Clinical uses of low-molecular-weight heparins

[Advances in heparin structural analysis by chromatography technologies]

Heparin （Hp） is the most widely used anticoagulant drug in the clinics， with an annual global output of over 10 billion dollars. Hp， a member of the glycosaminoglycans （GAGs）， is prepared from porcine intestinal mucosa via extraction， separation， and purification. Hp is a linear polysaccharide with repeating disaccharide units. Low-molecular-weight heparins （LMWHs） are depolymerized from Hp via chemical or enzymatic degradation. Compared with Hp， LMWHs exhibit less bleeding side effect， milder immunogenicity， and higher bioavailability when injected subcutaneously. In general， Hps， including LMWHs， are high complex drugs with large molecular weights （MWs）， inhomogeneous MW distributions， and structural heterogeneity， including different degrees and locations of sulfonation， and unique residues generated from different production processes. Thus， developing efficient analytical methods to elucidate the structures of Hps and characterize or quantitate their properties is extremely challenging. Unfortunately， this problem limits their quality control， production optimization， clinical safety monitoring， and new applications. Research has constantly sought to elucidate the complicated structures of Hp drugs. Among the structural analysis and quality control methods of Hp currently available， chromatographic methods are the most widely studied and used. However， no literature thoroughly summarizes the specific applications of chromatographic methods in the structural analysis， manufacturing process， and quality control of Hp drugs. This paper systematically organizes and describes recent research progresses of the chromatographic methods used to analyze Hp drugs， including the identification and composition of monosaccharides， disaccharides， oligosaccharides， and polysaccharides. The applications， innovations， and limitations of these chromatographic methods are also summarized in this review. The insights obtained in this study will help production and quality control personnel， as well as drug researchers， obtain a deeper understanding of the complex structures of Hp drugs. This paper also provides a comprehensive reference for the structural analysis and quality control of Hps， proposes ideas for the development of new quality control methods， and lays a strong foundation for the in-depth structural elucidation of Hp drugs.

Clinical Characteristics Associated With Higher Enoxaparin Dosing Requirements for Venous Thromboembolism Prophylaxis in Trauma Patients

INTRODUCTION

Enoxaparin dosed by an anti-Xa trough level is effective at reducing venous thromboembolism (VTE) in trauma patients. We identified the patient characteristics associated with higher enoxaparin dosing based on anti-Xa trough levels.

METHODS

A retrospective review was conducted on trauma patients admitted between August 2014 and February 2018 who received enoxaparin dosed by the anti-Xa trough level. Patients who received enoxaparin < 50 mg every 12 hours were compared to those who required ≥ 50 mg every 12 hours.

RESULTS

Of the 246 patients included, 32 (13.0%) required enoxaparin ≥ 50 mg every 12 hours to achieve the prophylactic trough level. Factors associated with a higher dose of enoxaparin were male (96.8% vs. 3.2%, P < .01), younger age (39.5 vs. 52.7 years, P < .01), higher creatinine clearance (CrCl) (125.9 vs. 93.7 mL/min, P < .01), higher body surface area (2 m² vs. 1.8 m², P < .01), and higher injury severity score (18.4 vs. 10.8, P < .01). Height, weight, and body mass index were not significant factors. On regression analysis, CrCl was the only independent predictor for higher enoxaparin dose. There was an increased deep venous thrombosis rate in the higher dose cohort (12.5% vs. 0, P < .01) but no significant differences in transfusion rates.

CONCLUSION

Trauma patients who require higher enoxaparin doses to achieve prophylactic anti-Xa trough levels have a higher CrCl. Patients with high CrCl may benefit from an initial higher dose of enoxaparin to achieve a target anti-Xa level in a shorter time interval to decrease VTE risk.

Clinical Feasibility of Monitoring Enoxaparin Anti-Xa Concentrations: Are We Getting It Right?

Background: Anti-Xa monitoring is utilized to measure the extent of anticoagulation in certain patient populations receiving enoxaparin. It is essential to accurately obtain this pharmacodynamic marker for safe and effective anticoagulation management. Objectives: To determine the frequency of correctly drawn anti-Xa concentrations in accordance with predefined institutional criteria and to determine the number of dose adjustments implemented based on incorrectly drawn anti-Xa concentrations. Methods: This was a retrospective, single-center, cohort study among adult patients who received treatment doses of enoxaparin with measured anti-Xa concentrations. Patients were excluded if they were pregnant, on hemodialysis, or received prophylactic dosing. Anti-Xa levels were defined as correctly measured if they were drawn 3 to 5 hours after the dose during steady state concentrations. Descriptive statistics were performed and analyzed via SPSS software. Results: Overall, 203 patients were reviewed and 59 patients with 74 anti-Xa levels were included. The majority of anti-Xa levels (57/74; 77%) were drawn incorrectly and often resulted in collection of repeat anti-Xa samples. There were 12 documented dose adjustments and approximately 42% (5/12) were based on incorrectly drawn anti-Xa levels. Anti-Xa levels were within target range approximately 45% of the time. Conclusions: Enoxaparin anti-Xa concentrations are frequently drawn incorrectly and dose adjustments are often performed based on these unsupported anti-Xa levels. This may present a potential risk to compromise patient safety.

Goal directed enoxaparin dosing provides superior chemoprophylaxis against deep vein thrombosis

INTRODUCTION

Optimal enoxaparin dosing for deep venous thrombosis (DVT) prophylaxis remains elusive. Prior research demonstrated that trauma patients at increased risk for DVT based upon Greenfield's risk assessment profile (RAP) have DVT rates of 10.8% despite prophylaxis. The aim of this study was to determine if goal directed prophylactic enoxaparin dosing to achieve anti-Xa levels of 0.3-0.5IU/ml would decrease DVT rates without increased complications.

MATERIALS AND METHODS

Retrospective review of trauma patients having received prophylactic enoxaparin and appropriately timed anti-Xa levels was performed. Dosage was adjusted to maintain an anti-Xa level of 0.3-0.5IU/ml. RAP was determined on each patient. A score of ≥5 was considered high risk for DVT. Sub-analysis was performed on patients who received duplex examinations subsequent to initiation of enoxaparin therapy to determine the incidence of DVT.

RESULTS

306 patients met inclusion criteria. Goal anti-Xa levels were met initially in only 46% of patients despite dosing of >40mg twice daily in 81% of patients; however, with titration, goal anti-Xa levels were achieved in an additional 109 patients (36%). An average enoxaparin dosage of 0.55mg/kg twice daily was required for adequacy. Bleeding complications were identified in five patients (1.6%) with three requiring intervention. There were no documented episodes of HIT. Subsequent duplex data was available in 197 patients with 90% having a RAP score >5. Overall, five DVTs (2.5%) were identified and all occurred in the high-risk group. All patients were asymptomatic at the time of diagnosis.

