BACKGROUND

Procoagulant activity and oxidative stress generated by balloon injury to normal vessels promote the migration of medial smooth muscle cells and their proliferation in the intima. We hypothesised that administering levo N-acetyl-cysteine (NAC) i.v. at the time of injury, and s.c. before and after injury would reduce neointimal formation 4 weeks later and would regulate procoagulant activity in vessels with neointima undergoing ballooning a second time.

RESULTS

at the time of injury rabbits received: NAC, unfractionated heparin (HEP) or both (NAC + HEP). Neointimal thickening at 28 days, calculated as the ratio between the intimal and medial area, was attenuated after NAC, HEP and NAC+HEP by 39%, 30% and 47% respectively when compared to untreated injured animals (CONTROLS) (p <0.05). At 28 days, bound thrombin activity and platelet adhesion 1 h after a repeated balloon injury decreased in animals receiving NAC, HEP and NAC+HEP bv 54%, 63% and 64% for thrombin activity (p <0.05 vs CONTROLS), and by 56%, 66% and 75% respectively for 111Indium-platelet deposition (p <0.05 vs CONTROLS).

CONCLUSIONS

NAC in-vivo was effective in reducing neointimal thickening and procoagulant response after balloon injury.

BACKGROUND

Patients with heparin-induced thrombocytopenia type II require an alternative to standard heparin anticoagulation. However, in patients with renal impairment, anticoagulation during cardiopulmonary bypass with agents such as danaparoid sodium or r-hirudin are associated with hemorrhage. Anticoagulation with unfractionated heparins combined with prostacyclin, a potent platelet aggregation inhibitor, is associated with severe hypotension. The authors investigated a new concept using unfractionated heparins after platelet inhibition with the short-acting platelet glycoprotein IIb-IIIa antagonist tirofiban.

METHODS

Ten patients with heparin-induced thrombocytopenia type II and renal impairment were enrolled in the investigation. All had heparin-induced thrombocytopenia type II antibodies present as proved by the heparin-induced platelet aggregation assay, the heparin-platelet factor 4 enzyme-linked immunosorbent assay, or both. In all patients, preoperative anticoagulation to an activated partial thromboplastin time of 40-60 s was performed with r-hirudin. Anticoagulation during cardiopulmonary bypass was achieved with a bolus of 400 IU/kg unfractionated heparins after a bolus of tirofiban 10 microg/kg followed by an infusion of tirofiban at a rate of 0.15 microg x kg(-1) x min(-1) until 1 h before conclusion of cardiopulmonary bypass. Additional unfractionated heparins were only administered if activated clotting time decreased below 480 s. Coagulation was monitored by a abciximab-modified TEG and the adenosine diphosphate-stimulated (20 microm) platelet aggregometry. D-dimer concentrations, as a marker of venous thromboembolism, were measured before and 12, 24, and 48 h after surgery. Postoperative antithrombotic therapy was started immediately with r-hirudin to anticoagulation to an activated partial thromboplastin time of 40-60 s.

RESULTS

The postoperative blood loss ranged from 110 to 520 ml. No patient needed reexploration. In no patient was there clinical evidence of thrombosis or embolism in the postoperative period or of a critical increase of the D-dimer concentrations, suggesting venous thromboembolism. Transfusion of platelets was necessary in only two patients.

CONCLUSIONS

The protocol is easy to perform and no increased postoperative bleeding and no thromboembolic complications occurred. The combination of unfractionated heparins and tirofiban may be an alternative to other anticoagulation strategies in patients with heparin-induced thrombocytopenia.

OBJECTIVE

To perform an evaluation from the societal perspective of the cost of treatment with enoxaparin sodium versus unfractionated heparin (UFH) in patients with unstable angina and non-Q wave myocardial infarction in France.

METHODS

Four complementary cost-minimisation analyses based on the results of the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q wave Coronary Events (ESSENCE) international trial were conducted. We assessed differences in medical resource consumption and in duration of hospital stay in the whole study population (n = 3171) and for the French patients (n = 133).

RESULTS

Results were consistent for the study group as a whole and for the French subgroup. Among patients treated with enoxaparin sodium, there was a statistically significant reduction in the use of angiography and percutaneous transluminal coronary angioplasty (whole group study: p = 0.024 and 0.006, respectively) and a trend towards shorter lengths of hospital stay. The differences in angiography and angioplasty rates led to estimated average net cost savings with enoxaparin sodium of French Francs (FF)1555 per treated patient (whole study population) and FF9993 (French subgroup) [1996 values]. The analyses based on the duration of hospital stay resulted in estimated net cost savings with enoxaparin sodium of between FF1014 per treated patient (whole study population) and FF2804 (French subgroup).

