. A clinically insignificant association existed between dose and BUN: there was an approximately 0.15 μg/kg/min dose decrease for each 10 mg/dL BUN increase. One patient developed thrombosis, 1 underwent finger amputation, 7 died (5 after argatroban cessation), and 4 had significant bleeding.

Conclusions:

These findings suggest that reduced initial argatroban doses (eg, 0.5 μg/kg/min), adjusted to achieve therapeutic aPTTs, provide rapid, adequate anticoagulation in postoperative CABG patients with presumed or previous HIT. Prospective study of reduced initial dosing in this setting is warranted.

Considerations for Drug Dosing Post Coronary Artery Bypass Graft Surgery

Acute physiologic changes after bypass graft surgery may temporarily result in reduced drug elimination and dosing requirements for the desired effect. Substantially lower doses for drugs such as the direct thrombin inhibitor argatroban may need to be considered when initiating therapy soon after surgery if the therapeutic window is narrow and impaired liver, kidney, or cardiac function is present. Initial dosing approaches, with follow-up infusion rate adjustments and allowances for the extended time needed to establish and maintain an activated partial thromboplastin time value in the target ratio range, also need to consider the risk of thrombosis or bleeding complications. The duration of reduced dosing may depend on several variables, and, as systems recover, the dosage may need to be adjusted upwards. Retrospective analysis for identifying heparin-induced thrombocytopenia may be difficult in situations where other causes of thrombocytopenia are present, suggesting that posttest scoring methods also be considered to confirm its presence until better, validated methods become available.

Reducing thrombotic complications in the perioperative setting: an update on heparin-induced thrombocytopenia

Heparins are widely used in the perioperative setting. Immune heparin-induced thrombocytopenia (HIT) is a serious, antibody-mediated complication of heparin therapy that occurs in approximately 0.5%-5% of patients treated with heparin for at least 5 days. An extremely prothrombotic disorder, HIT confers significant risks of thrombosis and devastating consequences on affected patients: approximately 38%-76% develop thrombosis, approximately 10% with thrombosis require limb amputation, and approximately 20%-30% die within a month. HIT antibodies are transient and typically disappear within 3 mo. In patients with lingering antibodies, however, re-exposure to heparin can be catastrophic. In the perioperative setting, heightened awareness is important for the prompt recognition, diagnosis, and treatment of HIT. HIT should be considered if the platelet count decreases 50% and/or thrombosis occurs 5-14 days after starting heparin, with other diagnoses excluded. On strong clinical suspicion of HIT, heparin should be discontinued and a parenteral alternative anticoagulant initiated, even before laboratory confirmation of HIT is obtained. Subsequent laboratory test results may help with the decision to continue with nonheparin therapy or switch back to heparin. Heparin avoidance in patients with current or previous HIT is feasible in most clinical situations, except perhaps in cardiovascular surgery. If the surgery cannot be delayed until HIT antibodies have disappeared, intraoperative alternative anticoagulation is recommended.

Argatroban Therapy in Women with Heparin-Induced Thrombocytopenia

OBJECTIVES

Women have increased risk of developing heparin-induced thrombocytopenia (HIT), a serious, immune-mediated prothrombotic condition, and have a worse prognosis when affected. We compared gender differences for treatment and outcomes in HIT patients administered argatroban therapy.

METHODS

From a multicenter retrospective registry of argatroban-treated patients, we identified females (n = 42) and males (n = 50) with clinically diagnosed HIT who were administered argatroban <or=10 microg/kg/min. Upon diagnosis of HIT, heparin was discontinued. Continuous intravenous argatroban was instituted, adjusted to achieve activated partial thromboplastin times (aPTTs) 1.5-3 times baseline. Between-gender comparisons were made of argatroban dosing, aPTT responses, and clinical outcomes (death, amputation, new thrombosis, major bleeding).