CONCLUSION

An increased anti-Xa range of 0.3-0.5IU/ml was attainable but frequently required titration of enoxaparin dosage. This produced a lower rate of DVT than previously published without increased complications.

No difference in bleeding risk between subcutaneous enoxaparin and heparin for thromboprophylaxis in end-stage renal disease

Enoxaparin, a low-molecular-weight form of heparin, is not approved for use in dialysis patients in the United States, because it is eliminated through the kidneys and could therefore accumulate and cause inadvertent bleeding. Accordingly, it is unknown if enoxaparin is as safe to prescribe as subcutaneous heparin for thromboprophylaxis in patients with chronic renal failure. Here we conducted a retrospective comparative effectiveness study in a large population of chronic maintenance dialysis patients initiated with subcutaneous injections of enoxaparin or heparin for thromboprophylaxis. The primary study end point was hospitalization or death related to bleeding, with a secondary end point of venous thromboembolism. Among 7721 dialysis patients started on subcutaneous enoxaparin or heparin at doses for thromboprophylaxis, the crude rate for bleeding requiring hospitalization or resulting in death was 15.2 (95% confidence interval (CI) 12.7-18.2) events per 100 patient-years in the enoxaparin group, which did not differ from the heparin group in which the crude rate was 16.2 (95% CI 14.0-18.7) events per 100 patient-years. In risk factor-adjusted Poisson models, enoxaparin was not associated with more bleeding in comparison to heparin (risk ratio, 0.98; 95% CI 0.78-1.23). The risk of venous thromboembolism was not associatively worse with enoxaparin (risk ratio, 0.77; 95% CI 0.49-1.22). Thus, in dialysis patients, daily enoxaparin for thromboprophylaxis was not associated with increased serious bleeding or less effective compared to subcutaneous heparin.

Are low-molecular-weight heparins appropriately dosed in patients with CKD stage 3 to 5?

The aims of this study were to determine the serum antifactor Xa levels in patients with impaired glomerular filtration receiving low-molecular-weight heparins (LMWHs), monitor efficacy and complications during treatment, and determine the approach to dose adjustments of LMWH by using antifactor Xa levels in different levels of kidney dysfunction in a real world clinical practice. Patients with chronic kidney disease who had subcutaneous enoxaparin administration during hospitalization were included in this study. We obtained data on patient demographics, glomerular filtration rate, bleeding complications, and antifactor Xa levels. Patients were divided into four groups based on glomerular filtration rate (>60 ml/min, 30-59 ml/min, 15-29 ml/min, <15 ml/min). Target levels for antifactor Xa were accepted as 0.1-0.4 IU/ml for prophylactic use and 0.4-1.1 IU/ml for therapeutic use. There were 61 patients and 18 controls (40 women, 39 men, mean age 68 ± 12 years) available for analysis. Interpretation of antifactor Xa with regard to target levels has shown that levels were in therapeutic range in 33 patients (41.8%), subtherapeutic range in 38 patients (48.1%), and supratherapeutic range in eight patients (10.1%). Less than half of the patients at each level of kidney dysfunction had antifactor Xa levels within the therapeutic range. Three patients suffered major bleeding, two with supratherapeutic, and one with therapeutic antifactor Xa level. There were no complications of ineffective anticoagulation in patients with subtherapeutic levels. Inappropriate dosing of LMWH suggested by subtherapeutic and supratherapeutic antifactor Xa levels were very high in patients with different levels of kidney dysfunction.

Enoxaparin versus unfractioned heparin as anticoagulant for continuous venovenous hemodialysis: a randomized open-label trial

AIM

In this study we aimed to compare the efficacy and safety of enoxaparin with unfractioned heparin (UFH) as anticoagulant for continuous venovenous hemodialysis (CVVHD).

METHODS

An open-label randomized controlled trial was carried out in an intensive care unit (ICU) where 40 patients with acute renal failure (ARF) who needed continuous renal replacement therapy were randomized to receive UFH (n=21) or enoxaparin (n=19). Coagulation parameters were evaluated, and antithrombotic activity of UFH was measured by activated partial thromboplastin time (aPTT) and for enoxaparin by anti-factor Xa activity. Primary outcomes were thrombosis of the extracorporeal circuit and bleeding, classified as major or minor.

RESULTS

Minor bleeding episodes were observed only in patients anticoagulated with enoxaparin (26 vs. 0%, p=0.018). Comparing patients with or without bleeding after 24 hours of therapy, the level of anticoagulation tended to be higher (anti-factor Xa: 1.62 vs. 1.13 IU/mL, p=0.09) and the platelet count to be lower [107+/-53 vs. 229+/-84 (x10(3)/microL), p=0.09] in patients who bled, but without statistical difference. Filter life span of enoxaparin and UFH groups was similar (43+/-15 vs. 52+/-18 hr, p=0.10), as well as the proportion of circuit clotting.

CONCLUSION

Weight-unadjusted enoxaparin in patients with ARF in CVVHD was associated with an increased rate of bleeding, a finding that addresses the need to adjust drug dose and to monitor anti-factor Xa activity during dialysis. No benefit to prolong dialysis circuit survival was found with enoxaparin. In patients who do not present contraindication for systemic anticoagulation, UFH remains an effective and low-cost option.

Heparin and low-molecular weight heparins in thrombosis and beyond

Heparin and its improved version, low-molecular weight heparin (LMWH), are known to exert polypharmacological effects at various levels. Early studies focused on the plasma anti-Xa and anti-IIa pharmacodynamics of different LMWHs. Other important pharmacodynamic parameters for heparin and LMWH, including effects on vascular tissue factor pathway inhibitor (TFPI) release, inhibition of inflammation through NFkappaB, inhibition of key matrix-degrading enzymes, selectin modulation, inhibition of platelet-cancer cell interactions, and inflammatory cell adhesion, help explain the diverse clinical impact of this class of agents in thrombosis and beyond.