CONCLUSIONS

Our study confirmed earlier results which show that enoxaparin sodium is cost saving in the treatment of unstable angina.

BACKGROUND

Few reports have addressed how current practice reflects uncertainty as to the optimal management of renal replacement therapy (RRT) in Western countries. Current dialytic practice for 2007 in the northwest of Italy was assessed.

METHODS

A total of 24 nephrology and dialysis centers covering all of the RRT provided in the intensive care units (ICUs) in northwest Italy took part in the survey. Consultant nephrologists of each center reported their own activities throughout the year 2007 by an e-mailed questionnaire.

RESULTS

RRT for a total of 7,842 days was provided by 24 dialysis centers in 79 ICUs for 1,118 patients. RRT median duration (5.76 days/patient) increased with the increasing number of hospital ICU beds. Of the RRT cases, 69.9% were due to acute kidney injury, 23.6% for continuation of a treatment in chronic dialysis patients and 4.2% for extrarenal indications. More than 90% of the patients were treated with high permeability membranes, at a median target dosage of 35.0 ml/kg per hour in continuous (39.4%) or extended modality (6-14 hours, 38.5%). Unfractionated heparin was the most common anticoagulant used (67.5%, median 500 IU/hour). In patients at high risk of bleeding, RRT without or with heparin at low-dose + saline flushes was the most commonly adopted line of treatment, followed by citrate (18% of days of dialysis). The decision to start RRT was made by nephrologists alone or in collaboration with intensivists, whereas dose prescriptions were given by nephrologists alone.

CONCLUSIONS

This survey may represent a useful starting point for further research into changes in RRT practice and the adoption of common, shared protocols.

Aerosolized unfractionated heparin GM1060 significantly inhibited allergen-induced eosinophil infiltration into the airways of guinea-pigs (as assessed both histologically and by bronchoalveolar lavage, or BAL) at doses of 160 and 1600 U/ml. Similarly aerosolized unfractionated heparin, Multiparin was effective at reducing eosinophil levels in the BAL fluid at 1000, 2000 and 5000 U/ml, but this reduction was statistically significant only at the highest dose used. Additionally, Fragmin (a low molecular weight heparin) significantly inhibited allergen-induced eosinophil infiltration into BAL fluid at a dose of 500 U/ml, an effect that was lost at the higher doses of 1000 and 2000 U/ml. Allergen-induced eosinophil infiltration was unaffected by dermatan sulphate. However, the glycosaminoglycans chondroitin sulphate A, chondroitin sulphate C and heparan sulphate were able to influence the extent of allergen-induced eosinophil infiltration into BAL fluid. These results suggest that heparin and some related glycosaminoglycans can inhibit allergen-induced eosinophil infiltration when administered directly to the airways.

The aim of this study was to assess the efficacy of enoxaparin for prevention of radial artery (RA) occlusion after transradial access for diagnostic and interventional cardiac procedures. RA occlusion is a potential complication of transradial cardiac catheterization. Conventionally, unfractionated heparin is used for prevention of RA occlusion. Effectiveness of low molecular weight heparins for prevention of this complication has not been tested before. Fifty transradial catheterizations were performed for diagnostic and/or interventional cardiac procedures in 39 patients. All the patients received 60 mg enoxaparin through the radial sheath at the beginning of the procedure for prevention of RA occlusion. RA patency was evaluated by Doppler examination. Patients were assessed for postprocedural RA occlusion at discharge and 5.5 +/- 2.8 days follow-up. RA occlusion was detected after 2 of the 50 transradial accesses, yielding a RA occlusion rate of % 4. In this study we found a low rate of RA occlusion with use of enoxaparin during transradial access. Enoxaparin is safe and effective in transradial procedures with a RA occlusion rate comparable to use of unfractionated heparin.