RESULTS

At baseline, females and males were generally well matched, excepting platelet count (medians, 101 x 10(9)/L vs. 170 x 10(9)/L, p = 0.01), with 9 (21%) females and 19 (38%) males having HIT-related thrombosis. Typically, argatroban was initiated and maintained at 1.0-1.1 mug/kg/min for approximately 6 days, irrespective of gender. No differences were detected between females and males in aPTTs during therapy (respective medians, 57.3 vs. 59.5 seconds) or time to therapeutic aPTTs (7.3 vs. 10.3 hours), or platelet count recovery (2.5 vs. 7.4 days). Of patients with available data, 20 of 35 (57%) females and 19 of 35 (54%) males were converted to warfarin. The composite end point of death, amputation, or new thrombosis within 37 days of argatroban initiation occurred in 10 (24%) females and 8 (16%) males (p = 0.43). Within 37 days, 7 (17%) females and 7 (14%) males died (2 while on argatroban), 1 (2%) female required amputation (off argatroban), and 3 (7%) females and 2 (4%) males developed new thrombosis (3 while on argatroban). Major bleeding occurred in 1 (2%) female and 1 (2%) male.

CONCLUSIONS

Argatroban can be used effectively and safely to manage HIT in females, with dosing requirements, aPTT responses, and clinical outcomes comparable to those in men. Future, larger studies are warranted in establishing the unique characteristics of HIT in females.

Heparin-induced thrombocytopenia in intensive care patients

OBJECTIVE

To summarize new information on frequency of heparin-induced thrombocytopenia (HIT) in patients treated in intensive care units (ICU), developments in the interpretation of assays for detecting anti-PF4/heparin antibodies, and treatment of HIT patients.

STUDY SELECTION

All data on the frequency of laboratory-confirmed HIT in ICU patients were included; for laboratory testing of HIT and treatment of patients, this review focuses on recent data that became available in 2005 and 2006.

DATA EXTRACTION AND SYNTHESIS

HIT is a potentially life-threatening adverse effect of heparin treatment caused by platelet-activating antibodies of immunoglobulin G class usually recognizing complexes of platelet factor 4 and heparin. HIT is more often caused by unfractionated heparin than low-molecular-weight heparin and is more common in postsurgical than in medical patients. In the ICU setting, HIT is uncommon (0.3-0.5%), whereas thrombocytopenia from other causes is very common (30-50%). For laboratory diagnosis of HIT antibodies, both antigen assays and functional (platelet activation) assays are available. Both tests are very sensitive (high negative predictive value) but specificity is problematic, especially for the antigen assays, which also detect nonpathogenic immunoglobulin M and immunoglobulin A class antibodies. Detection of immunoglobulin M or immunoglobulin A antibodies could potentially lead to adverse events such as bleeding if a false diagnosis of HIT prompts replacement of heparin by an alternative anticoagulant. For treatment of HIT, three alternative anticoagulants are approved: the direct thrombin inhibitors, lepirudin and argatroban, and the heparinoid, danaparoid (not approved in the United States). Recent data indicate that the approved dosing regimens of the direct thrombin inhibitors are too high, especially in ICU patients.

CONCLUSIONS

HIT affects <1% of ICU patients even though 30-50% develop thrombocytopenia. The choice of the optimal alternative anticoagulant depends on patient characteristics. Many ICU patients require lower doses of alternative anticoagulant than those recommended by the manufacturer.

Severe heparin-induced thrombocytopenia: when the obvious is not obvious, a case report

Thrombocytopenia commonly occurs in hospitalized patients, particularly critically ill patients. We present an exemplifying case of severe heparin-induced thrombocytopenia (HIT) in an effort to solidify its high priority in the differential diagnosis of thrombocytopenia. A 75-year-old female underwent cardiac surgery with intraaortic balloon pump (IABP) placement. A platelet count drop to 25 x 10(9)/L by the third postoperative day was attributed to the IABP, which was removed. Her thrombocytopenia remained refractory to multiple platelet transfusions over several days. Right hand cyanosis then developed, attributed to a right radial arterial catheter, which was removed. All toes and fingers then showed severe ischemic changes. Ten days after the initial platelet count drop, a critical care specialist new to the treating team suspected HIT. Heparin exposure was stopped and argatroban was initiated. A HIT antibody test was subsequently strongly positive. The patients thrombocytopenia gradually resolved. No additional thromboses occurred during a 27-day intensive care unit stay. This case underscores the need for vigilance in suspecting HIT in patients with thrombocytopenia and recent heparin exposure. To avoid catastrophic outcomes in such patients, heparin should be stopped and alternative anticoagulation should be initiated, at least until HIT is excluded.