Comparative Anticoagulant and Platelet Modulatory Effects of Enoxaparin and Sulodexide

Sulodexide represents a novel antithrombotic agent with multiple sites of action on blood coagulation and vascular processes. The purpose of this study was to compare sulodexide and enoxaparin on anticoagulant effects, tissue factor (TF)-induced activation of platelets, inhibition of microparticle generation and to investigate their effect on heparin-induced platelet aggregation (HIPA). Sulodexide was compared with enoxaparin at equigravimetric concentrations. When compared to enoxaparin, sulodexide produced a stronger anticoagulant effect in the prothrombin time (PT), activated partial thromboplastin time (APTT), Heptest, and thrombin time (TT) assays. In addition, sulodexide had a stronger inhibitory effect on TF-mediated microparticle generation (IC50 = 2.8 μg/ mL), P-selectin expression (IC50 = 4.8 μg/ml), and platelet aggregate formation (IC50 = 8.5 μg/mL) compared to higher IC50 values with enoxaparin. Sulodexide and enoxaparin exhibited a similar effect on heparin-induced thrombocytopenia (HIT) antibody-mediated platelet activation HIPA assays. These results suggest that sulodexide is a relatively stronger anticoagulant agent than enoxaparin. Sulodexide is subcutaneously absorbed. Its ability to inhibit TF-mediated platelet activation may contribute to the observed therapeutic effects of sulodexide in microvascular vasculopathy such as diabetic nephropathy. These results also suggest that inhibition of TF activation of platelets by sulodexide may be independent of its anticoagulant effects. These results warrant further investigation of sulodexide in additional preclinical and clinical studies.

Are all low molecular weight heparins equivalent in the management of venous thromboembolism?

Low molecular weight heparins are replacing unfractionated heparin in a number of clinical indications because of their improved subcutaneous bioavailability and more predictable antithrombotic response. Clinical trials have demonstrated that low molecular weight heparins are at least as safe and effective as unfractionated heparin for the initial treatment of venous thromboembolism, and unfractionated heparin and warfarin for primary and secondary thromboprophylaxis. The mechanism behind the antithrombotic action of low molecular weight heparins is not fully understood but is likely to involve inhibition of coagulation factors Xa and IIa (thrombin), release of tissue-factor-pathway inhibitor, and inhibition of thrombin activatable fibrinolytic inhibitor. Different low molecular weight heparins have been shown to have various effects on coagulation parameters. Seven low molecular weight heparins are currently marketed worldwide, each demonstrated distinct chemical entities with unique pharmacokinetic and pharmacodynamic profiles. Each low molecular weight heparin is approved for specific indications based on the available efficacy and safety data for that product. The relative efficacy and safety of the low molecular weight heparins are unclear because there have been very few direct comparisons in randomized clinical trials. While recommending low molecular weight heparins for the prevention and treatment of venous thromboembolism, clinical guidelines have not specified individual agents. National and international organizations recognize that low molecular weight heparins are distinct entities and that they should not be used interchangeably in clinical practice. Each low molecular weight heparin should be used at the recommended dose when efficacy and safety data exist for the condition being treated. When these data are not available, the dosing and administration of low molecular weight heparins must be adapted from existing data and recommendations.

Factors affecting the severity of spontaneous retroperitoneal hemorrhage in anticoagulated patients

BACKGROUND

Clinical manifestations of spontaneous retroperitoneal hemorrhage (SRH) range from a small decrease in hemoglobin to hypotension requiring transfer to the intensive care unit (ICU). Our goal was to identify which anticoagulated patients are at increased risk for SRH and its complications.

METHODS

We conducted a retrospective review of 180 patients with SRH. Age, sex, presence of comorbidities, hemoglobin decrease, transfusion requirement, ICU stay, and length of ICU stay were recorded. Patients were divided into 5 groups based on their anticoagulants: (1) heparin and Coumadin, (2) heparin only, (3) Coumadin only, (4) heparin +/- Coumadin and aspirin (ASA) +/- Plavix, and (5) other anticoagulants.

RESULTS

Group 4 patients were more likely to require ICU admission and have longer ICU stay compared to others (P = .021 & P < or = 0.0001, respectively, by Kruskall-Wallis test). Patients with coronary artery disease were more likely to require ICU admission (P = .01 by chi-square test).

CONCLUSIONS

Patients on combined anticoagulant-antiplatelet therapy are more likely to require ICU admission and longer ICU stay. Close observation is warranted in these patients for early detection of SRH.

Enoxaparin vs. unfractionated heparin for anticoagulation during continuous veno-venous hemofiltration: a randomized controlled crossover study

OBJECTIVE

The purpose of this study was to evaluate the efficacy and safety of the low molecular weight heparin enoxaparin as anticoagulant in continuous veno-venous hemofiltration (CVVH) compared with unfractionated heparin.

DESIGN

Prospective randomized controlled crossover study.

SETTING

Medical and Surgical Intensive Care Unit of a University Hospital.

PATIENTS

Forty consecutive adult medical and surgical ICU patients with normal anticoagulation parameters requiring CVVH.

INTERVENTION

CVVH was performed with pre-filter fluid replacement at 2500 ml/h and blood flow rates of 180 ml/min. Heparin-treated patients received an initial pre-filter bolus of 30 IU/kg and a maintenance infusion at 7 units/kg h(-1), titrated to achieve a systemic activated partial thromboplastin time (aPTT) of 40-45 s. Enoxaparin-treated patients received an initial pre-filter bolus of 0.15 mg/kg and a maintenance infusion starting at 0.05 mg/kg h(-1), which was subsequently adjusted to maintain systemic anti-factor Xa activity (anti-Xa) at 0.25-0.30 IU/ml. Each patient received both regimens in a crossover design. Maximum treatment duration for each set was 72 h.

RESULTS

Patients included had a mean APACHE II score of 22 (10-35). Thirty-seven patients completed both study arms. Mean filter life span was 21.7 h (+/- 16.9 h) for heparin and 30.6 h (+/- 25.3) for enoxaparin (p = 0.017, ANOVA for repeated measures). One major bleeding episode occurred during heparin as well as during enoxaparin treatment. Cost analysis showed average daily costs of 270 and 240 euro for heparin and enoxaparin, respectively.

CONCLUSION

Enoxaparin can be safely used for anticoagulation during CVVH resulting in higher filter lifespan compared with unfractionated heparin.

Percutaneous Arterial Embolization in the Management of Rectus Sheath Hematoma

OBJECTIVE

Spontaneous rectus sheath hematoma can become clinically relevant and necessitate hemostatic intervention. The aim of this study was to describe the efficacy of percutaneous arterial embolization in the management of this condition.

CONCLUSION

Selective transcatheter embolization is effective hemostatic treatment of patients with large, clinically relevant rectus sheath hematoma.

Epidemiology of venous thromboembolism in 9489 patients with malignant glioma

OBJECT

The authors sought to define the incidence of symptomatic venous thromboembolism (VTE) in patients harboring malignant gliomas.