Here we report results from the analyses by enzymatic digestion and reversed-phase ion-pairing liquid chromatography mass spectrometry (RPIP-LC-MS) of active pharmaceutical ingredient (API) unfractionated heparins (UFHs) from six different manufacturers and one USP standard sample. We employed a reverse phase ion-pairing chromatography method using a C(18) column and hexylamine as the ion-pairing reagent with acetonitrile gradient elution to separate disaccharides generated from the digestion of the heparins by lyase I and III (E.C. 4.2.2.7 and 4.2.2.8) before introduction into an ion-trap mass spectrometer by an electrospray ionization (ESI) interface. Extracted ion chromatograms (EICs) were used to determine the relative abundance of the disaccharides by mass spectrometry. Eight disaccharides were observed and a similar composition profile was observed from digests of 20 UFH samples. The compositional profile determined from these experiments provides a measure of the norm and range of variation in "good" heparin to which future preparations can be compared. Furthermore, the profile obtained in the RPIP-LC-MS assay is sensitive to the presence of the contaminant, oversulfated chondroitin sulfate A (OSCS), in heparin.

An unfractionated heparin (UFH) and a depolymerised derivative of low molecular weight heparin (LMWH) have been compared for their ability to activate platelets suspended in citrated plasma (PRP) or after washing and suspension in hepes buffered tyrode containing fibrinogen. Neither heparin alone induced aggregation of washed platelets, but UFH and to a much lesser extent LMWH, induced aggregation of platelets in PRP. Both heparins caused significant enhancement of a low concentration of ADP-induced activation of PRP and, again, the effect of LMWH was somewhat less than that of UFH. UFH produced a marked potentiation of ADP-induced activation of washed platelets and LMWH was about a third as potent. In addition, UFH induced a potentiation of PAF-induced aggregation and dense-granule release in PRP, a property not shared by LMWH. In PRP, UFH was three times more potent at inhibiting thrombin-induced aggregation and dense-granule release, as might be expected from their specific activities in the KCCT and thrombin time assay. However, with washed platelets, both heparins were equivalent at inhibiting thrombin-induced aggregation, dense-granule release and elevation of cytosolic free calcium ([Ca++]i) as monitored by quin 2 fluorescence. UFH and LMWH alone did not induce a change in [Ca++]i, nor had they any effect on ADP- or PAF-induced elevation of [Ca++]i.

The factor VII activating protease (FSAP) is a serine-protease present in human plasma that serves to activate single-chain plasminogen activators, as well as coagulation factor VII. FSAP was localized within atherosclerotic lesions, and a genetic polymorphism in FSAP is associated with carotid stenosis. Hence, this study was conducted to gain broader insights into the cellular effects of FSAP on vascular smooth muscle cells (VSMC). DNA synthesis and cell proliferation assays revealed an inhibitory action of FSAP on platelet-derived growth factor BB (PDGF-BB)-mediated proliferation of VSMC. FSAP also inhibited PDGF-BB-induced migration of VSMC. These cellular effects of FSAP could be neutralized by an anti-FSAP mAb as well as by protease inhibitors such as aprotinin or a chloromethylketone inhibitor. Moreover, unfractionated heparin promoted the antiproliferative effect of FSAP on VSMC and was essential for the inhibition of VSMC migration. FSAP inhibited PDGF-BB binding to human VSMC and concomitantly blocked PDGF-BB-dependent phosphorylation of mitogen activated protein kinase p42/p44 and tyrosine phosphorylation of other proteins. These results unravel a new function of FSAP as an inhibitor of the proatherogenic phenotype of vascular smooth muscle.

Although it is well established that long-term heparin therapy causes osteoporosis, it is unknown whether heparin-induced bone loss is reversible when heparin treatment is stopped. To address this question, we randomized rats to once daily subcutaneous injections of either unfractionated heparin (1.0 U/g or 0.5 U/g) or saline for 28 days and then followed the rats for an additional 28 days off treatment. Based on histomorphometric analysis of the distal third of the right femur proximal to the epiphyseal growth plate, 1.0 U/g heparin caused a 30% loss in cancellous bone volume over the first 28 days. This was accompanied by a 137% increase in osteoclast surface and a 60% decrease in both osteoblast and osteoid surface. One month after cessation of heparin treatment, no recovery in these parameters was observed. Similarly, serum levels of alkaline phosphatase, a biochemical marker of bone formation, which continued to decrease over the course of heparin treatment, showed no signs of recovery in the subsequent 28 days off treatment. To explore the mechanism responsible for the prolonged effect of heparin on bone, we repeated the experiment giving 125I-labeled heparin in place of unlabeled heparin. 125I-labeled heparin was found to accumulate in bone during the course of its administration, and be retained in bone for at least 56 days after stopping heparin treatment. These findings suggest that heparin-induced osteoporosis is not rapidly reversible because heparin is sequestered in bone for an extended period.