Heparin-Induced Thrombocytopenia: Treatment Options and Special Considerations

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse effect that typically manifests several days after the start of heparin therapy, although both rapid- and delayed-onset HIT have been described. Its most serious complication is thrombosis. Although not all patients develop thrombosis, it can be life threatening. The risk of developing HIT is related to many factors, including the type of heparin product administered, route of administration, duration of therapy, patient population, and previous exposure to heparin. The diagnosis of HIT is typically based on clinical presentation, exposure to heparin, and presence of thrombocytopenia with or without thrombosis. Antigen and activation laboratory assays are available to support the diagnosis of HIT. However, because of the limited sensitivity and specificity of these assays, bedside probability scales for HIT were developed. When HIT is suspected, prompt cessation of all heparin therapy is necessary, along with initiation of alternative anticoagulant therapy. Two direct thrombin inhibitors--argatroban and lepirudin--are approved for the management of HIT in the United States, and bivalirudin is approved for use in patients with HIT who are undergoing percutaneous coronary intervention. Other agents, although not approved to manage HIT, have also been used; however, their role in therapy requires further evaluation. A comprehensive HIT management strategy involves the evaluation of numerous factors. Many patients, including those undergoing coronary artery bypass surgery, those with acute coronary syndromes, those with hepatic or renal insufficiency, and children, require special attention. Clinicians must become familiar with the available information on this serious adverse effect and its treatment so that optimum patient management strategies may be formulated.

Effect of renal function on argatroban therapy in heparin-induced thrombocytopenia

BACKGROUND

Argatroban is considered to be an alternative anticoagulant of choice in patients with heparin-induced thrombocytopenia (HIT) and renal impairment. The recommended initial dose in HIT is 2 microg/kg/min (0.5 microg/kg/min in hepatic impairment), adjusted to achieve activated partial thromboplastin times (aPTTs) 1.5-3 times baseline. Although argatroban is predominantly hepatically metabolized with minimal renal clearance, recent limited data have suggested that a patient's renal function should also be considered when initiating argatroban therapy for HIT. We retrospectively evaluated the effect of renal function on argatroban therapy in HIT patients with normal hepatic function, with the goal of refining dosing guidance, if needed.

METHODS

From case records of previous prospective studies of argatroban in clinically diagnosed HIT, we identified patients who had baseline laboratory data on liver and renal function. Individuals with abnormal hepatic function (serum total bilirubin > 1.5 mg/dl or ALT or AST > 100 U/l) were excluded. Patients were stratified according to their estimated creatinine clearance (CL(cr)): normal or mild impairment (CL(cr) > 60 ml/min), moderate impairment (CL(cr) 30-60 ml/min), or severe impairment (CL(cr) < 30 ml/min). Argatroban doses, aPTTs, and clinical outcomes were summarized overall and by group. By-patient relationships between CL(cr) and dose or aPTT during therapy were explored using regression analyses.

RESULTS

The analysis population included 260 patients with normal to mild (n = 144), moderate (n = 80), or severe (n = 36) renal impairment. Argatroban was initiated at a mean infusion dose of 1.8 +/- 0.7 microg/kg/min (overall), titrated to achieve aPTTs 1.5-3 times baseline. Among renal function groups, no significant differences occurred in argatroban dose during therapy (overall value, 1.9 +/- 1.1 microg/kg/min), duration of therapy (7 +/- 6 days), or aPTTs (63 +/- 17 s). Regression analyses showed a 0.1 microg/kg/min increase in dose (r2 = 0.02) for each 30 ml/min increase in CL(cr). Within a 37 day follow-up, 46 (17.7%) patients died, most often when severe renal impairment was present. New thrombosis (11.5% overall) and major bleeding (5.0%) did not differ among groups.