METHODS

The authors conducted a retrospective analysis of data obtained in all cases of malignant glioma diagnosed in California during a 6-year period; the occurrence of a VTE was identified using linked hospital discharge data. The Cox proportional hazard model was used to analyze the association of specific risk factors with the development of a VTE or death within 2 years of the cancer diagnosis. Among 9489 cases, the 2-year cumulative incidence of VTE was 7.5% (715 cases), with a rate of 16.1 events per 100 person-years during the first 6 months. Three hundred ninety-one (55%) of these 715 cases were diagnosed within 61 days of major neurosurgery. Risk factors for VTE included older age (hazard ratio [HR] 2.6, confidence interval [CI] 2.0-3.4 for age range 65-74 years compared with < or = 45 years), glioblastoma multiforme histology (HR 1.7, CI 1.4-2.1), three or more chronic comorbidities (HR 3.5, CI 2.8-4.3 [compared with no comorbidity]), and neurosurgery within 61 days (HR 1.7, CI 1.3-2.3). Patients in whom a VTE was present were at higher risk of dying within 2 years (HR 1.3, CI 1.2-1.4). In a nested case-control analysis of all VTE cases, there was no association between insertion of a vena cava filter and the risk of a recurrent VTE.

CONCLUSIONS

In patients harboring a glioma there was a very high incidence of symptomatic VTEs, particularly within 2 months of neurosurgery. The development of a VTE was associated with a 30% increase in the risk of death within 2 years. Further studies are needed to determine if risk stratification and the use of medical prophylaxis after neurosurgery improves outcomes.

The role of low-molecular-weight heparins as supportive care therapy in cancer-associated thrombosis

Venous thromboembolism (VTE) is a common complication of malignant disease, affecting approximately 1 in 200 cancer patients. Oncology nurses are instrumental in identifying patients with cancer at high risk of venous thromboembolism. Risk factors include: stage of disease, chemotherapy, the patient's degree of immobility, a history of recent surgery, and the presence of a central venous catheter. The treatment of venous thromboembolism in patients with cancer usually involves a sequential combination of unfractionated heparin or low-molecular-weight heparin (LMWH), followed by oral warfarin or LMWH. LMWHs are an alternative to warfarin for secondary prophylaxis and long-term treatment. LMWH is given by subcutaneous injection, does not require hospitalization for administration or routine laboratory monitoring. Recent clinical trial results have shown that LMWH use is associated with improved survival in cancer patients with relatively good prognoses. Patients receiving any anticoagulant therapy should be monitored for signs of pulmonary embolism or bleeding and intravenous sites (if present) should be monitored for oozing. Appropriate patient selection, a carefully constructed treatment plan, extensive patient education, and regular patient contact are integral elements for the nursing care of patients with cancer-associated thrombosis treated in the outpatient setting.

Oral delivery of chemical conjugates of heparin and deoxycholic acid in aqueous formulation

INTRODUCTION

Heparin, one of the most potent anticoagulants widely used for the treatment and prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE), is currently available to patients only by parental administration. In this study, we propose a new oral delivery system of heparin by conjugating it with deoxycholic acid which reformulated by adding dimethyl sulfoxide to increase its bioavailability.

MATERIALS AND METHODS

The chemical conjugates (LMWH-DOCA) of low molecular weight heparin (4.5 kDa) with deoxycholic acid (DOCA) were synthesized by controlling the conjugation ratio. The absorption of LMWH-DOCA after its oral administration was measured by anti-FXa assay according to the conjugation ratio of DOCA, concentration of DMSO solution and dose of LMWH-DOCA, respectively. Furthermore, the incidences of mucosal damage by LMWH-DOCA in 10% DMSO solution were evaluated using H&E staining and SEM.

RESULTS

Three kinds of LMWH-DOCA were synthesized according to the DOCA conjugation ratios of LD1, LD2 and LD3, whose anticoagulant activities were 89, 86 and 85 IU/mg, respectively, and the activity of LMWH was 97 IU/mg. LMWH-DOCA was completely dissolved in 10% DMSO solution, and its bioavailability in the oral dose was significantly increased (17.6% for LD2 in 10% DMSO solution) without causing any damages in intestinal tissues.

CONCLUSIONS

The chemical conjugate of heparin and DOCA in the soluble state could be efficiently absorbed in the intestine. Therefore, we propose this system as a new strategy of oral heparin delivery for the treatment of patients who are at high risk to DVT and PE.

The Use of Central Neuraxial Techniques in Parturients with Factor V Leiden Mutation

The factor V Leiden (FVL) mutation is a leading cause of thrombosis, particularly during pregnancy. During pregnancy, women with thrombotic disorders including FVL are often considered candidates for antepartum anticoagulation with low molecular weight heparin. Pregnancy complications related to thrombosis and the unpredictable timing of labor cause unique challenges with regard to the provision of regional anesthesia. A patient with heterozygotic FVL presenting with thrombotic disease and a complicated anticoagulation status lead us to review 16 additional parturients with FVL. This report focuses on the anesthetic implications that arise in parturients with FVL. We recommend that anesthesiologists be made aware of FVL patients before their due date, anticoagulation with low molecular weight heparin should be transitioned to unfractionated heparin before the 38th gestational week, and multidisciplinary collaborative investigation and care should continue for this disorder.

Overuse of prothrombin and partial thromboplastin coagulation tests in medical inpatients

INTRODUCTION

In the monitoring of anticoagulant therapy, prothrombin time (PT) is used to measure the effect of warfarin, whereas the partial thromboplastin time (PTT) measures the therapeutic effect of unfractionated heparin. Low molecular weight heparin (LMWH) does not require routine monitoring.

OBJECTIVE

We collected data on the frequency of simultaneous PT and PTT requests, where only one or neither is indicated, and estimated the potential cost savings if ordering was appropriate.

METHODS

The study was performed at Nassau University Medical Center, a major teaching institution in East Meadow, New York. Inpatient charts were reviewed consecutively until 50 patients prescribed warfarin alone, intravenous heparin alone, or LMWH alone were selected. We then determined which coagulation tests were performed each day for these patients by review of their computerized laboratory results. The costs of laboratory tests were obtained from the hospital laboratory and were used to calculate potential savings.

RESULTS

PT and PTT coagulation tests were requested together in all 50 patients. Seventeen patients on LMWH alone had 30 sets of PT/PTT performed (60 tests). Seventeen patients on intravenous heparin had 87 PTs performed. Twelve patients on warfarin had 60 PTTs performed. In total, 232 unneeded PT or PTTs were ordered in these 50 patients, or 4.6 per patient during hospitalization.