Low-molecular-weight heparins have been suggested as providing well tolerated, efficient, convenient and possibly more cost-effective anticoagulation for haemodialysis than unfractionated heparins (UFHs). A single-bolus dose at the start of haemodialysis effectively prevents clot formation in the dialyser and air trap with fewer side effects and possible benefits on uraemic dyslipidaemia. The safety, clinical efficacy and cost of two anticoagulation regimens in 23 haemodialysis patients were compared over 12-month period. The study comprised two stages: the first stage in which UFH was used for 6 months and the second stage in which UFH was replaced by tinzaparin sodium. The relationship between the anticoagulant effect of tinzaparin sodium and clinical clotting during haemodialysis was recorded. Clinical clotting (grades 1-4) was evaluated by visual inspection after blood draining of the air trap every hour and by inspection of the dialyser after each session. The costs and effects of both anticoagulant protocols on the lipid profile were also compared. Anticoagulation with tinzaparin sodium resulted in less frequent dialyser and air-trap clotting compared with UFH (P = 0.001 and 0.04, respectively). Over 24 weeks, no changes in standard serum lipid profiles were observed. There was statistically significant improvement in dialysis adequacy - evidenced by improved single-pool Kt/V 6 months after tinzaparin sodium use (1.40 +/- 0.28 tinzaparin sodium versus 1.23 +/- 0.28 for UFH) without any change in the haemodialysis prescription. The total cost of 24-week use of tinzaparin sodium was 23% more expensive compared with that of UFH. Tinzaparin sodium should be considered as an effective, well tolerated and may be a superior alternative to conventional heparin anticoagulation in haemodialysis. However, at least - on the short term - tinzaparin sodium therapy did not affect lipid profile in haemodialysis patients. Currently, the direct cost in Saudi Arabia is a little more than standard heparin by about 23%.

OBJECTIVE

To study the effect of heparin on the development of laser-induced choroidal neovascularization (CNV) and to assess the underlying molecular mechanisms.

METHODS

Bone marrow transplantation (BMT) was conducted by intravenous injection of green fluorescence protein (GFP)-labeled bone marrow cells (1 × 10(7) cells) into irradiated (9 Gy) C57BL/6J mice. Laser photocoagulation was applied to induce CNV; subsequently, unfractionated heparin or phosphate-buffered saline was injected into mice that did or did not undergo BMT. The area of CNV, distribution of injected heparin, and quantities of infiltrating cells positive for Griffonia simplicifolia (GS) and GFP inside and outside the CNV were evaluated. Effects of heparin on the secretion of VEGF, CCL2, and TNF-α by ARPE19 cells and on the binding of VEGF, CCL2, TNF-α, and their receptors were analyzed in vitro.

RESULTS

Intravitreal injection of heparin at higher doses reduced the size of the CNV. Heparin localized at the vascular structures and photoreceptor layers adjacent to the laser scar. Only GS-positive cells infiltrating outside the CNV were reduced significantly, but not those inside the CNV or those expressing GFP. Relative decreases in VEGF and CCL2 levels were observed in media of ARPE19 cells at higher heparin concentrations. In vitro binding assays revealed that heparin and porcine ocular fluid, respectively, suppressed the binding of VEGF to VEGFR2 and CCL2 to CCR2.

CONCLUSIONS

Intravitreal heparin injection inhibited CNV development. Reduced VEGF and CCL2 secretion by RPE cells and suppression of VEGF-VEGFR2 and CCL2-CCR2 interactions at the laser site mediated by heparin may contribute to the pharmacologic effect.

Obstetric antiphospholipid syndrome (APS) is now being recognized as a distinct entity from vascular APS. Pregnancy morbidity includes >3 consecutive and spontaneous early miscarriages before 10weeks of gestation; at least one unexplained fetal death after the 10th week of gestation of a morphologically normal fetus; a premature birth before the 34th week of gestation of a normal neonate due to eclampsia or severe pre-eclampsia or placental insufficiency. It is not well understood how antiphospholipid antibodies (aPLs), beyond their diagnostic and prognostic role, contribute to pregnancy manifestations. Indeed aPL-mediated thrombotic events cannot explain the obstetric manifestations and additional pathogenic mechanisms, such as a placental aPL mediated complement activation and a direct effect of aPLs on placental development, have been reported. Still debated is the possible association between aPLs and infertility and the effect of maternal autoantibodies on non-vascular manifestations in the babies. Combination of low dose aspirin and unfractionated or low molecular weight heparin is the effective treatment in most of the cases. However, pregnancy complications, in spite of this therapy, can occur in up to 20% of the patients. Novel alternative therapies able to abrogate the aPL pathogenic action either by interfering with aPL binding at the placental level or by inhibiting the aPL-mediated detrimental effect are under active investigation.