CONCLUSIONS

In this large cohort of HIT patients with normal hepatic function and varying levels of renal function, argatroban administered in accordance with current recommendations provided adequate levels of anticoagulation and was well tolerated. Altered renal function did not clinically significantly affect argatroban doses, aPTT responses, or rates of thrombosis or bleeding. These findings further support argatroban as an alternative anticoagulant of choice, without need for initial dose adjustment, in most patients with HIT and renal impairment.

CONDENSED ABSTRACT

We retrospectively evaluated the effect of renal function on argatroban therapy in HIT patients with normal hepatic function, with the goal of refining current dosing guidance, if needed. From previous prospective studies of argatroban in HIT, we identified 260 patients with clinically diagnosed HIT, normal hepatic function, and varying degrees of renal function. Among patients whose renal function was normal or mildly impaired (estimated creatinine clearance, CL(cr) > 60 ml/min); moderately impaired (CL(cr) 30-60 ml/min), or severely impaired (CL(cr) < 30 ml/min), no significant differences occurred in the argatroban dose, aPTT response, duration of therapy, or rates of thrombosis or major bleeding. By regression analysis, there was a clinically insignificant 0.1 microg/kg/min increase in dose for each 30 ml/min increase in CL(cr). Overall, argatroban administered in accordance with current recommendations provided adequate levels of anticoagulation and was well tolerated, supporting its use as an alternative anticoagulant of choice, without need for initial dose adjustment, in most patients with HIT and renal impairment.

Prolonged anticoagulation after discontinuation of argatroban and warfarin therapy in an obese patient with heparin-induced thrombocytopenia

A 32-year-old, morbidly obese African-American woman developed bilateral pulmonary emboli 12 days after undergoing Roux-en-Y gastric bypass surgery. Three days later, after receiving heparin and warfarin, she developed heparin-induced thrombocytopenia type II (HIT-II). An argatroban 1.5-microg/kg/minute infusion was administered for approximately 2.5 days. The patient also received four doses of warfarin, totaling 37.5 mg. The argatroban infusion was discontinued early on hospital day 6, at which time the patient's international normalized ratio (INR) was 4.36 and activated partial thromboplastin time (aPTT) 85.9 seconds. Her INR and aPTT values continued to rise after the argatroban was discontinued and peaked 3 days later at 5.28 and 123.6 seconds, respectively. At this time her platelet count had improved from 139 x 10(3)/mm(3) to 543 x 10(3)/mm(3). No additional warfarin was administered before discharge. On hospital day 11, the patient was discharged home with an INR of 4.12 and an aPTT of 67.1 seconds. Her aPTT and INR values remained elevated for 19 days after receiving her last dose of warfarin and for 20 days after argatroban discontinuation. She experienced no bleeding complications from these supratherapeutic coagulation parameters. She resumed treatment with warfarin as an outpatient and completed a 6-month course of anticoagulation without further incident. Clinicians should be aware that coagulation parameters may remain elevated longer than expected after argatroban discontinuation in certain patients taking concomitant warfarin. Patients with liver dysfunction and obesity appear most likely to be affected.

Argatroban: update

Unfractionated heparin has historically been used as the anticoagulant of choice in the management of a number of thrombotic diseases. Recognition of the limitations of heparin has led to the development of a newer class of anticoagulants, the direct thrombin inhibitors. Argatroban is a synthetic small molecule that selectively inhibits thrombin at its active site. In preclinical studies, argatroban has been shown to be more effective than heparin in preventing arterial thrombosis and in promoting vessel patency in conjunction with thrombolysis in a number of animal models. In clinical trials, argatroban has been shown to be as effective as heparin in the management of ST-segment elevation myocardial infarction in conjunction with thrombolysis. It has been shown to be an effective anticoagulant in patients undergoing percutaneous coronary interventions. In patients with heparin-induced thrombocytopenia and heparin-induced thrombocytopenia complicated by thrombosis, argatroban significantly decreases the risk of thrombotic events. Small studies have demonstrated a potential role for its use in ischemic stroke and hemodialysis. Additional studies are warranted to confirm argatroban's efficacy in a wide variety of clinical settings.