CONCLUSION

The review of the records of 50 medical inpatients found that PT and PTT were invariably requested together, despite a lack of indication. The 50 patients incurred a total of $2434 in unneeded costs. If representative of common clinical practice, significant cost savings may be possible. Education, computerization, and information on costs of individual tests may reduce unneeded investigations.

Drug Insight: an overview of current anticoagulation therapy after heart valve replacement

Vitamin K antagonists, such as warfarin, are the gold standard approach for the long-term anticoagulant therapy of patients with mechanical heart valves. Management decisions are, however, based predominantly on expert consensus and on data from nonrandomized, follow-up studies, which have inherent limitations in their methods. Low-intensity anticoagulation therapy provides protection against thromboembolic complications in patients with most types of modern prosthetic heart valve. The addition of low-dose aspirin is safe if international normalized ratio values below 3.5 are maintained. A combined regimen should be considered in high-risk patients and those with coexistent coronary artery or cerebrovascular disease, and in patients who have suffered a thromboembolic event despite a therapeutic international normalized ratio. Thromboprophylaxis with unfractionated or low-molecular-weight heparins is restricted to specific situations, such as when a patient is intolerant to vitamin K antagonists, when surgical procedures require discontinuation of oral anticoagulation, or when the patient is pregnant. A lack of uniformity across practice guidelines make it difficult to reach treatment decisions. Each patient's preference, expressed after counseling about the risks and benefits of each treatment strategy, and an individual assessment of the patient's risk factors, should guide treatment decisions. At present, new anticoagulant agents such as factor Xa inhibitors do not represent a treatment option for heart valve recipients.

Optimal Dose of Enoxaparin in Critically Ill Trauma and Surgical Patients

BACKGROUND

Low-molecular-weight heparin is effective for prevention of venous thromboembolism. The efficacy of daily dosing in critically ill patients is unknown.

METHODS

Seventeen critically ill patients on 40 mg of enoxaparin subcutaneously daily were studied. Anti-Xa activity was measured 4 hours after the third dose and before the fourth dose. Adverse events were recorded.

RESULTS

Mean peak anti-Xa activity was 0.19 +/- 0.09 International Units/mL and mean trough was 0.044 +/- 0.04 International Units/mL. The recommended target range is 0.1 to 0.2 International Units/mL. The trough was below therapeutic levels in all but two patients. One thrombosis occurred in a patient despite a therapeutic trough.

CONCLUSION

Daily dosing of enoxaparin is inadequate for critically ill patients and should be abandoned. Further studies using twice daily dosing are needed. Patients with renal insufficiency may require an increased interval of administration (daily dosing). Anti-Xa levels may not correlate with the risk of thromboembolic complications. Patients with renal insufficiency and morbid obesity may require alternative dosing and monitoring of anti-Xa levels.

Endovascular Embolization of Spontaneous Retroperitoneal Hemorrhage Secondary to Anticoagulant Treatment

The purpose of this study was to report a single hospital's experience of endovascular treatment of patients with retroperitoneal hemorrhage (RPH) secondary to anticoagulant treatment. Ten consecutive patients treated in an intensive care unit and needing blood transfusions due to RPH secondary to anticoagulation were referred for digital subtraction angiography (DSA) to detect the bleeding site(s) and to evaluate the possibilities of treating them by transcatheter embolization. DSA revealed bleeding site(s) in all 10 patients: 1 lumbar artery in 4 patients, 1 branch of internal iliac artery in 3 patients and multiple bleeding sites in 3 patients. Embolization could be performed in 9 of them. Coils, gelatin and/or polyvinyl alcohol were used as embolic agents. Bleeding stopped or markedly decreased after embolization in 8 of the 9 (89%) patients. Four patients were operated on prior to embolization, but surgery failed to control the bleeding in any of these cases. Abdominal compartment syndrome requiring surgical or radiological intervention after embolization developed in 5 patients. One patient died, and 2 had sequelae due to RPH. All 7 patients whose bleeding stopped after embolization had a good clinical outcome. Embolization seems to be an effective and safe method to control the bleeding in patients with RPH secondary to anticoagulant treatment when conservative treatment is insufficient.

Delayed cutaneous reactions to heparin in antiphospholipid syndrome during pregnancy

BACKGROUND

Clinical symptoms related to antiphospholipid antibodies often first occur during pregnancy with the diagnosis of antiphospholipid syndrome (APS). Unfractionated heparin (UFH) and low-dose aspirin are considered as first-line treatments for pregnant women with APS and recurrent fetal loss. However, in addition to an increased incidence of hemorrhagic side-effects and thrombocytopenia there are a number of drug eruptions with cutaneous components secondary to the use of UFH. One of these eruptions has been classified as a delayed type I.V. hypersensitivity reactions at the sites of UFH injections. The majority of these reactions occur in pregnant women.

METHOD

We present three pregnant patients who developed delayed hypersensitivity reactions at the sites of UFH injections. Two patients had documented APS and the other patient had two previous spontaneous abortions.

RESULTS

The histopathologic and immunohistochemical findings in the biopsy specimens from the sites of the delayed reactions were distinctive. The inflammatory infiltrate contained CD3+ and CD4+ lymphoid cells with plasma cells, and eosinophils. There was a marked increased in mast cells with increased stromal cells within the dermis and increased vascular proliferation.

CONCLUSIONS

The distinctive histopathologic and immunohistochemical features seen in the delayed hypersensitivity reactions at the sites of UFH injections may be modulated by the immunomodulatory effects of UFH as well as the hormonal levels and cytokine patterns during pregnancy. Alternative therapies may not always be successful in resolving the reactions.

The use of enoxaparin in children with acute, nonhemorrhagic ischemic stroke

The use of low-molecular-weight heparin offers multiple advantages over unfractionated heparins in pediatric patients with acute ischemic stroke. The safety and efficacy of low-molecular-weight heparin have been demonstrated in adults, but less is known about their use in children. This study reviews retrospectively the use of low-molecular-weight heparin in children with acute, ischemic, nonhemorrhagic strokes. A database search was used to locate all children who experienced an ischemic stroke between July 1991 and January 2001 and who were subsequently treated with low-molecular-weight heparin. Eight children were identified (aged 37 months to 17 years; median age, 133 months) who were treated with the low-molecular-weight heparin enoxaparin. Enoxaparin was used in one case as the sole treatment, in six cases as a bridge to oral anticoagulant therapy with warfarin, and in one case as a replacement treatment after several days of warfarin therapy. The median duration of treatment with enoxaparin was 4 days. During this period, no major bleeding complications were observed, and no new thrombi or extensions of thrombi occurred. One patient did experience mild oozing at an intravenous site, and another experienced an episode of epistaxis. Enoxaparin was discontinued in one patient because of discomfort associated with the subcutaneous injections. Although the number of patients was limited, it appears that enoxaparin is a safe and efficacious alternative to the use of unfractionated heparin in children with acute, nonhemorrhagic ischemic stroke.