Clinical and imaging data suggest that Behçet's disease (BD) can present with a variety of neurologic complications, which may be subclassified into two forms. One is attributable to small venous inflammatory disease with focal or multifocal central nervous system involvement and is seen in the majority of patients. It is designated Central Nervous System-Neuro-Behçet syndrome (CNS-NBS). The other form is due to cerebral venous sinus thrombosis and has limited symptoms and a better prognosis. It is very uncommon for these two types of involvement to occur in the same individual. It is very likely that the two major forms have different pathogeneses. Patients with small vein inflammation should be considered for aggressive treatment. A substantial number of patients in this group will have a relapsing-remitting course; for some, this will evolve into a secondary progressive course. A few patients from this group will have progressive CNS dysfunction from the onset. Acute attacks of CNS-NBS are treated with either oral prednisone (1 mg/kg/d up to 4 weeks or until improvement is observed) or high-dose intravenous methylprednisolone (IVMP), 1 g/d for 5 to 7 days. After either treatment, an oral tapering dose of glucocorticoids should be given over 2 to 3 months to avoid early relapses. Some patients may require the long-term use of low maintenance doses of glucocorticoids to prevent exacerbations. Immunosuppressive agents (eg, azathioprine, cyclosporine A, cyclophosphamide, and chlorambucil), given either alone or in different combinations (eg, azathioprine with cyclosporine) for the long-term treatment of various systemic manifestations of BD, have not been shown to prevent the development of the neurologic complications of the disease, reduce its exacerbations, or stop its progression. Immunomodulatory treatments such as interferon alfa and thalidomide have been shown to be effective in treating some of the systemic manifestations of BD, but there is no information on their effects on the development and progression of CNS-NBS. Cerebral venous sinus thrombosis in BD is treated with either intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin given together with a short course of glucocorticoids. Evidence of benefit from this treatment, however, is weak.

BACKGROUND

Myeloperoxidase (MPO), a leukocyte-derived heme enzyme binds to the endothelium and depletes vascular nitric oxide (NO) bioavailability in animal models. Unfractionated heparins release vessel-bound MPO and increase endothelial NO bioavailability. Whether low molecular weight heparins also affect circulating MPO levels and NO dependent vasoreactivity however remains elusive.

RESULTS

In a randomized, double-blind, placebo-controlled trial patients with stable coronary artery disease received either 1 mg/kg enoxaparin or an equivalent volume of sodium chloride (NaCl) subcutaneously. Enoxaparin led to a significant improvement of FMD (5.51+/-0.53% vs. 6.55+/-0.58%, p=0.01) accompanied by a significant increase in plasma MPO levels (2.51 [IR: 2.04-3.62] ng/ml vs. 3.70 [IR: 2.80-5.50] ng/ml; p<0.001) whereas NaCl revealed neither a change in FMD (5.56+/-0.67% vs. 5.34+/-0.61%, p=ns) nor in plasma MPO levels (3.04 [IR: 2.22-4.67] ng/ml vs. 2.90 [IR: 1.95-4.32] ng/ml; p=ns). The extent of enoxaparin-induced MPO release and the improvement in endothelial function showed a good correlation (r=0.67, p<0.001).

CONCLUSIONS

This study confirms the concept that heparins improve endothelial function, an established read-out of vascular NO bioavailability, by mobilizing vessel bound MPO. These data not only support the notion of extracoagulant, anti-inflammatory properties of heparins but reinforce the concept of MPO-dependent NO oxidation as a central mechanism for regulation of vascular tone in inflammatory vascular disease. (Eudra-CT number: 2005-006113-40).

BACKGROUND

Management of post-operative bleeding has historically used topical bovine thrombin. However, possible harm through activation of coagulation inhibitors has encouraged investigation with other hemostatic agents. This study utilized a novel ordinal bleeding model to test whether a Gelfoam + human thrombin solution is superior at controlling bleeding when compared to Gelfoam + saline solution at different time intervals.

METHODS

Four swine underwent open laparotomy after receiving unfractionated heparin. Twenty open liver biopsies were performed in each swine; ten biopsies treated with Gelfoam + human thrombin solution and 10 biopsies treated with Gelfoam + saline solution. Three, 6 min, and 12 min after the procedure, bleeding was objectively graded by a four-point model.