Successful recovery after an overdose of argatroban

OBJECTIVE

To report the case of a critically ill man with heparin-induced thrombocytopenia (HIT) who received a 125 mg overdose of the direct thrombin inhibitor argatroban.

CASE SUMMARY

A 74-year-old man with a history of Crohn's disease underwent takedown of an ileorectal fistula. He developed HIT postoperatively and was treated with argatroban. He became critically ill and was transferred to the intensive care unit. On postoperative day 24, he accidentally received argatroban 125 mg over 1 hour (26 microg/kg/min). Treatment with fresh frozen plasma (FFP) was effective, and there were no significant complications. The partial thromboplastin time, however, continued to be prolonged 48 hours after the overdose.

DISCUSSION

Medication errors with direct thrombin inhibitors are common. However, there is no known reversal agent for this class of anticoagulants. This patient was treated with FFP and did well, with no bleeding complications. However, the clearance of argatroban was prolonged.

CONCLUSIONS

This case illustrates that supratherapeutic doses of argatroban can be managed with FFP and tolerated without significant complications.

Intimatan (dermatan 4,6-O-disulfate) prevents rethrombosis after successful thrombolysis in the canine model of deep vessel wall injury

INTRODUCTION

Intimatan (dermatan 4,6-O-disulfate), a heparin cofactor II (HCII) agonist, inhibits both the fluid phase and thrombus bound thrombin. The efficacy of Intimatan as an adjunctive anticoagulant during thrombolysis was evaluated in the canine model of arterial injury.

MATERIALS AND METHODS

After forming an occlusive thrombus in the right carotid artery (RCA), twenty-one dogs were administered recombinant tissue plasminogen activator (rt-PA) intra-arterially to achieve thrombolysis in the presence of either 0.9% NaCl or Intimatan (9 mg/kg bolus+300 mug/kg/min i.v. infusion). Next, the left carotid arteries (LCA) of the same animals were injured in the presence of either Intimatan or 0.9% NaCl.

RESULTS

The incidence of RCA rethrombosis between the Intimatan and control groups was 2/9 and 8/12, respectively. The quality of RCA blood flow, i.e., patency score (Scale of 0-3, i.e., no flow to high flow, respectively), was 2.3+/-0.4 (Intimatan) versus 0.9+/-0.4 (0.9% NaCl). The incidence of primary thrombosis was determined among the groups as 0/9 (Intimatan) versus 7/12 (0.9% NaCl); the patency score was 2.8+/-0.1 (Intimatan) versus 0.9+/-0.4 (0.9% NaCl). Intimatan resulted in a >90% ex vivo inhibition of gamma-thrombin-induced platelet aggregation whereas 0.9% NaCl had no inhibitory effect. Clot-bound thrombin activity was reduced significantly by Intimatan. Intimatan induced <2-fold change in aPTT and bleeding time (BT) when corrected for the 0.9% NaCl group.

CONCLUSIONS

Intimatan significantly reduces the incidence of both primary and secondary arterial thrombosis while maintaining a high-grade vessel patency score with only moderate increases in BT and aPTT.

Argatroban Anticoagulation in Patients with Heparin-Induced Thrombocytopenia Requiring Renal Replacement Therapy

BACKGROUND:

Argatroban, a direct thrombin inhibitor, is used for prophylaxis or treatment of thrombosis in heparin-induced thrombocytopenia (HIT). The recommended initial dose is 2 μg/kg/min (0.5 μg/kg/min in hepatic impairment), adjusted to achieve activated partial thromboplastin time (aPTT) values 1.5–3.0 times baseline. However, few argatroban-treated patients with HIT and renal failure requiring renal replacement therapy (RRT) have been described.

OBJECTIVE:

To evaluate the safety and efficacy of argatroban anticoagulation during RRT in patients with HIT.

METHODS:

We retrospectively reviewed records from 47 patients with HIT and renal failure requiring RRT who underwent 50 treatment courses with argatroban. Patients with HIT had received argatroban during prospective, multicenter studies. Outcomes, safety, and dosing information were summarized.