Randomized, pilot study of intermittent pneumatic compression devices plus dalteparin versus intermittent pneumatic compression devices plus heparin for prevention of venous thromboembolism in patients undergoing craniotomy

BACKGROUND

Unfractionated heparin and the low molecular weight heparin, dalteparin, are used for prophylaxis against venous thromboembolism in patients undergoing craniotomy. These drugs were compared in a randomized, prospective pilot study comparing intermittent pneumatic compression devices plus dalteparin to intermittent pneumatic compression devices plus heparin.

METHODS

One hundred patients undergoing craniotomy were randomly allocated to receive perioperative prophylaxis with subcutaneous (SC heparin, 5000 units every 12 hours, or dalteparin, 2,500 units once a day, begun at induction of anesthesia and continued for 7 days or until the patient was ambulating. Entry criteria were age over 18 years, no deep vein thrombosis (DVT) preoperatively as judged by lower limb duplex ultrasound and no clinical evidence of pulmonary embolism preoperatively. Patients with hypersensitivity to heparin, penetrating head injury or who refused informed consent were excluded. Patients underwent a duplex study 1 week after surgery and 1 month clinical follow-up. All patients were treated with lower limb intermittent pneumatic compression devices.

RESULTS

There were no differences between groups in age, gender, and risk factors for venous thromboembolism. There were no differences between groups in intraoperative blood loss, transfusion requirements or postoperative platelet counts. Two patients receiving dalteparin developed DVT (one symptomatic and one asymptomatic). No patient treated with heparin developed DVT and no patient in either group developed pulmonary embolism. There were two hemorrhages that did not require repeat craniotomy in patients receiving dalteparin and one that did require surgical evacuation in a patient treated with heparin. Drug was stopped in two patients treated with dalteparin because of thrombocytopenia. None of these differences were statistically significant.

CONCLUSION

There was no significant difference in postoperative hemorrhage, venous thromboembolism or thrombocytopenia between heparin and dalteparin. The results suggest that, given the small sample size of this trial, both drugs appear to be safe and the incidence of venous thromboembolism by postoperative screening duplex ultrasound appears to be low when these agents are used in combination with intermittent pneumatic compression devices.

Heparin, low-molecular-weight heparins, and heparin pentasaccharide: basic and clinical differentiation

As a result of advanced technology, dramatic developments in the area of new anticoagulant and antithrombotic drugs appear to have made a profound impact on the use of LMWHs. Furthermore, because porcine mucosal heparin is used for the preparation of these agents, it is likely that alternative drugs with comparable pharmacologic and clinical efficacy are sought. Antithrombin drugs such as argatroban and hirudin are already approved for alternative management of heparin-compromised patients. Their efficacy in other indications is less superior. The development of specific anti-Xa drugs is slow. Although these agents may inhibit factor Xa and thrombin generation, none of them are capable of mimicking the polytherapeutic effects of LMWHs and thus can only be given in drug combinations. Synthetic and recombinant protein-derived anti-tissue factor agents have also been developed. These drugs only inhibit the tissue factor-mediated process and are limited in their therapeutic spectrum. Plasma-derived and recombinant serine protease inhibitors (serpins) are also available for the management of thrombotic and inflammatory disorders, but these agents cannot be given subcutaneously. Furthermore, because they are proteins, antibodies to these agents are generated. Nucleic acid derivatives (natural and synthetic aptomers) are developed for intravenous administration, but they are relatively weak antithrombotic agents. Dermatans, heparans, and chondroitin sulfates represent nonheparin GAGs, and, in mono-compositional and polycompositional form, these drugs are mainly used for the intravenous management of DVT prophylaxis. They can be given to patients who are heparin compromised. Synthetic heparinomimetics include heparin consensus-binding oligosaccharides and synthetic oligosaccharides with non-serpin affinity. In addition, binding oligosaccharides are conjugated with antithrombin agents to mimic the anti-Xa/anti-IIa activities of heparin. Biotechnology using bacterial and yeast cultures, aqua cultures for marine products, and plant carbohydrates have been the focus of developing heparin analogues. Development of these agents is in the early phase; however, it is likely that this approach may provide a reasonable alternative to LMWHs. Despite these developments, it is unlikely that any of these drugs will have a profound impact on the use of LMWHs in the near future. Unfractionated heparin and LMWHs collectively represent an important group of polypharmacologic drugs without which the management of thrombosis and vascular disorders would not be possible. The continual development of LMWHs in expanded indications did not comprise the use of unfractionated heparin in surgical and interventional cardiovascular indications. Ever since their introduction in the 1980s, the use of LMWHs has continually increased. This is primarily because of expanded indications and growing awareness among the clinicians. It is likely that once an antidote is developed and additional information is available on the mechanism of action of LMWHs, these drugs may gradualty be used for surgery patients. Despite these developments, it is likely that unfractionated heparin will continue to be used for specific indications. Drug combinations with heparins may necessitate dose adjustments, but it is unclear whether unilateral reduction of heparins will be optimal. The coming years will provide useful clinical and applied data on the improved use of unfractionated heparin. LMWHs, and pentasaccharide in the management of thrombotic and cardiovascular disorders. In addition, use of these drugs will be extended to many conditions, including cancer, inflammation, sepsis, and autoimmune diseases. Polytherapeutic approaches emphasizing LMWHs as primary and secondary drugs will also have an impact on the management of thrombotic and nonthrombotic disorders. Ultra-LMWHs and synthetic heparinomimetics, such as fondaparinux, that exhibit a narrow pharmacologic spectrum will only be useful in specific indications and in combination with other drugs.

Spontaneous splenic rupture following the administration of intravenous heparin: case report and retrospective case review

We report the case of a 40-year-old African-American female who presented to the Emergency Department with unstable angina. The patient, who had multiple risk factors for coronary artery disease, was admitted to the coronary care unit for cardiac work-up and management. Shortly after the intravenous administration of unfractionated heparin, she suffered the acute onset of upper abdominal pain and shock. A CT scan of the abdomen revealed splenic rupture with hemoperitoneum. The patient, who was managed surgically, had complete recovery before discharge. A review of systems and medical records revealed no obvious risk factors or other potential etiology for this rupture. We herein provide the characteristics of this rarely documented causal relationship between heparin and spontaneous splenic rupture and retrospectively review similar cases in the literature.