RESULTS

There was a significant (P < 0.017), treatment effect on each success/failure outcome (success = bleeding score <or= 1; failure = bleeding score>> 1) at 3 (P < 0.001), 6 (P < 0.001), and 12 (P = 0.003) min, based on a 2 x 2 Fisher's exact test. Similarly, there was a significant treatment effect on each success/failure outcome and four-point bleeding score based on a multiple logistic regression analysis controlling for pig, lesion weight, and initial bleeding taking into consideration repeated measures at three time points.

CONCLUSIONS

The results demonstrate a superior treatment effect for control of bleeding using human thrombin compared to a saline solution. Future studies should compare bovine thrombin versus human thrombins ability to control bleeding as well as the hazard of each in activating coagulation inhibitors.

The present study aimed to determine the protective effects and the underlying mechanisms of unfractionated heparin on lipopolysaccharide (LPS)-induced endotoxemia and lung injury in rats. Rats were injected intravenously with LPS at 6 mg/kg. We examined the therapeutic effects of unfractionated heparin (100 or 300 U/kg) on LPS-induced endotoxemia by dosing intravenously simultaneously after LPS challenge. The animal lung edema degree was evaluated by wet/dry weight ratio. The levels of inflammatory mediators including interleukin-1β (IL-1β) and interleukin-6 (IL-6) were assayed by enzyme-linked immunosorbent assay and quantitative real-time RT-PCR. The activation of nuclear factor-κB (NF-κB) was evaluated by Western blotting. The investigations revealed that treatment with unfractionated heparin can attenuate inflammatory responses in a rat model of LPS-induced acute lung injury, and the effect was much better in 300 U/kg group. The mechanisms by which unfractionated heparin exerts its anti-inflammatory effect are correlated with inhibition of IL-1β and IL-6 production via inactivation of NF-κB.

The goals of therapy for unstable angina and non-Q-wave myocardial infarction (MI) are to maintain myocardial perfusion by inhibiting platelet aggregation and fibrin deposition at sites of plaque rupture, thereby preventing ongoing or new myocardial ischemia and cardiac death. Although aspirin and heparin sodium are cornerstones in the management of unstable angina and non-Q-wave MI, both have significant limitations that have prompted the development of new agents. The thienopyridines, ticlopidine hydrochloride and clopidogrel, appear to be at least as effective as aspirin in the management of unstable angina. Glycoprotein IIb/IIIa receptor antagonists are a new class of platelet inhibitors that are more potent than aspirin, because they target the final common pathway of platelet aggregation. Low-molecular-weight heparins provide a more stable pharmacodynamic response and are more convenient to use than unfractionated heparin. Direct thrombin inhibitors show promise for inhibiting thrombin-mediated platelet aggregation and fibrin deposition. We focus on the opportunities presented by these agents, detailing mechanisms of action, advantages over aspirin and heparin, and performance in recent clinical trials.

BACKGROUND

We prospectively evaluated 30-day thromboembolic and bleeding events in 2 groups of laparoscopic gastric bypass patients receiving different anticoagulation regimens.

METHODS

The first cohort of patients received enoxaparin 40 mg subcutaneously preoperatively, 40 mg subcutaneously on postoperative day 0, and twice daily until discharge. The second cohort of patients received unfractionated heparin 5,000 units subcutaneously preoperatively, nothing on postoperative day 0, and 5,000 units 3 times per day until discharge.

RESULTS

The incidence of deep venous thrombosis in both cohorts was 0. There was 1 pulmonary embolism in the heparin cohort (P = .999). Fourteen patients (5.9%) in the enoxaparin cohort required postoperative transfusions compared with 3 patients (1.3%) in the heparin cohort (P = .011). Four patients (1.7%) in the enoxaparin cohort required re-exploration for bleeding.

CONCLUSIONS

Both enoxaparin and heparin are effective at preventing thromboembolic events following laparoscopic gastric bypass. Heparin is the preferred agent due to the excessive bleeding complications encountered with enoxaparin.

Heparin interacts strongly with the histone component of chromatin, forming heparin-histone complexes which resist dissociation by 0.2 M H2SO4. Heparin treatment of unfractionated histones isolated from nuclei of Chinese hamster cells indicates that the affinities of the histone classes for heparin appear in the order from greatest to least: (H3, H4) greater than (H2A, H2B) greater than H1. However, when isolated nuclei are treated with heparin, H1 is released from the chromatin more readily than the other four histone classes. The release of these four histones (H2A, H2B, H3, and H4) is coordinate and occurs in a highly cooperative manner, as indicated by (1) dependence of the initial kinetics of histone removal upon heparin concentration, (2) analysis of DNA and histones in the fractions obtained from differential sedimentation of heparin-treated nuclei, and (3) analysis of the products from heparin-treated nuclei by equilibrium centrifugation in metrizamide density gradients. The results suggest rapid procedures for using heparin as an agent for studying the accessibility of histones in chromatin of intact nuclei. The relationship of these results to current models of chromatin structure is discussed.