RESULTS:

In the multicenter experience, no patient died due to thrombosis and 2 (4%) patients developed new thrombosis while on argatroban. No adverse outcomes occurred during argatroban reexposure. Starting doses were typically 2 μg/kg/min in patients without hepatic impairment and <1.5 μg/kg/min in those with hepatic impairment. Median (range) infusion doses were 1.7 (0.2–2.8) and 0.7 (0.1–1.7) μg/kg/min, respectively, with associated median (range) aPTT ratios, relative to baseline, of 2.2 (1.6–3.6) and 2.0 (1.4–4.1), respectively. Major bleeding occurred in 3 (6%) of 50 treatment courses.

CONCLUSIONS:

Argatroban provides effective anticoagulation upon initial and repeated administration in patients with HIT and renal impairment requiring RRT, with an acceptably low bleeding risk. Current dosing recommendations are adequate for these patients.

Argatroban in Post-Cardiovascular Surgery Patient with Heparin-Induced Thrombocytopenia Requiring Hemodialysis and Continuous Hemofiltration

Objective:

To describe the use of argatroban in a postoperative cardiovascular surgery patient with heparin-induced thrombocytopenia (HIT) requiring hemodialysis and continuous veno-veno hemofiltration (CVVH).

Case Summary:

A 23-year-old white woman with HIT developed acute renal failure after cardiovascular surgery. Argatroban was used as a substitute for heparin during hemodialysis and CVVH. Both activated partial thromboplastin time (aPTT) and activated clotting time (ACT) were used to guide the dosage of argatroban. The patient was successfully dialyzed without clotting of the circuit. The dosage required in our patient was much lower than the manufacturer's recommendation.

Discussion:

Argatroban is a selective thrombin inhibitor that does not cross-react with heparin-induced antibodies. It is metabolized by the liver, and dosage adjustment is recommended in patients with severe hepatic impairment. The correct dosage for patients with unstable hemodynamics is not known. Our patient had apparently normal hepatic function at the initiation of therapy, but the dosage of argatroban recommended by the manufacturer resulted in prolonged elevation of the aPTT and ACT with associated gastrointestinal bleeding. This may be due to hepatic congestion secondary to poor cardiac function and/or severe generalized edema.

Conclusions:

When argatroban is considered for therapy in place of heparin for CVVH, it needs to be used with extreme caution since the correct initial dosage in patients with mild hepatic impairment and unstable hemodynamics is unclear.

Extensive prolongation of aPTT with argatroban in an elderly patient with improving renal function, normal hepatic enzymes, and metastatic lung cancer

OBJECTIVE

To report a case of an elderly male with improving renal function and normal hepatic function who sustained an elevated activated partial thromboplastin time (aPTT) after an infusion of argatroban was discontinued.

CASE SUMMARY

A 77-year-old white male with a history of heparin-induced thrombocytopenia (HIT) and metastatic lung disease was started on argatroban for treatment of a right upper-extremity deep vein thrombosis (DVT). The infusion was initiated at 2.0 microg/kg/min and was titrated to a goal aPTT of 60-80 seconds. Argatroban was discontinued due to an aPTT elevated to >100 seconds; the aPTT remained elevated for 130 hours after discontinuation of the infusion.

DISCUSSION

Argatroban dose reductions in patients with impaired liver and renal function test values have been reported. Elderly subjects may have a prolonged clearance compared with young healthy subjects, although the duration of effect has not been established. As of April 18, 2005, the effect of liver metastasis on argatroban pharmacokinetics in the setting of normal liver function enzyme levels has not been reported. An objective causality assessment using the Naranjo probability scale showed that the prolonged aPTT was probably attributable to argatroban.

CONCLUSIONS

Clinicians should exercise caution when initiating argatroban at a dose of 2.0 microg/kg/min in elderly patients with underlying comorbidities, such as metastatic disease and renal impairment, since this may lead to excessive and prolonged anticoagulation and increased risk of bleeding.