The low molecular weight heparin, tinzaparin, in thrombosis and beyond

Standard unfractionated heparin (UFH) has been in clinical use for over 50 years. The commercial use of low molecular weight heparins (LMWHs) began in the mid 1980s for hemodialysis and the prophylaxis of deep vein thrombosis (DVT). Initially, the clinical development of LMWHs was concentrated on the European continent. Subsequently, LMWHs were introduced in North America as well. In the initial stages of development of these drugs only nadroparin, dalteparin and enoxaparin were used. Subsequently, several other LMWHs such as ardeparin, tinzaparin, reviparin and parnaparin were introduced. LMWHs constitute a group of important medications with total sales reaching nearly 2.5 billion dollars with expanded indications reaching far beyond the initial indications for the prophylaxis of post-surgical DVT. This review highlights the pharmacology of tinzaparin. Unlike other LMWHs, tinzaparin is prepared by enzymatic hydrolysis with heparinase, while various chemical depolymerization methods are used for the synthesis of other LMWHs. As compared with the standard heparin, LMWHs have different pharmacodynamic, and pharmacokinetic properties; they also differ in clinical benefits.

Retroperitoneal haematoma associated with low molecular weight heparin

Enoxaparin (a low molecular weight heparin) has been used extensively for its antithrombotic properties. Complications of its haemorrhagic side-effects have previously been described. We report two cases of extensive retroperitoneal haematoma requiring blood transfusion and inotropic support. One patient developed acute renal failure and did not respond to intensive resuscitative efforts.

Coagulation status using thromboelastography in patients receiving warfarin prophylaxis and epidural analgesia

To determine the coagulation status of patients receiving postoperative warfarin and epidural analgesia using thromboelastography (TEG(R)).Prospective, observational, clinical study.Orthopedic postoperative division at a university hospital.52 ASA physical status II and III patients undergoing knee arthroplasty and receiving prophylactic warfarin and epidural analgesia.Patients' preoperative and postoperative coagulation status was determined by TEG(R). Daily TEG(R) parameters were obtained until the epidural catheter was removed. TEG(R) parameters include reaction time (R-time or time until the first significant levels of detectable clot formation), K-time (clot firmness), maximum amplitude (MA-clot strength), alpha angle (clot development), and coagulation index (overall coagulation). In addition, daily international normalized ratios (INRs) were obtained as per our routine practice. On the day of catheter removal reaction time was significantly increased compared with preoperative values (p < 0.0001), but it remained within normal ranges. There was no change in the coagulation index. However, INR was abnormal and significantly increased (INR = 1.48+/-0.3; p < 0.0001), compared with preoperative values, on the day when the epidural catheter was removed. When the epidural catheters are removed, overall coagulation status, as measured by TEG(R), and despite an elevated INR (mean INR <1.5), remained within normal limits in patients receiving low-dose warfarin prophylaxis.

The use of low-molecular-weight heparins in outpatient oral surgery for patients receiving anticoagulation therapy

BACKGROUND

When planning oral surgery, dentists occasionally will have patients who first need to have their anticoagulation regimen altered. To minimize the side effects and not adversely affect the patient's health, therapeutic anticoagulation should be interrupted for as short a time as possible. Low-molecular-weight heparins, or LMWHs, recently have emerged as an alternative in the management of patients whose anticoagulant status should not be modified for lengthy periods.

CASE DESCRIPTION

A 72-year-old man, who had a history of deep venous thrombosis, needed to have 19 teeth extracted and an alveoloplasty performed. An LMWH was substituted for warfarin a few days before surgery, and it was withheld from the patient for only a few hours the day of the surgery.

CLINICAL IMPLICATIONS

LMWHs are administered on an outpatient basis and do not require hospitalization, as does unfractionated heparin. As a result, they are more cost-effective and offer greater convenience than heparin therapy. Depending on the procedure and the degree to which patients are medically compromised, dentists may not feel comfortable treating patients who continuously receive anticoagulation therapy. As a result, patients' physicians may prescribe LMWH injections to be administered by patients, family members or caregivers to more safely manage the patients' care during oral surgery. As part of the health care team, dentists must be familiar with LMWH and its use to help guide patients safely through treatment.

Treatment of venous thromboembolism

Venous thromboembolism (VTE), comprised of pulmonary embolism (PE) and deep vein thrombosis (DVT), is a disease entity with a significant morbidity and mortality. Anticoagulation, initially with intravenous heparin and followed with long term warfarin treatment is the traditional therapy for VTE. Low molecular weight heparin, (LMWH) has a greater bioavailability than unfractionated heparin and can be administered subcutaneously. LMWH has resulted in shorter hospitalizations, reduced inicidents of major bleeding complications, and has moved the treatment of VTE for selected patients to the out-patient setting. Thrombolytic therapy has been recommended in patients with life threatening PE such as those with right ventricular dysfunction or hypotension. There are advances in the technology for clot removal with catheter embolectomy and clot fragmentation. Inferior vena cava filters can be place percutaneously in patients who are at high risk for VTE or those in whom anticoagulation is contraindicated. Since VTE is often asymptomatic, prevention is the most effective means to reduce morbidity and mortality.

Low-molecular-weight heparin for the treatment of patients with mechanical heart valves

BACKGROUND

The interruption of oral anticoagulant (OAC) administration is sometimes indicated in patients with mechanical heart valves, mainly before noncardiac surgery, non-surgical interventions, and pregnancy. Unfractionated heparin (UH) is currently the substitute for selected patients. Low-molecular-weight heparin (LMWH) offers theoretical advantages over UH, but is not currently considered in clinical guidelines as an alternative to UH in patients with prosthetic valves.

HYPOTHESIS

The aim of the present study was to review the data accumulated so far on the use of LMWH in this patient population and to discuss its applicability in common practice.

METHODS

For this paper, the current medical literature on LMWH in patients with mechanical heart valves was extensively reviewed.

RESULTS

There were eight series and six case reports. None of the studies was randomized, and only one was prospective. Data to establish the thromboembolic risk were incomplete. After excluding case reports, the following groups were constructed: (a) short-term administration, after valve insertion (n = 212); (b) short-term, perioperative (noncardiac)/periprocedural (n = 114); (c) long-term, due to intolerance to OAC (n = 16); (d) long-term, in pregnancy (n = 10). The incidence rate of thromboembolism was 0.9% for all the studies and 0.5, 0, 20, and 0% in groups a, b, c, and d, respectively; for hemorrhage, the overall rate was 3.4% (3.8, 2.6, 10, and 0% for the respective groups).