Lipoprotein-associated coagulation inhibitor (LACI) is a plasma-derived protein that inhibits tissue factor (TF)/factor VIIa-induced coagulation in a factor Xa-dependent manner. The roles of endogenous plasma LACI and exogenously added LACI and heparin, in the regulation of coagulation, initiated via the intrinsic and extrinsic pathways, were studied using the activated partial thromboplastin time (APTT) and the modified prothrombin time (PT) assays, respectively. Both LACI-depleted plasma and normal plasma have identical APTTs and similar prolongations of the APTT in response to heparin; both are fully anticoagulated (arbitrarily defined as clotting times of greater than 1 hour) at similar concentrations of heparin. These results indicate that heparin is an effective anticoagulant when coagulation is initiated by the intrinsic pathway and that endogenous LACI is not significantly involved in the regulation of this pathway. The PT of normal plasma is only marginally longer than that of LACI-depleted plasma in the absence of heparin, suggesting that endogenous plasma LACI has a very limited capacity to inhibit TF-induced clotting. However, in the presence of heparin, the PTs of LACI-depleted plasma and normal plasma are different. Prolongation of the PT occurred only moderately and linearly with increasing concentrations of heparin in LACI-depleted plasma. In contrast, normal plasma showed a greater extent of PT prolongation in response to heparin and the plasma became fully anticoagulated at a certain threshold concentration of heparin. These results suggest that LACI serves as a cofactor for heparin and thus greatly enhances the inhibition of TF-induced coagulation. LACI-depleted plasma was supplemented with purified recombinant LACI and/or heparin and the effects on TF-induced clotting were studied. A combination of LACI and heparin greatly enhanced anticoagulation compared with LACI or heparin alone. Many sulfated polysaccharides were also found to enhance the LACI-dependent inhibition of TF-induced clotting. By weight, the relative potencies of these compounds are: low molecular weight heparin (mean Mr, 5,100) greater than unfractionated heparin greater than low molecular weight heparin (mean Mr, 3,700) greater than pentosan polysulfate greater than dermatan sulfate greater than dextran sulfate greater than heparan sulfate. Based on the above results, it is concluded that LACI is a cofactor for heparin in the inhibition of TF-induced clotting and that LACI and sulfated polysaccharides act synergistically in whole plasma.

Primary hemostasis begins with endothelial injury. VWF, produced by endothelial cells, binds to platelets and links them to subendothelial collagen. Platelet-derived ADP and thromboxane activate non-adhered platelets via their GPIIb/IIIa receptors, allowing these platelets to participate in platelet aggregation. Secondary hemostasis is initiated with the binding of factor VII to extravascular tissue factor (TF). Factors II, VII, IX and X are vitamin K-dependent factors. The role of vitamin K is to assist in the addition of gamma carboxylate groups to glutamic acids in the "GLA" domains of these factors.In vitro the intrinsic pathway is initiated when fresh whole blood is placed in a glass tube. The negative charge of the glass initiates the "contact pathway" where FXII is activated and then FXIa cleaves FIX to FIXa. The extrinsic pathway is triggered when tissue factor, phospholipid and calcium are added to plasma anticoagulated with citrate. In vitro, FVII is activated to FVIIa, and TF-FVIIa preferentially converts FX to FXa activating the common pathway.The prothrombin time is commonly used to monitor warfarin anticoagulant therapy. To correct for differences in reagent and instrument, the international normalized ratio was developed to improve standardization of PT reporting globally. The activated partial thromboplastin time (aPTT) is used to evaluate the intrinsic and common pathways of coagulation. The aPTT is useful clinically as a screening test for inherited and acquired factor deficiencies as well as to monitor unfractionated heparin therapy although the anti-Xa assay is now the preferred measure of the effects of unfractionated heparin. The Clauss assay is the most commonly performed fibrinogen assay and uses diluted plasma where clotting is initiated with a high concentration of reagent thrombin.The mixing study assists in the assessment of an abnormally prolonged PT or aPTT. An equal volume of citrated patient plasma is mixed with normal pooled plasma and the PT or aPTT are repeated on the 1:1 mix. Factor activity assays are most commonly performed as a one-stage assay. The patient's citrated plasma is diluted and mixed 1-to-1 with a single factor-deficient substrate plasma. A PT or aPTT is performed on the above mix, depending on the factor being tested.Factor inhibitors are antibodies that are most commonly diagnosed in male patients with severe hemophilia A (FVIII deficiency) where they are induced by factor replacement therapy.Factor inhibitors can also appear in the form of spontaneous autoantibodies in both male and female individuals who were previously well. This is an autoimmune condition called "acquired hemophilia."Most coagulation laboratories can measure the plasma concentration of VWF protein (VWF antigen) by an immunoturbidimetric technique. Testing the functional activity of VWF, utilizes the drug ristocetin.The state of multimerization of VWF is important and is assessed by electrophoresis on agarose gels. Type 2a and 2b VWD are associated with the lack of intermediate- and high molecular weight multimers.The antiphospholipid syndrome (APLS) is an acquired autoimmune phenomenon associated with an increased incidence of both venous and arterial thromboses, as well as fetal loss. Typically, there is a paradoxical prolongation of the aPTT in the absence of any clinical features of bleeding. This is the so-called "lupus anticoagulant (LA) effect." The laboratory definition of the APLS requires the presence of either a "lupus anticoagulant" or a persistent titer of antiphospholipid antibodies.There are now 2 broad classes of direct-acting oral anticoagulants (DOACs): [1] The oral direct thrombin inhibitors (DTIs) such as dabigatran; and [2] The oral direct factor Xa inhibitors such as rivaroxaban and apixaban. The PT and aPTT are variably affected by the DOACs and are generally unhelpful in monitoring their concentrations. Most importantly, a normal PT or aPTT does NOT exclude the presence of any of the DOACs.

Aldosterone suppression and subsequent hyperkalemia are well described reversible side effects of prolonged treatment with heparin. This study was designed to examine whether the discontinuous use of heparin three times a week to prevent thrombosis formation during hemodialysis sessions could also induce hypoaldosteronism and might contribute to increased predialysis kalemia in hemodialysis patients. Two different heparinization regimens were prospectively compared in a crossover study of 11 chronic hemodialysis patients. During 2 consecutive weeks, the patients were dialyzed each week with either their usual doses of unfractionated heparin (UH) (6,160 IU +/- 1,350 IU) or low molecular weight heparin (LMWH) (15 anti-Xa activity [aXa] U/kg + 5 aXa U/kg/h). In all but 2 patients, the predialysis level of plasma K+ was higher with UH than with LMWH, and the mean value was higher (5.66+/-0.83 versus 5.15+/-0.68 mM, p = 0.01) while no differences in the predialysis plasma concentrations of creatinine, phosphate, urea, and bicarbonate were observed, excluding the potential role of differences in diet and dialysis efficacy in explaining the higher plasma K+ concentration with UH. The mean plasma aldosterone to plasma renin activity (pRA) ratio was higher with LMWH than with UH (149.54+/-123.1 versus 111.91+/-86.22 pg/ng/ h, p < 0.05). Individual plasma aldosterone values were found to be correlated to pRAs both during the UH period and the LMWH period, and the slope of the positive linear relation between plasma aldosterone and pRA was lower during the UH treatment period (63 versus 105 pg/ng/h). Finally, a negative linear correlation was found between the differences in individual predialysis plasma K+ observed during the 2 protocols and the differences in the corresponding plasma aldosterone levels, suggesting a link between the higher kalemia and the lower aldosterone responsiveness to angiotensin with unfractionated heparin. Although it cannot be concluded whether or not LMWH inhibits aldosterone synthesis, should LMWH decrease aldosterone production, this side effect is 33% less marked than that of UH so that the predialysis plasma K+ levels are 10% lower. This property makes LMWH use preferable to that of UH in patients with elevated predialysis kalemia.

Immune heparin-induced thrombocytopenia (HIT) is a life-threatening adverse effect of heparin. It can result from any type of heparin exposure and by any route of administration; however only a few cases are reported after exposures to small quantities of heparin from catheter flushes. The major clinical problem associated with HIT is thrombosis. Early detection and institution of alternative, non-heparin anticoagulation are important. We report a patient with HIT associated with use of therapeutic-dose unfractionated heparin in whom immune sensitization to heparin was triggered by two 500-unit exposure to UFH associated with intravascular catheter flushing for antineoplastic chemotherapy in a patient with colon adenocarcinoma.