CONCLUSIONS

In patients with mechanical heart valves, short-term LMWH therapy compares favorably with UH. Data on mid- and long-term LMWH administration in these patients are sparse. Further randomized studies are needed to confirm the safety and precise indications for the use of LMWH in patients with mechanical heart valves.

Medical management of patients with brain tumors

The most common medical problems in brain tumor patients involve the management of seizures, peritumoral edema, medication side effects, and venous thromboembolism. Despite the importance of these issues, there are very few studies specifically addressing them. Nonetheless, there has been some progress in recent years. There is increasing evidence that brain tumor patients who have not had a seizure do not benefit from prophylactic antiepileptic medications. Patients taking corticosteroids are at greater risk of Pneumocystis carinii pneumonia and may benefit from prophylactic therapy. There is also growing evidence suggesting that anticoagulation may be more effective than inferior vena cava filtration devices for treating venous thromboembolism in brain tumor patients and that the risk of hemorrhage with anticoagulation is relatively small.

Atherothrombosis: plaque instability and thrombogenesis

Hemostasis involves a carefully regulated balance between circulating and endothelium-derived prothrombotic and antithrombotic factors. The unstable or vulnerable plaque facilitates thrombosis, clinically manifest as an acute coronary syndrome (ACS), by creating an environment that favors thrombus formation over prevention of lysis. Endothelial cell dysfunction is integral to both the development of the atherosclerotic lesion as well as its destabilization. The transformation of a stable plaque to an unstable one involves complex interactions among T lymphocytes, macrophages, endothelial cells, and smooth muscle cells. Degradation of the fibrous cap of the atherosclerotic lesion as well as the overexpression of prothrombotic and underexpression of antithrombotic factors by cells within the plaque precede thrombus formation. Accordingly, pharmacological interventions for the treatment of ACS are directed against the initiation and propagation of thrombosis, as well as toward improvement of endothelial function.

Acute respiratory failure in critically ill patients with cancer. Diagnosis and management

Respiratory failure remains a common cause of admission to the ICU for patients with cancer, regardless of the nature of malignancy. The diagnosis and management of ARF in patients with cancer poses special challenges to the intensivist. Depending on the type of cancer, the degree of immunosuppression, underlying comorbidities, the modality of cancer treatment, progression or spread of underlying cancer, and disease- or therapy-associated complications are the most common causes of ARF in these patients. Despite significant advances in antineoplastic therapies and supportive management in the ICU, the mortality rate of patients with cancer with ARF remains high. Severity-of-illness scoring systems and mortality probability models, although useful in discriminating between survivors and nonsurvivors in large groups of critically ill patients, should not be used alone to justify reluctance in admitting individual patients with cancer with potentially reversible respiratory failure to the ICU. Close collaboration between oncologists and intensivists will ensure the establishment of clear goals and direction of treatment for every patient with cancer who requires mechanical ventilation.

Bleeding and thrombotic complications in critically ill patients with cancer

Alterations in hemostasis are common in patients with cancer admitted to the ICU. Depending on the underlying disease and specific hemostatic abnormality, the patient with cancer may develop bleeding, thrombosis, or both, such as DIC. Bleeding complications usually result from abnormalities in platelets or deficiency of coagulation factors and require specific blood or coagulation factor replacement. Similarly, critically ill patients with cancer are predisposed to thrombotic complications such as DVT, PE, and central vein thrombosis, the last as a result of the widespread use of long-term indwelling catheter devices. Advances in diagnostic imaging and the availability of newer and more potent anticoagulant agents have facilitated the care of these patients greatly. Ultimately, it is hoped that a thorough understanding of the various disturbances in hemostasis, innovative treatment approaches, and implementation of preventive strategies in patients with cancer will lead to decreased morbidity and improved survival rates of critically ill patients with cancer in the ICU.

Pharmacology department

Traditionally administered unfractionated heparin (UH) is a heterogeneous mixture of polysaccharide chains of varying length. Heparin is now available in new formulations, most notably the low-molecular-weight heparins (LMWHs), which possess pharmacology that is similar to but distinct from UH. Key advantages of LMWHs include improved bioavailability and longer half-life, more predictable anticoagulation that requires less laboratory monitoring, and fewer serious side effects. The article reviews the pharmacology of heparin and discusses the addition of LMWHs to the family of anticoagulant drugs.

Interventional therapy for pulmonary embolism

Venous thromboembolism is a common cause of death. Acute massive pulmonary embolism (PE) is life-threatening and may require vigorous more invasive treatment. Several risk factors are related to increased incidence of massive PE. Anticoagulation is the most traditional treatment for PE but may not suffice in cases of massive PE. Systemic thrombolytic therapy, catheter-directed thrombolysis, percutaneous embolectomy, and more recently, percutaneous thrombus fragmentation techniques with a multitude of devices are now available to treat the most severe cases of massive PE. Successful treatment of PE includes implementation of a treatment protocol and the use of associated techniques and devices.

Dosing and monitoring of low-molecular-weight heparins in special populations

As a result of numerous clinical trials and meta-analyses supporting the superior efficacy and relative safety of low-molecular-weight heparins (LMWHs) compared with unfractionated heparin (UFH), LMWHs are emerging as the antithrombotic agents of choice for the prevention and treatment of deep vein thrombosis and pulmonary embolism. In addition, data indicate that enoxaparin given with low-dosage aspirin is more effective than UFH in treating acute coronary syndromes. Anti-Xa activity can be used as a biologic marker of LMWH activity. Because of the more predictable anticoagulant response to subcutaneous administration of LMWHs compared with UFH, routine monitoring of anti-Xa activity in clinically stable adults with uncomplicated disease is not recommended. Because the optimal dosage of LMWHs has not been established for patients with renal insufficiency or extremes of body weight, during pregnancy, or for children, anti-Xa activity monitoring may be warranted in these subsets.

New antithrombotics for the intensive care unit setting: GP IIb/IIIa inhibitors, low-molecular-weight heparins, and direct thrombin inhibitors

Thromboembolic disease (TED) is a frequent problem encountered by clinicians in the intensive care unit (ICU). Traditionally, unfractionated heparin (UFH) has been used in the treatment and prophylaxis of TED. However, newer antithrombotic agents have evolved as effective alternatives to UFH. Low-molecular-weight heparins are effective for both the treatment and prophylaxis of TED. Lepirudin is useful for patients with TED and a history of heparin-induced thrombocytopenia. The platelet glycoprotein IIb/IIIa inhibitors are synergistic with UFH for the treatment of acute coronary syndromes and percutaneous coronary interventions (PCI). Several drugs are now available to clinicians for the treatment and prophylaxis of TED.